WO2016149815A1

WO2016149815A1 - Switchable polysaccharides, methods and uses thereof

Info

Publication number: WO2016149815A1
Application number: PCT/CA2016/050325
Authority: WO
Inventors: Pascale Champagne; Philip G. Jessop; Kyle J. BONIFACE; Michael F. Cunningham; Haidong Wang; Omar Garcia Valdez; Alex Cormier; Shijian Ge; Joaquin Arredondo Luna
Original assignee: Queen's University At Kingston
Priority date: 2015-03-20
Filing date: 2016-03-21
Publication date: 2016-09-29
Also published as: CA2918904A1

Abstract

The present application provides a reversibly switchable composite material comprising a polysaccharide and a polysaccharide-supported switchable moiety that is switchable between a neutral first form and an ionized second form. The composite material converts to, or is maintained in, its second form when the switchable moiety is exposed to an ionizing trigger, such as CO₂, at amounts sufficient to maintain the ionized form. The composite material converts to, or is maintained in, the first form when CO₂is removed or reduced to an amount insufficient to maintain the ionized form. Also provided are uses of these composite materials including, but is not limited to, manipulating and/or controlling dispersibility (e.g., CNC dispersibility); surface cleaning; separation applications (e.g., membranes); absorption/flocculation applications; and water treatment.

Description

SWITCHABLE POLYSACCHARI DES, METHODS AND USES THEREOF

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of US provisional application No. 62/136,050 filed on March 20, 2015, and Canadian application No. 2,918,904 filed January 26, 2016, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present application pertains to the field of stimuli-responsive materials. More particularly, the present application relates to switchable polysaccharides, and their methods of manufacture and uses thereof.

INTRODUCTION

[0003] Certain types of polysaccharide-based materials have been investigated due to their physical and chemical properties and/or characteristics, which have made them desirable for particular applications. For example, cellulose nanocrystals (CNCs) have been investigated for their biodegradability, low density, high specific surface area, as well as interesting optical and mechanical properties [Habibi, Y.; et al., O. J. Chem. Rev. 2010, 110, 3479- 3500; Eichhorn, S. J. Soft Matter 2011 , 7, 303-315; Habibi, Y. Chem. Soc. Rev. 2014, 43, 1519-1542; Klemm, D.; et al.. Angew. Chem., Int. Ed. 2011 , 50, 5438-5466]. Due to their properties, CNCs have been considered for use as nanofillers, and absorbents/flocculants, etc. CNCs can be produced by acid hydrolysis (e.g., via use of concentrated sulfuric acid or hydrochloric acid) from a variety of cellulose sources; after which, amorphous cellulose is removed and cellulose nanocrystal (CNC) residue remains, generally as nanorod-shaped CNCs measuring 100 - 200 nm in length, and 10 nm in width [Habibi, Y.; et al. Chem. Rev. 2010, 110, 3479-3500; Klemm, D et al. Angew. Chem., Int. Ed. 2011 , 50, 5438-5466]. CNCs prepared by sulfuric acid hydrolysis have negatively charged sulfate groups residing on the surface that provide electrostatic repulsion among CNC crystals, thereby yielding stable aqueous dispersions [Dong, X. M.; Revol, J. F.; Gray, D. G. Cellulose 1998, 5, 19-32]. In addition to the sulfate groups, the CNC surface may also possess a large concentration of hydroxyl groups, which can be chemically modified to manipulate CNC surface properties. Various chemical approaches have been applied to CNC surface modification, such as sulfonation [Dong, X. M.; et al. Cellulose 1998, 5, 19-32], TEMPO-mediated oxidation [Way, A. E.; et al. J. ACS Macro Lett. 2012, 7, 1001 -1006; Habibi, Y. ; et al. Cellulose 2006, 13, 679-687], amidation [Way, A. E.; et al. ACS Macro Lett. 2012, 7, 1001 -1006; Hemraz, U. D.; et al. Can. J. Chem. 2013, 97, 974-981 ], etherification [Hasani, M.; et al. Soft Matter 2008, 4, 2238-2244; Zaman, M.; et al. Carbohydr. Polym. 2012, 89, 163-170], and polymer grafting [Morandi, G.; et al. Langmuir 2009, 25, 8280-8286; Azzam, F.; et al. Biomacromolecules 2010, 77, 3652-3659; Harrisson, S.; et al. Biomacromolecules 2011 , 72, 1214-1223; Araki, J.; et al. Langmuir 2001 , 77, 21-27; Majoinen, J.; et al. Biomacromolecules 2011 , 72, 2997- 3006; Kan, K. H. M.; et al. Biomacromolecules 2013, 74, 3130-3139; Zoppe, J. O.; et al. Biomacromolecules 2010, 77, 2683-2691 ; Kloser, E.; Gray, D. G. Langmuir 2010, 26, 13450- 13456; Yi, J.; et al. Polymer 2008, 49, 4406-4412], to improve dispersibility of CNCs through electrostatic [Dong, X. M.; et al. Cellulose 1998, 5, 19-32; Way, A. E.; et al. ACS Macro Lett.

2012, 7, 1001-1006; Habibi, Y.; et al. Cellulose 2006, 13, 679-687; Hemraz, U. D.; et al. Can. J. Chem. 2013, 97, 974-981 ; Hasani, M. ; et al. Soft Matter 2008, 4, 2238-2244; Kan, K. H. M. ; et al. Biomacromolecules 2013, 74, 3130-3139] or steric stabilization [Azzam, F.; et al. Biomacromolecules 2010, 77, 3652-3659; Harrisson, S.; et al. Biomacromolecules 2011 , 72, 1214-1223; Araki, J.; et al. Langmuir 2001 , 77, 21-27; Majoinen, J.; et al.

Biomacromolecules 2011 , 72, 2997-3006; Zoppe, J. O.; et al. Biomacromolecules 2010, 77, 2683-2691 ; Kloser, E.; Gray, D. G. Langmuir 2010, 26, 13450-13456]. Some of these modified CNCs were based on either small molecule modification with carboxyl [Way, A. E.; et al. ACS Macro Lett. 2012, 7, 1001-1006; Habibi, Y.; et al. Cellulose 2006, 13, 679-687], amine [Way, A. E.; et al. ACS Macro Lett. 2012, 7, 1001-1006; Hemraz, U. D.; et al.. Can. J. Chem. 2013, 97, 974-981 ], or quaternary ammonium cation [Hasani, M.; et al. Soft Matter 2008, 4, 2238-2244] functionalities or polymer grafting with carboxyl [Majoinen, J.; et al. Biomacromolecules 2011 , 72, 2997-3006] pyridine [Kan, K. H. M.; et al. Biomacromolecules

2013, 74, 3130-3139], or tertiary amine [Tang J.T. et al. (2014) Biomacromolecules

15(8):3052-3060] side groups. Carboxyl/amine-terminated [Way, A. E.; et al. ACS Macro Lett. 2012, 7, 1001-1006], poly(4-vinylpyridine)-grafted [Kan, K. H. M.; et al.

Biomacromolecules 2013, 74, 3130-3139], and poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA)-grafted [Tang J.T. et al. (2014) Biomacromolecules 15(8):3052-3060] CNCs have exhibited pH-responsiveness: Rowen et al. [Way, A. E.; et al. ACS Macro Lett. 2012, 7, 1001 -1006] and Cranston et al. [Kan, K. H. M.; et al. Biomacromolecules 2013, 74,

3130-3139] reported pH-responsive gels/nanocomposites and flocculants, respectively; and, Tang et al. [Tang J.T.; et al. (2014) Biomacromolecules 15(8):3052-3060] reported pH/thermal dual responsive heptane-in-water and toluene-in-water emulsions stabilized by PDMAEMA-grafted CNC. However, adjusting pH by liquid acid/base addition for controlling dispersibility might not be an ideal approach: removal of acid, base or salt (added for pH adjustment) from final colloidal particles can be time-consuming and incomplete; and, repeated pH adjustments can result in salt accumulation and a commensurate increase in ionic strength, which negatively affects colloidal stability.

[0004] Other examples of polysaccharide materials that have been investigated due to their physical and chemical properties and/or characteristics include: cellulose, which has been sought after as a material for fabric for clothes, membranes (e.g., osmosis, dialysis, filtration, ultrafiltration, etc.), paper, chromatography, insulation, for conversion to cellulose derivatives such as viscose, celluloid, cellophane, cellulose acetate (e.g., polymer films, cigarette filters, etc.), and nitrocellulose (e.g., gun cotton, gunpowder, films, etc); chitin/chitosan, which has been used in edible films, food additives, binders (e.g., in dyes, fabrics, adhesives, etc.), threads, membranes, chromatography (e.g., ion exchange chromatography, etc.), filtration, wine making, and seed treatment in agriculture; starch, which has been used in food, pharmaceutical tablets, paper, corrugated cardboard, clothing, laundry, wallboards, glues, textiles, drilling fluids, ceiling tiles, for chemical modification to make other chemicals such as cationic starches (e.g., flocculants), maltose (malt sugar for food), glutamic acid (food additive known as MSG), cyclodextrins (e.g., Febreze, etc.), dextrins (e.g., adhesives, binders, froth flotation, etc.), and starch acetate (e.g., clear films for packaging, etc.);

dextran, which has been used for medical, biological, and chromatographic applications; and, hemicellulose, which has been used in animal feed, and has been industrially converted to xylose (chemical precursor to xylitol and furfural) and then to xylitol (sweetener in chewing gum).

[0005] Carbon dioxide (CO2) is a relatively benign, inexpensive, and abundant reagent that has found use in various industrial processes. In view of that, Jessop et al. have developed switchable technologies that can be switched "on" and "off in the presence and absence of C0₂; such as, switchable solvents [Jessop, P. G.; et al. Nature 2005, 436, 1 102-1 102] and surfactants [Liu, Y. X.; et al. Science 2006, 313, 958-960]. In addition, C0₂ switchable concepts have been applied to a synthesis of worm-like micelles [Su, X.; et al. Chem.

Commun. 2013, 49, 2655-2657], as well as polymer latexes prepared by emulsion polymerization using a switchable surfactant and initiator [Mihara, M.; et al. Macromolecules 2011 , 44, 3688-3693; Fowler, C. I.; et al. Macromolecules 2011 , 44, 2501-2509; Fowler, C. I.; et al. Macromolecules 2012, 45, 2955-2962], switchable co-monomer and initiator

[Pinaud, J.; et al. ACS Macro Lett. 2012, 1, 1 103-1 107] or only switchable initiator [Su, X.; et al. Macromolecules 2012, 45, 666-670]. These polymer latexes could be dispersed and aggregated upon exposure to and removal of C0₂, respectively [Fowler, C. I.; et al.

Macromolecules 2011 , 44, 2501-2509; Fowler, C. I.; et al. Macromolecules 2012, 45, 2955- 2962; Pinaud, J.; et al. ACS Macro Lett. 2012, 1, 1 103-1 107; Su, X.; et al. Macromolecules 2012, 45, 666-670].

[0006] Zhu et al. [Zhang Q.; et al. (201 1) Macromolecules 44(16) :6539-6545; Zhang Q.; et al. (2012b) Macromol Rapid Commun 33(10):916-921 ; Zhang Q.; et al. (2012c) Langmuir 28(14):5940-5946; Zhang Q.; et al. (2013) Macromolecules 46(4): 1261 -1267] and Zhao et al. [Zhao Y.; et al. (2012) Soft Matter 8(46)A 1687-1 1696] have studied C0₂-switchable polymer latexes. Zhu et al. also developed C0₂-switchable lignin nanoparticles for Pickering emulsion application [Qian Y.; et al. (2014) Green Chem 16(12):4963-4968]. C0₂-switchable technology has been applied to polymers [Han D.H.; et al. (2012b) ACS Macro Lett 1 (1):57- 61], polymer gels [George M, Weiss RG (2001) J Am Chem Soc 123(42):10393-10394; Han D.H.; et al. (2012a) Macromolecules 45(18): 7440-7445], polymer vesicle [Yan B.; et al. (2013) Soft affer 9(6) :201 1-2016], and switchable surfaces [Kumar S.; et al. (2013) Chem Commun 49(1):90-92]. In addition, C0₂-switchable polymers and surfactants have been used for nanoparticle modification (e.g., carbon nanotubes (Ding et al. 2010; Guo et al. 2012) and gold nanoparticles (Zhang et al. 2012a) to render their surfaces C0₂-switchable.

[0007] For manipulating colloidal dispersibility, for example, (e.g., polymer latexes or nanoparticle dispersions), using C0₂ as a trigger, rather than acid or base addition, allows for facile removal of the trigger from aqueous media by sparging with inert gases and/or applying heat [Liu, Y. X.; et al. Science 2006, 313, 958-960]; resulting in minimal to no additional residual ionic strength after removal of C0₂. In contrast, stimuli-responsive CNCs, for example, have used pH [Way, A. E.; et al. ACS Macro Lett. 2012, 1, 1001-1006; Kan, K. H. M.; et al. Biomacromolecules 2013, 14, 3130-3139], temperature [Zoppe, J. O.; et al. Biomacromolecules 2010, 11, 2683-2691], or solvent [Capadona, J. R.; et al. Science 2008, 319, 1370-1374] for switching.

[0008] The above information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention. SUMMARY OF THE INVENTION

[0009] An object of the present application is to provide switchable polysaccharides, and methods and uses thereof. In accordance with an aspect of the present application, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and polysaccharide- supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, wherein the switchable moiety comprises an amine, amidine, or guanidine.

[0010] In accordance with another aspect of the present application, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and at least one polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, wherein the switchable moiety comprises an amine, amidine, or guanidine.

[001 1] In accordance with one embodiment, there is provided a composite material wherein the switchable moiety is an amine and the neutral form of the switchable moiety is bound to the polysaccharide via a linker XY; and

wherein the first form of the composite material has the structure of formula 1

the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker XY has the structure of formula 2

(2);

wherein: n is an integer 1 , 2 or 3; p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent;

E is O, S, or a combination thereof;

Y is absent, or a divalent moiety bonded to the polysaccharide and X, and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, each of which may be substituted; or, Y is a divalent cycle, or heterocycle, each of which may be substituted;

each X is a divalent moiety bonded Y, or to the polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C 1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X is independently is a divalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or two of R¹ and R², together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

wherein each X optionally comprises one or more amine, amide, amidine, guanidine, carbamate ester, carbonate diester, ether, ester, thioether, thioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched carbon chain, or at one of said chain's termini; and

NR¹R² and NR¹R²⁺ are each a switchable functional group, wherein R¹ and R² are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic, a CnSim group where n and m are independently a number from 0 to 10 and n + m is a number from 1 to 10, a Cs to Cio aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or R¹ and R², together with the atoms to which they are attached, are connected to form a cycle, or heterocycle, each of which may be substituted; or

R² is repeat unit -(X-NR¹)_m-Z, wherein m, X and R¹ are as defined above, and Z is a monovalent moiety bonded to the switchable functional group, and is a linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, or a siloxane, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

wherein, [X(NR¹R²)_n]_m and [X(NR¹R²⁺)_n]_m constitute a chain of repeat units that is linear or branched, each repeat unit in said chain being the same, or different, relative to other repeat units; and

wherein, (a) if both of R¹ and R² are H, than X is a sterically hindered group or, (b) if one of R¹ and R² is H, then either (i) the other one of R¹ and R² is a sterically hindered group, or (ii) X is a sterically hindered group.

[0012] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is an amine and the switchable moiety is bound to the polysaccharide via a linker XY; and

wherein the first form of the composite material has the structure of formula 1

(1); and

the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysacchari has the structure of formula 2

(2);

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X, and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted;

each X is a divalent linker moiety, or a multivalent linker moiety bonded to Y, or to the polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, each X is independently is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or two of R¹ and R², together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

wherein each X and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched carbon chain, or at one of said chain's termini; and

NR¹R² and NR¹R²⁺ are each a switchable functional group, wherein R¹ and R² are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic, a CqSir group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to C10 aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or R¹ and R², together with the atoms to which they are attached, are connected to form a cycle, or heterocycle, each of which may be substituted; or R² is repeat unit -(X-NR¹)s-Z, wherein X and R¹ are as defined above, s is an integer between 1 and 10 000 wherein m x p x s is 10 000 or less, and Z is a monovalent moiety bonded to the switchable functional group, and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thiol, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched carbon chain, or at one of said chain's termini;

wherein each of [X(NR¹R²)_n]_m and [X(N⁺R¹R²)_n]_m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit is the same or different relative to other repeat units; and

[0013] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 1 a when Y is absent, p is 1 , and R² is repeat unit -(X-NR¹)_m-Z or -(X-NR¹)_S-Z,

the second form of the composite material has the structure of formula 2a,

(2a). [0014] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 1 c when Y is absent, p is 1 , and m is 1 ,

the second form of the composite material has the structure of formula 2c,

[0015] In accordance with another embodiment, there is provided a composite material comprising a polysaccharide and polysaccharide-supported switchable moiety, wherein the switchable moiety is an amine and the neutral form of the switchable moiety is bound to a polysaccharide via a linker X, wherein the first form of the composite material has the structure of formula 1 , with a proviso that, when the polysaccharide is a CNC, Y is absent, p is 1 , and X is -CH2-C(CH₃)2-C02-(CH2)2-, only one of R¹ and R² is CH₃.

[0016] In accordance with another embodiment, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and at least one polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, wherein the switchable moiety comprises an amine, and wherein the first form of the composite material has the structure of formula 1 or (I), with a proviso that, when the polysaccharide is CNC, Y is absent, p is 1 , and X or X' is -CH₂-C(CH₃) -C0₂-(CH₂)2- or - C(CH₃) -C0₂-(CH₂)2-, only one of R¹ and R² is CH₃.

[0017] In accordance with another embodiment, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and at least one polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, wherein the switchable moiety comprises an amine, and wherein the first form of the composite material has the structure of formula (I), with a proviso that, when the polysaccharide is CNC, cellulose, cellulose membrane, or filter paper, Y is present or absent, p is 1 , and X' is -CH₂-C(CH₃) -C0₂-(CH₂)2- or -C(CH₃) -C0₂-(CH₂)2-, only one of R¹ and R² is CH₃.

[0018] In accordance with another embodiment, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and at least one polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, wherein the switchable moiety comprises an amine, and wherein the first form of the composite material has the structure of formula (I), with a proviso that, when Y is present or absent, p is 1 , and X' is -CH₂-C(CH₃) -C0₂-(CH₂)₂- or -C(CH₃) -C0₂-(CH₂)₂-, only one of R¹ and R² is CH₃.

[0019] In accordance with another embodiment, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and at least one polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, wherein the switchable moiety comprises an amine, with a proviso that, when the first form of the composite material has the structure of formula 1 or (I), the composite material does not comprise PDMAEMA.

[0020] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is an amidine and the neutral form of the switchable moiety is bound to the polysaccharide via a linker XY; and

wherein the first form of the composite material has the structure of formula 3a, 3b, or

3c,

(3a) (3b) (3c); and the second form of the composite material comprising the ionized form of the switchable saccharide via a linker XY has the structure of formula 4a 4b 4c,

(4b) (4c); wherein:

n is an integer 1 , 2 or 3; p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent;

E is O, S, or a combination thereof;

each X is a divalent moiety bonded Y, or to the polysaccharide when Y is absent, and the switchable functional group; each X is independently a linear or branched Ci-

Ci5 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X is independently is a divalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or more of R³, R⁴, and R⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; and

N=CR³NR⁴R⁵ , R³N=CNR⁴R⁵, R³N=CR⁴NR⁵, and (N=CR³NR⁴R⁵)⁺, (R³N=CNR⁴R⁵)⁺, (R³N=CR⁴NR⁵)⁺ are each switchable functional groups, wherein R³, R⁴, and R⁵ are independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a CnSim group where n and m are independently a number from 0 to 10 and n + m is a number from 1 to 10, a C₅ to C10 aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R³, R⁴, and R⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; or,

any one of R³, R⁴, and R⁵ is repeat unit -(X-N=CR³NR⁴)_m-Z, -(X-N=CNR⁴R⁵)_m-Z; or -(X-C=NR³NR⁴)m-Z, -(X-C=NNR⁴R⁵)_m-Z; or -(X-NCR⁴=NR³)_m-Z, -(X-NR⁵CR⁴=N)_m- Z, -(X-NR⁵C=NR³)m-Z, wherein X and R³, R⁴, and R⁵ are as defined above, and

Z is a monovalent moiety bonded to the switchable functional group, and is a linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, or a siloxane, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

wherein, [X(N=CR³NR⁴R⁵)_n]_m, [X(R³N=CNR⁴R⁵)_n]_m, [X(R³N=CR⁴NR⁵)_n]_m, and [X(N=CR³NR⁴R⁵⁺)n]m , [X(R³N=CNR⁴R⁵⁺)n]m , [X(R³N=CR⁴NR⁵⁺)n]m constitute a chain of repeats units that is linear or branched, each repeat unit in said chain being the same, or different, relative to other repeat units.

[0021 ] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is an amidine and the switchable moiety is bound to the polysaccharide via a linker XY; and

3c,

(3a) (3b) (3c); and the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker XY has the structure of formula 4a, 4b, 4c,

(4a) (4b) (4c); wherein:

E is O, S, or a combination thereof;

each X is a divalent linker moiety, or a multivalent linker moiety bonded to Y, or to the polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C 1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1 -C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, each X is independently is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or more of R³, R⁴, and R⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; wherein each X and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and

N=CR³NR⁴R⁵ , R³N=CNR⁴R⁵, R³N=CR⁴NR⁵, and (N=CR³NR⁴R⁵)⁺, (R³N=CNR⁴R⁵)⁺, (R³N=CR⁴NR⁵)⁺ are each switchable functional groups, wherein R³, R⁴, and R⁵ are independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a CqSir group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to C10 aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R³, R⁴, and R⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; or,

any one of R³, R⁴, and R⁵ is repeat unit -(X-N=CR³NR⁴)_S-Z, -(X-N=CNR⁴R⁵)_S-Z; or -(X-C=NR³NR⁴)s-Z, -(X-C=NNR⁴R⁵)s-Z; or -(X-NCR⁴=NR³)_S-Z, -(X-NR⁵CR⁴=N)_S-Z, -(X-NR⁵C=NR³)s-Z, wherein X and R³, R⁴, and R⁵ are as defined above, s is an integer between 1 and 10 000 wherein m x p x s is 10 000 or less, and Z is a monovalent moiety bonded to the switchable functional group, and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched carbon chain, or at one of said chain's termini; and

wherein each of [X(N=CR³NR⁴R⁵)_n]_m, [X(R³N=CNR⁴R⁵)_n]_m, [X(R³N=CR⁴NR⁵)_n]_m, and [X((N=CR³NR⁴R⁵)⁺)n]m, [X((R³N=CNR⁴R⁵)⁺)_n]_m, [X((R³N=CR⁴NR⁵)⁺)_n]_m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit is the same or different relative to other repeat units.

[0022] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 3d, 3d', 3e, 3e', 3f, 3f, or 3f" when Y is absent, p is 1 , and R³, R⁴, or R⁵ is repeat unit -(X-N=CR³NR⁴)_m-Z, - (X-N=CNR⁴R⁵)m-Z; or -(X-C=NR³NR⁴)_m-Z, -(X-C=NNR⁴R⁵)_m-Z; or -(X-NCR⁴=NR³)_m-Z, -(X- NR⁵CR⁴=N)_m-Z, -(X-NR⁵C=NR³)_m-Z; or -(X-N=CR³NR⁴)_S-Z, -(X-N=CNR⁴R⁵)_S-Z; or -(X- C=NR³NR⁴)s-Z, -(X-C=NNR⁴R⁵)s-Z; or -(X-NCR⁴=NR³)_S-Z, -(X-NR⁵CR⁴=N)_S-Z, -(X- NR⁵ =NR³)s-Z,

(3f); and the second form of the composite material has the structure of formula 4d, 4d', 4e, 4e", 4f, 4f, or 4f,

(ΑΠ-

[0023] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 3g, 3h, or 3i when Y is

(3g) (3h) (3¾; and the second form of the composite material has the structure of formula 4g, 4h, or 4i,

[0024] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is a guanidine, and the neutral form of the switchable moiety is bound to the polysaccharide via a linker XY; and

wherein the first form of the composite material has the structure of formula 5a, 5b,

5c,

(5a); (5b); (5c);

the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker XY has the structure of formula 6a, 6b, 6c,

(6a); (6b) (6c); or wherein: n is an integer 1 , 2 or 3; p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent;

E is O, S, or a combination thereof;

each X is a divalent moiety bonded Y, or to the polysaccharide when Y is absent, and the switchable functional group; each X is independently a linear or branched Ci- Ci5 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X is independently is a divalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or more of R⁶, R⁷, R⁸, R⁹ and R¹⁰, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; and

N=CNR⁶R⁷NR⁸R⁹, R¹⁰N=CNR⁶NR⁸R⁹, R¹⁰N=CNR⁶R⁷NR⁹, and

(N=CNR⁶R⁷NR⁸R⁹)⁺, (R¹⁰N=CNR⁶NR⁸R⁹)⁺, (R¹⁰N=CNR⁶R⁷NR⁹)⁺ are each switchable functional groups, wherein R⁶, R⁷, R⁸, R⁹ and R¹⁰ are independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_nSi_m group where n and m are independently a number from 0 to 10 and n + m is a number from 1 to 10, a C5 to C10 aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R⁶, R⁷, R⁸, R⁹ and R¹⁰, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; or,

any one of R⁶, R⁷, R⁸, R⁹ and R¹⁰ is repeat unit -(X-N=CNR⁶R⁷NR⁸)_m-Z,

-(X-N=CNR⁷NR⁸R⁹)_m-Z, or -(X-NR⁶C=NNR⁸R⁹)_m-Z, -(X-NR⁶C=NR¹⁰NR⁸)_m-Z, -(X-NC= NR¹⁰NR⁸R⁹)m-Z, wherein X and R⁶, R⁷, R⁸, R⁹ and R¹⁰ are as defined above, and Z is a monovalent moiety bonded to the switchable functional group, and is a linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, or a siloxane, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

wherein at least one of R⁶, R⁷, R⁸, R⁹ and R¹⁰ is an electron withdrawing group; and

wherein, [X(N=CNR⁶R⁷NR⁸R⁹)_n]_m , [X(R¹⁰N=CNR⁶NR⁸R⁹)_n]m ,

[X(R¹⁰N=CNR⁶R⁷NR⁹)n]m , [X(N=CNR⁶R⁷NR⁸R⁹)⁺ _n]_m , [X(R¹⁰N=CNR⁶NR⁸R⁹)⁺ _n]_m , [X(R¹⁰N=CNR⁶R⁷NR⁹)⁺n]m constitute a chain of repeats units that is linear or branched, each repeat unit in said chain being the same, or different, relative to other repeat units.

[0025] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is a guanidine, and the switchable moiety is bound to the polysaccharide via a linker XY; and

(5a); (5b); (5c);

(6a); (6b) (6c); and wherein: n is an integer 1 , 2 or 3; p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent;

E is O, S, or a combination thereof;

each X is a divalent linker moiety, or a multivalent linker moiety bonded to Y, or to the polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, each X is independently is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or more of R⁶, R⁷, R⁸, R⁹ and R¹⁰, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

wherein each X and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and

N=CNR⁶R⁷NR⁸R⁹, R¹⁰N=CNR⁶NR⁸R⁹, R¹⁰N=CNR⁶R⁷NR⁹, and

(N=CNR⁶R⁷NR⁸R⁹)⁺ , (R^{1 0}N=CNR⁶N R⁸R⁹)⁺ , (R¹⁰N=CNR⁶R⁷NR⁹)⁺ are each switchable functional groups, wherein R⁶, R⁷, R⁸, R⁹ and R¹⁰ are independently H , a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to Cio aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R⁶, R⁷, R⁸, R⁹ and R¹⁰, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; or,

any one of R⁶, R⁷, R⁸, R⁹ and R^{1 0} is repeat unit -(X-N=CNR⁶R⁷N R⁸)_S-Z, -(X-N=CNR⁷NR⁸R⁹)s-Z, or -(X-NR⁶C=NNR⁸R⁹)_S-Z, -(X-NR⁶C=NR¹⁰NR⁸)_S-Z, -(X-NC= NR¹⁰NR⁸R⁹)s-Z, wherein X and R⁶, R⁷, R⁸, R⁹ and R¹⁰ are as defined above, s is an integer between 1 and 10 000 wherein m x p x s is 10 000 or less, and Z is a monovalent moiety bonded to the switchable functional group, and is a hydrogen, a halogen, linear or branched C1 -C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

wherein at least one of R⁶, R⁷ , R⁸, R⁹ and R¹⁰ is an unsaturated functional group (e.g., aryl) or an an electron withdrawing group; and

wherein each of [X(N=CNR⁶R⁷NR⁸R⁹)_n]_m , [X(R¹⁰N=CNR⁶NR⁸R⁹)_n]_m , [X(R¹⁰N=CNR⁶R⁷NR⁹)n]m , [X((N=CNR⁶R⁷NR⁸R⁹)⁺)_n]m , [X((R¹⁰N=CNR⁶NR⁸R⁹)⁺)_n]m , [X((R¹⁰N=CNR⁶R⁷NR⁹)⁺)n]m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit is the same or different relative to other repeat units. [0026] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 5d, 5d', 5d", 5e, or 5e' when Y is absent, p is 1 , and R⁶, R⁷, R⁸, R⁹ or R¹⁰ is repeat unit -(X-N=CNR⁶R⁷NR⁸)_m- Z, -(X-N=CNR⁷NR⁸R⁹)m-Z, or -(X-NR⁶C=NNR⁸R⁹)_m-Z, -(X-

NR⁶C=NR¹⁰NR⁸)_m-Z, -(X-NC=NR¹⁰NR⁸R⁹)_m-Z; or -(X-N=CNR⁶R⁷NR⁸)_S-Z, -

(X-N=CNR⁷NR⁸R⁹)s-Z, or -(X-NR⁶C=NNR⁸R⁹)s-Z, -(X-NR⁶C=NR¹⁰NR⁸)s-Z,

-(X-NC= ¹⁰NR⁸R⁹)s-Z,

(5e) (5e'); and

the second form of the composite material has the structure of formula 6d, 6d', 6d", '

(6e) (6e').

[0027] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 5f, 5g, or 5h when Y is absent, p is 1 , and m is 1 ,

(5f) (5g) (5h); and the second form of the composite material has the structure of formula 6f, 6g, or 6h,

[0028] In accordance with another embodiment, there is provided a composite material whereinthe switchable moiety is a pyridine, and the neutral form of the switchable moiety is bound to the polysaccharide via a linker XY; and

wherein the first form of the composite material has the structure of formula 7,

(7); and the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker XY has the structure of formula 8,

(8),

wherein: n is an integer 1 , 2 or 3;

o is an integer 1 , 2 or 3; p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent;

E is O, S, or a combination thereof;

Y is absent, or a divalent moiety bonded to the polysaccharide and X, and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, each of which may be substituted; or,

Y is a divalent cycle, or heterocycle, each of which may be substituted; each X is a divalent moiety bonded Y, or to the polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X is independently is a divalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or two of R¹ and R², together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

is a switchable functional group, wherein R 15 is H, a Ci to Cio aliphatic group that is linear, branched, or cyclic, a C_nSi_m group where n and m are independently a number from 0 to 10 and n + m is a number from 1 to 10, a C₅ to Cio aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or any two of R¹⁵, together with the atoms to which they are attached, are connected to form a cycle, or heter of which may be substituted; or

any one of R¹⁵ is repeat unit

, wherein X and R¹⁵ are as defined above, q is integer 1 or 2, and Z is a monovalent moiety bonded to the switchable functional group, and is a linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, or a siloxane, each of which may be substituted; or, Z is a monovalent cycl or heteroc cle, each of which ma be substituted;

wherein,

and constitute a chain of repeat units that is linear or branched, each repeat unit in said chain being the same, or different, relative to other repeat units.

[0029] In accordance with another embodiment, there is provided a composite material The composite material of claim 1 , wherein the switchable moiety is a pyridine, and the switchable moiety is bound to the polysaccharide via a linker XY; and

the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker XY has the structure of formula 8,

(8),

wherein: n is an integer 1 , 2 or 3; o is an integer 1 , 2 or 3; p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent;

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X, and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X is a divalent linker moiety, or a multivalent linker moiety bonded to Y, or to the polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, each X is independently is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or more of R¹⁵ , together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

is a switchable functional group, wherein R¹⁵ is H, a Ci to C10 aliphatic group that is linear, branched, or cyclic, a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to C10 aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or any two of R¹⁵, together with the atoms to which they are attached, are connected to form a cycle, or heterocycle, each of which may be substituted; or

any one of R¹⁵ is repeat unit , wherein X and R¹⁵ are as defined above, q' is integer 1 or 2, s is an integer between 1 and 10 000 wherein m x p x s is 10 000 or less, and Z is a monovalent moiety bonded to the switchable functional group, and is a hydrogen, a halogen, linear or branched C 1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and

wherein each of

comprises a chain of repeat units that is linear or branched, wherein each repeat unit is the same or different relative to other repeat units.

[0030] In accordance with another embodiment, there is provided a composite material wherein the first form of the com osite material has the structure of formula 7a when Y is

absent, p is 1 , and R¹⁵ is repea

the second form of the

[0031] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 7b when Y is absent, p is 1 , and m is 1 ,

the second form of the c ructure of formula 8b,

[0032] In accordance with another embodiment, there is provided a composite material wherein the neutral form of the switchable moiety is bound to the polysaccharide via a linker XY; and

wherein the first form of the composite material has the structure of formula 9a, 9b, 9c, or 9d,

(9a); (9b);

(9c); (9d); and

the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker XY has the structure of formula 10a, 10b, 10c, or 10d,

(10c); (10d); and

wherein: n is an integer 1 , 2 or 3; p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent; E is O, S, or a combination thereof;

each X is a divalent moiety bonded Y, or to the polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X is independently is a divalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or two of R¹ and R², together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

R¹¹ , R¹², R¹³, and R¹⁴ are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_nSi_m group where n and m are independently a number from 0 to 10 and n + m is a number from 1 to 10, a C₅ to C10 aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R¹¹ , R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a cycle or heterocycle, each of which may be substituted; or

any one of R¹¹ , R¹², R¹³, and R¹⁴ is repeat unit -(X-lm)_m-Z, wherein X is as defined above, Im is an optionally substituted imidazole ring, and Z is a monovalent moiety bonded to the switchable functional group, and is a linear or branched C 1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, or a siloxane, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

wherein, the repeat unit [X(lm)_n]_m and [X(lm)⁺ _n]_m constitute a chain of repeat units that is linear or branched, each repeat unit in said chain being the same, or different, relative to other repeat units. [0033] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is bound to the polysaccharide via a linker XY; and

(9c); (9d); and

(10a); (10b);

(10c); (10d); and

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X, and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X is a divalent linker moiety, or a multivalent linker moiety bonded to Y, or to the polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, each X is independently is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or more of R¹¹, R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; wherein each X and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini;

R¹¹, R¹², R¹³, and R¹⁴ are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to Cio aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R¹¹, R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a cycle or heterocycle, each of which may be substituted; or

any one of R¹¹, R¹², R¹³, and R¹⁴ is repeat unit -(X-lm)s-Z, wherein X is as defined above, Im is an optionally substituted imidazole ring, s is an integer between 1 and 10 000 wherein m x p x s is 10 000 or less, and Z is a monovalent moiety bonded to the switchable functional group, and is a hydrogen, a halogen, linear or branched C 1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, sulphide, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted; wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and

wherein each of [X(lm)_n]_m and [X((lm)⁺)_n]_m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit is the same or different relative to other repeat units.

[0034] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 9e, 9f, 9g, or 9h when Y is absent, p is 1 , and m is 1 ,

-36- [0035] In accordance with another aspect, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, the switchable moiety comprising an amine, amidine, or guanidine;

with the proviso that, when the first form of the composite material has a structure of formula 9f,

(9f); wherein: n is an integer 1 , 2 or 3;

X is a divalent moiety bonded to the polysaccharide and the switchable moiety; X is independently a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, each of which may be substituted; or, X is independently is a divalent cycle, or heterocycle, each of which may be substituted; or, X, and one or more of R¹¹, R¹², and R¹⁴, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

wherein X optionally comprises halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and

R¹¹, R¹², and R¹⁴ are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_nSi_m group where n and m are independently a number from 0 to 10 and n + m is a number from 1 to 10, a Cs to Cio aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R¹¹, R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a cycle or heterocycle, each of which may be substituted;

and, when the polysaccharide is a CNC, n is 1 , and X is -C(0)-NH-(CH2)3- or - C0₂-NH-(CH₂)₃- then only two of R¹¹, R¹², or R¹⁴ is H.

[0036] In accordance with another embodiment, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and at least one polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, wherein the switchable moiety comprises an amine, and wherein the first form of the composite material has the structure of formula 9f, with a proviso that, when the polysaccharide is CNC and n is 1 , and X is -C(0)-NH-(CH₂)3- or -C0₂-NH-(CH₂)3-, -C(0)-(p- C₆H₄)-CH₂- or -C(0)-(p-C₆H₄)-CH(CH₃)-, only two of R¹¹, R¹², or R¹⁴ is H.

[0037] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure

and the second form of the composite material has the structure

[0038] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is an amine and the switchable moiety is bound to the polysaccharide via a linker ΧΎ; and

wherein the first form of the composite material has the structure of formula I

(I); and

the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker ΧΎ has the structure of formula II

(II);

wherein: p is an integer between 1 and 4, wherein when Y is absent, p is 1 m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent;

E is O, S, or a combination thereof; Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X', and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted;

each X' is independently a linear or branched C1-C15 alkanetriyl, a C15-C30 alkanetriyl, a C1-C15 alkenetriyl, a C15-C30 alkenetriyl, a C1-C15 alkynetriyl, a C15-C30 alkynetriyl, an aryltriyl, a heteroaryltriyl, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X' is independently is a trivalent cycle, or heterocycle, each of which may be substituted; or, each X', and one or two of R¹ and R², together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

wherein each X' and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini;

NR¹R² and N⁺R¹R² are each a switchable functional group, wherein R¹ and R² are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic, a CqSir group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C5 to C10 aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or R¹ and R², together with the atoms to which they are attached, are connected to form a cycle, or heterocycle, each of which may be substituted; and

Z is a monovalent moiety bonded to X', and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thiol, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

wherein each of [X'(NR¹R²)]_m and [X'(N⁺R¹R²)]_m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit in said chain is the same or different relative to other repeat units; and

wherein, (a) if both of R¹ and R² are H, then X' is a sterically hindered group or, (b) if one of R¹ and R² is H, then either (i) the other one of R¹ and R² is a sterically hindered group, or (ii) X' is a sterically hindered group.

[0039] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is an amidine and the switchable moiety is bound to the polysaccharide via a linker ΧΎ; and

wherein the first form of the composite material has the structure of formula Ilia, II or lllc,

(Ilia) (1Mb) (lllc); and

the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker ΧΎ has the structure of formula IVa, IVb, IVc,

(IVa) (IVb) (IVc); wherein:

p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent;

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X', and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted;

each X' is independently a linear or branched C1-C15 alkanetriyl, a C15-C30 alkanetriyl, a C1-C15 alkenetriyl, a C15-C30 alkenetriyl, a C1-C15 alkynetriyl, a C15-C30 alkynetriyl, an aryltriyl, a heteroaryltriyl, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X' is independently is a trivalent cycle, or heterocycle, each of which may be substituted; or, each X', and one or more of R³, R⁴, and R⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

N=CR³NR⁴R⁵ , R³N=CNR⁴R⁵, R³N=CR⁴NR⁵, and (N=CR³NR⁴R⁵)⁺, (R³N=CNR⁴R⁵)⁺, (R³N=CR⁴NR⁵)⁺ are each switchable functional groups, wherein R³, R⁴, and R⁵ are independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a CqSir group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to C10 aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R³, R⁴, and R⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; and

wherein each of [X'(N=CR³NR⁴R⁵)]_m, [X'(R³N=CNR⁴R⁵)]_m, [X'(R³N=CR⁴NR⁵)]_m, and [X'(N=CR³NR⁴R⁵⁺)]_m, [X'(R³N=CNR⁴R⁵⁺)]_m, [X'(R³N=CR⁴NR⁵⁺)]_m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit in said chain is the same or different relative to other repeat units.

[0040] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is a guanidine, and the switchable moiety is bound to the polysaccharide via a linker ΧΎ; and

wherein the first form of the composite material has the structure of formula Va, Vb,

(Va); (Vb); (Vc); and

the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker ΧΎ has the structure of formula Via, Vlb, Vic,

(Via); (Vlb); (Vic); wherein: p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent;

E is O, S, or a combination thereof;

each X' is independently a linear or branched C1-C15 alkanetriyl, a C15-C30 alkanetriyl, a C1-C15 alkenetriyl, a C15-C30 alkenetriyl, a C1-C15 alkynetriyl, a C15-C30 alkynetriyl, an aryltriyl, a heteroaryltriyl, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X' is independently is a trivalent cycle, or heterocycle, each of which may be substituted; or, each X', and one or more of R⁶, R⁷, R⁸, R⁹ and R¹⁰, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

wherein each X' and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; N=CNR⁶R⁷NR⁸R⁹, R¹⁰N=CNR⁶NR⁸R⁹, R¹⁰N=CNR⁶R⁷NR⁹, and

(N=CNR⁶R⁷NR⁸R⁹)⁺ , (R^{1 0}N=CNR⁶N R⁸R⁹)⁺ , (R¹⁰N=CNR⁶R⁷NR⁹)⁺ are each switchable functional groups, wherein R⁶, R⁷, R⁸, R⁹ and R¹⁰ are independently H , a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to Cio aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R⁶, R⁷, R⁸, R⁹ and R¹⁰, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; and

wherein each of [X'(N=CNR⁶R⁷NR⁸R⁹)]_m , [X'(R¹⁰N=CNR⁶NR⁸R⁹)]_m, [X'(R¹⁰N=CNR⁶R⁷NR⁹)]_m , [X'(N=CNR⁶R⁷NR⁸R⁹)⁺]_m , [X'(R^{1 0}N=CNR⁶NR⁸R⁹)⁺]_m , [X'(R¹⁰N=CNR⁶R⁷NR⁹)⁺]m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit in said chain is the same or different relative to other repeat units.

[0041] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is a pyridine, and the switchable moiety is bound to the polysaccharide via a linker ΧΎ; and wherein the first form of the composite material has the structure of formula VII,

the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker ΧΎ has the structure of formula VIII,

(VIII),

wherein: o is an integer 1 , 2 or 3; p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent;

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X', and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X' is independently a linear or branched C1-C15 alkanetriyl, a C15-C30 alkanetriyl, a C1-C15 alkenetriyl, a Ci₅-C₃₀ alkenetriyl, a C1-C15 alkynetriyl, a Ci₅-C₃₀ alkynetriyl, an aryltriyl, a heteroaryltriyl, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X' is independently is a trivalent cycle, or heterocycle, each of which may be substituted; or, each X', and one and one or more of R¹⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

wherein each X' and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched.carbon chain, or at one of said chain's termini; and

is a switchable functional group, wherein R¹⁵ is H, a Ci to Cio aliphatic group that is linear, branched, or cyclic, a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to Cio aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or any two of R¹⁵, together with the atoms to which they are attached, are connected to form a cycle, or heterocycle, each of which may be substituted; and

wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched carbon chain, or at one of said chain's termini; and wherein each of

optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit in said chain is the same or different relative to other repeat units.

[0042] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is bound to the polysaccharide via a linker ΧΎ; and

wherein the first form of the composite material has the structure of formula IXa, IXb, IXc, or IXd,

(IXc); (IXd); and the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker ΧΎ has the structure of formula Xa, Xb, Xc, or Xd,

E is O, S, or a combination thereof;

each X' is independently a linear or branched C1-C15 alkanetriyl, a C15-C30 alkanetriyl, a C1-C15 alkenetriyl, a C15-C30 alkenetriyl, a C1-C15 alkynetriyl, a C15-C30 alkynetriyl, an aryltriyl, a heteroaryltriyl, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X' is independently is a trivalent cycle, or heterocycle, each of which may be substituted; or, each X', and one or more of R¹¹ , R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

R¹¹ , R¹², R¹³, and R¹⁴ are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to Cio aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R¹¹ , R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a cycle or heterocycle, each of which may be substituted;

wherein, each of [X'(lm)]_m and [X'(lm)⁺]_m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit in said chain is the same or different relative to other repeat units, wherein Im is an optionally substituted imidazole ring.

[0043] In accordance with another embodiment, there is provided a composite material wherein the polysaccharide is cellulose nanocrystal (CNC), cellulose, dextran, cotton, starch, chitin, chitosan, or any combination thereof. [0044] In accordance with another embodiment, there is provided a composite material wherein the polysaccharide comprises cellulose nanocrystal (CNC), cellulose, dextran, starch, chitin, chitosan, glycogen, pectin, arabinoxylan, or any combination or modification thereof.

[0045] In accordance with another embodiment, there is provided a composite material wherein the polysaccharide is comprised within cotton, cotton linen, paper, flax, hemp jute, sisal, linen, or any combination or modification thereof.

[0046] In accordance with another embodiment, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and at least one polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, with a proviso that the polysaccharide is not CNC, cellulose, or filter paper.

[0047] In accordance with another embodiment, there is provided a composite material wherein said first form of the composite material is neutral and hydrophobic, and the second form of the composite material is ionized and hydrophilic.

[0048] In accordance with another embodiment, there is provided a composite material wherein the composite material converts to, or is maintained in, said second, ionized form when the switchable moiety is exposed to an ionizing trigger at an amount sufficient to maintain said switchable moiety in its ionized form; and, wherein the composite material converts to, or is maintained in, said first form when said ionizing trigger is removed or reduced to an amount insufficient to maintain said switchable moiety in its ionized form. In one embodiment, the ionizing trigger is an acid gas. In another embodiment, the acid gas is C0₂, COS, CS₂, or a combination thereof.

[0049] In accordance with another embodiment, the ionizing trigger is removed or reduced by exposing the composite material to: (i) an at least partial vacuum; (ii) heat; (iii) a flushing inert gas (iv) a liquid substantially devoid of an ionizing trigger; or, (v) any combination thereof; in the presence or absence of agitation. In one embodiment, the inert gas is N₂, Ar or air. In another embodiment, exposing to heat is heating to≤ 60 °C,≤ 80 °C, or≤ 150 °C. [0050] In accordance with another embodiment, the ionizing trigger is a Bronsted acid sufficiently acidic to ionize said switchable moiety from its neutral form; or, any Bronsted base sufficiently basic to de-ionize said switchable moiety from its ionized form.

[0051 ] In accordance with another embodiment, there is provided a second form of the composite material wherein % ionization of the material's switchable moieties is <100%; or alternatively,≤75%; or alternatively≤50%.

[0052] In accordance with another embodiment, there is provided a composite material wherein each repeating unit of formulas 1 and 2, or 1 a and 2a; 3a, 3b, 3c and 4a, 4b, 4c, or 3d, 3d', 3e, 3e", 3f, 3Γ, 3f" and 4d, 4d", 4e, 4e", 4f, 4Γ, 4f"; 5a, 5b, 5c and 6a, 6b, 6c, or 5d, 5d', 5d", 5e, 5e' and 6d, 6d', 6d", 6e, 6e'; 7 and 8, or 7a and 8a; or 9a, 9b, 9c, 9d, and 10a, 10b, 10c, 10d; or (I) and (II); (Ilia), (1Mb), (lllc) and (Iva), (IVb), (IVc); (Va), (Vb), (Vc) and (Via), (VIb), (Vic); (VII) and (VIII); (IXa), (IXb), (IXc), (IXd) and (Xa), (Xb), (Xc), (Xd) is either the same, or different, relative to other repeat units, thus forming a homopolymer or a copolymer. In one embodiment, said copolymer is a graft copolymer or block copolymer. In another embodiment, the copolymer is a random copolymer.

[0053] In accordance with another aspect of the application, there is provided a method for switching a composite material, as described herein, between its first form and second form, comprising: exposing the neutral and hydrophobic composite material to (i) an aqueous liquid, or (ii) a non-aqueous liquid and water, to form a mixture, and exposing said mixture to an ionizing trigger, thereby protonating the switchable moiety and rendering the composite material ionized and hydrophilic; and/or

exposing the neutral and hydrophobic composite material to an aqueous carbonated liquid to form a mixture, wherein the carbonated liquid protonates the switchable moiety to render the composite material ionized and hydrophilic; and

optionally, separating the ionized hydrophilic composite material from the mixture.

[0054] In accordance with another aspect of the application, there is provided a method for switching a composite material, as described herein, between its first form and second form, comprising:

exposing the neutral composite material to (i) an aqueous liquid, or (ii) a nonaqueous liquid and water, to form a mixture, and exposing said mixture to an ionizing trigger, thereby protonating the switchable moiety and rendering the composite material ionized; and/or

exposing the neutral composite material to an aqueous liquid comprising an ionizing trigger to form a mixture, wherein the liquid protonates the switchable moiety to render the composite material ionized; and

optionally, separating the ionized composite material from the mixture.

[0055] In accordance with another aspect of the application, there is provided a method comprising changing ionization of a composite material comprising a polysaccharide and a polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, wherein the switchable moiety comprises an amine, amidine or guanidine, and wherein said composite material has a first, neutral form and a second, ionized form, the step of changing ionization comprising:

contacting the composite material in its first, neutral form with a liquid that is an aqueous liquid or a combination of water and a non-aqueous liquid and introducing an ionizing trigger to protonate the switchable moiety and switch the composite material to its second, ionized form; or

contacting the composite material with an aqueous liquid comprising an ionizing trigger to protonate the switchable moiety and switch the composite material to its second, ionized form; and,

optionally, separating the composite material in its second form from the liquid.

[0056] In accordance with another aspect of the application, there is provided a method for switching a composite material, as described herein, between its second form and first form, comprising:

exposing an ionized hydrophilic composite material to: (i) an at least partial vacuum; (ii) heat; (iii) a flushing inert gas; (iv) a liquid substantially devoid of an ionizing trigger; or, (v) any combination thereof; in the presence or absence of agitation, thereby expelling the ionizing trigger from the switchable moiety and rendering the composite material neutral and hydrophobic; and

optionally, separating the neutral and hydrophobic composite material from the mixture. [0057] In accordance with one embodiment, there is provided a method wherein the ionizing trigger is a Bronsted acid, an acid gas. In another embodiment, the acid gas is C0₂, COS, CS₂, or a combination thereof.

[0058] In accordance with another embodiment, there is provided a method wherein the inert gas is N₂, Ar or air.

[0059] In accordance with another embodiment, there is provided a method wherein exposing to heat is heating to≤ 60 °C,≤ 80 °C, or≤ 150 °C.

[0060] In accordance with another embodiment of the application, there is provided a method the composite material is a membrane (e.g., a separation membrane), an absorbent material, a drying agent, a flocculent, material for water or wastewater treatment, a fabric, a filter (e.g. , filter paper), an emulsion stabilizer/destabilizer, a viscosity modifier, or a chromatography support or resin.

[0061 ] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, for manipulating and/or controlling dispersibility, for example, CNC dispersibility.

[0062] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, as a separation membrane.

[0063] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, for formation of a membrane comprising a chiral nematic liquid crystalline structure.

[0064] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, as an absorbent or adsorbent.

[0065] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, as a drying agent.

[0066] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, as a flocculent.

[0067] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, for water or wastewater treatment. In accordance with one embodiment, the water or wastewater treatment comprises removal of organic contaminants or metal contaminants. In accordance with another embodiment, the metal contaminant is nickel.

[0068] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, for cleaning a surface.

[0069] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, for formation of a switchable fabric.

[0070] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, for formation of a switchable filter paper.

[0071] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, for stabilizing an emulsion.

[0072] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, as a switchable viscosity modifier.

[0073] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, for use in chromatography.

[0074] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, for use in algae harvesting and/or microalgae recovery.

BRIEF DESCRIPTION OF TABLES AND FIGURES

[0075] For a better understanding of the application as described herein, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying tables and drawings, where:

[0076] Table 1 delineates zeta potential and z-average size of native CNC (ca. 0.5 mg/ml dispersion) in response to continuous repeated CO2/N2 sparging;

[0077] Table 2 delineates elemental analysis data for 1-(3-aminopropyl)imidazole functionalized CNC (CNC-APIm)and native CNC;

[0078] Table 3 delineates Z-average sizes of CNC-APIm (ca. 0.5 mg/mL dispersion) in response to continuous repeated C0₂/N₂ sparging; [0079] Table 4 delineates zeta potential and z-average size of CNC-APIm in discarded supernatant (ca. 0.5 mg/ml dispersion) in response to continuous repeated C0₂/N₂ sparging;

[0080] Table 5 delineates time-dependent Z-average size and zeta potential changes of CNC-APIm (ca. 0.5 mg/mL dispersion) in response to CO2/N2 sparging;

[0081] Table 6 delineates degree of protonation of HPIm calculated by different protons in different conditions measured by ¹H NMR (see Figure 3 for assignment of different protons in HPIm);

[0082] Table 7 delineates mass of water absorbed by Cotton-API m versus non- functionalized Cotton;

[0083] Table 8 delineates contact angle analysis via the sessile drop method for unfunctionalized cotton linen and functionalized Cotton-API m;

[0084] Table 9 delineates contact angle analysis via the sessile drop method for native and functionalized (i.e. waxy) filter paper;

[0085] Table 10 delineates contact angle analysis via sessile drop method for

unfunctionalized cotton linen and functionalized Linen-pDEAEMA via "grafting-from" method;

[0086] Table 1 1 delineates investigation of switchable celluloses, prepared via synthetic method 1 , as drying agents;

[0087] Table 12 delineates investigation of switchable celluloses, prepared via synthetic method 2, as drying agents;

[0088] Table 13 delineates elemental analysis (C%, H%, N%) of switchable polymers grafted on crystalline nanocellulose via nitroxide-mediated polymerization;

[0089] Table 14 delineates percent composition of switchable polymers grafted on crystalline nanocellulose via nitroxide-mediated polymerization;

[0090] Table 15 delineates ζ-potential and pH measurements for CNC-g-PDMAEMA in the presence of glycolic acid (GIAc) 0.5 M and NaOH 0.5 M;

[0091 ] Table 16 delineates ζ-potential and pH measurements for CNC-g-PDEAEMA in the presence of glycolic acid (GIAc) 0.5 M and NaOH 0.5 M; [0092] Table 17 delineates ζ-potential and pH measurements for CNC-g-PDMAPMAm in the presence of glycolic acid (GIAc) 0.5 M and NaOH 0.5 M;

[0093] Table 18 delineates ζ-potential and pH measurements for CNC-g-PDMAEMA in the presence of C0₂/N₂;

[0094] Table 19 delineates ζ-potential and pH measurements for CNC-g-PDEAEMA in the presence of CO2/N2;

[0095] Table 20 delineates ζ-potential and pH measurements for CNC-g-PDMAPMAm in the presence of of C0₂/N₂;

[0096] Table 21 delineates atomic and mass compositions of bromine functionalized CNC (CNC-Br) by XPS analysis;

[0097] Table 22 delineates elemental analysis of unmodified CNC, PDEAEMA-g-CNC and PDMAEMA-g-CNC;

[0098] Table 23 delineates comparative CHNS analysis by elemental analysis in weight percent for CNC-CTP and native CNC;

[0099] Table 24 delineates comparative elemental analysis of unmodified CNC, CNC-g- PDMAEMA by RAFT polymerization;

[00100] Table 25 delineates molarities of each ion in modified Bold's Basal Medium used for microalgal growth;

[00101 ] Table 26 delineates parameters used in

Derjaguin-Landau-Verwey-Overbeek (DLVO) theory equations;

[00102] Table 27 delineates pH of microalgae solution under different APIm-modified CNC dose during three harvesting steps; dose was calculated based on the dry weights of microalgal biomass and APIm-modified CNC;

[00103] Table 28 delineates harvesting performance at different pH conditions adjusted by HCI and NaOH to mimic C0₂/air-treated samples; dose was calculated based on the dry weights of microalgal biomass and APIm-modified CNC (see p values in Table 29);

[00104] Table 29 delineates p values for the f-tests on HE, RE and RC using pH adjustment compared to C0₂/air treatment; [00105] Table 30 delineates p values for t-tests on three performance indicators (HE, RE, and RC) with air and nitrogen;

[00106] Table 31 delineates p values for t-tests on three indicators (HE, RE, and RC) with three flow rates;

[00107] Table 32 delineates Ni adsorption results of chitosan material (CTS-g- GMA)(x)-g-PDMAEMA) and (CTS-g-GMA) (x)-g-P(DEAEMA) respectively, where x indicates degree of insertion of GMA;

[00108] Table 33 delineates investigation of switchable celluloses, prepared via synthetic method 3, as drying agents; and

[00109] Table 34 delineates contact angle analysis via a sessile drop method for unfunctionalized cotton linen and functionalized Linen-pDEAEMA via "grafting-from" method;

[001 10] Figure 1 depicts synthesis of 1-(3-aminopropyl)imidazole functionalized CNC (CNC-APIm) through CDI-mediated coupling with APIm;

[001 1 1] Figure 2 depicts reversible aggregation and redispersion of CNC-APIm in absence and presence of CO2;

[001 12] Figure 3 depicts a DRIFT-IR spectra of native CNC and CNC-APIm, wherein band A is carbonyl C=0 stretching, band B is amide II N-H bending, and band C is C-0 stretching;

[001 13] Figure 4 depicts (a) zeta potential changes of CNC-APIm (ca. 0.5 mg/mL dispersion) in response to continuous repeated C0₂/N₂ sparging; (b) turbidities of CNC- APIm and native CNC dispersions (ca. 2.5 mg/mL) measured at 500 nm wavelength in response to continuous repeated C0₂/N₂ sparging cycles (some standard deviations were smaller than data point symbol);

[001 14] Figure 5A/5B depicts (a~c), (e) and (f): C0₂-switchability of CNC-APIm at different concentrations (C0₂ and N₂ sparging for 5 and 30 min, respectively); in (a), sample vials (under N₂) were held against light so that CNC-APIm aggregates could be clearly observed; (d) sedimentation of CNC-APIm after sparging N₂ for 30 min (arrow indicates upper level of aggregates); (g) native CNC dispersions in presence of C0₂ and N₂ (C0₂ and N₂ sparging for 5 and 30 min, respectively); [001 15] Figure 6A depicts ¹H nuclear magnetic resonance (NMR) spectra of HPIm in 90% H₂O+10% D₂0 without and with water presaturation;

[001 16] Figure 6B depicts ¹H nuclear magnetic resonance (NMR) spectra of HPIm in 90% H₂O+10% D₂0 in different conditions;

[001 17] Figure 7 depicts transmission electron microscope (TEM) images of native CNC (a) and CNC-APIm (b);

[001 18] Figure 8 depicts synthesis of1-(3-Aminopropyl)imidazole functionalized cellulose dialysis bag (Cellulose-APIm);

[001 19] Figure 9 depicts a comparison of non-functionalized and functionalized cellulose dialysis bag via % transmittance Infrared Spectroscopy (IR) spectra to

demonstrate, at least qualitatively, that at least part of the cellulose dialysis bag was functionalized;

[00120] Figure 10 depicts contact angle analysis of Cellulose-APIm;

[00121] Figure 11 depicts a demonstrative, non-limiting example of a proposed, alternative synthesis to switchable polysaccharides involving a coupling reaction between a switchable group-functionalized carboxylic acid and CDI;

[00122] Figure 12 depicts a demonstrative, non-limiting example of a proposed, alternative synthesis to switchable polysaccharides involving a coupling reaction between a switchable group-functionalized amine and methyl chloroformate;

[00123] Figure 13 depicts a demonstrative, non-limiting example of a investigation into functionalizing filter paper via a CDI-medited coupling reaction;

[00124] Figure 14 depicts functionalization of chitosan (CTS) with glycidyl methacrylate (GMA);

[00125] Figure 15 depicts a synthesis of poly((diethylamino)ethyl methacrylate) (PDEAEMA) via nitroxide mediated polymerization (NMP);

[00126] Figure 16 depicts grafting PDEAEMA to CTS-g-GMA via NMP;

[00127] Figure 17 depicts a ¹H NMR spectra of chitosan-g- glycidyl methacrylate

CTS-g-GMA with the integrated signals; [00128] Figure 18 depicts a gel permeation chromatography trace of synthesized PDEAEMA;

[00129] Figure 19 depicts Ή NMR spectra of CTS-g-GMA-PDEAEMA;

[00130] Figure 20 depicts thermogravimetric analysis (TGA) of CTS -g-GMA- PDEAEMA;

[00131] Figure 21 (A)-(C) depicts a) CTS-g-GMA-PDEAEMA before bubbling C0₂; b) CTS-g-GMA-PDEAEMA right after bubbling C0₂; and c) CTS-g-GMA-PDEAEMA right after bubbling N₂;

[00132] Figure 22 depicts results of Ni(ll) sorption equilibrium studies with CTS -g- PDEAEMA and native CTS;

[00133] Figure 23 depicts results of C0₂ regeneration studies with CTS-g- PDEAEMA and native CTS;

[00134] Figure 24 depicts functionalization of CNC with glycidyl methacrylate (GMA);

[00135] Figure 25 depicts grafting PDEAEMA to CNC-g-GMA via nitroxide-mediated polymerization;

[00136] Figure 26 depicts modification of CNC-g-GMA with PDEAEMA via free radical polymerization;

[00137] Figure 27 depicts a CP/MAS ¹³C NMR spectra of CNC and CNC-g-GMA;

[00138] Figure 28 depicts CP/MAS ¹³C NMR spectra of CNC-g-GMA-PDEAEMA obtained via nitroxide-mediated polymerization;

[00139] Figure 29 depicts TGA of a) CNC, b) PDEAEMA and c) CNC-g-PDEAEMA (obtained via nitroxide-mediated polymerization);

[00140] Figure 30 depicts CP/MAS ¹³C NMR spectra of CNC-g-GMA-PDEAEMA obtained via free radical polymerization;

[00141] Figure 31 depicts TGA of a) CNC, b) PDEAEMA and c) CNC-g-PDEAEMA

(obtained via free radical polymerization); [00142] Figure 32 depicts a demonstrative, non-limiting example of a switchable starch synthesis involving a coupling reaction between a switchable group-functionalized amine and CDI;

[00143] Figure 33 depicts functionalization of cotton linen with PDEAEMA;

[00144] Figure 34 depicts an Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) of non-functionalized linen (bottom) compared to Linen-pDEAEMA (top).

[00145] Figure 35 depicts preparation of cellulose functionalized with switchable group 3-(dimethylamino)-1-propylamine via synthetic method 1 ;

[00146] Figure 36 depicts preparation of cellulose functionalized with switchable group 3-(dimethylamino)-1-propylamine via synthetic method 2;

[00147] Figure 37 depicts a preparation of a functionalized filter paper via a CDI- medited coupling reaction (Method 2);

[00148] Figure 38 depicts a preparation of a functionalized filter paper via a CDI- medited coupling reaction (Method 3);

[00149] Figure 39 depicts a preparation of a functionalized filter paper via a CDI- medited coupling reaction (Method 4);

[00150] Figure 40 depicts grafting switchable polymers from crystalline nanocellulose via nitroxide-mediated polymerization

[00151 ] Figure 41 depicts a graphical representation of ζ-potential and pH

measurements for CNC-g-PDMAEMA in the presence of glycolic acid (GIAc) 0.5 M and NaOH 0.5 M;

[00152] Figure 42 depicts a graphical representation of ζ-potential and pH

measurements for CNC-g-PDEAEMA in the presence of glycolic acid (GIAc) 0.5 M and NaOH 0.5 M;

[00153] Figure 43 depicts a graphical representation of ζ-potential and pH

measurements for CNC-g-PDMAPMAm in the presence of glycolic acid (GIAc) 0.5 M and NaOH 0.5 M; [00154] Figure 44 depicts a graphical representation of ζ-potential and pH

measurements for CNC-g-PDMAEMA in the presence of C0₂/N₂;

[00155] Figure 45 depicts a graphical representation of ζ-potential and pH

measurements for CNC-g-PDEAEMA in the presence of C0₂/N₂;

[00156] Figure 46 depicts a graphical representation of ζ-potential and pH

measurements for CNC-g-PDMAPMAm in the presence of of C0₂/N₂;

[00157] Figure 47 depicts a graphical representation of pKaH values required for a base to have a specified % protonation when mixed with water at 25 ^°C. Dashed lines show required pKaH to obtain specified % protonation in absence of C0₂. Solid lines show pKaH required to obtain specified % protonation values in presence of 0.1 MPa of C0₂;

[00158] Figure 48 depicts a graphical representation of pKaH values required for a base to have a specified % protonation when mixed with water at 60 ^°C. Dashed lines show required pKaH to obtain specified % protonation in absence of C0₂. Solid lines show pKaH required to obtain specified % protonation values in presence of 0.1 MPa of C0₂;

[00159] Figure 49 depicts FT-IR spectra of CNC, CNC-g-PDMAEMA, CNC-g- PDEAEMA and CNC-g-PDMAPMAm;

[00160] Figure 50 depicts CNC surface functionalization with 2-Br-2-methyl propionic acid;

[00161] Figure 51 depicts a grafting-from reaction of CNC-Br with DEAEMA/DMAEMA ([Mo]/ [Br]/ [HMTETA]= 65/1/4/, [CuBr₂]= 100 ppm);

[00162] Figure 52 depicts ¹³C CP-MAS NMR spectra of two different batches of bromine functionalized CNC (CNC-Br);

[00163] Figure 53 depicts comparative FT-IR spectra of native and bromine functionalized CNC (CNC-Br);

[00164] Figure 54 depicts a XPS low-resolution spectrum of bromine functionalized CNC (CNC-Br);

[00165] Figure 55 depicts comparative CP-MAS ¹³C NMR spectra of polymer grafted CNC with PDEAEMA and PDMAEMA; [00166] Figure 56 depicts a thermogram showing wt.% loss and derivative wt.% loss of grafted and raw materials;

[00167] Figure 57 depicts atomic form microscopy (AFM) micrographs of a) native CNC and b) PDEAEMA-1-g-CNC;

[00168] Figure 58 depicts CNC surface functionalization with 4-cyano-4- ((phenylcarbonothioyl)thio)pentanoic acid;

[00169] Figure 59 depicts a grafting-from approach of DMAEMA/DEAMA onto CNC- CTP;

[00170] Figure 60 depicts comparative CP-MAS ¹³C NMR spectra of native CNC and CNC-CTP;

[00171] Figure 61 depicts comparative FT-IR spectra of native CNC and CNC-CTP;

[00172] Figure 62 depicts comparative FT-IR spectra of CNC-CTP and CNC-g- PDMAEMA;

[00173] Figure 63 depicts comparative thermogravimetric analysis of CNC-g- PDMAEMA synthesized by grafting-from via RAFT polymerization;

[00174] Figure 64 depicts: (a) and (c) Z-average size (nm) and zeta potential (mV), as well as (b) and (d) pH of native and APIm-modified CNC (90 rng-L^" ) as a function of C0₂ and air sparging times in deionized (Dl) water (18.2 ΜΩ-cm); (e) Zeta potential changes of native and APIm-modified CNC (90 mg-L^"1) in response to continuous repeated C0₂/air sparging cycles; (f) Zeta potentials (mV) of C. vulgaris in MBBM, native and APIm-modified CNC (90 mg-L^"1) in deionized (Dl) water at varied pH conditions;

[00175] Figure 65 depicts zeta potentials (mV) of native and APIm-modified CNC in microalgal medium as a function of CNC suspension particle concentration (pH=5.0 ± 0.2) in Dl water (18.2 ΜΩ-cm);

[00176] Figure 66 depicts harvesting efficiency (HE, %) and recovery efficiency (RC, g-algae.g^~1-CNC) of C. vulgaris as a function of mass ratio of native and APIm-modified CNC to microalgae under three conditions (Scenario 1 : APIm-modified CNC, C0₂ and air sparging for 1 min and 10 min; Scenario 2: native CNC, C0₂ and air sparging for 1 min and 10 min; Scenario 3: APIm-modified CNC, only air sparging for 10 min) under room light. Initial microalgal concentations were 0.2~0.4 g- L¹. ; dose was calculated based on the dry weights of microalgal biomass and native or APIm-modified CNC;

[00177] Figure 67 depicts photographs of C. vulgaris with APIm-modified CNC with different mass ratios of APIm-modified CNC to microalgae: (a) CO2 and air sparging for 1 min and 10 min (dose from left to right: 0.01 , 0.02, 0.05, 0.10, 0.20, 0.29, 0.39 and 0.49 g- modified CNC g^~1-algae); (b) only air sparging for 10 min (dose from left to right: 0.02, 0.07, 0.12, 0.20, 0.22, 0.27, 0.30, 0.39 and 0.49 g-modified CNC g^"1-algae);

[00178] Figure 68 depicts a schematic view of electrostatic attraction and

enmeshment mechanisms involved in interactions between C. vulgaris and APIm-modified CNC;

[00179] Figure 69 depicts a graph of total interaction energy as a function of separation distance between different interacting entities: (a) Native-CNC-to- native-CNC and (b) APIm-modified CNC-to-APIm-modified CNC; simulated interaction occurred in microalgal medium with pH of 4.9 and ionic strength of approximately 0.0104 M;

[00180] Figure 70 depicts a graph pf total interaction energy as a function of the separation distance between different interacting entities: Native CNC-to-algae and APIm- modified CNC-to-algae, with an insert figure of microalgae-to-microalgae; ionic strength and pH of microalgal suspension after C0₂ sparging was approximately 0.0104 M and 4.9, respectively;

[00181 ] Figure 71 depicts HE (%), RE (%), and RC (g-algae-g ^-modified CNC) of C. vulgaris as a function of air sparging time at two APIm-modified CNC doses of (a) 0.05 g- modified CNC-g ¹-algae and (b) 0.49 g-modified CNC.g^~1-algae, with an air flow rate of 25 mL min ¹ and an initial microalgal concentration of ~0.4 g- L ¹ ;

[00182] Figure 72 depicts comparisons of HE (%), RE (%) and RC (g-algae-g ¹- modified CNC) of C. vulgaris with different inert gases (left: pure N₂ and right: air) under various flow rates (25, 80 and 140 ml min ¹) for 10 min; APIm-modified CNC dose was 0.05 g-modified CNC g-algae ¹ with the initial microalgal concentration of ^"0.4 g -L ¹ ;

[00183] Figure 73 depicts (a) microalgal growth in reused medium after harvesting using APIm-modified CNC and alum as coagulants after adjusting nutrient to level of new MBBM; (b) HE (%) comparison of reuse of microalgae-modified CNC aggregates for five times.; initial dose was 0.49 g-CNC.g^~1-algae, with a flow rate of 25 mL min ¹ and microalgal concentration of ~0.4 g- L ¹ ;

[00184] Figure 74 depicts Langmuir adsorption isotherms (linear regression) of Ni²⁺ ions adsorbing to material CTS-g-PDMAEMA at 25 °C ;

[00185] Figure 75 depicts Langmuir adsorption isotherms (linear regression) of Ni²⁺ ions adsorbing to material CTS-g-PDEAEMA at 25 °C.

[00186] Figure 76 depicts a ¹H NMR spectrum of chitosan functionalized with GMA

(f=0.09) and grafted with PDMAEMA (M_n = 2526 g/mol, D = 1 .43);

[00187] Figure 77 depicts thermogravimetric analysis curves of chitosan

functionalized with GMA (f=0.09) and grafted with PDMAEMA (M_n = 2526 g/mol, D = 1.43);

[00188] Figure 78 depicts an attenuated total reflectance (ATR) FT-IR spectrum of a poly-[(dimethylamino)propyl]methacrylamide functionalized filter paper (attempt 2);

[00189] Figure 79 depicts functionalization of linen using SI-ATRP with DEAEMA;

[00190] Figure 80 depicts a diffuse reflectance infrared fourier transform (DRIFT)-IR spectrum of Linen-p-DEAEMA, with a ketone peak representative of the DEAEMA ester at -1725 cm ¹ ; and

[00191 ] Figure 81 depicts a L-shaped glass tube (top joint diameter 24/29; hose adater opening / linen 7/16 inner) to which PDEAEMA-functionalized linen was tied to an end.

DETAILED DESCRIPTION [00192] Definitions

[00193] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[00194] As used in the specification and claims, the singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise. [00195] The term "comprising" as used herein will be understood to mean that the list following is non-exhaustive and may or may not include any other additional suitable items, for example one or more further feature(s), component(s) and/or ingredient(s) as

appropriate.

[00196] As used herein, "switchable moiety" refers to a N-comprising functional group that exists in a first form, such as a hydrophobic form, at a first partial pressure of an acid gas, such as, but not limited to C0₂, and, in the presence of water or an aqueous solution, exists in a second form, such as a hydrophilic form, at a second partial pressure an acid gas, such as, but not limited to CO2, that is higher than the first partial pressure. This term also applies to cases wherein acid gases such as, but not limited to, COS, CS₂, or a mixture of any or all of C0₂, COS, or CS₂, is employed in place of C0₂ recited above. The switchable moiety can be an amine, amidine, or guanidine that comprises a nitrogen atom sufficiently basic to be protonated by an ionizing trigger such as an acid gas (e.g., C0₂, COS, CS₂, or a combination thereof).

[00197] As used herein, the term "unsubstituted" refers to any open valence of an atom being occupied by hydrogen. Also, if an occupant of an open valence position on an atom is not specified then it is hydrogen.

[00198] As used herein, "substituted" means having one or more substituent moieties present that either facilitates or improves desired reactions and/or functions of the invention, or does not impede desired reactions and/or functions of the invention. Examples of substituents include, but are not limited to, alkyl, alkenyl, alkynyl, aryl, aryl-halide, heteroaryl, cyclyl (non-aromatic ring), Si(alkyl>3, Si(alkoxy)3, halo, alkoxyl, amino, amide, amidine, hydroxyl, thioether, alkylcarbonyl, alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy, carbonate, alkoxycarbonyl, aminocarbonyl, alkylthiocarbonyl, phosphate, phosphate ester, phosphonato, phosphinato, cyano, acylamino, imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate, dithiocarboxylate, sulfate, sulfato, sulfamoyl, sulfonamide, nitro, nitrile, azido, heterocyclyl, ether, ester, silicon-comprising moieties, thioester, or a combination thereof. Preferable substituents are alkyl, aryl, heteroaryl, and ether. Certain substituents, such as, but not limited to, alkyl halides, are known to be quite reactive, and are acceptable so long as they do not interfere with the desired reaction.

[00199] As used herein, "aliphatic" refers to hydrocarbon moieties that are linear, branched or cyclic, may be alkyl, alkenyl or alkynyl, and may be substituted or

unsubstituted. "Aryl" means a moiety including a substituted or unsubstituted aromatic ring, including heteroaryl moieties and moieties with more than one conjugated aromatic ring; optionally it may also include one or more non-aromatic ring. "C₅ to C10 Aryl" means a moiety including a substituted or unsubstituted aromatic ring having from 5 to 10 carbon atoms in one or more conjugated aromatic rings. Examples of aryl moieties include phenyl, biphenyl, naphthyl and xylyl.

[00200] As used herein, "alkyl", "alkylene", "alkanetriyl" refers to a linear, branched or cyclic, saturated hydrocarbon, which consists solely of single-bonded carbon and hydrogen atoms, which can be unsubstituted or is optionally substituted with one or more substituents; for example, a methyl or ethyl group. Examples of saturated straight or branched chain alkyl groups include, but are not limited to, methyl, ethyl, 1 -propyl, 2-propyl, 1 -butyl, 2-butyl, 2- methyl-1 -propyl, 2-methyl-2-propyl, 1-pentyl, 2-pentyl, 3-pentyl, 2-methyl-1 -butyl, 3-methyl-1- butyl, 2-methyl-3-butyl, 2,2-dimethyl-1-propyl, 1-hexyl, 2-hexyl, 3-hexyl, 2-methyl- 1-pentyl,

3- methyl-1-pentyl, 4-methyl-1-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl,

4- methyl-2-pentyl, 2,2-dimethyl-1-butyl, 3,3-dimethyl-1-butyl and 2-ethyl-1 -butyl, 1-heptyl and 1-octyl. As used herein the term "alkyl" encompasses cyclic alkyls, or cycloalkyl groups.

[00201] As used herein, "alkenyl", "alkenylene", or "alkenetriyl" refers to a

hydrocarbon moiety that is linear, branched or cyclic and comprises at least one carbon to carbon double bond which can be unsubstituted or optionally substituted with one or more substituents. "Alkynyl" or "alkynylene" refers to a hydrocarbon moiety that is linear, branched or cyclic and comprises at least one carbon to carbon triple bond which can be unsubstituted or optionally substituted with one or more substituents.

[00202] As used herein, "aryl", "arylene", or "aryltriyl" refers to hydrocarbons derived from benzene or a benzene derivative that are unsaturated aromatic carbocyclic groups from 5 to 100 carbon atoms, or from which may or may not be a fused ring system, in some embodiments 5 to 50, in other embodiments 5 to 25, and in still other embodiments 5 to 15. The aryls may have a single or multiple rings. The term "aryl" or "arylene" as used herein also include substituted aryls. Examples include, but are not limited to, phenyl, naphthyl, xylene, phenylethane, substituted phenyl, substituted naphthyl, substituted xylene, substituted 4-ethylphenyl, etc.

[00203] As used herein, "cycloalkyl" refers to a non-aromatic, saturated monocyclic, bicyclic or tricyclic hydrocarbon ring system comprising at least 3 carbon atoms. Examples of C3-C_n cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, norbornyl, adamantyl, bicyclo[2.2.2]oct-2-enyl, and bicyclo[2.2.2]octyl.

[00204] As used herein, "cycle" refers to an aromatic or nonaromatic monocyclic, bicyclic, or other multicyclic rings of carbon atoms, and which can be substituted or unsubstituted. Included within the term "cycle" are cycloalkyls and aryls, as defined above.

[00205] As used herein, "heteroaryl" or "heteroaryltriyl" refers to a moiety including a substituted or unsubstituted aryl ring or ring system having from 3 to 20, or 4 to 10 carbon atoms and at least one heteroatom in one or more conjugated aromatic rings. As used herein, "heteroatom" refers to non-carbon and non-hydrogen atoms, such as, for example, O, S, and N. Examples of heteroaryl moieties include pyridyl, bipyridyl, indolyl, thienyl, and quinolinyl.

[00206] As used herein, a "heterocycle" is an aromatic or nonaromatic monocyclic, bicyclic, or other multicyclic rings of carbon atoms and from 1 to 10, or 1 to 4, heteroatoms selected from oxygen, nitrogen and sulfur, and which can be substituted or unsubstituted. Included within the term "heterocycle" are heteroaryls, as defined above.

[00207] As used herein, the term "linker" refers to a divalent, trivalent or multivalent moiety that bonds two or more molecules by a covalent bond. As used herein, the linker moieties are used to bond at least one switchable moiety to a polysaccharide in such a manner that it either (i) facilitates or improves desired reactions and/or functions of the switchable moiety(ies), or (ii) does not impede or interfere with desired reactions and/or functions of the switchable moiety(ies). Examples of suitable linker moieties are C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, each of which may be substituted; or the corresponding trivalent or multivalent moieties. Alternatively, each linker is independently is a cycle, or heterocycle, each of which may be substituted, and may be divalent, trivalent or multivalent for bonding of at least one switchable moiety to a polysaccharide.

[00208] As used herein, "polysaccharide" refers to polymeric carbohydrate molecules composed of chains of monosaccharide monomer units, which range in structure from linear to highly branched. Repeating units in the polysaccharide may include one or more rings. The polysaccharide may comprise chains, or chains of rings, wherein the monomer units are non-repeating. The polysaccharide may contain some sections or branches of repeating monomer units and some sections or branches that comprise non-repeating monomers. The polysaccharide may be branched or linear. As used herein, "polysaccharides" also refer to oligosaccharides, which may encompass, but is not limited to di- and tri-saccharides.

Examples of polysaccharide include, but are not limited to, cellulose, hemicellulose, cellulose nanocrystals (CNCs), starch, pectin, glycogen cellulose, dextran, and chitin/chitosan.

Examples of "polysaccharide materials" or "polysaccharide-containing" materials include, but are not limited to cellulose-containing materials, such as, certain fabrics, (e.g., linens and cottons, hemp, jute, and sisal), and paper, such as filter papers.

[00209] The term "switch/switched" means that physical properties have been modified. "Switchable" means able to be converted from a first form with a first set of physical properties, e.g., a hydrophobic form, to a second form with a second set of physical properties, e.g., a hydrophilic form, or vice-versa from the second state to the first state. As one skilled in the art would understand and appreciate, the terms "first set of physical properties" and "second set of physical properties" are considered different relative to each other. For example, as used herein, terms such as "hydrophilic" and "hydrophobic" are relative with respect to each other: a first, hydrophobic form of a switchable polysaccharide is considered to be more hydrophobic relative to a second, hydrophilic form of the same switchable polysaccharide. A "trigger" is a change of conditions (e.g., introduction or removal of a gas, change in temperature) that causes a change in physical properties. The term "reversible" means that a reaction can proceed in either direction (backward or forward) depending on reaction conditions.

[00210] It should be understood, for the purposes of this application, that any switch that can be induced by C0₂ can also be induced by COS, CS₂, a combination thereof, or a mixture of CO2 with any one of, or both of, COS and CS2. Further, as would be readily understood by one skilled in the art, CS₂ is a volatile liquid if its partial pressure in the gas phase is greater than its normal vapour pressure at that temperature; and, it's a gas if its partial pressure is lower than its normal vapour pressure at that temperature.

[0021 1] As used herein, "carbonated water" means a solution of water in which carbon dioxide has been dissolved, at any partial pressure.

[00212] As used herein, an "inert gas" means that the gas has insufficient carbon dioxide, CS₂ or COS content to interfere with removal of carbon dioxide, CS₂ or COS from a switchable moiety and/or a gas that has insufficient acidity to maintain a switchable moiety in its second, hydrophilic form. For some applications, air may be a gas that has substantially no carbon dioxide, CS2 or COS and is insufficiently acidic. Untreated air may also be successfully employed, i.e., air in which the carbon dioxide, CS₂ or COS content is unaltered; this would provide a cost saving. For instance, air may be an insufficiently acidic gas that has substantially no carbon dioxide because in some circumstances, the approximately 0.04% by volume of carbon dioxide present in air is insufficient to maintain a switchable moiety in its second form, such that air can be a trigger used to remove carbon dioxide from a switchable moiety and cause switching.

[00213] As used herein, the term "hydrogen carbonate" refers to a counter ion of a switchable moiety's second form, with a formula [HCO3]^". However, when CS2, COS, or a combination thereof has been used, the counter ion will have a formula [HCE₃]^", where E is O, S, or a combination thereof.

[00214] As used herein, "amidine" refers to a switchable functional group with a structure such as X-N=CR³NR⁴R⁵, R³N=C(-X)NR⁴R⁵, R³NH=CR⁴N(-X)R⁵ where R³ through R⁵ are hydrogen or alkyl, alkenyl, alkynyl, aryl, or heteroaryl, each of which may be substituted, and X indicates a point of attachment. The second, ionic form of an amidine after exposure to carbon dioxide, CS₂ or COS is termed an "amidinium hydrogen carbonate". As would be readily appreciated by a worker skilled in the art, the structures drawn herein to depict amidines encompass all rotational isomers thereof.

[00215] As used herein, "amine" refers to a switchable functional group with a structure -NR¹R² where R¹ and R² are hydrogen or alkyl, alkenyl, alkynyl, aryl, or heteroaryl, each of which may be substituted. The second, ionic form of an amine after exposure to carbon dioxide, CS2 or COS, or a combination thereof, is termed an "ammonium hydrogen carbonate".

[00216] As used herein, "guanidine" refers to a switchable functional group with a structure such as X-N=CNR⁴R⁵NR⁶R⁷, R³N=CN(X)R⁵NR⁶R⁷, R³N=CNR⁴R⁵N(X)R⁷where R³ through R⁷ are hydrogen or alkyl, alkenyl, alkynyl, aryl, or heteroaryl, each of which may be substituted, and X indicates a point of attachment. The second, ionic form of an guanidine after exposure to carbon dioxide, CS₂ or COS is termed an "guanidinium hydrogen carbonate". As would be readily appreciated by a worker skilled in the art, the structures drawn herein to depict guanidines encompass all rotational isomers thereof.

[00217] As used herein, "sterically hindered group" refers to any functional group or substituent that causes steric crowding. Inclusion of a sterically hindered group around a switchable moiety, as defined herein, can inhibit formation of a carbamate salt upon exposure of the switchable moiety to an ionizing trigger.

[00218] As used herein, "ionic" means comprising or involving or occurring in the form of positively or negatively charged ions, i.e., charged moieties. "Neutral" as used herein means that there is no net charge. "Ionic salt" and "salt" as used herein are used interchangeably to refer to compounds formed from positively and negatively charged ions. These terms do not imply a physical state (i.e., liquid, gas or solid). It is important to note, however, that the terms "neutral form" and "ionic form" when used to refer to switchable polysaccharides do not refer to the overall ionized state of the polysaccharide. As would be readily appreciated by a worker skilled in the art, the switchable polysaccharide can comprise other functional groups that do not change their ionic state in response to the addition or removal of an ionizing trigger. Furthermore, in switching a switchable

polysaccharide, each switchable moiety of the polysaccharide may not be, or may not become ~100% ionized or neutralized - either prior to or following addition or

reduction/removal of C0₂, respectively. As used herein, the first, neutral form refers to a form wherein a sufficient number of switchable moieties are non-ionized such that the polysaccharide has a first set of physical properties; and, the second, ionized form refers to a form wherein a sufficient number of the switchable moieties have become ionized such that the polysaccharide has a second set of physical properties different from the first (i.e., the switchable polysaccharide has switched, as defined above).

[00219] As used herein, "hydrophobic" is a property of a switchable moiety or composite material that results in it repelling water. Hydrophobic moieties or materials are usually nonpolar, and have little or no hydrogen bonding ability. Such molecules are, thus, compatible with other neutral and nonpolar molecules.

[00220] As used herein, "hydrophilic" is a property of a switchable moiety or composite material that results in it attracting water. Hydrophilic moieties or materials are usually polar/ionized, and have a hydrogen bonding ability. Such molecules are thus compatible with other ionized/polar molecules.

[00221] As used herein, the term "contaminant" refers to one or more compounds that is intended to be removed from a mixture and/or surface and is not intended to imply that the contaminant has no value. For example, oil, which has significant value, may conveniently be called a contaminant when describing oil sands. [00222] Embodiments

[00223] A composite material has been developed, and is herein described, that comprises a polysaccharide and polysaccharide-supported switchable moiety. The switchable moiety includes a functional group that is switchable between a first form and a second form. Such composite materials are termed switchable natural materials. The composite material's first form is neutral and, in some embodiments, hydrophobic; and its second form is ionized and, in some embodiments, hydrophilic. The composite material converts from one form to another when in the substantial presence of or substantial absence of an ionizing trigger. Descriptions of such triggers, and uses for these materials will follow a description of the composite material.

[00224] Jessop et al. have described previously switchable materials having switchable stimuli-responsive properties (see International Patent Application No.

PCT/CA2014/050897 entitled Switchable Materials, Methods and Uses Thereof). That is, materials that can reversibly switch between a neutral and/or hydrophobic form and an ionized and/or hydrophilic form upon application of external stimuli. Such switchable materials are used, for example, as switchable drying agents and/or surfaces. As described, these switchable materials comprised non-ionized forms of general formulas (A) and (Bi, Bii and Biii):

(Bi); (Bii); (Biii); wherein X is bound to a solid. [00225] The switchable materials of PCT/CA2014/050897 comprised ionized forms of general formulas (C) and (Di-iii):

(Di); (Dii); (Diii); wherein X is bound to a solid.

[00226] These switchable materials relied on a known, readily reversible, reaction of water with an acid gas, such as C0₂, COS, CS₂, or a mixture thereof, that allowed it to bind to amines, amidines and related compounds; for example, see Equation 1 :

NR₃ + H₂0 + C0₂→ [NR₃H⁺][HC0₃ ^"] (1).

[00227] These switchable materials can be used as switchable drying agents, such as switchable particle beads; switchable chromatography supports for separation applications; and switchable surfaces to provide hydrophobic / hydrophilic, super-hydrophobic / super- hydrophilic, or super-oleophilic / super-oleophobic surfaces, for example, for cleaning applications. The solid to which the switchable group of the switchable materials was bound, as described in PCT application PCT/CA2014/050897, comprised polymeric materials, such as polymeric beads thin films, or monoliths; silica-based materials, such as glass, mesoporous silica or silica gel; semi-metallic or metallic composite materials such as steel, silicon wafers, silicon oxides, or gold-films.

[00228] None of the materials described in PCT application PCT/CA2014/050897 comprised a switchable moiety bound to the surface of polysaccharide-based material such as CNCs or other similar polysaccharides (e.g., cellulose, cotton, starch, hemicellulose, dextran, and chitin/chitosan).

[00229] Stimuli-responsive Polvsaccharide-based Materials

[00230] As discussed above, stimuli-responsive polysaccharides have been previously investigated and described. For example, pH-responsive CNCs have been prepared by covalently introducing, for example, carboxyl or amine functionalities onto CNC surface through small molecule modification or polymer grafting [Tang J.T. et al. (2014) Biomacromolecules 15(8):3052-3060]. Thermoresponsive CNCs has also been prepared via surface grafting of thermoresponsive polymers such as poly(N-isopropylacrylamide) (PNIPAM) or polyethylene glycol (PEG) [Zoppe, J. O.; Habibi, Y.; Rojas, O. J.; Venditti, R. A.; Johansson, L. S.; Efimenko, K.; Osterberg, M.; Laine, J. Biomacromolecules 2010, 11, 2683-2691]. However, manipulation of colloidal dispersibility by either pH or temperature presents challenges, particularly if applying such systems to industrial processes; for example, with pH-responsive CNC dispersions, pH adjustment generally occurs by adding acid or base, though removal of resultant electrolytes from final CNC products can be time- consuming and potentially incomplete. Further, repeated pH adjustment can result in salt accumulation, and a commensurate increase in ionic strength that may negatively affect colloidal stability.

[00231] For thermoresponsive CNC dispersions, manipulation of dispersion temperature can be energy-consuming and/or time-consuming, which could become problematic when a large volume of CNC dispersion is used.

[00232] Other approaches for collecting/redispersing CNC have utilized centrifugation or membrane process, with techniques such as sonication has been used for redispersion. Centrifugation of CNC dispersions generally requires high centrifugal force using potentially costly instruments. Membrane processes are generally considered to be cost-effective processes that can be scaled up for industrial production, however, these processes are often inefficient with respect to fouling when separating nanoparticles, such as CNC.

Sonication for redispersing CNC cakes, which may be physically hard and thus difficult to redisperse, after centrifugation or membrane process is also energy-intensive, and not easily scaled up [Habibi, Y.; Lucia, L. A.; Rojas, O. J. Chem. Rev. 2010, 110, 3479-3500; Klemm, D.; Kramer, F.; Moritz, S.; Lindstrom, T.; Ankerfors, M.; Gray, D.; Dorris, A. Angew. Chem., Int. Ed. 2011, 50, 5438-5466]. [00233] It has generally been observed that such stimuli-responsive materials (e.g., non-acid gas pH- and/or thermo-responsive materials) do not exhibit a reproducible switch from one form to another, such as is reproducibly observed with the previously discussed switchable technologies (e.g., switchable materials, switchable surfactants, etc.); further, it has been observed that many pH-responsive materials lack a sufficient C0₂-responsiveness to function as a herein described switchable material or technology (e.g., lack a pH responsive moiety sufficiently basic to be protonated by an acid gas, such as C0₂).

[00234] Switchable Polysaccharides, Synthesis and Applications Thereof

[00235] Switchable Polysaccharides

[00236] It has now been found that composite materials having switchable properties can be successfully prepared by incorporation of one or more switchable moieties on a polysaccharide via a linker. Accordingly, the present application provides composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, wherein the switchable moiety comprises an amine, amidine, or guanidine.

[00237] Accordingly, the present application also provides composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and at least one polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, wherein the switchable moiety comprises an amine, amidine, or guanidine.

[00238] In accordance with one embodiment, there is provided a composite material wherein the switchable moiety is an amine and the neutral form of the switchable moiety is bound to the polysaccharide via a linker XY; and

wherein the first form of the composite material has the structure of formula 1

(1) ;and

(2);

E is O, S, or a combination thereof;

wherein each X optionally comprises one or more amine, amide, amidine, guanidine, carbamate ester, carbonate diester, ether, ester, thioether, thioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and

NR¹R² and NR¹R²⁺ are each a switchable functional group, wherein R¹ and R² are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic, a CnSim group where n and m are independently a number from 0 to 10 and n + m is a number from 1 to 10, a C₅ to Cio aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or R¹ and R², together with the atoms to which they are attached, are connected to form a cycle, or heterocycle, each of which may be substituted; or

[00239] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is an amine and the switchable moiety is bound to the polysaccharide via a linker XY; and

wherein the first form of the composite material has the structure of formula 1

(1); and the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysacchari has the structure of formula 2

(2);

E is O, S, or a combination thereof;

NR¹R² and NR¹R²⁺ are each a switchable functional group, wherein R¹ and R² are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic, a CqSir group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a Cs to Cio aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or R¹ and R², together with the atoms to which they are attached, are connected to form a cycle, or heterocycle, each of which may be substituted; or

R² is repeat unit -(X-NR¹)_S-Z, wherein X and R¹ are as defined above, s is an integer between 1 and 10 000 wherein m x p x s is 10 000 or less, and Z is a monovalent moiety bonded to the switchable functional group, and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thiol, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

[00240] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 1 a when Y is absent, p is 1 , and R² is repeat unit -(X-NR¹)_m-Z or -(X-NR¹)_S-Z,

the second form of the composite material has the structure of formula 2a,

z

HN— 1 HCE₃ ⁰

(2a).

[00241] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 1 c when Y is absent, p is 1 , and m is 1 ,

the second form of the co tructure of formula 2c,

[00242] In accordance with another embodiment, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and at least one polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, wherein the switchable moiety comprises an amine, and wherein the first form of the composite material has the structure of formula 1 or (I), with a proviso that, when the polysaccharide is CNC, Y is absent, p is 1 , and X or X' is -CH2-C(CH3) -CO2- (CH₂)₂- or -C(CH₃) -C0₂-(CH₂)₂-, only one of R¹ and R² is CH₃.

[00243] In accordance with another embodiment, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and at leaset one polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, wherein the switchable moiety comprises an amine, and wherein the first form of the composite material has the structure of formula (I), with a proviso that, when the polysaccharide is CNC, cellulose, cellulose membrane, or filter paper, Y is present or absent, p is 1 , and X' is -CH₂-C(CH₃) -C0₂-(CH₂)₂- or -C(CH₃) -C0₂-(CH₂)₂-, only one of R¹ and R² is CH₃.

[00244] In accordance with another embodiment, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and at least one polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, wherein the switchable moiety comprises an amine, and wherein the first form of the composite material has the structure of formula(l), with a proviso that, when Y is present or absent, p is 1 , and X' is -CH₂-C(CH₃) -C0₂-(CH₂)₂- or -C(CH₃) -C0₂-(CH₂)₂-, only one of R¹ and R² is CH₃.

[00245] In accordance with another embodiment, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, wherein the switchable moiety comprises an amine, with a proviso that, when the first form of the composite material has the structure of formula 1 or (I), the composite material does not comprise PDMAEMA. [00246] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is an amidine and the neutral form of the switchable moiety is bound to the polysaccharide via a linker XY; and

3c,

wherein:

E is O, S, or a combination thereof;

Y is absent, or a divalent moiety bonded to the polysaccharide and X, and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, each of which may be substituted; or, Y is a divalent cycle, or heterocycle, each of which may be substituted; each X is a divalent moiety bonded Y, or to the polysaccharide when Y is absent, and the switchable functional group; each X is independently a linear or branched C 1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1 -C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X is independently is a divalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or more of R³, R⁴, and R⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; and

N=CR³NR⁴R⁵ , R³N=CNR⁴R⁵, R³N=CR⁴NR⁵, and (N=CR³NR⁴R⁵)⁺, (R³N=CNR⁴R⁵)⁺, (R³N=CR⁴NR⁵)⁺ are each switchable functional groups, wherein R³, R⁴, and R⁵ are independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a CnSim group where n and m are independently a number from 0 to 10 and n + m is a number from 1 to 10, a C5 to C10 aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R³, R⁴, and R⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; or,

wherein, [X(N=CR³NR⁴R⁵)_n]_m, [X(R³N=CNR⁴R⁵)_n]_m, [X(R³N=CR⁴NR⁵)_n]_m, and [X(N=CR³NR⁴R⁵⁺)n]m , [X(R³N=CNR⁴R⁵⁺)n]m , [X(R³N=CR⁴NR⁵⁺)n]m constitute a chain of repeats units that is linear or branched, each repeat unit in said chain being the same, or different, relative to other repeat units. [00247] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is an amidine and the switchable moiety is bound to the polysaccharide via a linker XY; and

3c,

(3a) (3b) (3c); and the second form of the composite material comprising the ionized form of the switchable moiet bound to the ol saccharide via a linker XY has the structure of formula 4a, 4b 4c,

(4a) (4b) (4c); wherein:

E is O, S, or a combination thereof;

[00248] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 3d, 3d', 3e, 3e', 3f, 3f, or 3f" when Y is absent, p is 1 , and R³, R⁴, or R⁵ is repeat unit -(X- N=CR³NR⁴)m-Z, -(X-N=CNR⁴R⁵)m-Z; or -(X-C=NR³NR⁴)_m-Z, -(X-C=NNR⁴R⁵)_m-Z; or -(X- NCR⁴=NR³)_m-Z, -(X-NR⁵CR⁴=N)_m-Z, -(X-NR⁵C=NR³)_m-Z; or -(X-N=CR³NR⁴)_S-Z, -(X- N=CNR⁴R⁵)s-Z; or -(X-C=NR³NR⁴)_S-Z, -(X-C=NNR⁴R⁵)_S-Z; or -(X-NCR⁴=NR³)_S-Z, -(X- NR^{5 4}=N)s-Z, -(X-NR⁵C=NR³)s-Z,

(3e') (30 (3f)

[00249] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 3g, 3h, or 3i when Y is absent, p is 1 , and m is 1 ,

(3g) (3h) (3i); and the second form of the composite material has the structure of formula 4g, 4h, or 4i,

(4g); (4h); (4i).

[00250] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is a guanidine, and the neutral form of the switchable moiety is bound to the polysaccharide via a linker XY; and

5c,

(5a); (5b); (5c);

E is O, S, or a combination thereof;

wherein each X optionally comprises one or more amine, amide, amidine, guanidine, carbamate ester, carbonate diester, ether, ester, thioether, thioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched carbon chain, or at one of said chain's termini; and N=CNR⁶R⁷NR⁸R⁹, R¹⁰N=CNR⁶NR⁸R⁹, R¹⁰N=CNR⁶R⁷NR⁹, and

(N=CNR⁶R⁷NR⁸R⁹)⁺ , (R^{1 0}N=CNR⁶N R⁸R⁹)⁺ , (R¹⁰N=CNR⁶R⁷NR⁹)⁺ are each switchable functional groups, wherein R⁶, R⁷, R⁸, R⁹ and R¹⁰ are independently H , a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_nSi_m group where n and m are independently a number from 0 to 10 and n + m is a number from 1 to 10, a C₅ to Cio aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R⁶, R⁷, R⁸, R⁹ and R¹⁰, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; or,

any one of R⁶, R⁷, R⁸, R⁹ and R¹⁰ is repeat unit -(X-N=CNR⁶R⁷N R⁸)_m-Z, -(X-N=CNR⁷NR⁸R⁹)m-Z, or -(X-NR⁶C= NNR⁸R⁹)_m-Z, -(X-NR⁶C=NR¹⁰NR⁸)_m-Z, -(X-NC= NR¹⁰NR⁸R⁹)_m-Z, wherein X and R⁶, R⁷, R⁸, R⁹ and R¹⁰ are as defined above, and Z is a monovalent moiety bonded to the switchable functional group, and is a linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, or a siloxane, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

wherein at least one of R⁶, R⁷ , R⁸, R⁹ and R¹⁰ is an unsaturated functional group (e.g., aryl) or an electron withdrawing group; and

wherein, [X(N=CNR⁶R⁷NR⁸R⁹)_n]_m , [X(R¹⁰N=CNR⁶NR⁸R⁹)_n]_m ,

[00251] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is a guanidine, and the switchable moiety is bound to the polysaccharide via a linker XY; and

5c,

(5a); (5b); (5c);

the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker XY has the structure of formula

E is O, S, or a combination thereof;

N=CNR⁶R⁷NR⁸R⁹, R¹⁰N=CNR⁶NR⁸R⁹, R¹⁰N=CNR⁶R⁷NR⁹, and

(N=CNR⁶R⁷NR⁸R⁹)⁺, (R¹⁰N=CNR⁶NR⁸R⁹)⁺, (R¹⁰N=CNR⁶R⁷NR⁹)⁺ are each switchable functional groups, wherein R⁶, R⁷, R⁸, R⁹ and R¹⁰ are independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to C10 aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R⁶, R⁷, R⁸, R⁹ and R¹⁰, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; or,

any one of R⁶, R⁷, R⁸, R⁹ and R¹⁰ is repeat unit -(X-N=CNR⁶R⁷NR⁸)_S-Z, -(X-N=CNR⁷NR⁸R⁹)s-Z, or -(X-NR⁶C=NNR⁸R⁹)s-Z, -(X-NR⁶C=NR¹⁰NR⁸)s-Z, -(X-NC=NR¹⁰NR⁸R⁹)s-Z, wherein X and R⁶, R⁷, R⁸, R⁹ and R¹⁰ are as defined above, s is an integer between 1 and 10 000 wherein m x p x s is 10 000 or less, and Z is a monovalent moiety bonded to the switchable functional group, and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

wherein at least one of R⁶, R⁷, R⁸, R⁹ and R¹⁰ is an unsaturated functional group (e.g., aryl) or an an electron withdrawing group; and

[00252] wherein each of [X(N=CNR⁶R⁷NR⁸R⁹)_n]_m, [X(R¹⁰N=CNR⁶NR⁸R⁹)_n]_m,

[X(R¹⁰N=CNR⁶R⁷NR⁹)n]m, [X((N=CNR⁶R⁷NR⁸R⁹)⁺)_n]m, [X((R¹⁰N=CNR⁶NR⁸R⁹)⁺)_n]m,

[X((R¹⁰N=CNR⁶R⁷NR⁹)⁺)n]m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit is the same or different relative to other repeat units.

[00253] Note that at least one of R⁶, R⁷, R⁸, R⁹ and R¹⁰ is an unsaturated functional group or an electron withdrawing group in order to ensure that the guanidine moiety is not too basic, which could result in substantial protonation of the guanidine moiety prior to exposure to an ionizing trigger.

[00254] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 5d, 5d', 5d", 5e, or 5e' when Y is absent, p is 1 , and R⁶, R⁷, R⁸, R⁹ or R¹⁰ is repeat unit -(X- N=CNR⁶R⁷NR⁸)_m-Z, -(X-N=CNR⁷NR⁸R⁹)_m-Z, or -(X-NR⁶C=NNR⁸R⁹)_m-Z, -(X- NR⁶C=NR¹⁰NR⁸)m-Z, -(X-NC=NR¹⁰NR⁸R⁹)_m-Z; or -(X-N=CNR⁶R⁷NR⁸)_S-Z, -(X- N=CNR⁷NR⁸R⁹)s-Z, or -(X-NR⁶C=NNR⁸R⁹)_S-Z, -(X-NR⁶C=NR¹⁰NR⁸)_S-Z,

-(X-NC= ¹⁰NR⁸R⁹)s-Z,

(5d); (5d'); (5<T);

(5e) (5e'); and

(6e) (6e').

[00255] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 5f, 5g, or 5h w

(60; (6g) ; (6h).

[00256] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is a pyridine, and the neutral form of the switchable moiety is bound to the polysaccharide via a linker XY; and

(7); and

E is O, S, or a combination thereof;

is a switchable functional group, wherein R¹⁵ is H, a Ci to C10 aliphatic group that is linear, branched, or cyclic, a C_nSi_m group where n and m are independently a number from 0 to 10 and n + m is a number from 1 to 10, a C₅ to C10 aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or any two of R¹⁵, together with the atoms to which they are attached, are connected to form a cycle, or heterocycle, each of which may be substituted; or any one of R¹⁵ is repeat unit

, wherein X and R¹⁵ are as defined above, q is integer 1 or 2, and Z is a monovalent moiety bonded to the switchable functional group, and is a linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, or a siloxane, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

wherein, and ^m constitute a chain of repeat units that is linear or branched, each repeat unit in said chain being the same, or different, relative to other repeat units.

[00257] In accordance with another embodiment, there is provided a composite material The composite material of claim 1 , wherein the switchable moiety is a pyridine, and the switchable moiety is bound to the polysaccharide via a linker XY; and

(8),

E is O, S, or a combination thereof;

each X is a divalent linker moiety, or a multivalent linker moiety bonded to Y, or to the polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, each X is independently is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or more of R¹⁵ , together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

is a switchable functional group, wherein R¹⁵ is H, a Ci to Cio aliphatic group that is linear, branched, or cyclic, a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to Cio aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or any two of R¹⁵, together with the atoms to which they are attached, are connected to form a cycle, or hetero be substituted; or

any one of R¹⁵ is repeat unit

wherein X and R¹⁵ are as defined above, q' is integer 1 or 2, s is an integer between 1 and 10 000 wherein m x p x s is 10 000 or less, and Z is a monovalent moiety bonded to the switchable functional group, and is a hydrogen, a halogen, linear or branched C 1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and [00258] wherein each of

and "optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit is the same or different relative to other repeat units.

[00259] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 7a

1 , and R ⁵ is repeat unit or

the second form of the composite material has the structure of formula 8a,

[00260] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 7b when Y is absent, p is 1 , and m is 1 ,

the second form of the cture of formula 8b,

[00261] In accordance with another embodiment, there is provided a composite material wherein the neutral form of the switchable moiety is bound to the polysaccharide via a linker XY; and

(9a); (9b);

(9c); (9d); and

(10c); (10d); and

E is O, S, or a combination thereof;

any one of R¹¹ , R¹², R¹³, and R¹⁴ is repeat unit -(X-lm)_m-Z, wherein X is as defined above, Im is an optionally substituted imidazole ring, and Z is a monovalent moiety bonded to the switchable functional group, and is a linear or branched C 1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, or a siloxane, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted; wherein, the repeat unit [X(lm)_n]_m and [X(lm)⁺ _n]_m constitute a chain of repeat units that is linear or branched, each repeat unit in said chain being the same, or different, relative to other repeat units.

[00262] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is bound to the polysaccharide via a linker XY; and wherein the first form of the composite material has the structure of formula 9a, 9b, 9c, or 9d,

(9c); (9d); and

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X, and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X is a divalent linker moiety, or a multivalent linker moiety bonded to Y, or to polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, each X is independently is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or more of R¹¹ , R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

wherein each X and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini;

R¹¹ , R¹², R¹³, and R¹⁴ are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to C10 aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R¹¹ , R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a cycle or heterocycle, each of which may be substituted; or

any one of R¹¹ , R¹², R¹³, and R¹⁴ is repeat unit -(X-lm)s-Z, wherein X is as defined above, Im is an optionally substituted imidazole ring, s is an integer between 1 and 10 000 wherein m x p x s is 10 000 or less, and Z is a monovalent moiety bonded to the switchable functional group, and is a hydrogen, a halogen, linear or branched C 1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, sulphide, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted; wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and [00263] wherein each of [X(lm)_n]_m and [X((lm)⁺)_n]_m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit is the same or different relative to other repeat units.

[00264] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure of formula 9e, 9f, 9g, or 9h when Y is absent, p is 1 , and m is 1 ,

(10e); (10f);

(10g); (10h).

[00265] In accordance with another aspect, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, the switchable moiety comprising an amine, amidine, or guanidine;

wherein: n is an integer 1 , 2 or 3;

R¹¹, R¹², and R¹⁴ are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_nSi_m group where n and m are independently a number from 0 to 10 and n + m is a number from 1 to 10, a C₅ to Cio aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R¹¹, R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a cycle or heterocycle, each of which may be substituted;

and, when the polysaccharide is a CNC, n is 1 , and X is -C(0)-NH-(CH₂)3- or - C0₂-NH-(CH₂)₃- then only two of R¹¹, R¹², or R¹⁴ is H.

[00266] In accordance with another embodiment, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and at least one polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, wherein the switchable moiety comprises an amine, and wherein the first form of the composite material has the structure of formula 9f, with a proviso that, when the polysaccharide is CNC and n is 1 , and X is -C(0)-NH-(CH₂)3- or -C0₂-NH-(CH₂)₃-, -C(O)- (p-C₆H₄)-CH₂- or -C(0)-(p-C₆H₄)-CH(CH₃)-, only two of R¹¹, R¹², or R¹⁴ is H.

[00267] In accordance with another embodiment, there is provided a composite material wherein the first form of the composite material has the structure

and the second form of the the structure

[00268] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is an amine and the switchable moiety is bound to the polysaccharide via a linker ΧΎ; and

wherein the first form of the composite material has the structure of formula I

wherein: p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent;

E is O, S, or a combination thereof;

NR¹R² and N⁺R¹R² are each a switchable functional group, wherein R¹ and R² are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic, a CqSir group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a Cs to Cio aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or R¹ and R², together with the atoms to which they are attached, are connected to form a cycle, or heterocycle, each of which may be substituted; and

[00269] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is an amidine and the switchable moiety is bound to the polysaccharide via a linker ΧΎ; and

wherein the first form of the composite material has the structure of formula Ilia, 1Mb, or lllc,

(Ilia) (1Mb) (lllc); and

(IVa) (IVb) (IVc); wherein:

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X', and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X' is independently a linear or branched C1-C15 alkanetriyl, a C15-C30 alkanetriyl, a C1-C15 alkenetriyl, a C15-C30 alkenetriyl, a C1-C15 alkynetriyl, a C15-C30 alkynetriyl, an aryltriyl, a heteroaryltriyl, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X' is independently is a trivalent cycle, or heterocycle, each of which may be substituted; or, each X', and one or more of R³, R⁴, and R⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

Z is a monovalent moiety bonded to X', and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thiol, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted; wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched carbon chain, or at one of said chain's termini; and

wherein each of [X'(N=CR³NR⁴R⁵)]_m, [X'(R³N=CNR⁴R⁵)]_m, [X'(R³N=CR⁴NR⁵)]_m, and [X'(N=CR³NR⁴R⁵⁺)]m, [X'(R³N=CNR⁴R⁵⁺)]_m, [X'(R³N=CR⁴NR⁵⁺)]_m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit in said chain is the same or different relative to other repeat units.

[00270] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is a guanidine, and the switchable moiety is bound to the polysaccharide via a linker ΧΎ; and

(Va); (Vb); (Vc); and

(Via); (Vlb); (Vic); wherein: p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent; E is O, S, or a combination thereof;

N=CNR⁶R⁷NR⁸R⁹, R¹⁰N=CNR⁶NR⁸R⁹, R¹⁰N=CNR⁶R⁷NR⁹, and

(N=CNR⁶R⁷NR⁸R⁹)⁺, (R¹⁰N=CNR⁶NR⁸R⁹)⁺, (R¹⁰N=CNR⁶R⁷NR⁹)⁺ are each switchable functional groups, wherein R⁶, R⁷, R⁸, R⁹ and R¹⁰ are independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C5 to C10 aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R⁶, R⁷, R⁸, R⁹ and R¹⁰, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; and

Z is a monovalent moiety bonded to X', and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thiol, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted; wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched carbon chain, or at one of said chain's termini;

wherein each of [X'(N=CNR⁶R⁷NR⁸R⁹)]_m, [X'(R¹⁰N=CNR⁶NR⁸R⁹)]_m, [X'(R¹⁰N=CNR⁶R⁷NR⁹)]m, [X'(N=CNR⁶R⁷NR⁸R⁹)⁺]_m, [X'(R¹⁰N=CNR⁶NR⁸R⁹)⁺]_m, [X'(R¹⁰N=CNR⁶R⁷NR⁹)⁺]m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit in said chain is the same or different relative to other repeat units.

[00271] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is a pyridine, and the switchable moiety is bound to the polysaccharide via a linker ΧΎ; and wherein the first form of the composite material has the structure of formula VII,

(VIII),

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X', and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X' is independently a linear or branched C1-C15 alkanetriyl, a C15-C30 alkanetriyl, a C1-C15 alkenetriyl, a C15-C30 alkenetriyl, a C1-C15 alkynetriyl, a C15-C30 alkynetriyl, an aryltriyl, a heteroaryltriyl, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X' is independently is a trivalent cycle, or heterocycle, each of which may be substituted; or, each X', and one and one or more of R¹⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

wherein each X' and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and

is a switchable functional group, wherein R¹⁵ is H, a Ci to C10 aliphatic group that is linear, branched, or cyclic, a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to C10 aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or any two of R¹⁵, together with the atoms to which they are attached, are connected to form a cycle, or heterocycle, each of which may be substituted; and Z is a monovalent moiety bonded to X', and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thiol, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted;

wherein each of

[00272] In accordance with another embodiment, there is provided a composite material wherein the switchable moiety is bound to the polysaccharide via a linker ΧΎ; and wherein the first form of the composite material has the structure of formula IXa, IXb, IXc, or IXd,

(IXa); (IXb);

the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker ΧΎ has the structure of formula Xa, Xb, Xc, or Xd,

(Xc); (Xd);

E is O, S, or a combination thereof;

each X' is independently a linear or branched C1-C15 alkanetriyl, a C15-C30 alkanetriyl, a C1-C15 alkenetriyl, a C15-C30 alkenetriyl, a C1-C15 alkynetriyl, a C15-C30 alkynetriyl, an aryltriyl, a heteroaryltriyl, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X' is independently is a trivalent cycle, or heterocycle, each of which may be substituted; or, each X', and one or more of R¹¹, R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

R¹¹, R¹², R¹³, and R¹⁴ are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C5 to C10 aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R¹¹, R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a cycle or heterocycle, each of which may be substituted;

wherein, each of [X'(lm)]_m and [X'(lm)⁺]_m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit in said chain is the same or different relative to other repeat units.

[00273] In accordance with another embodiment, there is provided a composite material wherein the polysaccharide is cellulose nanocrystal (CNC), cellulose, dextran, cotton, starch, chitin, chitosan, or any combination thereof.

[00274] In accordance with another embodiment, there is provided a composite material wherein the polysaccharide comprises cellulose nanocrystal (CNC), cellulose, dextran, starch, chitin, chitosan, glycogen, pectin, arabinoxylan, or any combination or modification thereof.

[00275] In accordance with another embodiment, there is provided a composite material wherein the polysaccharide is comprised within cotton, cotton linen, paper, flax, hemp jute, sisal, linen, or any combination or modification thereof.

[00276] In accordance with another embodiment, there is provided a composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and at least one polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, with a proviso that the polysaccharide is not CNC, cellulose, or filter paper.

[00277] In accordance with another embodiment, there is provided a composite material wherein said first form of the composite material is neutral and hydrophobic, and the second form of the composite material is ionized and hydrophilic. [00278] In accordance with another embodiment, there is provided a second form of the composite material wherein % ionization of the material's switchable moieties is≤100%; or alternatively,≤75%; or alternatively≤50%.

[00279] In accordance with another embodiment, there is provided a composite material wherein each repeating unit of formulas 1 and 2, or 1 a and 2a; 3a, 3b, 3c and 4a, 4b, 4c, or 3d, 3d', 3e, 3e', 3f, 3Γ, 3f" and 4d, 4d', 4e, 4e', 4f, 4Γ, 4f"; 5a, 5b, 5c and 6a, 6b, 6c, or 5d, 5d', 5d", 5e, 5e' and 6d, 6d', 6d", 6e, 6e'; 7 and 8, or 7a and 8a; or 9a, 9b, 9c, 9d, and 10a, 10b, 10c, 10d; or (I) and (II); (Ilia), (lllb), (lllc) and (Iva), (IVb), (IVc); (Va), (Vb), (Vc) and (Via), (Vlb), (Vic); (VII) and (VIII); (IXa), (IXb), (IXc), (IXd) and (Xa), (Xb), (Xc), (Xd) is either the same, or different, relative to other repeat units, thus forming a homopolymer or a copolymer. In one embodiment, said copolymer is a graft copolymer or block copolymer. In another embodiment, the copolymer is a random copolymer.

[00280] Synthesis

[00281 ] As herein described, there are now provided modification processes for preparation of switchable polysaccharides, wherein at least a portion of a polysaccharides' surface is functionalized with a switchable group, as defined above. Once modified, the polysaccharides can be switched from a neutral form to an ionized form in the presence of aqueous media and ionizing triggers, such as C0₂, COS, CS₂, or a combination thereof, via protonation/ionization of the polysaccharides' switchable group; while exposure to heat, reduced pressure (e.g. vacuum), sparging with a flushing gas (e.g. air, N₂), or any combination thereof, either with agitation or no agitation, can switch the polysaccharides from an ionized form to a neutral form via deprotonate/de-ionize the polysaccharides' switchable group.

[00282] Examples of polysaccharides that can be functionalized to form a switchable polysaccharide as described herein include, but are not limited to, CNC, cellulose, hemicellulose, cotton, starch, dextran, glycogen, pectin, arabinoxylan, and chitin/chitosan, etc. Examples of polysaccharide materials or polysaccharide-containing materials that can be functionalized to form a switchable polysaccharide include, but are not limited to cellulose-containing materials, such as, certain fabrics, (e.g., linens and cottons, hemp, jute, and sisal), and paper, such as filter papers.

[00283] In one embodiment, there is described a one-step modification process for preparation of switchable CNCs, wherein the CNCs' surface is functionalized with a switchable group, as defined above. Once modified, the CNCs were dispersed into aqueous media in the presence of ionizing triggers, such as C0₂, COS, CS₂, or a combination thereof via protonation/ionization of the CNCs' switchable group; while exposure to heat, reduced pressure (e.g., vacuum), sparging with a flushing gas (e.g., air, N 2) , or any combination thereof, deprotonate/de-ionize the CNCs' switchable group and separated the CNCs from the aqueous phase. Further, surfaces of switchable CNCs may be switched between hydrophilic and hydrophobic states; a switch between hydrophilic and hydrophobic states may provide a difference in adsorption properties, which may be beneficial for adsorption for different adsorbates.

[00284] In another embodiment, there is a switchable polysaccharide comprising an imidazole switchable functional group. It has been found that the imidazole group, as a switchable group, can be ionized when in the presence of an aqueous solution and an acid gas, such as C0₂, COS, CS₂, or a combination thereof, within a time frame at least comparable to previously described switchable systems. However, it has been found that the imidazole group can be more completely, quickly and/or facilely de-protonated/de-ionized when exposed to flushing gases (e.g. air, N₂), heat, or a vacuum, as compared to previously described switchable systems; for example, it has been experimentally observed that imidazole-based switchable groups switch off within seconds, versus minutes for previous systems [Liu, Y. X.; Jessop, P. G.; Cunningham, M. ; Eckert, C. A. ; Liotta, C. L. Science

2006, 313, 958-960; Chai et al. J. Surfact. Deterg. 2014, 17, 383-390.]

[00285] Although the present application may generally refer to use of C0₂ gas as the external stimulus, or ionizing trigger, to switch a material from its non-protonated/non-ionized form to its protonated/ionized form, it should be understood that the C0₂ can be replaced with another acid gas, such as COS, CS₂, or a mixture of acid gases. In the case where the acid gas is COS or CS₂, the product of the reaction would be a protonated switchable polysaccharide as a salt with a sulfur substituted bicarbonate analogue. Removal of the C0₂ trigger (or other acid gas or mixture thereof) to an amount insufficient to maintain or convert a switchable polysaccharide to its protonated/ionized form, will trigger a switch of the polysaccharide back to its neutral/non-protonated/non-ionized form. This trigger can be, as described above, reduced pressure, a flushing gas, heat, or a combination thereof, either with agitation or no agitation. The flushing gas can be air or an inert gas. Agitation may also be a viable means for removing the C0₂ trigger, so long as it is energetically favourable to do so. [00286] In an embodiment, it has been considered that said switchable

polysaccharides can be synthesized via a coupling reaction between CDI and a carboxylic acid, which is terminally-functionalized to comprise either: (a) a switchable moiety, such as an amine, amidine, or guanidine; or, (b) a functional group that can be synthetically transformed into, or coupled to, a switchable moiety. For a demonstrative, non-limiting example of one such synthesis, see Figure 1 1.

[00287] In another embodiment, it has been considered that said switchable polysaccharides can be synthesized via a coupling reaction between methyl chloroformate and an amine terminally functionalized with a switchable moiety, such as, but not limited to, an amine, amidine, or guanidine. For a demonstrative, non-limiting example of one such synthesis, see Figure 12.

[00288] In yet another embodiment, it has been considered that the switchable polysaccharides can be synthesized via a coupling reaction using 1 -ethyl-3-(3- dimethylaminopropyl) carbodiimide with, for example, an primary amine functionalized with a switchable moiety.

[00289] In an embodiment, the switchable polysaccharides were synthesized via a "grafting to" or "grafting from" approach, which are two methods used to synthesize graft polymers. For the "grafting to" approach, polymerization was carried out prior to attachment of the desired switchable polymer to a polysaccharide's surface, and it was required that the polysaccharide's surface possessed functional groups capable of reacting with a terminal functional group of the previously synthesized switchable polymers. Functional groups of the polysaccharide's surface and the chains of switchable polymer acted as a bridge or link between the surface and the graft polymer. Using the "grafting to" approach, allowed for properties of the resultant material to be well controlled. However, generally, lower grafting densities were achieved; for example, due to steric hindrance induced by polymeric chains already attached to the surface; or, the reaction mixture exhibiting higher viscosities due to a presence of macromolecular chains.

[00290] The "grafting from" approach, also known as surface-initiated polymerization

(SIP), was used to synthesize switchable polysaccharides when higher grafting densities were desired. With the "grafting from" approach, chains of switchable polymers were grown from a polysaccharide's surface, which was first functionalized with an initiator prior to carrying out graft polymerization in the presence of a desired monomer. These reaction mixtures tended to have a lower viscosity, and exhibited fewer limitations as a result of steric hindrance. However, other factors were important; for example: control over, and precise determination of molecular weight of the grafted polymer, which was sometimes limited to a lower degree of polymerization; and, the quantity of homopolymer (non-grafted) was also be relatively more difficult to quantify.B

[00291] Grafting polymeric amines to polysaccharides, polysaccharide materials, or polysaccharide-containing materials is known in the art. For example, Roy et al. [Roy et al., Biomacromolecules, 2008, 9, 91-99] and Lee et al. [Lee et al., Biomacromolecules, 2004, 5, 877-882] grafted poly(2-(dimethylamino)ethyl methacrylate (PDMAEMA) to filter paper, subsequently quarternized the tertiary amino groups using alkyl halides, and then tested the resultant material for antimicrobial properties. Roy et al. [Roy et al., Soft Matter, 2008, 4, 145 - 155] grafted PDMAEMA onto a cellulosic substrate, after which the PDMAEMA was co- polymerized with polystyrene to investigate changes in relative surface hydrophobicity / hydrophilicity before and after co-polymerization. Bhut et al. [Bhut et al., Journal of

Membrane Science, 325, 2008, 176-183] grafted PDMAEMA nanolayers from pore surfaces of commercially available regenerated cellulose membranes in order to prepare high- capacity anion-exchance membranes. And Yi et al. [Yi et al., Cellulose, 2009, 16, 989-997] grafted PDMAEMA to cellulose nanocrystals to investigate temperature-induced chiral nematic phase changes of suspenions of the same. However, not one of Roy et al., Lee et al., Roy et al., Bhut et al., or Yi et al. disclosed, taught, recognized or took advantage of the switchablility (if any) of their PDMAEMA-g rafted material; nor did they manufacture grafted products or use their grafted- products as switchable polysaccharides, as described herein.

[00292] In another embodiment of the application as described herein, the switchable polysaccharides are synthesized via a polymerization "grafting through" approach, which is similar to the above-described "grafting to" or "grafting from" approach. In a "grafting through" approach, however, a polymerizable group, which is either similar to, or the same as a monomer to be polymerized, is attached to a polysaccharide's surface. This polymerizable group then reacts with initiator, and with free monomer and/or polymer in solution. As polymerization occurs in solution, some polymer chains include one or more surface-bound polymerizable groups / monomer units, in addition to many free monomer. As a result, some polymer chains are bound to a surface by one or more repeat units derived from the surface-bound polymerizable group / monomer, while other chains, which did not include a surface-bound monomer, are free in solution and not attached to the surface. Those latter chains can be washed away [00293] Applications

[00294] It has now been found that composite materials having switchable properties can be prepared by incorporation of one or more switchable moieties on a polysaccharide via a linker; the present application also provides uses for the composite materials, as described herein.

[00295] Thus, in accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, for: (i) manipulating and/or controlling dispersibility, for example, CNC dispersibility; (ii) for formation of a membrane comprising a chiral nematic liquid crystalline structure; (iii) for water or wastewater treatment, wherein, in one embodiment, the water or wastewater treatment comprises removal of organic contaminants or metal contaminants; (iv) for cleaning a surface; (v) for formation of a switchable fabric; (vi) for formation of a switchable filter paper; (vii) for stabilizing an emulsion; (viii) for use in chromatography; or (ix) any combination thereof.

[00296] In accordance with another aspect of the application, there is provided a use for the composite materials, as herein described, as: (i) a separation membrane; (ii) an absorbent; (iii) a drying agent; (iv) a flocculent; (v) a switchable viscosity modifier; or (vi) any combination thereof.

[00297] In accordance with an embodiment, as described herein, there are switchable polysaccharides having a surface with switchable hydrophilic/hydrophobic properties: in their neutral/ non-ionized form ('switched off), the switchable polysaccharides are hydrophobic; in their ionized/protonated form ('switched on'), the switchable polysaccharides are hydrophilic. It has been considered that such switchable hydrophilic / hydrophobic systems may be used in separation applications, or used as adsorbents/flocculants in water/wastewater treatment.

[00298] Such a switch in hydrophilic/hydrophobic properties may be useful in adsorption processes to remove hydrophobic organic contaminants from water (e.g.

hydrophobic dyes, aromatics, etc.). For example, switchable polysaccharides, such as switchable CNCs, could be dispersed with aid of an ionizing trigger such as C0₂ into wastewater comprising hydrophobic contaminants; after complete dispersion of the switchable polysaccharides, a flushing gas (for example), such as N₂, could be sparged through the dispersion, thereby precipitating the polysaccharides. During this process, the hydrophobic polysaccharides may adsorb hydrophobic contaminants from the wastewater prior to precipitation; after which the at least partially purified water could be separated from the precipitate, the precipitate could be diluted with water and redispersed in the presence of the ionizing trigger.

[00299] In an embodiment, the herein described switchable polysaccharides may be used to isolate and/or recover desired organic materials from aqueous solutions. For example:

[00300] Microalgae have been considered a third generation feedstock for biofuel production due to their higher photosynthetic efficiency and lipid contents (15-77 % of cell mass) [J. Milledge, S. Heaven. Rev Environ Sci Biotechnol. 12 (2013) 165-78; E. Suali, R. Sarbatly. Renew Sust Energ Rev. 16 (2012) 4316-42; Y. Chisti. Biotechnol Adv. 25 (2007) 294-306] than common feedstocks such as crops [Y.C. Sharma, B. Singh, J. Korstad. Green Chem. 13 (201 1) 2993-3006.]. Additionally, microalgae have been shown to be problematic in water systems due to their rapid increase or accumulation during algal blooms [S.O. Lee, S. Kim, M. Kim, K.J. Lim, Y. Jung. Water. 6 (2014) 399-413; X. Lou, C. Hu. Remote Sens Environ. 140 (2014) 562-72; Q. Jiang, Y. Jie, Y. Han, C. Gao, H. Zhu, M. Willander, X. Zhang, X. Cao. Nano Energy. 18 (2015) 81-8]. Thus, efficient microalgal isolation / harvesting or removal from water has been considered, not only for biofuel production, but also for mitigation of aquatic systems.

[00301] Conventional microalgal separation methods have included gravity, precipitation, centrifugation, microstraining, flotation and filtration [M. Agbakpe, S. Ge, W. Zhang, X. Zhang, P. Kobylarz. Bioresour Technol. 166 (2014) 266-72]. However, these methods have been considered energy- and/or time-consuming [A.L. Ahmad, N.H.M. Yasin, C.J.C. Derek, J.K. Lim. Environ Technol. 35 (2014) 2244-53]. Other methods have included chemical flocculants such as cationic inorganics or polymers [N. Rashid, S.U. Rehman, J. -I. Han. Process Biochem. 48 (2013) 1 107-10], magnetophoretic separation using native or cationic polymer coated magnetic nanoparticles (NPs) [S. Ge, M. Agbakpe, W. Zhang, L. Kuang. ACS Appl Mater Interfaces. 7 (2015) 6102-8; Y.-D. Chiang, S. Dutta, C.-T. Chen, Y.- T. Huang, K.-S. Lin, J.C.S. Wu, N. Suzuki, Y. Yamauchi, K.C.W. Wu. ChemSusChem. 8 (2015) 789-94] and bio-flocculation induced by microbes (e.g. bacteria, fungi) [M. Agbakpe, S. Ge, W. Zhang, X. Zhang, P. Kobylarz. Bioresour Technol. 166 (2014) 266-72; R.L.

Taylor, J.D. Rand, G.S. Caldwell. Mar Biotechnol. 14 (2012) 774-81]. However, these methods have involved use of additives, which may contaminate and adversely effect microalgal cells and culture media when using microalgae as either inocula and/or recycling supernatant after harvesting. [00302] To allow for recovery and reuse of flocculants or coagulants in methods of microalgal separation, detachment of the flocculants or coagulants from microalgae must be achieved, for example by inducing changes in their surface properties, such as surface charge and wetting properties [S. Ge, M. Agbakpe, W. Zhang, L. Kuang. ACS Appl Mater Interfaces. 7 (2015) 6102-8; S. Ge, M. Agbakpe, W. Zhang, L. Kuang, Z. Wu, X. Wang. ACS applied materials & interfaces. 7 (2015) 1 1677-82; G. Prochazkova, N. Podolova, I. Safarik, V. Zachleder, T. Branyik. Colloid Surface B. 1 12 (2013) 213-8]. Such changes may be triggered by a presence of switchable or stimuli-responsive groups on surfaces of flocculants or coagulants.

[00303] It has been considered that the ionized form of the herein described switchable polysaccharides can promote coagulation or attachment of microalgae cells carrying negative charges [D. Vandamme, S. Eyley, G. Van Den Mooter, K. Muylaert, W. Thielemans. Bioresour Technol. 194 (2015) 270-5]. Further, herein described switchable polysaccharides, such as the switchable CNCs, were found to disperse in water in the presence of an acid gas, as such C0₂; and, to aggregate with subsequent removal of said gas (e.g., C0₂) through sparging with inert gases, such as N₂. Thus, herein described switchable polysaccharides, such as the switchable CNCs, with its ability to repeatedly disperse/aggregate, were applied to a microalgal harvesting process (see Example 1 F).

[00304] Use of functionalized CNC for algal harvesting is known in the art. For example, Vandamme et al. [D. Vandamme, S. Eyley, G. Van Den Mooter, K. Muylaert, W. Thielemans. Bioresour Technol. 194 (2015) 270-5; S. Eyley, D. Vandamme, S. Lama, G. Van Den Mooter, K. Muylaert, W. Thielemans. Nanoscale. 7 (2015) 14413-21] demonstrated applicability of pH-responsive CNC functionalized with cationic pyridinium (pH trigger - sodium carbonate) and imidazole groups (pH trigger - C0₂) for microalgal flocculation. However, contrary to the embodiments described herein, the concentration of functionalized CNC required by Vandamme et al. to facilitate flocculation was higher, and there was no demonstration of reuse and recyclablily of functionalized CNC and culture medium for continued algal growth and flocculation. Contrary to this, the embodiments described herein required only 0.05 g-switchable polysaccharide (i.e., CNC) / 1 g-algae to achieve a harvesting efficiency of 100%; however, to achieve the same efficiency, Vandamme et al. required 0.1 g-CNC/ 1 g-algae with pyridinium-modified CNC, and 0.57 g-CNC/ 1 g-algae with imidazole-modified CNC. Further, Vandamme et al. did not use, disclose, or teach initially sparging systems comprising functionalized CNC and algae with C0₂ followed by air in order to facilitate algal settling, as described herein; in contrast, Vandamme et al. relied only on charge neutralization.

[00305] Other switchable adsorption applications can include removal of ionic species from wastewater (e.g. heavy metals). In an embodiment, as described herein, switchable polysaccharides, such as switchable chitosans, can be used to adsorb metal ions from aqueous solutions. Once such contaminants are captured, the metal-laden chitosan can be separated from the aqueous solution and collected for a) combustion or digestion to liberate the captured metal, b) disposal or e) regeneration.

[00306] In another embodiment, as described herein, there is provided the use of switchable polysaccharides for controlling colloidal dispersibility. For example: typically, native or modified CNC can be dispersed in aqueous or organic medium, typically via electrostatic or steric stabilization [Dong, X. M.; Revol, J. F.; Gray, D. G. Cellulose 1998, 5, 19-32]. Once well dispersed, native or modified CNCs can offer a platform for

chemical/physical adsorption applications that could utilize CNCs high specific surface area. However, collecting CNCs from a dispersion may eventually be required; for example, when adsorbate-saturated CNCs have to be removed from a dispersion medium, washed and reused (if possible).

[00307] It is generally understood that colloidal particle dispersibility can be dependent on surface charge and steric effect. Thus, controlling of CNC dispersibility, by adjusting electrostatic or steric stabilization, can facilitate CNC collection/redispersion. This could be further facilitated by exerting control via application of benign stimuli, such as application of an ionizing trigger to a switchable CNC, to form an ionized CNC.

[00308] Use of an ionizing trigger such as C0₂, COS, CS₂, or a combination thereof for a particular application (e.g., when manipulating colloidal dispersibilities), allows for removal of the triggers from aqueous media by sparging with inert flushing gases (e.g. air, N₂), applying heat or vacuum such that minimal residual ionic strength remains after removal of the C0₂ - unlike pH-responsive colloidal dispersions, as described above.

[00309] Contrasted with other stimuli, use of ionizing triggers such as C0₂, COS,

CS₂, or a combination thereof, can be more cost-effective (e.g. time cost and energy cost). Moreover, the ionizing trigger-switchable technique can be scaled up for industrial application, as it does not require additional chemicals, special equipment or significant amounts of energy. [00310] Without wishing to be bound by theory, it has been further considered that switchable polysaccharides could be applied to many applications for which polysaccharides are used.

[0031 1 ] For example, when the herein described switchable polysaccharides are manufactured as porous membranes (e.g., microfiltration cellulose membrane, linens, filter papers, etc.), they can be applied to separations of hydrophilic/lyophilic species; for example, when separating an oil/water mixture using a switchable polysaccharide membrane, it is expected that water would pass through a membrane when the membrane's switchable functionality is in its protonated, hydrophilic state (i.e. , 'switched on'), whereas oil would not pass through, such that the oil/water mixture is separated. Herein described switchable polysaccharides, such as switchable cellulose, can also be manufactured as a super adsorbent material, such as for use in reusable diapers. For example, once in contact with urine, a relatively weak acid, the diaper's switchable polysaccharide(s) is 'switched on' to a hydrophilic state by protonation of its switchable groups, thereby adsorbing the urine; the diaper can be regenerated after laundering with a relatively weakly basic laundry detergent, which would 'switch off the switchable polysaccharide(s) by deprotonating its switchable groups, thereby re-establishing the diaper's hydrophobicity.

[00312] In yet another application, switchable polysaccharides can be used in desorption processes wherein a precipitated and/or hydrophobic ('switched off) switchable polysaccharide comprising hydrophobic species can selectively release the species when exposed to ionizing triggers such as C0₂. Further, it has been found that herein described switchable CNCs will gel above a certain concentration. It has been considered that this capacity for the CNCs to gel can provide a protective layer around any species that interacts with the 'switched off CNC through a hydrophobic interaction (e.g., protein); after which, the contents can be released upon application of an ionizing trigger.

[00313] With respect to another application of the present switchable polysaccharides, it is known that aqueous dispersions, or alternatively some organic dispersions, of, for example, native CNC, undergo isotropic to anisotropic chiral nematic liquid crystalline phase change when the dispersion passes a critical concentration [Dong, X. M.; Revol, J. F. ; Gray, D. G. Cellulose 1998, 5, 19-32]. Following solvent evaporation, these native CNC

dispersions transform into semi-translucent CNC membranes that retain the chiral nematic liquid crystalline structure formed in dispersion. These membranes can be iridescent, and they reflect left-handed circularly polarized light determined by the chiral nematic pitch of the liquid crystal structure. These membranes show visible iridescence colors when the pitch of their helix is comparable with wavelengths of visible light. Thus, it has been considered that at least some switchable polysaccharides, such as switchable CNCs, can retain a chiral nematic structure, and that their helical pitch can be manipulated by controlling the CNCs switchable groups' degree of protonation, by way of ionizing triggers such as C0₂, thereby adjusting the switchable CNCs' surface charge and subsquently influencing distances between CNC particles [Dong, X. M.; Revol, J. F.; Gray, D. G. Cellulose 1998, 5, 19-32]. As such, after drying the switchable CNC aqueous dispersion at room temperature to form membranes, the membrane thus prepared may have different iridescent properties that result from different dispersibilities under different protonation conditions.

[00314] Further to the aforementioned absorption/adsorption/desorption applications, the herein described switchable polysaccharides may be useful for cleaning delicate surfaces and removing hydrophobic contaminants (e.g. removing dust, dirt, oils, etc). For example, a surface to be cleaned can be dipped into a dispersion of protonated, hydrophilic switchable polysaccharides ('switched on'), such as switchable CNCs, following which the dispersion can be sparged with an inert flushing gas (e.g. air, N₂), thereby de-protonating the switchable CNCs, rendering them hydrophobic. The hydrophobic CNC can then 'adsorb' or 'encompass' the surface's hydrophobic impurities and remove them via precipitation or settling. The resultant wet, clean surface can then be dried; for example, by further sparging with an inert flushing gas.

[00315] Further, the herein described switchable polysaccharides may be a switchable fabric, such as cotton, cotton linen, paper, flax, hemp, jute, sisal, linen, or any combination thereof, wherein at least a portion of a fabric is functionalized with one or more switchable moieties, such as an amine or imidazole moiety, to allow the fabric to be switched between a first, neutral form and a second, ionized form (e.g., a hydrophobic form and a hydrophilic form). Once functionalized, the fabric can be maintained in its neutral and/or hydrophobic form until exposed to an ionizing trigger, such as CO2, COS, CS2, or a combination thereof, in an aqueous solution; at that point, the switchable moieties of the functionalized fabric would be ionized, and would thus maintain the fabric in its ionized and/or hydrophilic state. Consequently, once the fabric was switched into its ionized state, hydrophobic materials contained within the linen can be expelled out of, or off of the fabric. As would be readily appreciated by a worker skilled in the art, in order for the fabric to switch to its ionized form, it is necessary to expose the fabric to an ionizing trigger in an amount greater than that present under ambient conditions. For example, where C0₂ is the ionizing trigger, the fabric must be exposed to CO2 at an amount greater than that present in air in order to become ionized. This can allow fabric materials, such as but not limited to clothes, mats, carpets, curtains, etc., to be washed with or washed in water/carbonated water rinse cycles, in the absence of detergents. In another embodiment, a switchable fabric can be used as a separation membrane, facilitating separation of a mixture of hydrophobic and hydrophilic components by switching the fabric between its first, neutral form and its second, ionized form, as described above.

[00316] The herein described switchable polysaccharides may also be switchable starches (for example, see Example 4). The switchable starches, once ionized in the presence of an ionizing trigger, such as C0₂, COS, CS₂, or a combination thereof, and an aqueous solution, can be dissolved and/or dispersed throughout the aqueous solution, and used to capture water-born/aqueous solution-born pollutants such as metal ions. Once the contaminants are captured, the starch could then be switched from its ionized state to a neutral state, thus rendering the starch insoluble in the aqueous solution, and allowing the metal-laden starch to be separated from the aqueous solution and collected for a) combustion or digestion to liberate the captured metal, b) disposal or c) regeneration.

[00317] Further, said switchable starches may be used as drying agents, to capture and remove water from reaction media, organic solvents, etc. For a demonstrative, non- limiting example: a switchable starch was added to a wet organic solvent (for example, 5 wt% water content), and the mixture wase exposed to C0₂. In the presence of the organic solvent's water content and C0₂, the switchable starch switched to its ionized/hydrophilic form, capturing some of the water content in the bicarbonate anion that forms as part of the switchable moiety's ionized form. It is considered that, most, if not all, of any remaining water interacts with the hydrophilic surface of the switchable starch (via a hydration sphere), and that consequently, the now 'wet' starch can be separated from the organic solvent via filtration. The 'wet' switchable starch can then be switched to its neutral/hydrophobic form in the presence of heat and/or a flushing gas, etc.; thus, releasing the captured water, and be ready for re-use.

[00318] The herein described switchable polysaccharides may be used to generate switchable filter paper (for example, see Example 5). At least a portion of the filter paper can be functionalized with one or more switchable moieties capable of switching from one form to a second form, in the presence of an ionizing trigger such as C0₂, COS, CS₂, or a combination thereof, and an aqueous solution. Thus functionalized, such switchable filter paper can be used to selectively filter polar and non-polar species from a mixture; for example, if switched to its ionized/hydrophilic state, the filter paper allows any hydrophilic species in a mixture to pass through, while preventing hydrophobic species from doing the same. Similarly, switchable filter paper can function as a solid phase extraction substitute, using a carbonated aqueous mobile phase to selectively separate particular analytes in a mixture.

[00319] Without wishing to be bound by theory, it has been envisioned that switchable polysaccharides may find applicability as nanocomposites (improved strength, barrier properties and rheology), biodegradeable polymers, and iridescent films (e.g. inks, varnishes, cosmetic and architectural industries, security paper). Further, switchable polysaccharides may be applicable for: oil absorption or oil recovery applications (for example, removal of oil from aqueous environments or from non-aqueous phase liquids, such as oil spills); as metal adsorbents; metal separation applications; or, providing paper- based membrane filters for desalinization.

[00320] To gain a better understanding of the invention described herein, the following examples are set forth. It should be understood that these examples are for illustrative purposes only. Therefore, they should not limit the scope of this invention in any way.

WORKING EXAMPLES

[00321 ] EXAMPLE 1 : Cellulose Nanocrystals with C0₂ - Switchable Aggregation and Redispersion Properties

[00322] General Experimental:

[00323] Materials: Cellulose nanocrystals (CNC), provided by FPInnovations, were prepared by sulfuric acid hydrolysis of a commercial bleached softwood kraft pulp. 1 , 1 '- Carbonyldiimidazole (CDI, reagent grade), 1-(3-aminopropyl)imidazole (APIm,≥97%), and NaOH (>98%) were used as received from Sigma-Aldrich. 1-(3-Hydroxypropyl)-1 H-imidazole (HPIm, >98%) was purchased from Oakwood Products Inc. and used as received. Dimethyl sulfoxide (DMSO, 99.8%, water content <50 ppm), and dichloromethane (DCM, 99.8%, water content≤50 ppm) were used as received from EMD chemicals. HCI and absolute ethanol were used as received from Fisher Scientific Canada and Commercial Alcohols, respectively. CO2 (99.995%) and N2 (99.9999%) gases were used as received from MEGS. Deionized water (DIW) from a Direct-Q 3 UV System (Millipore Corporation) had a resistivity of 18.2 ΜΩ-cm.

[00324] Instrumentation: Particle size and zeta potential of CNC samples (after C0₂ and N2 sparging for 5 and 30 min respectively at room temperature) were measured at 25°C on a Malvern Zetasizer Nano ZS instrument (size range: 0.3 nm~10.0 μητι) using DTS1060 disposable folded capillary cells. No sonication, vortex, stirring or filtration was applied to samples throughout the overall C0₂ and N₂ sparging processes, or prior to any size and zeta potential measurements. Particle concentration was kept at ca. 0.5 mg/mL for all measurements.

[00325] Each measurement was performed in triplicate with any data presented (particle size, PDI, and zeta potential) being an averaged value. ¹H nuclear magnetic resonance (NMR) spectra were recorded on a Bruker Avance 400 NMR spectrometer (400.13 MHz) at 25°C using 90% H₂0 + 10% D₂0 as solvent. Chemical shifts of protons on the HPIm imidazole ring were recorded at 1 .0 M HCI and 1.0 M NaOH for 100% and 0% degree of protonation, respectively. HPIm concentration was fixed at 15 mg/mL for all measurements. No additional internal reference was used to avoid any interference.

[00326] All measurements were conducted at least in triplicate. Turbidities of CNC samples (with C0₂ or N₂ sparging for 5 and 30 min respectively at 25^°C prior to

measurements) were recorded on a UV-Vis spectrometer (PerkinElmer Lambda Bio/XLS) at 500 nm wavelength and room temperature with 2.5 mg/mL sample concentration. Each measurement was performed in triplicate with any data presented being averaged. DRIFT-IR spectra of CNC samples were recorded on a Varian 660 IR instrument equipped with a PIKE DiffusIR accessory; 2 mg of sample was ground with 100 mg of dried KBr to form a homogeneous mixture which was then measured. For each measurement, a total of 32 scans were averaged with a resolution of 4 cm ¹.

[00327] Elemental analysis was performed by Micro Analysis Inc.

(Wilmington DE, USA). Samples were freeze-dried for 48 h, and then further oven-dried at

50°C under vacuum for at least 12 h before measurement. Two CNC-APIm samples prepared in two independent batches (with identical recipes and experimental procedures), together with native CNC, were analyzed for C, H, N, and S concentrations. TEM images were taken on a Hitachi H-7000 instrument operating at 75 kV. Native CNC or CNC-APIm

(under C0₂) aqueous dispersions were prepared using a vortex mixer with a concentration of ca. 1.0 mg/mL; the sample was then deposited on a carbon coated copper grid and left for 1 min before excess dispersant was removed. The sample was then stained by 2% uranyl acetate aqueous solution for 5 min before taking TEM images.

[00328] EXAMPLE 1 A: Selection of Functional Groups for C0₂-Switchable

Compounds

[00329] To determine whether a compound is suitable to act as a switchable functional group at a particular pH, one needs to understand the relationship between pH, basicity of the switchable group (as measured by the pKaH), and concentration of switchable species in water (moles of switchable groups per litre of solution). If it is assumed, for a simplest case, that the switchable compounds are fully dissolved in water in both neutral and protonated forms, then % protonation can be obtained using activity coefficients, or reasonably approximated using equation (2):

% protonation = — -

[H₃0⁺] + K_aH

(2)

Switching of C0₂-switchable compounds using equation 2 requires that pH of the aqueous solution in the absence of C0₂ is above a system midpoint, and pH in the presence of C0₂ is below said system midpoint. The system midpoint is defined as pH at which number of moles of unprotonated base in the system is equal to number of moles of protonated base in the system. Contrast this to a definition of an aqueous phase midpoint, which is defined as pH at which number of moles of unprotonated base in the aqueous phase is equal to number of moles of protonated base in the aqueous phase. In the simplest case, where the switchable species is fully dissolved in an aqueous phase in both its neutral form and cationic form, then the system midpoint and aqueous phase midpoint are equal, and occur when pH is equal to pKaH. In order for a compound to be "switched" adequately by C0₂ addition, so that its properties are significantly changed, it must be converted from a largely unprotonated state (low % protonation) to a largely protonated state (high % protonation). Therefore, the best switchable functional group to choose is one that will ensure that pH without C0₂ and pH with C0₂ are on opposite sides of the system midpoint.

[00330] Because C0₂ is acidic, and therefore lowers pH, pH without C0₂ should be above the system midpoint (meaning at a pH higher than the system midpoint); and, pH with C0₂ should be below the system midpoint (meaning at a pH lower than the system midpoint). Equation (3) predicts [H₃0⁺] concentration at any particular concentration of switchable species in water, for this simplest case where a switchable species is fully dissolved in both its neutral and cationic forms. From the [H₃0⁺] obtained using equation (3), one can use equation (2) to calculate % protonation of switchable groups when C0₂ is absent.

[00331] With regard to Equation (3), when a base is added to pure water at a concentration [B]o, under air, the resulting pH is in the basic region. The base is partly protonated due to production of hydroxide salt [BH⁺][OH^~]. From [H₃0⁺], % protonation can be calculated (equation (2)). For an ideal switchable compound, % protonation would be very low (for example, below 20%, ideally below 5%). Equation (4) can be used to calculate [H₃0⁺] (and then via equation (2), % protonation of the switchable groups) when C0₂ is present at a pressure Ρ_∞2. Ideally, % protonation of switchable groups would be high (for example: above 60%, ideally above 95%)

0 = [H₃0⁺]³ + (KaH+[B]₀)[H₃O⁺]² - Kw[H₃0⁺] -KwKaH (3)

0 = [H₃0⁺]³ + (KaH+[B]₀)[H₃O⁺]² - (K*al KHPc02+Kw)[H₃0⁺] - (K*al K_HPc02+Kw)KaH (4)

[00332] If one chooses a correct switchable compound for a desired set of conditions (temperature and concentration), then simply adding that compound to water at that concentration will give a pH at which % protonation is low, and then adding an atmosphere of C0₂ will give a pH at which % protonation is high. Figures 47 and 48, which were derived from equations (1) and (2), show limitations on the basicity of the switchable group (as measured by its pKaH). Using equations (1), (2), and (3), similar graphs could be prepared for other temperatures (using appropriate values of the equilibrium constants) and/or other pressures of CO2. This information removes guesswork associated with designing and/or selecting switchable compounds.

If switchable compounds are bonded to insoluble materials such as linen, then trends will be similar but the numbers may not be exactly the same. The exact numbers may not be the same because, in cases where the switchable compounds are not completely dissolved in an aqueous phase, the system midpoint and the aqueous midpoint may differ. As before, the best switchable functional group to choose is one that will ensure that pH without C0₂ and pH with C0₂ are on opposite sides of the system midpoint; but, in cases of partial or complete insolubility, the system midpoint may differ from the aqueous phase midpoint. [00333] EXAMPLE 1 B: Preparation of 1 -(3-Aminopropyl)imidazole Functionalized CNC (CNC-APIm)

[00334] 600.0 mg of CNC (1 1 .1 mmol of total hydroxyls) was mixed with 12 mL of anhydrous DMSO. The mixture was then vortexed at 3000 rpm until CNCs were completely dispersed. To the dispersion, 24 mL of DCM was added and the mixture was vortexed again. The mixture was subjected to centrifugation (15000 g force, 20 ^°C, 15 min). A resulting centrifugation cake of CNC was redispersed into 40 mL of DCM.

[00335] Afterwards 899.9 mg (5.6 mmol) of CDI, dissolved in 18 mL DCM, was added to the CNC dispersion. The dispersion was then stirred, warmed to 25 ^°C by a water bath. After 2 h stirring, 1387.5 mg (1 1 .1 mmol) of APIm was slowly added to the CNC dispersion over 1 min with vigorous stirring. The reaction mixture was then stirred at 25^°C for another 6 h and then centrifuged (15000 g force, 20^°C, 15 min).

[00336] The resultant cake was redispersed into 60 mL of absolute ethanol and vigorously stirred overnight at room temperature. This dispersion was then centrifuged (15000 g force, 20 ^°C, 6 min), and the resultant cake was vortexed with 60 mL of absolute ethanol for 6 min (3 times at 3000 rpm for 2 min each, with 30 s intervals) before being centrifuged (15000 g force, 20^°C, 6 min).

[00337] This dispersion-into-ethanol-with-vortex-and-centrifugation process was repeated until the centrifugation supernatant became turbid. The resultant cake (CNC-APIm) was redispersed into ca. 20 mL of deionized water (DIW) and dialyzed (cellulose dialysis tubing cut-off size: 14000 Da) against 950-1000 ml of DIW at 40 ^°C, with the DIW changed 2~3 times daily for around 10 days until pH and conductivity of the DIW reservoir stabilized.

[00338] The dialysis-purified CNC-APIm dispersion was then centrifuged (15000 g force, 20 ^°C, 30 min), and then the resultant cake was vortexed with 30 mL of DIW for 15 min (5 times at 3000 rpm for 3 min each, with 30 s intervals) before another centrifugation (15000 g force, 20 ^°C, 30 min). This centrifugation-vortex-centrifugation process was repeated until supernatant tubidity became such that further centrifugation could have caused substantial loss of samples.

[00339] Finally, the thoroughly purified CNC-APIm was redispersed into 40 mL of DIW with 15 min vortex (3 min by 5 times at 3000 rpm with 30 s intervals) and stored at 4 ^°C in a fridge as stock dispersion. Before each characterization, part of CNC-APIm stock dispersion was vortexed (2 min by 3 times at 3000 rpm with 30 s intervals), sparged with CO2 for at least 15 min, and centrifuged briefly (15000 g force, 20°C, 1 min) to remove a small amount of floating particles. Then the supernatant, used as prepared or diluted with carbonated DIW, was characterized or used for experiments.

[00340] EXAMPLE 1 C: Calculation of Surface Imidazole and Sulfate Densities

[00341 ] Elemental analysis data (Table 2) demonstrated that two CNC-APIm samples were consistent, suggesting high reproducibility of the CNC-APIm preparation and purification procedures as described above; and, S concentrations for native CNC and CNC- APIm were similar, indicating that sulfate groups were not likely significantly hydrolyzed after CNC-APIm preparation and purification processes. According to TEM images (Figure 5), native CNC and CNC-APIm showed similar lengths, ranging from around 100 nm to 300 nm, and diameters of ca. 10 nm. Treating CNC as a nanorod with a square cross-section, assumptions were made before conducting an approximate calculation of APIm and sulfate densities on a CNC surface:

1 . Both CNC and CNC-APIm were nanorods with a square cross-section of 7.1 nm χ 7.1 nm (diagonal: 10 nm), having non-reactive ends;

2. Any cross-section of CNC and CNC-APIm, along an axial direction, was packed with cellulose Ιβ unit cells in an identical pattern, where these cellulose unit cells, as determined by X-ray diffraction [Sugiyama, J. ; Vuong, R.; Chanzy, H.

Macromolecules 1991 , 24, 4168-4175], had cross-sectional dimensions of 0.61 nm x 0.54 nm in directions parallel to two sides of CNC square cross-section

[Habibi, Y.; Chanzy, H.; Vignon, M. R. Cellulose 2006, 13, 679-687];

3. Anhydrous glucose units (AGUs) were evenly distributed on four sides of each cellulose unit cell with two ends having no AGU;

4. Sulfate remained intact after the APIm coupling reaction;

5. CNC-APIm had same density as native CNC, which was around 1 .6x 10 ²¹ g/nm³ [Habibi, Y.; Lucia, L. A.; Rojas, O. J. Chem. Rev. 2010, 110, 3479-3500; Majoinen, J.; Walther, A.; McKee, J. R.; Kontturi, E.; Aseyev, V.; Malho, J. M.; Ruokolainen, J.; Ikkala, O. Biomacromolecules 2011 , 12, 2997-3006].

[00342] It was assumed that, if a 1 nm length (one unit volume) of CNC-APIm was taken (side of cross-section = 7.1 nm, as determined in above assumption), its volume and surface area would be 50.4 nm³ and 28.4 nm², respectively. In the elemental analysis results (Table 2), an average of two CNC-APIm measurements was used for this calculation. So, imidazole and sulfate molarities in one unit volume were calculated to be

(50.4x 1 .6x 10-²¹) x3.75%/42=7.20x 10^"23 mol, and

(50.4x 1 .6x 10^"21) x0.72%/32= 1 .81 x 10 ²³ mol, respectively. Assuming that all of these groups were at the surface, it was found that:

Surface imidazole density: 1 .53 units/nm²

Surface sulfate density: 0.38 units/nm².

[00343] In the same unit volume of CNC-APIm, there was calculated to be

(50.4x 1 .6x 10^"21)/162=4.98x 10-²² mol of AGUs.

[00344] The CNC-APIm surface cellulose units accounted for approximately

2x[(7.1 /0.61 +7.1 /0.54)-2]/[7.1 x7.1 /(0.61 x0.54)]=0.3 (30%) of the total mass. Consequently:

Surface AGU to imidazole molar ratio: 4.98χ 10-²²χ0.3/(7.20χ 10^"23)=2.08; Surface AGU to sulfate molar ratio: 4.98x 10-²²x0.3/(1 .81 x 10^"23)=8.25.

[00345] Overall Results and Discussion

[00346] A one-step 1 , 1 '-carbonyldiimidazole (CDI)-mediated coupling with 1 -(3- aminopropyl)imidazole (APIm) was used to chemically immobilize imidazole functionalities onto a CNC surface (CNC-APIm's; Figure 1 ) [Liebert, T. F.; Heinze, T. Biomacromolecules 2005, 6, 333-340]. Imidazole functionality has been used for preparations of C0₂-switchable polymers and surfactants [Quek, J. Y.; Roth, P. J.; Evans, R. A.; Davis, T. P. ; Lowe, A. B. J. Polym. Sci., Part A: Polym. Chem. 2013, 57, 394-404; Chai, M. F.; Zheng, Z. B.; Bao, L; Qiao, W. H. J. Surfactants Deterg. 2014, 77, 383-390].

[00347] The modified CNC-APIm's structure was confirmed by DRIFT-IR (Figure 3): a strong carbonyl absorption band (C=0 stretching) was observed at ca. 1710 cm ¹ ; a typical amide II absorption (N-H bending) was observed at ca. 1550 cm ¹ ; and, a C-0 stretching band was observed at ca. 1268 cm ¹. These IR bands were not observed for native CNC, suggesting that APIm was chemically immobilized onto the CNC surface hydroxyl groups, forming carbamate linkages.

[00348] A C0₂-switchable aggregation/redispersion mechanism of CNC-APIm is depicted in Figure 2: imidazole functionalities on the CNC surface, with a pK_aH 6.0~6.5 [Kim, T.; Rothmund, T.; Kissel, T.; Kim, S. W. J. Control. Release 2011 , 752, 1 10-1 19; Lin, W.; Kim, D. Langmuir 2011 , 27, 12090-12097], formed charged, bicarbonate salts with C0₂ in an aqueous environment; sparging with N₂ through the dispersion reversed the bicarbonate formation, thereby removing the charge from the imidazole group.

[00349] CNC surface sulfate groups were not removed since it was an additional step, which would have added to process costs and lowered product yields. The CNC surface imidazole density was higher than the sulfate density (see Table 2, as well as calculation of surface imidazole and sulfate densities in Example 1 B). Therefore, upon exposure to C0₂, the imidazole rings' positive charge exceeded the sulfate's negative charges, and yielded a positively charged CNC-APIm. When C0₂ was removed, neutral hydrophobic propyl- imidazole gave rise to aggregation of CNC-APIm, due to a combined effect of surface hydrophobicity and a decrease in surface charge.

[00350] CNC-APIm dispersions exhibited reversible C0₂-switchable behaviours (Figure 4). Under a C0₂ atmosphere of, CNC-APIm's zeta potential was 55~60 mV due to formation of imidazolium bicarbonate salts; N₂ sparging reduced that zeta potential to 20~35 mV.

[00351 ] For colloidal dispersions, a zeta potential of less than 30 mV (absolute value) can give rise to the destabilization of the system [Freitas, C; Muller, R. H. Int. J. Pharm. 1998, 768, 221-229]. Under a N₂ atmosphere, CNC-APIm's zeta potential was approximately 30 mV or lower (Figure 4), which led to flocculation into macroscopically visible aggregates (Table 3; Figures 5A and 5B). Turbidity measurements also demonstrated the reversible C02-switchability of CNC-APIm (Figure 4b). In the presence of CO2 and N2, % transmittance of CNC-APIm dispersions continuously switched between around 80% and 20%, suggesting reversible transitions between a transparent dispersion and a turbid dispersion containing macroscopically visible aggregates. Transmittance of CNC-APIm dispersions returned to a consistent level (78~83%) after sparging C0₂, suggesting reversible switching of the CNC- APIm from an aggregated to a dispersed state.

[00352] Dynamic light scattering (DLS) was used to provide a relative measure of CNC particle sizes. The DLS software functioned by calculating a spherical equivalent diameter; while this was not considered an accurate measure of an anisotropic material like CNC, it was useful for monitoring size changes attributed to processes such as aggregation and redispersion.

[00353] CNC-APIm experienced a relatively large, but reversible change in particle size when C0₂ was added or removed (Table 3): dispersed CNC-APIm (under C0₂) had a Z-average size of 201 nm; after N₂ sparging, it increased to several tens of microns

(macroscopically visible aggregates). After 6 cycles of C0₂/N₂ sparging, the CNC-APIm still retained dispersibility (no macroscopically visible aggregates under C0₂). No sonication, vortex or stirring was used during these tests for either native CNC or CNC-APIm; reversible size and zeta potential changes for CNC-APIm were observed by alternatively sparging with

[00354] Native CNC particles differed from CNC-APIm in responsiveness to C0₂ (Table 1). Sulfate groups on native CNC surface did not respond to C0₂ stimuli due to its weak basicity, as shown by a lack of response when CO2 and then N2 were sparged through dispersions of native CNC. Native CNC remained well dispersed throughout three C0₂/N₂ sparging cycles, with Z-average sizes staying between 130~160 nm. Particle size varied slightly with each sparging cycle, but there was no apparent evidence of C0₂-switchability. It was noted that CNC-APIm's original size was a larger than the native CNC (Zeta-average size: 201 vs. 159 nm).

[00355] Following the dialysis process (see Example 1A), repeated centrifugations were performed to further purify CNC-APIm. The centrifugation supernatants discarded in the repeated centrifugations contained ca. 15~20% of the total CNC-APIm; without wishing to be bound by theory, it was considered that centrifuging the samples may have separated heavier (read: larger) particles from lighter (read: smaller) particles. Consequently, discarded supernatant was analyzed and found to have a smaller particle size than the CNC-APIm that settled during centrifugation (Zeta-average size: 167 nm); it was observed that these smaller particles also exhibited reversible C0₂-switchability (Table 4).

[00356] CNC-APIm dispersion/aggregation behavior with varying sparging times was also investigated (Table 5). Only 30 seconds of CO2 sparging was needed to convert macroscopically visible aggregates of CNC-APIm to a dispersion without visible aggregates. For the reverse process, as N2 was sparged through fully dispersed CNC-APIm, the zeta potential decreased, and continued to decrease even after 20 minutes. It was observed that the Z-average particle size showed little change as the zeta potential decreased from 57 mV to 47 mV. However, when the zeta potential approached ca. 35 mV, particle size rose to over 10 μητι and the CNC-APIm dispersion showed macroscopically visible aggregates. After a total of 20 min of N₂ sparging, the zeta potential was reduced to 31.7 mV. Lowest zeta potential achieved was ca. 20 mV (after 30 min N₂ sparging at 50°C), suggesting that there were still some charged surface imidazoles after N₂ sparging. This was found to be consistent with previous observations using amidine-based switchable surfactants to stabilize polymer colloids [Fowler, C. I.; Jessop, P. G.; Cunningham, M. F. Macromolecules 2012, 45, 2955-2962].

[00357] C0₂-switchability and sedimentation of aggregates were studied over a wide range of concentrations (0.02-10 mg/ml; Figures 5A and 5B). All CNC-APIm dispersions, regardless of concentration, showed C0₂-switchability upon being alternatively exposed to C0₂ and N₂, while native CNCs had no visible responsiveness to C0₂. Even a CNC-APIm dispersion with a concentration as low as 0.025 mg/ml formed aggregates that settled out of solution within ~60 min after sparging N₂ (Figure 5A (a)).

[00358] At a concentration approximately 5.5 mg/ml or above, CNC-APIm showed reversible dispersion/gelation properties upon alternating exposure to C0₂ and N₂ (Figures 5A (e) and (f)). Without wishing to be bound by theory, it was considered that this dispersion/gelation property followed a hydrogen-bonding-driven mechanism: well-dispersed charged CNC-APIm surfaces (under C0₂) would not promote formation of hydrogen-bonding among surface hydroxyls; however, upon aggregation (under N₂), surface hydroxyls would be brought into close proximity with hydroxyls on adjacent nanocrystals, which could lead to network formation and gelation. Such a gelation process was expected to be concentration- dependent, given that a minimum particle density would likely be required for gel formation. It was found that the "gelation concentration" of CNC-APIm dispersions was approximately 5.5-10 mg/ml. [00359] The hydrogen-bonding-driven gelation process was similar to Weder et al.'s findings [Capadona, J. R.; Shanmuganathan, K.; Tyler, D. J.; Rowan, S. J.; Weder, C.

Science 2008, 319, 1370-1374]; wherein, switching hydrogen-bonding "on" or "off among CNCs by removal or addition of water enabled formation of, or breaking of, CNC percolating networks. This led to stiffness changes in the CNC nanocomposites. Figure 5A (d) depicts images where CNC-APIm (0.25 mg/ml dispersion) aggregated and sedimented relatively quickly (under N₂): within 16 min, the CNC-APIm settled, leaving a clear transparent upper layer. For CNC-APIm dispersions with higher concentrations, settling was observed to occur in a similar manner within a similar time frame; for the 0.025 mg/ml dispersion, it took longer (approximately one hour) for complete sedimentation.

[00360] 1 -(3-Hydroxypropyl)-1 H-imidazole (HPIm) was used as a model for APIm to estimate, by ¹H NMR spectroscopy, a fraction of protonated imidazole groups under C0₂ and N₂, respectively, so that an estimate of CNC-APIm surface charge density could be obtained (Figure 6). Presaturation was used for water signal suppression, and it was found that all chemical shifts obtained with and without presaturation were identical (Figure 6A). Fortunately, the water peak did not overlap or interfere with HPIm peaks. Therefore, all calculations were based on the original ¹H NMR spectra without applying presaturation.

[00361 ] Chemical shifts of three protons on the HPIm imidazole ring were used to calculate the degree of protonation of imidazole under C0₂ and N2, using a method described previously [Fowler, C. I. ; Jessop, P. G. ; Cunningham, M. F. Macromolecules 2012, 45, 2955-2962; Scott, L. M.; Robert, T.; Harjani, J. R.; Jessop, P. G. RSC Adv. 2012, 2, 4925-4931 ]. Under the aformentioned experimental conditions (15 mg/ml HPIm in 90% H2O + 10% D₂0 as solvent), data showed that up to 94% of imidazole rings could be protonated upon exposure to CO2, while sparging with N2 decreased degree of protonation down to 26% (Table 6). All three protons examined on the imidazole ring showed decent reversibilities, i.e. sparging N₂ restored the chemical shifts to near their original values (Figure 6 and Table 6). This observation was consistent with the reversible zeta potential and particle size changes discussed above. NMR measurements and calculations were based on HPIm's solution properties; while it was recognized that this was unlikely to be exactly the same as on a CNC surface, it was considered a reasonable qualitative representation of APIm behaviour on a CNC surface.

[00362] Transmission electron microscope (TEM) images of native CNC and CNC- APIm are presented in Figure 7. CNC-APIm showed similar dimensions and morphologies to those of native CNCs, which suggested that the CNC crystalline structure was preserved after the CDI-mediated coupling reaction with APIm. Particle size information from TEM images, together with elemental analysis data (Table 2), was used to obtain an approximate estimate of CNC-APIm surface imidazole and sulfate densities (see Example 1 B). The calculated surface imidazole and sulfate densities were 1.53 units/nm² (surface anhydrous glucose units to imidazole molar ratio: 2.1) and 0.38 units/nm² (surface anhydrous glucose units to sulfate molar ratio: 8.3), respectively.

[00363] Taking into consideration the degree of protonation data as measured by NMR spectroscopy the model compound (Table 6), the surface imidazole charge density after sparging C0₂ (94% charged imidazole) was 1.44 e/nrti², and thus net surface charge was 1.06 e/nm². After sparging N₂, only 26% of the surface imidazole groups were charged (Table 6), with surface imidazole charge and net charge densities decreasing to 0.4 e/nm² and 0.02 e/nm², respectively. This suggested a surface charge difference between C0₂ and N₂ sparged CNC-APIm dispersions, which was consistent with the above findings on zeta- potentials and sizes of CNC-APIm (Figure 4 and Table 3).

[00364] Conclusions

[00365] Described herein is a one-step approach for preparation of switchable CNCs that reversibly respond to C0₂/N₂ stimuli. The prepared CNC-APIm showed fast and reversible C0₂ switchable dispersion behaviours (no sonication, vortex, or stirring was used for re-dispersion of CNCs), while CNC-APIm dispersions with higher concentrations (5.5-10 mg/ml) were switched between gels and dispersions. It was considered that the herein described C0₂-switchable CNCs could have potential in applications such as C0₂- switchable adsorbents or flocculants, taking advantage of their high specific surface area.

[00366] EXAMPLE 1 D: Synthesis and Characterization of C0₂ Responsive Crystalline Nanocellulose-g-Poly(alkylethylaminoethyl methacrylate) by Copper (0) mediated atom transfer radical polymerization (Cu°-ATRP) with DMAEMA and DEAEMA

[00367] Materials:

[00368] 2-(Diethylamino)ethyl methacrylate (DEAEMA; Aldrich, 99%), 2- (Dimethylamino)ethyl methacrylate (DMAEMA; Aldrich, 99%), were dried in calcium hydride (Aldrich, 95%), and distilled under vacuum to remove inhibitor. Copper (II) bromide (CUBr₂; Aldrich, 99%), copper wire (Aldrich, gauge 40), 2-bromo-2-methyl propionic acid (Aldrich, 98%), 1 , 1 ,4,7, 10, 10-Hexamethyltriethylenetetramine (HMTETA; Aldrich, 97%) 1 , 1 '- carbonyldiimidazole (CDI; Aldrich, reagent grade), chloroform-D (Aldrich, 99.8 atom % D, 0.03 % (v/v) TMS), methanol (APC, 99.8%), Acetone (APC, 99%), were used as received. Dichloromethane (APC, 99%) dimethyl sulfoxide (APC, 99%) were dried under calcium hydride (Aldrich, 95%) and distilled under nitrogen atmosphere and vacuum respectively. Crystalline nanocellulose (CNC) was provided by FP Innovations. Nitrogen gas (UHP 5.0) was acquired from Praxair Inc. Water used in this project was in-house water (18.2 ΜΩ-cm) passed through a Millipore Synergy water purification system equipped with SynergyPak purification cartridges

[00369] Instrumentation:

[00370] Solid state ¹³C cross polarized magic angle spinning nuclear magnetic resonance (CP-MAS NMR) spectroscopy was performed on an FT-NMR Bruker Avance 600 MHz spectrometer with a total of 3000 scans, at room temperature at 12KHz. Fourier Transform Infrared (FT-IR) spectroscopy was carried out on a Bruker ALPHA FT-IR with an ATR accessory with a total of 64 scans and a resolution of 8 cm ¹. X-ray Photoelectron Spectroscopy (XPS) spectra were measured on a Microlab 310-F spectrometer equipped with an XR-4 twin anode (Al/Mg); manufacturer of this system was VG Scientific; samples were mounted on a stub-type stainless steel holder using double-sided adhesive Cu tape and kept under high vacuum (10^~8 mbar) overnight inside a preparation chamber before being transferred into an analysis chamber (10 ⁹ mbar) of the spectrometer; XPS data were collected using MgKa radiation at 1253.6 eV (280 W, 14 kV) and a spherical sector analyzer (SSA) operating in CAE (constant analyzer energy) mode; binding energies were referred to a C1 s peak at 284 eV; survey spectra were recorded from -5 to 1000 eV at a pass energy of 40 eV; high resolution spectra were measured for C1 s, 01 s, and Br3d in an appropriate region at a pass energy of 20 eV; samples were analyzed in triplicate at different locations. Elemental analysis was performed on a Perkin Elmer 2400 Series II CHNS/O System in CHN mode using Argon as carrier gas.; acetanilide was used as a calibration standard; all the samples were freeze-dried before analysis. Atomic Force Microscope (AFM) images were taken using a Bruker Nanoscope IV multimode scanning probe microscope with an E scanner in tapping mode using silicon nitride cantilevers with a resonance frequency of 200 - 400 kHz, spring constants of 13-77 N/m, and a tip radius <10 nm. Thermogravimetric analysis (TGA) was performed using a TA Instruments Q500 TGA analyser by heating a sample using the following ramp: 10°C min ¹ from 30 to 75°C, held for 15 min at a plateau of 75°C, with a subsequent temperature ramp at 10 °C min ¹ up to 600°C. [00371 ] Synthesis of bromine functionalized cellulose nanocrystals (CNC-Br):

[00372] CNC-Br was synthesized following a methodology published by Wang, Hai- Dong et al. [Wang, H.-D.; Jessop, P.; Bouchard, J.; Champagne, P.; Cunningham, M., Cellulose 2015, 22 (5), 3105-31 16] applying a few minors modifications (Figure 50).

Carbonyl diimidazole (CDI) (18 g, 1 1 1 .5 mmol) was added to a 250 mL three-necked round- bottom flask (14/20) with an attached 60 mL addition funnel (14/20), and 15 mL of fresh distilled anhydrous dichloromethane (DCM) was added via cannula (61 cm long, gauge 18). 2-Br-2-methyl propionic acid (BMPA) (18.53 g, 1 1 1 mmol) was dissolved in 30 mL of fresh distilled anhydrous DCM in a septum-sealed 250 mL single necked round-bottom flask, the solution then being transferred to the 60 mL addition funnel via cannula using nitrogen gas flow. The solution was added drop-wise to the CDI-containing flask via constant magnetic stirring using an egg-shaped stir bar (size: 1 .90 x 0.95 cm) under nitrogen atmosphere at room temperature. The reaction was stopped after 4h when it stopped releasing C0₂ as a by-product, maintaining the solution under inert atmosphere (Pot 1).

[00373] Following the initial reaction between CDI and BMPA, 2.2 g (37 mmol OHs) of CNC were divided into two portions (1 .1 g / portion), and each portion was dispersed in 20 mL of freshly distilled anhydrous DMSO and stirred with a vortex agitator in a 50 mL centrifuge tube until the CNC was completely dispersed. Then, freshly distilled anhydrous DCM (30 mL) was added to each CNC dispersion tube, then vortexed again and centrifuged (6,000 rpm) and finally decanted. The resultant CNC cake was re-dispersed in 30 mL of dry DCM (each tube) and then transferred with a cannula (61 cm long, gauge 12) to a three- necked round bottom flask (14/20) equipped with a 60 mL addition funnel, a condenser and an egg-shaped stir bar (size: 1 .90 x 0.95 cm) (Pot 2).

[00374] Pot 1 solution was transferred via cannula to the addition funnel attached to Pot 2 containing dispersed CNC in DCM. Pot 1 solution was then added drop-wise under constant magnetic stirring under nitrogen atmosphere at room temperature. Then the reaction was stirred for three days, followed by a solvent exchange process with acetone: the final dispersion was separated equally into 50 mL centrifuge tubes, and centrifuged at 6000 rpm for 30 min; each tube containing a CNC cake was decanted, and 30 mL of acetone was added; each tube was vortexed using a vortex mixer, and then centrifuged at 6000 rpm; this process was repeated three times. The final CNC cake recovered from each centrifuge tube was put into a coarse frit glass thimble inside a soxhlet apparatus, and left under constant acetone reflux for five days to remove any excess reactants and side products. After the soxhlet extraction, the isolated product was stored in ethanol at 4°C, and a portion of the sample was freeze-dried for solid-state NMR, FT-IR, XPS and TGA analysis (see Figures 52, 53, 54 and Table 21).

[00375] Grafting-from approach by Cu°-ATRP with DMAEMA and DEAEMA:

[00376] A grafting-from approach off CNC with DMAEMA/DEAEMA was based on a previous publication of our research group [Wang, H.-D.; Roeder, R. D. ; Whitney, R. A. ; Champagne, P.; Cunningham, M. F. , Journal of Polymer Science Part A: Polymer Chemistry 2015, 53 (24), 2800-2808] with modification (Figure 51). CNC-Br (0.303 g, 0.23 mmol Br determined by XPS) was added into a 250 mL round bottom flask containing 100 mL of MeOH, and sonicated until there were no visible CNC aggregates in suspension. Afterwards, the suspension was transferred via cannula (61 cm long, gauge 12) into a 250 mL Schlenk round-bottom flask equipped with an egg-shaped stir bar (size: 1 .90 x 0.95 cm), followed by 3 mL of CuBr₂ for a final CuBr₂ concentration of 100 ppm, and then by 1 mL of 1 , 1 ,4,7, 10, 10- Hexamethyltriethylenetetramine (HMTETA) and DMAEMA (2 g, 12.72 mmol) or DEAEMA (2.35 g, 12.72 mmol). Additionally, three, 1 cm length copper wires (14 gauge, wires were pretreated with HCI 35% and rinsed with methanol) were added. Finally, the Schlenk round- bottom flask was degassed via three freeze-pump-thaw cycles, sealed under vacuum, and put in an oil bath at 60°C for 24h. After the specified reaction time, resultant product was allowed to sediment and the methanolic solution was removed via cannula under argon atmosphere to prevent Cu¹⁺ from oxidizing and staining the final product. More degassed methanol was added to wash the product via cannula under constant Argon flow, and was removed via cannula after washing. Finally, the product was stored in methanol at 4 °C to avoid bacteria growth and a small portion was freeze-dried for characterization.

[00377] Results:

[00378] CNC-Br was obtained via an esterification reaction using carbonyl diimidazole (CDI) as a coupling agent. Different batches of bromine functionalized CNC (CNC-Br) were made with good reproducibility with respect to bromine content. Esterification of two different batches were qualitatively compared by CP-MAS ¹³C NMR: signals compared included a signal corresponding to the ester's carbonyl (170 ppm), and a signal corresponding to an anomeric carbon from the cellulose backbone (120 ppm). It was found that the intensities for these signals were similar across each batch of bromine functionalized CNC, suggesting that esterification had been successful for both batches (Figure 52). FT-IR analysis further supported that esterification of the CNC surface had been successful, as a carbonyl stretching band of an ester group was observed at ~1 ,770 cm ¹ (Figure 53).

[00379] Surface bromine content of three different CNC-Br batches was determined by XPS (Table 21). Figure 54 depicts a low-resolution XPS spectrum of CNC-Br, wherein typical signals of carbon and oxygen elements were observed. The bromine presence on the CNC surface was further supported by a Br signal appearing at a binding energy of 70.5 eV.

[00380] CNC-Br was grafted with PDMAEMA and PDEAEMA via a Cu°-ATRP approach. Figure 55 depicts a CP-MAS ¹³C NMR of both CNC-g-PDMAEMA and CNC-g- PDEAEMA grafted products, where the presence of characteristic polymer signals are evident, such as an ester group of the methacrylate ester (177 ppm), aliphatic carbons (40 and 50 ppm), and the cellulose backbone.

[00381 ] To determine whether grafting occurred on the CNC surface, and that the above-referenced NMR spectrum did not represent a physical mixture of functionalized CNC with free polymer, final products were analyzed by TGA. Figure 56 depicts a thermogram of native CNC, CNC-Br, CNC-g-PDMAEMA and CNC-g-PDEAEMA. It was observed that CNC- Br decomposed at 200°C with no subsequent onset temperatures, and native CNC decomposed at 300°C. Both grafted products did not show starting material decomposition at 200°C, suggesting that the grafted products did not contain CNC-Br, as they

demonstrated different thermal behaviour than either CNC-Br or native CNC.

[00382] To determine amount of polymer grafted to the CNC surface, grafted products were analyzed by elemental analysis. Weight percent of grafted polymer per gram of CNC (dry wt. basis) was then calculated based on nitrogen content obtained by elemental analysis, as reported elsewhere [Hemraz, U. D.; Campbell, K. A.; Burdick, J. S.; Ckless, K. ; Boluk, Y.; Sunasee, R., Biomacromolecules 2015, 76 (1), 319-325.] Table 22 delineates elemental composition of different materials, indicating presence of nitrogen coming from the polymeric grafts attached to the CNC surface, as well as an increase in carbon and hydrogen content as compared to native CNC.

[00383] AFM analysis was performed on PDEAEMA-g-CNC. Figure 57 shows both micrographs of native CNC (a) and PDEAEMA-g-CNC (b). In micrograph (a), well-defined nanorod shapes of native CNC were observed. In micrograph (b), PDEAEMA-g-CNC was shown, and while CNC nanorods were observed, similar to those observed for the unmodified CNC, several of the nanocrystals surfaces comprised observable surface abnormalities; there were presumed to be associated with polymeric material (PDEAEMA) grafted onto the CNC surface.

[00384] EXAMPLE 1 E: Synthesis and Characterization of C0₂ Responsive Crystalline Nanocellulose-g-Poly(alkylethylaminoethyl methacrylate) by Reversible

Addition-Fragmentation Chain-Transfer (RAFT) Polymerization approach

[00385] Materials:

[00386] 2-(Diethylamino)ethyl methacrylate (DEAEMA; Aldrich, 99%), 2- (Dimethylamino)ethyl methacrylate (DMEAEMA; Aldrich, 99%), were dried in calcium hydride (Aldrich, 95%), and distilled under vacuum to remove inhibitor. 1 , 1 '- carbonyldiimidazole (CDI; Aldrich, reagent grade), phenyl magnesium bromide (Aldrich, 1 M in THF), carbon disulfide anhydrous (Aldrich, 99.9%), potassium ferricyanide (III) (Aldrich, 99%), 4,4'-Azobis(4-cyano pentanoic acid) (V-501) (Aldrich, 98%), sodium hydroxide (Aldrich, 97%), silica gel (Aldrich, 60 A 70-230 mesh), chloroform-D (Aldrich, 99.8 atom % D, contains 0.03 % (v/v) TMS), methanol (APC, 99.8%), ethanol (CA, absolute), acetone (APC, 99%), dimethyl formamide (APC, 99%), ethyl acetate (ACP, 99%), n-hexanes (ACP 98.5%), tetrahydrofuran (ACP, 99%) were used as received. Dichloromethane (APC, 99%) dimethyl sulfoxide (APC, 99%) were dried under calcium hydride (Aldrich, 95%) and distilled under nitrogen and vacuum respectively. Nitrogen and argon gas (UHP 5.0) were acquired from Praxair Inc. Crystalline nanocellulose (CNC) was provided by FP Innovations. Water used in this project was in-house water (18.2 ΜΩ-cm) passed through a Millipore Synergy water purification system equipped with SynergyPak purification cartridges.

[00387] 4-cyano-4-((phenylcarbonothioyl)thio)pentanoic acid was synthesized as follows using a combined procedure as reported elsewhere [Mitsukami, Y.; Donovan, M. S.;

Lowe, A. B.; McCormick, C. L, Macromolecules 2001 , 34 (7), 2248-2256; Wager, C. M.;

Haddleton, D. M.; Bon, S. A. F., European Polymer Journal 2004, 40 (3), 641 -645]: 100 ml of phenyl magnesium bromide in tetrahydrofuran (THF) (0.1 mol) was transferred via cannula

(61 cm long, gauge 16) to a 250 mL a three-necked round bottom flask (14/20) equipped with an egg-shaped stir bar (size: 1 .90 x 0.95 cm) previously torched under vacuum, and it was then submerged in an ice bath. Then 6.6 mL (0.1 1 mol) of carbon disulfide was added drop-wise with a gas-tight syringe and it was left under magnetic stirring for two hours.

Deionized water (5 mL) was added to quench the reaction. The solution was concentrated on a rotary evaporator, and then diluted with 100 mL of deionized water. HCI (35%) was then added until the solution turned from brown to purple. The final solution was extracted three times with dichloromethane (DCM) and concentrated on a rotary evaporator. To the resultant purple oil, 600 mL of sodium hydroxide (NaOH) 1 M was added, and the final solution was divided into two 500 mL round bottom flasks equipped with an octagonal magnetic stir bar (0.8 x 1.2 cm).

[00388] To each round bottom flask, 32.93 g (0.1 mol) of potassium ferricyanide (III) dissolved in 250 mL of deionized water, was added drop-wise via an addition funnel under vigorous stirring for 2h. A resultant red precipitate was filtered and washed with deionized water until the washing liquors were colorless. The resultant red product was dried under vacuum at room temperature and recrystallized from ethanol. Once recrystallized and dried, 14.3 g of the red product was added to a 500 mL round bottom flask equipped with an egg- shaped stir bar (size: 1.90 x 0.95 cm) along with 14.5 g (51.7 mmol) of V-501 dissolved in 350 ml of ethyl acetate. A condenser (14/20) was attached to the round bottom flask, and the reaction was heated at reflux using a heating mantle for 18h. The ethyl acetate was then removed under vacuum. The resultant crude product was purified through column chromatography (silica gel 60 A 70-230 mesh) using ethyl acetate: hexane 1 :1 as eluent. Red purple fractions were collected and concentrated under vacuum. The resultant red oil product was placed in a freezer (-4°C) upon which it crystallized. Yield: 82%. ¹H NMR (500 MHz, CDC ) δ 7.92 (d, J = 7.6 Hz, 2H), 7.58 (t, J = 7.4 Hz, 1 H), 7.41 (t, J = 7.8 Hz, 2H), 2.75 (dt, J = 8.9, 6.4 Hz, 2H), 2.64 (ddd, J = 15.8, 9.5, 6.3 Hz, 1 H), 2.46 (ddd, J = 14.5, 10.2, 6.0 Hz, 1 H), 1.95 (s, 3H).

[00389] Instrumentation:

[00390] ¹H NMR spectroscopy was performed using a Bruker Avance 500 MHz spectrometer with a total of 64 scans, at room temperature in CDCI₃. Solid state ¹³C cross polarized magic angle spinning nuclear magnetic resonance (CP-MAS NMR) spectroscopy was performed on an FT-NMR Bruker Avance 600 MHz spectrometer with a total of 3000 scans, at room temperature at 12KHz. Fourier Transform Infrared (FT-IR) spectroscopy was carried out on a Bruker ALPHA FT-IR with an attenuated total reflectance (ATR) accessory with a total of 64 scans and a resolution of 8 cm ¹. Elemental analysis was performed on a Perkin Elmer 2400 Series II CHNS/O System in CHNS mode using helium as carrier gas. 4- Acetyl-N-[(cyclohexylamino)carbonyl]benzenesulfonamide was used as a calibration standard. All samples were freeze-dried before analysis. Thermogravimetric analysis (TGA) was performed using a TA Instruments Q500 TGA analyser by heating a sample using the following ramp: 10°C min ¹ from 30 to 75°C, held for 15 min at a plateau of 75°C, with a subsequent temperature ramp at 10 °C min ¹ up to 600°C.

[00391 ] Synthesis of 4-cyano-4-((phenylcarbonothioyl)thio)pentanoic acid functionalized cellulose nanocrystals (CNC-CTP):

[00392] CNC-CTP was synthesized following a methodology published by Wang, Hai- Dong et al. [Wang, H.-D.; Jessop, P.; Bouchard, J. ; Champagne, P. ; Cunningham, M., Cellulose 2015, 22 (5), 3105-31 16] with a few modifications (Figure 58). Carbonyl diimidazole (CDI) (18 g, 1 1 1 .5 mmol) was added to a 250 mL three-necked round-bottom flask (14/20) with an attached 60 mL addition funnel (14/20), to which 15 mL of fresh distilled anhydrous dichloromethane (DCM) was added via cannula (61 cm long, gauge 18). 4- Cyano-4-((phenylcarbonothioyl)thio)pentanoic acid (CTP) (31 g, 1 1 1 mmol) was dissolved in 30 mL of fresh distilled anhydrous DCM in a septum-sealed 250 mL single necked round- bottom flask, the resultant solution being transferred to the 60 mL addition funnel via cannula using nitrogen gas flow. The solution was added drop-wise under a nitrogen atmosphere at room temperature with constant magnetic stirring via an egg-shaped stir bar (size: 1 .90 x 0.95 cm). The reaction was then stopped after 4h when it stopped releasing C0₂ as a byproduct, while maintaining the reaction under inert atmosphere (Pot 3).

[00393] Following the initial reaction between CDI and CTP, 2.2 g (37 mmol OHs) of CNC were divided into two portions (1 .1 g / portion) and each portion was dispersed in 20 mL of freshly distilled anhydrous DMSO and stirred with a vortex agitator in a 50 mL centrifuge tube until the CNC was completely dispersed. Then, freshly distilled anhydrous DCM (30 mL) was added to each CNC dispersion tube, then vortexed again and centrifuged (6,000 rpm) and finally decanted. The resultant CNC cake was re-dispersed in 30 mL of dry DCM (each tube) and then transferred with a cannula (61 cm long, gauge 12) to a three- necked round bottom flask (14/20) equipped with a 60 mL addition funnel, a condenser and an egg-shaped stir bar (size: 1 .90 x 0.95 cm) (Pot 4).

[00394] Pot 3 solution was transferred via cannula to the addition funnel attached to

Pot 4 containing the dispersed CNC in DCM. Pot 3 solution was then added drop-wise under constant magnetic stirring under nitrogen atmosphere at room temperature. Then the reaction was stirred for three days, followed by a solvent exchange process with acetone, as described above. The final, resultant CNC cake recovered from each centrifuge tube was put into a coarse frit glass thimble inside a soxhlet apparatus, and left under constant acetone reflux for five days to remove any excess reactants and side products. After the soxhlet extraction, the product was stored in ethanol at 4°C, and a portion of the product was freeze- dried for solid state NMR, FT-IR, elemental analysis and TGA analysis, (see Figures 60, 61 , 63 and Table 23)

[00395] Grafting-from approach by RAFT polymerization with DMAEMA and DEAEMA:

[00396] Grafting-from approach off CNC with DMAEMA/DEAEMA was undertaken via RAFT polymerization using CTP as chain transfer agent (CTA) (Figure 59). CNC-CTP (1 g of wet product) was added into a 250 mL Schlenk round bottom flask equipped with an egg- shaped stir bar (size: 1.90 x 0.95 cm), along with 10 mL of MeOH and V-501 (20 mg, 0.07 mmol). The Schlenk flask was degassed by bubbling argon for 30 min. It was then sealed and put in an oil bath at 60°C for 24h. After cooling, the resultant product was washed and subjected to solvent exchange with 30 mL of THF by vortex shaking/centrifuge cycles (6,000 rpm) to remove any free polymer in solution. The resultant final product cake was solvent exchanged with methanol by adding 30 mL of methanol, vortexing the mixture using a vortex mixer, and centrifuging the mixture at 6000 rpm, and decanting to remove solvent. This process was repeated three times, and the final, isolated CNC cake was stored in 30 mL of methanol at 4°C to avoid bacteria growth. A fraction of grafted product was fully dried for analysis purposes.

[00397] Results:

[00398] CNC-CTP was obtained via an esterification reaction using carbonyl diimidazole (CDI) as a coupling agent. Two different batches of CTP functionalized CNC (CNC-CTP) were made, and it was determined that sulfur contents was similar across both batches, suggesting successful functionalization. Figure 60 depicts CP-MAS ¹³C NMR spectra of CNC-CTP and native CNC, where: a signal corresponding to the product's ester carbonyl group was observed at 173 ppm; carbons corresponding to CTP's aromatic ring was observed at 130 ppm; methyl and methylenes carbons were observed at 20-35 ppm; and, cellulosic backbone of CNC which was observed to have not changed as compared to native CNC. FT-IR analysis further supported that esterification of the CNC surface had been successful, as a carbonyl stretching band of an ester group was observed at ~1 ,770 cm ¹ (Figure 61).

[00399] Two different batches of CNC-CTP and native CNC were analyzed by elemental analysis (Table 23) in CHNS mode, where the sample was combusted and the resultant combustion products were detected by thermal conductivity detector to quantitatively analyze the sample. As delineated in Table 23, analysis determined that native CNC had a sulfur content of 0.5%, whereas the two CNC-CTP batches had a sulfur content of approximately 2%. In view of the above-described elemental, FT-IR, and NMR analysis, it was considered that functionalization of CNC with CTP has been successful.

[00400] CNC-CTP was grafted with PDMAEMA via grafting-from approach by RAFT polymerization. Figure 62 depicts FT-IR spectra of both CNC-CTP and polymer-grafted product, showing a considerable increase in intensity of a carbonyl stretching band at 1 ,723 cm ¹, which was indicative of carbonyl groups along the polymeric backbone. Further, the CNC-g-PDMAEMA FT-IR spectrum depicted CH₂- stretching bands at 2,900 cm ¹, which were not present in the CNC-CTP spectrum. Relative intensities of the carbonyl signal with respect to the OH signal intensities at 3,300 cm ¹ were noted: for the grafted material, the carbonyl signal due to its polymeric backbone was relatively more intense than the carbonyl signal of the CNC-CTP, as was expected.

[00401] To confirm that grafting occurred on the CNC surface, and that NMR spectra were not representative of a physical mixture of functionalized CNC with free polymer or free CTP, final products were analyzed by TGA. Figure 63 depicts thermograms of native CNC, CNC-CTP, CNC-g-PDMAEMA, CTP and PDMAEMA. It was observed that CTP decomposed at 167°C with a secondary onset temperature at 209 °C, and that native CNC decomposed at 300°C. TGA analysis of CNC-CTP and CNC-g-PDMAEMA did not indicate the presence of any starting materials (CTP or native CNC), suggesting that CNC had been successfully modified. CTP-functionalized and polymer-grafted materials had different degradation profiles, suggesting successful surface modification. Further, PDMAEMA's thermogram depicted two characteristic onset temperatures at 307 °C and 380 °C, which were shifted to lower temperatures on the grafted CNC, suggesting that they are two different materials.

[00402] To determine amount of polymer grafted to the CNC surface, grafted products were analyzed by elemental analysis. The weight percent (wt.%) of grafted polymer per gram of CNC (dry wt. basis) was then calculated based on nitrogen content obtained by elemental analysis, as reported elsewhere [Hemraz, U. D.; Campbell, K. A.; Burdick, J. S.; Ckless, K.; Boluk, Y.; Sunasee, R., Biomacromolecules 2015, 16 (1), 319-325]. Table 24 delineates elemental composition of the different materials, indicating presence of nitrogen coming from the polymeric grafts attached to the CNC surface, as well as an increase in carbon and hydrogen content compared to the native CNC.

[00403] EXAMPLE 1 F: Microalgae Recovery from Water for Biofuel Production under Environmentally Relevant Conditions Using C02-Switchable Crystalline Nanocellulose

[00404] The herein described C0₂-switchable CNC material, prepared by surface modification with 1 -(3-aminopropyl)imidazole (APIm), became positively charged in the presence of C0₂ due to protonation of the APIm groups by carbonated water. It has been considered this property of the herein described C0₂-switchable CNC material may promote coagulation or attachment of microalgae cells carrying negative charges [D. Vandamme, S. Eyley, G. Van Den Mooter, K. Muylaert, W. Thielemans. Bioresour Technol. 194 (2015) 270- 5]. Further, the herein described the APIm-modified CNC material was found to repeatedly disperse in water in the presence of C0₂, and aggregate with subsequent removal of C0₂ through sparging with N₂. It has thus been considered that the herein described C0₂- switchable CNC material, with its ability to repeatedly disperse/aggregate, could be applied to the microalgal harvesting process.

[00405] Materials and Methods:

[00406] Microalgal Culture:

[00407] A 25 L glass carboy was used to grow C. vulgaris in modified Bold's Basal Medium (MBBM) at room temperature (23.0 ± 0.5°C) [M. Agbakpe, S. Ge, W. Zhang, X. Zhang, P. Kobylarz. Bioresour Technol. 166 (2014) 266-72]. The MBBM contained major ions of Na⁺, K⁺, Mg²⁺, Ca²⁺, Fe²⁺, Zn²⁺, Mn²⁺, Cu²⁺, Co²⁺, H⁺, N0₃ ^" , H₂P0₄ ^" , HP0₄ ^2", B0₃ ^3", SC ^2", CI^", OH^", MOC ^2", and EDTA^2" with a total ionic strength of 10.4 mM. Molarity of each ion is listed in Table 25. Initial solution pH, dissolved oxygen, and oxidation reduction potential of the culture medium were 6.8 ± 1 .0, 12 ± 2 mg-L ¹ , and 170 ± 31 mV, respectively. System was aerated with filtered ambient air (0.039 % C0₂) at a rate of 200 mL min ¹.

Continuous irradiation (27.4 pmoles m ² s ¹) was applied. During cultivation, samples were collected to measure optical density at 680 nm (OD₆8o) using a spectrophotometer (Hach Method 8171) [Z. Arbib, J. Ruiz, P. Alvarez-Diaz, C. Garrido-Perez, J.A. Perales. Water Res. 49 (2014) 465-74]. Biomass concentration (g L ¹) was gravimetrically quantified by dry cell weights (DCW), which was performed by drying 0.45 μιη membrane-filtered microalgae in an oven at 105 °C to a constant weight [M. Agbakpe, S. Ge, W. Zhang, X. Zhang, P. Kobylarz. Bioresour Technol. 166 (2014) 266-72]. [00408] Preparation and characterization of APIm-modified CNC:

[00409] Native CNC was provided by FPInnovations, Canada. APIm-modified CNC was synthesized as described above, using 1 , 10-carbonyldiimidazole (CDI, reagent grade, Sigma-Aldrich) and 1 -(3-aminopropyl)imidazole (APIm,≥ 97 %, Sigma-Aldrich). Zeta potentials, average hydrodynamic diameters, and particle size distributions (PSD) of both native and APIm-modified CNC suspended in water, under various experimental conditions mentioned below, were characterized at 25 °C by dynamic light scattering (DLS) on a Zetasizer Nano ZS instrument (Malvern Instruments, UK) using DTS 160 disposable folded capillary cells. Refractive indices of 1.500 and 1 .347 were used, respectively, for APIm- modified CNC and C. vulgaris cells for calculating the scattering wave vector.

[00410] Microalgae separation with APIm-modified CNC:

[0041 1 ] Harvesting experiments began once C. vulgaris had reached their exponential growth stage. APIm-modified CNC stock dispersion in water (~10.5 g-L \ 35 mL) was vortexed (3 times at 3000 rpm for 2 min each, with 30 s intervals), sparged with CO2 (99.995%, MEGS) for 10 min, and briefly centrifuged (15,000 xg, 20°C, 1 min) to remove floating particles. Then supernatant containing well-dispersed APIm-modified CNC was mixed into a 20 mL suspension of C. vulgaris in a 50 mL glass specimen bottle or falcon tube at room temperature with an initial microalgal concentration of 0.2-0.4 g-L¹. Afterwards, C0₂ was sparged into the suspension for 1 min. After sparging with air (lab air system) or N₂ (99.9999%, MEGS) gas for a specified time (5-10 min), microalgae-CNC aggregates were allowed to flocculate and settle for 10 min. Gas sparging was conducted under 1 atm of C0₂, N2 or air. Finally, liquid samples were taken from 1 .0 cm below the surface of a microalgal suspension for an optical absorbance measurement at 680 nm using a Hach Method 8171 spectrophotometer. Three indicators including harvesting efficiency (HE) for evaluation of efficiency of proposed harvesting technique, recovery efficiency (RE) for efficiency of coagulant (native or modified CNC), and recovery capacity (RC) for harvesting performance as attributed to microalgal quantities (gram algae) per gram CNC, were used to evaluate microalgal separation performance [Y.-R. Hu, F. Wang, S.-K. Wang, C.-Z. Liu, C. Guo.

Bioresour Technol. 138 (2013) 387-90; S. Ge, M. Agbakpe, Z. Wu, L. Kuang, W. Zhang, X. Wang. Environ Sci Technol. 49 (2015) 1 190-6]:

HE (%)=[l-(C_t/C₀)]xl00% (i) RE (%)=[!-( c_t/c₀ )] l00%

c;/c

(c₀ -c_t)v

RC (g-algae-g-CNC ¹)

m where C₀ and C_t are microalgal concentrations in the supernatant before and after separation (g - L ¹), Co and Ct are microalgal concentrations without addition of API m-modified CNC in a control group (g-L¹), V is volume (20 mL) of microalgal suspension and m is mass of API m- modified CNC added (g) . APIm-modified CNC concentrations were gravimetrically quantified by dry cell weights (g-L¹). Microalgal separation was studied by varying APIm-modified CNC dosage, non-acidic gas (pure N₂ or air) addition, and air sparging time as described below. All experiments below were performed in duplicate or triplicate.

[00412] Effect of CNC surface modification:

[00413] Different amounts of native or APIm-modified CNC were added to the C. vulgaris suspension at 0.2~0.4 g-DCW L ¹ to achieve different mass ratios (0.01 , 0.02, 0.05, 0.1 , 0.2, 0.3, 0.4, and 0.5 g-CNC g-algae^-1) . All doses were calculated based on dry weights of both microalgae and CNC. Mixtures were then sparged with CO2 for 1 min followed by only air at a gas flow rate of 140 mL min ¹ for 10 min.

[00414] Effect of inert gas and flow rates:

[00415] Sparging of nitrogen-containing gas (either pure N2 gas or air) was used to flush C0₂ from aqueous phase. These two nitrogen-containing gases (N₂ or air) were compared to evaluate their effectiveness for microalgal separation. In addition, three flow rates (25, 80 and 140 mL min ¹) were applied. Separation experiments were performed with an optimized dose (0.05 g-CNC g-algae ¹) of APIm-modified CNC determined above.

[00416] Effect of air sparging time:

[00417] After 1 min C0₂ sparging, different air sparging times (0, 1 , 3, 5, 7, 10, 13, 20 min) were investigated to optimize the sparging time required for gelation. Two APIm- modified CNC doses (0.05 and 0.49 g-CNC g-algae ¹) were compared.

Effect of pH adjustment: [00418] Different pH cycles (4.9/7.9, 4.6/7.8 and 4.2/7.2) were artificially generated through addition of 1 M HCI and 1 M NaOH to mimic C0₂/air-treated samples for three APIm-modified CNC doses (0.05, 0.29 and 0.49 g-modified CNC.g-¹-algae, respectively). In another pH adjustment experiment, use of HCI/air treatment was compared. A control experiment having only pH adjustment of 4.6/7.8 (with 1 M HCI and 1 M NaOH) but without any APIm-modified CNC was also tested.

[00419] Assessment of supernatant and APIm-modified CNC reuse:

[00420] After harvesting microalgae with APIm-modified CNC, concentrations of nitrate and phosphorus in used medium were adjusted to levels in MBBM. The medium was then reused to cultivate C. vulgaris. For comparison, another two microalgal culture supernatants were used, which were obtained after harvesting by either centrifugation (as a control) or alum coagulation (20 mg-L¹). Both recycled supernatants were then reused for microalgal cultivation. In all three cases, biomass growth in recycled medium was monitored for 7 days in 250 mL flasks.

[00421 ] To determine recyclability of APIm-modified CNC (0.49 g-modified CNC.g ¹- algae), collected microalgae-CNC aggregates (~2.0-2.5 g-algae- L ¹ in ~3 mL) were reused to harvest new microalgae following the same harvesting procedures noted above. The process was repeated for five cycles.

[00422] Comparison of colloidal interaction:

[00423] Quantitative information on nonspecific interactive forces between CNC particles and microalgal cells were obtained with Ohshima's soft-particle DLVO theory, assuming that Lifshitz-van der Waals and electrostatic forces were the dominant forces [H. Ohshima. Advances in colloid and interface science. 62 (1995) 189-235; H. Hayashi, S. Tsuneda, A. Hirata, H. Sasaki. Colloids and Surfaces B: Biointerfaces. 22 (2001) 149-57]. Computation methods for van der Waals and electrostatic forces varied with geometry of interacting entities. Diameter of spherical microalgal cells was approximately 2-5 μηι [L.E. De-Bashan, Y. Bashan, M. Moreno, V.K. Lebsky, J.J. Bustillos. Can J Microbiol. 48 (2002) 514-21 ], and CNCs were approximately 100-300 nm in length and 10-20 nm in width. In this study, CNC was assumed to be spherical to simplify analysis to sphere-to-sphere geometry, as was employed in other studies and to allow for comparison of interaction between microalgae and flocculants such as metal oxide NPs, or bacteria [M. Agbakpe, S. Ge, W. Zhang, X. Zhang, P. Kobylarz. Bioresour Technol. 166 (2014) 266-72; S. Ge, M. Agbakpe, Z. Wu, L. Kuang, W. Zhang, X. Wang. Environ Sci Technol. 49 (2015) 1 190-6; P.Y. Toh, B.W. Ng, A.L. Ahmad, D.C.J. Chieh, J. Lim. Nanoscale. 6 (2014) 12838-48; S. Ma, K. Zhou, K. Yang, D. Lin. Environ Sci Technol. 49 (2015) 932-9]. Retarded Lifshitz-van der Waals and electrostatic interaction energy (linearized version of Poisson-Boltzmann expression) for sphere-to-sphere geometry were calculated as per Equations (iv) and (v) when η<λ< 4π and h<a, [J. Schenkel, J. Kitchener. Transactions of the Faraday Society. 56 (1960) 161-73], respectively. All equation parameters are summarized in Table 26.

A_l32a_la₂ 1

(iv)

6h + a₂ ) 1 + 1 1.12 2 /

[00424] Statistical analysis:

[00425] All experiments were performed at room temperature (23.0±0.5°C) with triplicate testing and sampling. Results presented are mean values ± standard deviation from three independent experiments. Differences in HE, RE, and RC values between test groups were tested for significance using one way analysis of variance at a significant level of 0.05.

[00426] Results and Discussion:

[00427] Characterization of microalgae and APIm-modified CNC:

[00428] Influence of C0₂ and air sparging time on size and zeta potentials of CNC particles:

[00429] As shown in Figure 64(a) and 1 (c), during CC^/air sparging cycles, relatively consistent negative zeta potentials (-31 .6~-29.1 mV) and hydrodynamic particle sizes (155 ± 4 nm) were observed for native CNC. In contrast, different observations were obtained for APIm-modified CNC. Specifically, after 1 -10 mins of C0₂ sparging, zeta potentials increased from 20.5 ± 2.8 mV to ca 30.5~33.5 mV, and size decreased from an initial 4287 ± 49 nm to ca 189-201 nm, implying that APIm-modified CNC aqueous dispersion was well-dispersed. Introduction of air led to a gradual increase in size (ca 3603-4319 nm) with macroscopically visible gel-like aggregates, here referred to as a gelation process, while zeta potentials gradually returned to ca 20.3-21 .2 mV. Similar pH trends were observed for both native and APIm-modified CNCs under air and CO2 sparging. For APIm-modified CNC, after sparging of C0₂, pH decreased to 4.09±0.01 and then increased to 6.73 ±0.03 after 10 min of air sparging (Figure 64(b) and 1 (d)).

[00430] From Figure 64(e), it was observed that native CNC was not noticeably responsive to either C0₂ or air sparging. However, surface charges (zeta potentials) and dispersion/gelation (size) of APIm-modified CNC weree reversibly adjusted by alternatively sparging C0₂/air into the APIm-modified CNC aqueous dispersion. It was considered that such C0₂-switchable properties may attributed to the imidazole functionalities chemically immobilized onto the CNC surface hydroxyl groups, forming carbamate linkages [H.-D. Wang, P. Jessop, J. Bouchard, P. Champagne, M. Cunningham. Cellulose. (2015) 1 -12]. Other important characterizations such as ¹H NMR spectroscopy, TEM, and elemental analysis of native and APIm-modified CNC are described above.

[00431 ] Zeta potentials of microalgae and CNC particles at different pHs and/or particle concentrations:

[00432] C. vulgaris exhibited negative zeta potentials, which were pH-independent (3.0-1 1 .7) and reached --20.2 ±2.9 mV at a pH of 8.5 ± 0.2 in MBBM (Figure 64(f)). It was considered that these negative potentials arose due to a variety of functional groups in the microalgal cell walls, including deprotonated carboxylic acid, phosphoric acid ,

phosphodiester and hydroxyl groups [M. Agbakpe, S. Ge, W. Zhang, X. Zhang, P. Kobylarz. Bioresour Technol. 166 (2014) 266-72; S. Hadjoudja, V. Deluchat, M. Baudu. J Colloid Interf Sci. 342 (2010) 293-9].

[00433] It was found that both particle concentration and pH influenced the surface charge of native and APIm-modified CNC. A shift in zeta potential to a less negative or more positive value was observed with increasing particle concentration (pH=5.0±0.2) for both native and APIM-modified CNC particles (Figure 65). Similar concentration-dependent zeta potentials observed for metal oxide NPs were reported to be due to specific adsorption of

HCO3^" ions from dissolved ambient CO2, which were shown to neutralize and/or even exceed the NPs surface charge [N. Wang, C. Hsu, L. Zhu, S. Tseng, J.-P. Hsu. J Colloid

Interf Sci. 407 (2013) 22-8]. Moreover, native CNC carried negative charges at all pH levels investigated, while APIm-modified CNC particles were positively charged at lower pH conditions (< 6.2) and negatively charged at higher pH. Figure 64(f) depicts data for modifed

CNC at a 90 mg- L^"1 loading as an example, however, it should be noted that similar behaviour was observed over a range of native or APIM-modified CNC loadings. Specifically, zeta potentials of APIm-modified CNC were 25.6 ± 0.4 mV at 10 mg-L^" and 27.4 ± 2.1 mV at 90 mg-L^-1 (pH ca. 5.0), which were used for the DLVO coagulation calculation in the following section. It was considered that opposite surface charges between microalgae and APIm-modified CNC may promote destabilization and aggregation interactions between these suspended particles.

[00434] Application of APIm-modified CNC to microalgal harvesting:

[00435] The ability for CNC or modified CNC to promote microalgal harvesting was evaluated under two different scenarios. Scenario 1 used APIm-modified CNC with C0₂ and then air sparging. HE of C. vulgaris was found to increase with increasing CNC:algae mass ratio (theoretical mass ratio of modified CNC added to microalgal mass), and reached 100% when mass ratio exceeded 0.05 g-modified CNC g^~1-algae. As expected, RC, which describes harvesting capacity in terms of microalgal quantities (gram algae) per gram CNC, decreased with increasing mass ratio of CNC, but maintained high levels (22.9-43.4 g- algae g ¹-modified CNC) with mass ratios below 0.05. In contrast, Scenario 2, which used native CNC with C0₂ and air sparging, appeared to be ineffective. Native CNC addition into a microalgal suspension failed to induce observable coagulation or settling; and the suspension appeared to be as stable as noted without use of additives. Coagulation of the suspension was also not observed with increases in mass ratio, as shown by a low HE and RC of 0.13-3.65 % and 0.05-2.04 g-algae g ¹-CNC, respectively. Similarly, coagulation of microalgae with only CDI or APIm addition using C0₂/air treatment applied to the microalgal suspension (at a dose of 22.5 g-L¹ for CDI and 34.7 g-L¹ for APIm; maximum relevant concentrations of CDI and APIm employed during preparation of APIm-modified CNC) was not substantially improved, indicative of critical properties (i.e. increasing available surface area for interactions) imparted by CNC in this coagulation process. It was considered that the successful separation of C. vulgaris cells achieved in Scenario 1 may be attributed to protonation of the imidazole groups introduced on the CNC surface, resulting in an increased electrostatic attraction of CNC to negatively charged microalgae.

[00436] Sparging of C0₂ through the medium was found to influence microalgal suspension stabilities (Figure 66). HE profiles in Scenario 3, which used APIm-modified CNC without any C0₂ treatment, were found to be similar to that of the C0₂-treated Scenario 1 , but with RC values that were different. HE continuously increased and reached a maximum at a mass ratio of 0.2 g-modified CNC g^~1-algae. However, it was noted that the dose requirement (0.05 g-modified CNC g^~1-algae) of APIm-modified CNC to achieve 100 % HE in Scenario 1 was lower than in Scenario 3 (0.22 g-modified CNC g^~1-algae); only half the dose (0.1 g-CNC g^~1-algae) and one tenth (0.57 g-CNC g^~1-algae) required with pyridinium- modified CNC [D. Vandamme, S. Eyley, G. Van Den Mooter, K. Muylaert, W. Thielemans. Bioresour Technol. 194 (2015) 270-5] and 4-(1-bromo-methyl)benzoic acid-modified CNC respectively [S. Eyley, D. Vandamme, S. Lama, G. Van Den Mooter, K. Muylaert, W.

Thielemans. Nanoscale. 7 (2015) 14413-21 ]. Harvested microalgae quantities increased as indicated by the RCs at the same doses (Figure 66). Figure 67 illustrates different microalgal suspension settling behaviours exhibited with (Figure 67a) or without (Figure 67b) C0₂- treatment. Thus, it was considered that the presence or absence of a CO2 sparging step influenced dispersion of APIm-modified CNC, affected interactions between CNC particles and microalgae cells, and affected microalgal separation from suspension.

[00437] Air sparging appeared to facilitate formation of large gel-like microalgae- modified CNC aggregates, which aided in subsequent settling. Accordingly, it was considered that sparging air following C0₂ sparging may facilitate high harvesting efficiencies and accelerate the settling process, particularly when high doses of APIm- modified CNC were used. For example, at a dose of 0.49 g-modified CNC g^~1-algae and with C0₂ sparging treatment alone, although a fraction of small microalgae-modified CNC floes was produced, it was found that they were not large, dense or heavy enough to readily settle within 30 mins, resulting in a low HE. Conversely, at a lower dose (0.10 g-modified CNC g ¹- algae), it was found that such coagulation and settling difficulty was not present, and a high harvesting performance was observed. Also, at such a low dose, similar harvesting performances were exhibited irrespective of air sparging after CO2 sparging; without wishing to be bound by theory, it was considered that this may be because the interparticle attraction during CO2 sparging offered enough interaction forces leading to coagulation between low concentrations of APIm-modified CNC and microalgae, as discussed below.

[00438] Mechanism of microalgal harvesting with APIm-modified CNC:

[00439] As illustrated in Figure 68, the APIm-modified CNC-based microalgal harvesting process mainly consisted of three steps including C0₂ sparging, air sparging and settling. Each treatment step led to pH changes in solution, and therefore it was considered worthwhile to determine whether microalgal separation could be achieved through these pH changes alone or whether other C0₂ effects were involved. Table 27 lists pH values of microalgal suspensions for each of the three steps with different APIm-modifed CNC doses. With introduction of CO2, pH was lowered and the imidazole groups protonated. Subsequent air sparging raised pH and deprotonated the imidazole groups.

[00440] To mimic the pH changes observed with C0₂ and air, HCI and NaOH were used to adjust the pH of APIm-modified CNC and microalgal suspensions under three loadings (0.05, 0.29 and 0.49 g-modified CNC.g ¹-algae). pH of the suspensions (4.9, 4.6, or 4.2) that would have been observed after CO2 addition for the three loadings respectively was achieved with addition of 1 M HCI rather than C0₂ treatment. After 1 min (same as time as required for initial C0₂ sparging), pH levels were subsequently increased to 7.9, 7.8 or 7.2, respectively, using 1 M NaOH rather than sparging air. After another 10 min (same as time as required for initial air sparging), suspension samples were collected to compare harvesting parameters. Results (Table 28) suggested that pH adjustment alone (Groups 1 , 2, and 3), and with air treatment (Group 4), with APIm-modified CNC could also promote microalgal coagulation - but HEs were lower than those obtained using the CO ₂/air treatment (all p<0.001 , Table 29). However, without an APIm-modified CNC additive (Group 5), pH adjustment alone did not significantly improve microalgal coagulation with HE only of 3.5 ± 0.1 % (p<0.001 , Table 29), suggesting that APIm-modified CNC was the primary material responsible for inducing harvesting of microalgae cells. Nevertheless, coagulation between microalgae and APIm-modified CNC cannot be explained by pH alone.

[00441] As shown in Figure 68, it has been considered that integration of multiple mechanisms, including electrostatic attraction in the C0₂ sparging step, and enmeshment in the air sparging step, may contribute to a successful interaction between APIm-modified CNC and microalgae, and subsequent coagulation (destabilization), flocculation

(agglomeration) and removal (sedimentation).

[00442] C0₂ treatment step:

[00443] Well-dispersed APIm-modified CNC was obtained after 1 min of C0₂ sparging. This was supported by a pronounced total interaction energy

barrier present between APIm-modified CNC particles (Figure 69), suggesting that repulsive electrostatic repulsion may be preventing particle homo-aggregation. However, electrostatic attraction between positively charged APIm-modified CNC and negatively charged microalgal cells resulted in successful coagulation, which was not observed with native CNC particles. It was considered that this difference may be explained by comparing total interaction energies for native and APIm-modified CNC, as shown Figure 70. As can be seen, for negatively charged native CNC, a high energy barrier was present, thereby preventing or limiting the coagulation process. However, with APIm modification, the energy barrier was decreased, suggesting that the attractive forces of van der Waals were greater than the electrostatic repulsive force, thereby resulting in a net particle attraction and negative interaction energy.

[00444] Similarly, a significant energy barrier was noted between microalgal cells, as shown in the inset of Figure 70, suggesting that microalgal suspensions may generally be expected to be relatively stable and not undergo spontaneous coagulation [M. Agbakpe, S. Ge, W. Zhang, X. Zhang, P. Kobylarz. Bioresour Technol. 166 (2014) 266-72].

[00445] Air treatment step:

[00446] After 5-10 min of air sparging, the positive surface charges of APIm-modified CNC were still detectable, as indicated by a zeta potential of 20.3-21.2 mV for the suspension. It was considered that this factor, to some extent, may have contributed to maintaining attraction between APIm-modified CNC and microalgae. It was further considered that hydrogen-bonding-driven gelation of APIm-modified CNC, upon the application of air treatment, may have contributed to further adsorption or enmeshment of adjacent microalgae cells and/or microalgae-modified CNC aggregates, thereby producing larger macroscopic aggregates through network or particle bridging mechanisms. As such, said aggregates were able to settle relatively readily. Moreover, it was considered that the multiple mechanisms involved may have led to a shorter separation time (10 min) for the work herein described, as compared to that of 1 h in total (including mixing (30 min) and settling step (30 min)) in another study using pyridinium-modified CNC, where the harvesting mechanism relied on charge neutralization alone and a process need for mixing and power [D. Vandamme, S. Eyley, G. Van Den Mooter, K. Muylaert, W. Thielemans. Bioresour Technol. 194 (2015) 270-5].

[00447] Optimization of air sparging time required at different dose conditions:

[00448] During the dose effect experiment, it was noted that different air treatment times were required to achieve complete settling of microalgae-CNC aggregates when different doses of APIm-modified CNC were employed. Thus, application of different air treatment times was investigated further at different APIm-modified CNC loadings. As can be seen in Figure 71 , APIm-modified CNC doses or their mass ratios influenced the sparging time required. For example, under a lower CNC dose condition (0.05 g-modified CNC.g ¹- algae), 5 min air sparging sufficed for flocculation and subsequent settling of APIm-modified CNC and microalgae, while twice the time was required for a higher dose (0.49 g-modified CNC-g ¹-algae). Lower doses or mass ratios of APIm-modified CNC required less air sparging time and yielded conditions that were considered more favourable for coagulation, potentially because of the presence of fewer protonated imidazolium sites to be

deprotonated and lower viscosities; however, no visible gelation was clearly observed for the lower doses, as was observed for the high doses, which, without wishing to be bound by theory, may be attributed to an insufficient concentration of APIm-modified CNC to facilitate gelation.

[00449] Effect of inert gas and flow rates on harvesting performance:

[00450] Effects of using air rather than nitrogen gas (99.9999 %), and corresponding flow rate requirements (25, 80 and 140 mL-min ¹) on microalgal harvesting with APIm- modified CNC were examined. As shown in Figure 72 and Table 30, no significant difference (p>0.05) in harvesting performance was observed when using air rather than nitrogen gas. Similar performance indicator parameter values (HE, RE and RC values) were obtained for the two gases. For example, at a flow rate of 80 mL-min^"1, the HE, RE and RC reached approximately 99.7 %, 99.7 %, and 41.3 g-algae g ¹-modified CNC, respectively with pure nitrogen, while with air they reached 99.5 %, 99.4 %, 41.2 g-algae g ¹-modified CNC (all p>0.05). Therefore, it was considered that air may be used effectively in place of nitrogen and serve to flush away C0₂ added previously in the APIm-modified CNC-based microalgal harvesting process.

[00451] Moreover, harvesting performance, as measured by HE, RE and RC, was not found to be further improved through application of higher inert gas flow rates (Figure 72 and Table 31 , p>0.05). Without wishing to be bound by theory, tt was considered that the lowest flow rate (25 mL-min ¹) was likely able to remove C0₂ from the suspension and convert the imidazolium bicarbonate groups to neutral imidazole groups on the modified CNC surface, thereby influencing the surface charge of the APIm-modified CNC and their interactions with microalgae.

[00452] Reuse of culture medium and APIm-modified CNC after harvesting:

[00453] To reduce primary water demand associated with microalgal cultivation, a potential for supernatant reuse in subsequent cultivations was investigated. Supernatant remaining after harvesting with two different coagulants (APIm-modified CNC and alum) was centrifuged and recycled to the cultivation medium following addition of nutrient

supplements. As shown in Figure 73 (a), due to the lower pH levels (2.95-3.48) in the suspension, inhibition of growth was observed when the alum supernatant was reused, which was consistent with results reported by Lee et al. [K. Lee, S.Y. Lee, J.-G. Na, S.G. Jeon, R. Praveenkumar, D.-M. Kim, W.-S. Chang, Y.-K. Oh. Bioresour Technol. 149 (2013) 575-8]. In contrast, only a relatively slight decrease in cell growth compared to MBBM was observed in the supernatant recycled after harvesting with API-modified CNC. It was considered that these results suggested that APIm-modified CNC was a biocompatible microalgal-harvesting alternative without requiring pH modification, likely due to the average pH of the medium, which was 7.31 ±0.28 after harvesting with different API-modified CNC loadings. Further, it was observed that microalgae started growing in the CNC-harvested recycled medium. Large clusters of microalgae-modified CNC were observed during the growth period, some of which were attached to the CNC particles, which made microalgal biomass settle readily in subsequent cycles after aeration was stopped. Thus, it was considered that APIm-modified CNC supernatant may be a favorable growth medium alternative, which may be recycled and potentially lead to development of more cost- effective cultivation processes in large scale applications.

[00454] It was found that collected concentrated microalgae-modified CNC aggregates could be separated using C0₂ sparging following centrifugation, when added to a new microalgal medium: APIm-modified CNC could be redispersed in the suspension and reused to harvest microalgae. Figure 73(b) compares HE of C. vulgaris harvested using microalgae-modified CNC aggregates through five cycles (recycled). HE was noted to decrease slightly, however >95 % RE was achieved with each cycle, which suggested that following C0₂ sparging, the re-dispersed APIm-modified CNC particles have sufficient adsorption sites to coagulate additional microalgal cells. As such, it was considered that this recyclable C02-switchable APIm-modified CNC had potential to provide a sustainable solution to microalgal harvesting and cultivation.

[00455] For example, an integrated process including a microalgal cultivation tank followed by a secondary clarifier for harvesting may be designed. After settling, the clear supernatants may be recycled to the cultivation tank while the settled microalgae-CNC aggregates may be reused to harvest microalgae until a minimum specified HE value is achieved. Moreover, it has been considered that saturated microalgae-modified CNC aggregates may have potential for use in biofuel production through subsequent anaerobic digestion, hydrothermal liquefaction or other conversion technologies. It has been further considered that, to some extent, such recycling and biofuel conversion may compensate for use of more expensive CNC materials as coagulants.

[00456] Conclusions:

[00457] A C0₂-switchable CNC was investigated for separation of C. vulgaris from culturing suspensions. CNC was modified through a one-step 1 ,1 '-carbonyldiimidazole

(CDI)-mediated coupling with APIm. After APIm modification, the well-dispersed CNC with positive charges interacted with negatively charged microalgae after C0₂ sparging. DLVO theory predicted a strong attractive force between APIm-modified CNC and C. vulgaris, which supported microalgal separation from suspension. Subsequent air sparging gave rise to gelation between APIm-modified CNC, which facilitated adsorption of adjacent microalgae-modified CNC aggregates, leading to more and more macroscopically large microalgae-CNC floes produced through network or particle bridging mechanism. Because the dispersion/gelation cycle was reproducible by alternatively sparging C0₂/air, harvested microalgae-CNC aggregates were re-dispersed upon C0₂ treatment and then repeatedly used to harvest microalgae (5+ cycles). Biocompatibility of APIm-modified CNC has suggested that reuse of culture medium for seeding subsequent cultivations may also increase the material's sustainability and economical viability.

[00458] EXAMPLE 2A: Preparation and Analysis of 1 -(3-Aminopropyl)imidazole Functionalized Cotton Linen (Cotton-APIm)

[00459] Ν,Ν-dimethylformamide (DMF; dry, 50 mL, >99%) was added to a 100 mL round bottom flask. Cotton (0.419 g; unbleached, undyed cotton muslin) was then added to the flask, and stirred in DMF for 10 min; following which, 1 , 1 '-Carbonyldiimidazole (0.908 g, 5.601 mmol) was added, and stirred for an additional 2 hours. 1 -(3-aminopropyl)imidazole (1 .312 g, 10.48 mmol) was then added to the flask drop-wise over 1 min, and was stirred for 24 hours. The cotton was then removed, washed 3 times with DMF (20 mL), and left to dry for 24 h in air, in a fume hood.

[00460] Once prepared, a quantitative analysis of the Cotton-APIm's surface tension was undertaken to measure the cotton's surface hydrophilicity or hydrophobicity when it was 'switched on' (protonated) and 'switched off (non-protonated) using contact angle analysis. A contact angle is the angle at which a liquid interface meets a solid surface, which can be measured via contact angle goniometry using a Goniometer. To measure the Cotton-APIm's contact angle, the material was held rigidly in place on an observation deck of the

Goniometer. The Goniometer was then used to deposit a droplet of Millipore™, carbonated water (0.75 uL), and hexadecane (0.75 uL) onto the non-functionalized cotton linen's surface and Cotton-APIm's surface, and capture a high-resolution image of the droplet. Using the Goniometer's software, a contact angle could then be calculated (see Table 8). This procedure is commonly referred to as a sessile droplet method.

[00461 ] Further to contact angle analysis, water absorption analysis was undertaken. Millipore water (100ml_) was placed into a 150 mL beaker. The Cotton-APIm was weighed, and the dry mass recorded. The Cotton-APIm was placed into the water for 30 seconds, and then carefully removed so as to not disturb bound water on the Cotton-APIm's surface, and held above the water for an additional 30 seconds to 'drip dry'. Resultant "wet" weight was then recorded.

[00462] Results and Discussion:

[00463] It was qualitatively observed that, once functionalized, the cotton was more physically ridged than non-functionalized cotton.

[00464] Once functionalized, Cotton-APIm was analyzed, by way of contact angle tests, to investigate its hydrophobic / hydrophilic properties. The contact angle of water, carbonated water, and oil were measured from the Cotton-APIm's surface, and contrasted with non-functionalized cotton. It was observed, as is delineated in Table 8, that the non- functionalized cotton linen was hydrophilic in the presence of water and carbonated water; and, oleophilic in the presence of hexadecane. It was observed that the Cotton-APIm was hydrophilic in the presence of water and carbonated water; and, oleophilic in the presence of hexadecane; however, qualitatively, it was observed that the carbonated water absorbed into the linen faster than the water.

[00465] In addition to analyzing the Cotton-APim by way of contact angle, water absorption tests were also undertaken, wherein Cotton-APIm was submerged in water to further test its affinity for water. The functionalized cotton was weighed before and after being submerged, and the amount of water absorbed (by mass) was determined; this was then contrasted with non-functionalized cotton that received equal treatment (Table 7). It was found that the Cotton-APIm absorbed 0.55 ± 0.06 g, while the non-functionalized cotton absorbed 0.33 ± 0.02 g. Without wishing to be bound by theory, this was considered at least qualitatively indicative of Cotton-APIm's increased hydrophilicity as compared to the non- functionalized cotton.

[00466] EXAMPLE 2B: Preparation and Analysis of Poly(diethylamino)ethyl methacrylate (p-DEAEMA) Functionalized Cotton Linen (Cotton-APIm) via Surface-initiated Atom-Transfer Radical-Polymerizaion (SI-ATRP)

[00467] Linen Preparation:

[00468] Cotton linen (0.2 g) was first subjected to a surface oil extraction by refluxing in tetrahydrofuran (THF) 100 mL for 1 hour. After, the linen was air-dried and placed in a 250 mL schlenk two-neck round bottom flask and heated at 120°C overnight under vacuum to remove excess water.

[00469] Grafting polymer from cotton linen surface via Surface Initiated Atom Transfer Radical Transfer (SI-ATRP):

[00470] Please note: assumed 20 mmol/g of functionalizable surface hydroxyls on linen surface.

[00471 ] Cotton linen (0.2 g) was placed into a two-neck schlenk round bottom flask was first flame-dried under vacuum to remove excess water. The prepared linen, still stored in the two-neck round bottom flask, was purged 3 times with Ar<_g). Anhydrous

dichloromethane (DCM; 100 mL) was then cannula transferred into the linen-containing round bottom flask. Next, diisopropylethylamine (0.70 mL) was added to the same round bottom flask and stirred for 1 hr. The resultant linen mixture was then cooled down to 0 ^"C using an ice bath, and 0.50 mL 2-bromo-2-methylpropionyl bromide (BIBB) was added dropwise. This mixture was then heated to 40°C and left to stir for 24 h.

[00472] Next, the linen was removed from the flask and washed with 3 x 50 mL of dichloromethane (DCM), and then with water and subsequently air-dried. While the linen was left to dry, 2-(diethylamino)ethyl methacrylate (DEAEMA, 41 mL) was run through a basic alumina column to extract any inhibitor. The dried linen was then placed into a 250 mL schlenk round bottom flask, and flame dried under vacuum and purged 3 times with Ar gas. Dry methanol (40 mL) was then cannula transferred into the linen-containing round bottom flask followed by DEAMEA (41 mL). Cu(l)Br (0.60 g) was weighed into an oven dried vial using an Ar-filled glove bag. Next, dry methanol (25 mL) was cannula transferred into the dried vial along with ligand Ν,Ν,Ν',Ν',Ν''-pentamethyldiethylenetriamine (PMDETA; 0.84 g). Contents of the dried vial and linen-containing flask were stirred and degassed for 1 h.

[00473] The catalyst mixture was then cannula transferred to the linen-containing flask and left to stir under reflux at 70°C for 48 h. The final solution turned deep blue and the linen was rinsed first in methanol, then in a ethylenediaminetetraacetic acid (EDTA) water mixture to remove excess copper. See Figure 33.

[00474] Contact Angle Analysis:

[00475] Once prepared, a quantitative analysis of the pDEAEMA-functionalized linen surface tension was undertaken to measure the linen's surface hydrophilicity or

hydrophobicity when it was 'switched on' (protonated) and 'switched off (non-protonated) using contact angle analysis. See Table 10.

[00476] Switching the linen surface "on" was achieved by using glycolic acid in water. Contact angles were measured via a sessile drop method using Millipore™ water.

Approximately 0.75 μΙ_ droplets of water were exposed to the surface and images were taken using a Veho VMS-004 USB Microscope and processed using ImageJ and DropSnake software [A.F. Stalder, G. Kulik, D. Sage, L. Barbieri, P. Hoffmann, Colloids And Surfaces A: Physicochemical And Engineering Aspects, vol. 286, no. 1-3, pp. 92-103, September 2006].

[00477] Discussion:

[00478] Grafting switchable polymer DEAEMA onto a cotton linen surface was achieved through SI-ATRP/ "grafting-from" approach. The cotton linen's surface, after extracting from it natural oil, was hydrophilic. Following surface functionalization with PDEAEMA, the linen's surface became hydrophobic, as demonstrated by contact angles before and after functionalization (Table 10). Presence of PDEAEMA on the linen's surface was also corroborated by ATR-FTIR (see Figure 34): a peak was observed at ~1727 cm ¹ in the IR spectrum, which was considered to correspond with the PDEAEMA ketone functional group. The functionalized linen was then subjected to glycolic acid to "switch-on", or ionize, the switchable polymer, thereby charging the surface to allow for water to be absorbed.

[00479] Preliminary results indicated that cotton linen can be functionalized with a switchable functional group, such that the surface properties of the linen can be switched from hydrophobic to hydrophilic in the presence of a trigger (e.g., glycolic acid). It has been considered that such switchable polysaccharides are applicable to cotton linen diapers; for example: a diaper functionalized with a switchable polymer, such as PDEAEMA, is switched on by an infant's naturally acidic urine; the acidic urine changes the linen diaper's surface properties by ionizing the switchable polymer; and the ionized surface results in water- uptake by the polymer, thereby absorbing the infant's urine. It has also been considered that such switchable polysaccharides are applicable to membrane applications: the "switched- on", ionic, hydrophilic form of the switchable linen allows water to filter through, while simultaneously capturing and filtering out hydrophobic compounds, such as oil. Commonly, membranes, such as cellulose membranes, foul over time; but a switchable polysaccharide allows for self-cleaning. For example, a switchable-functionalized linen's properties are switched on and off, in the presence of a trigger, thereby releasing any hydrophobic compounds fouling its surface.

[00480] EXAMPLE 2C: Further Preparation and Analysis of Poly(diethylamino)ethyl methacrylate (p-DEAEMA) Functionalized Cotton Linen via Surface-initiated Atom-Transfer Radical-Polymerizaion (SI-ATRP)

[00481 ] A cellulosic substrate (cotton linen, 0.8 g, assuming 10 mmol/g_CH20H) was rinsed thoroughly in acetone, followed by soaking in tetrahydrofuran overnight at room temperature. The cellulosic substrate was then sonicated in tetrahydrofuran for 30 min. In a 250 mL Schlenk 2-neck round bottom flask that was flame dried and purged with argon, a solution of diisopropylethylamine (DIPEA, 1 .1 eq., 8.8 mmol, 1 .4 mL), 2-bromo-2- methylpropionyl bromide (BIBB, 1 eq., 8.0 mmol, 1 .0 mL) and a catalytic amount of 4- dimethylaminopyridine (0.05 eq., 0.4 mmol, 50 mg) was prepared in 100 mL of dry

tetrahydrofuran under argon. The solution was cooled to ca. 1 ^°C with an ice bath. The cellulosic substrate was immersed into the solution under argon and subsequently sealed. The ice bath was removed after 15 min and the solution was left to react overnight at room temperature (ca. 26 ^°C). The resultant BIBB-functionalized substrate was then rinsed and sonicated in tetrahydrofuran, followed by sonication in methanol. The functionalized substrate was left in dry methanol until it was ready to be polymerized.

[00482] This procedure has been slightly adapted from Calmark and Malmstrom, Journal of applied polymer science, 2006, 100, 4155-5162.

[00483] The BIBB-functionalized cotton linen (assuming 10 mmol/g of BIBB on surface) was placed inside a 250 mL round bottom flask, which was charged with 2-

(diethylamino)ethyl methacrylate (DEAEMA, 25 eq. 200 mmol, 41 mL; Aldrich, 99%) and 150 mL of anhydrous methanol. A stir bar was added and the flask was degassed with argon via a needle for 1 h. Radical inhibitor monomethylether of hydroquinone (MEHQ) was was removed from DEAEMA by flowing the monomer over basic alumina. In a separate flask, catalyst was prepared: copper(l)bromide (0.2 eq., 8.0 mmol, 300 mg) was mixed with

N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA, 0.4 eq., 16.0 mmol, 0.84 mL) in 15 mL of anhydrous methanol. The catalyst solution was degassed via needle with argon for 0.5 h. The solution containing the monomer and cotton linen bound initiator was heated to 45 ^°C and the catalyst solution was transferred into it via cannula under argon. Polymerization was left to react over 48 h. The switchable polymer-grafted cotton linen was sonicated for 20 min in fresh methanol (3x) to remove physisorbed polymer, excess monomer, ligand, and catalyst. The product cotton linen was sonicated in 0.1 M EDTA solution to remove physisorbed copper (see Figure 79). Diffuse reflectance infrared fourier transform (DRIFT) IR spectroscopy analysis suggested presence of polymer on the cotton linen, given that an ester peak representative of the DEAEMA ester was observed at ~1725 cm ¹ (see Figure 80).

[00484] Contact Angle Testing:

[00485] Once prepared, a quantitative analysis of the Linen-pDEAEMA surface tension was undertaken to measure the cotton's surface hydrophilicity or hydrophobicity when it was 'switched on' (protonated/ionized) and 'switched off (non-protonated/non- ionized) using contact angle analysis. Switching the linen surface "on" was achieved by using glycolic acid in water, for demonstrative purposes only. Contact angles were measured via a sessile drop method using Millipore™ water. Approximately 0.75 μί droplets of water were exposed to the surface, and images were taken using the Veho VMS-004 USB Microscope and processed using ImageJ and DropSnake software [A.F. Stalder, G. Kulik, D. Sage, L. Barbieri, P. Hoffmann Colloids And Surfaces A: Physicochemical And Engineering Aspects, vol. 286, no. 1-3, pp. 92-103, September 2006]. Results are outlined in Table 34.

[00486] C0₂ - switchability testing:

[00487] The PDEAEMA-functionalized linen was analyzed to determine if C0₂ could act as a trigger to turn the linen membrane from a hydrophobic to hydrophilic state in the presence of water.

[00488] The PDEAEMA-functionalized linen was tied to an end of a L-shaped glass tube (top joint diameter 24/29; hose adater opening / linen 7/16 inner), with an opening diameter of 1 cm and a total volume of 10 mL (see Figure 81). Deionized water (9 mL) was then added to the glass tubing with the linen attached at the bottom. C0₂ was then bubbled into the system with a needle near the linen-sealed opening of the tube. After 2 hours, it was observed that water passed through the linen, suggesting a switch from a hydrophobic to a hydrophilic state. Then, Ar_(g) was passed through the needle, and the passage of water through the linen stopped after 15 minutes, suggesting a switch from a hydrophilic to a hydrophobic state. Again, C0₂ was reintroduced through the needle, and it was observed that water passed through the linen again after 10 minutes. A blank run was completed with the functionalized linen with no CO2 present, and it was not observed that water passed through the linen, even after 3 hours.

[00489] The above has suggested that linen functonalized with switchable moieties can be cycled between hydrophobic and hydrophilic state in the presence of water, with C0₂ and Ar_(g) as triggers. It was considered that the initial 2 hours required to switch the linen from its hydrophobic state to its hydrophilic state in th presense of C0₂ switch may have been attributed to mass transfer due to the linen not being saturated with water immediately. Without wishing to be bound by theory, it was considered that the initially slow switching rate may have been a consequence of the water only being able to pass through the linen as the polymer itself became protonated and water-saturated. Once saturated with water however, Ar<g) was able to release the CO2, creating a hydrophobic membrane again; and, once CO2 was re-introduced, the linen was already saturated with water, and thus could switch back to its hydrophilic state faster.

EXAMPLE 3: Preparation and Analysis of a 1 -(3-Aminopropyl)imidazole Functionalized Cellulose Dialysis Bag (Cellulose-APIm)

[00490] Preparation of Cellulose-APIm membrane: Cellulose membrane (ca. 0.5 g; cut-off size 14,000) was placed in a 100 ml three-neck flask together with a magnetic stir bar; following which, approximately 25 mL of N'N-dimethylformamide (DMF) was added, the flask was sealed with three rubber stoppers, and then the mixture was magnetically stirred at room temperature for 1 h. The DMF was then decanted.

[00491 ] In a 100 mL beaker, 50 mL of fresh DMF was added, following which 1 , 1 '- carbonyldiimidazole (CDI; 1 g) was added, together with a magnetic stir bar. The 100 mL beaker was then magnetically stirred at room temperature for 3 min to dissolve CDI into DMF. The CDI in DMF solution was then transferred into the 100 mL three-neck flask containing the cellulose membrane. The three-neck flask was sealed again with rubber stoppers, and magenitcally stirred while partially submersed into a 50 °C oil bath. Two 16G needles were inserted into the two side rubber stoppers of the three-neck flask, and then the mixture continued to be stirred for 4 h in the 50 °C oil bath. Folowing that, 1-(3-Aminopropyl) imidazole (APIm; 2.0 mL) was added into the mixture, and the reaction proceeded for another 12 h in the 50 °C oil bath; after which, the membrane was removed, added to a separate flask, and magnetically stirred in 50 mL absolute ethanol, three separate times (15 min each time; absolute ethanol was refreshed each time). The membrane was then rinsed extensively with deionized water (DIW) until pH and conductivity of the DIW, after rising, was close to that of pure DIW. The purified, modified membrane (Cellulose-APIm) was sandwiched between two filter papers, and dried in an oven at 80 °C for 2 h. After 2 h, the dried Cellulose-APIm was ready for characterization. As a control group, native cellulose membrane was stirred with 100 mL of DIW in a 50 °C water bath for 2 h, during which the DIW was refreshed once after 1 h of stirring. The native cellulose membrane was then sandwiched between two filter papers, and dried in an oven at 80 °C for 2 h.

[00492] FT-IR characterization: FT-IR spectra of dried membranes were collected on a Varian 660 IR instrument. Transmission measurements were conducted with 16 scans at a resolution of 4 cm ¹. Each sample was measured three times at a different location of the membrane to check reproducibility of measurements (see Figure 8).

[00493] Membrane surface hydrophilic-lipophilic property characterizations: Dried Cellulose-APIm or native cellulose membrane was placed on Parafilm M® on a bench top. A micropipette was used to quickly and gently place 30 μί DIW or Dodecane on the Cellulose- APIm or native cellulose membrane. A photo of DIW or dodecane droplet on each membrane's surface was then taken from different angles. DIW and dodecane droplets were places at different locations of the membrane to check reproducibility of measurements.

[00494] Discussion:

[00495] A 1-(3-aminopropyl)imidazole surface-functionalized cellulose dialysis bag was prepared via the CDI chemistry used to immobilize 1-(3-aminopropyl)imidazole (APIm) onto CNC and cotton, and analyzed by Infrared spectroscopy (IR). The IR analysis was compared and contrasted with that of non-functionalized cellulose (Figure 8).

[00496] It was found that the functionalized and non-functionalized cellulose membranes were too thin for Attenuated Total Reflectance IR spectroscopy (ATR-IR), in that no signal was observed. Despite the thickness of the membranes being a hindrance for % transmittance IR spectroscopy, as many peaks' full height could not be observed, % transmittance IR was still used for analysis; a carbonyl band, indicative of Cellulose-APIm, could still be observed and identified in the IR spectrum (Figure 9).

[00497] Once functionalized, the Cellulose-APIm was investigated by way of contact angle analysis. At least four different positions on the membrane were analyzed for contact angle measurements. Each time, two drops of water (30 μΙ_ each: deionized (DIW) and carbonated water) were added to the membrane, one right after the other (Figure 10).

[00498] It was observed that, generally, carbonated water contacted the Cellulose- APIm at a relatively smaller contact angle than noncarbonated water. Without wishing to be bound by theory, it was considered that this was a result of the protonated APIm on the cellulose membrane, and its hydrophilicity. It was observed that the contact angles did not change significantly with time (at least within a couple of minutes). The difference in contact angles observed using the DIW suggests that the functionalized membrane is more hydrophobic under these conditions than when in the presence of CO2 from the carbonated water.

[00499] As a means of comparing and contrasting the effect surface functionalization had on the cellulose bag, a non-functionalized cellulose dialysis bag was similarly treated: two drops of water (30 μΙ_ each: DIW and carbonated water) were added to the non- functionalized membrane, one right after the other. It was observed that the water droplets collapsed/absorbed upon contact with the membrane surface. Without wishing to be bound by theory, it was considered that this was a result of the membrane's hydrophilicity even in the absence of CO2.

[00500] EXAMPLE 4A: Synthesis of Switchable Starches [00501 ] Synthesis #1 :

[00502] Starch (CAS 9005-84-9, J.T. Baker; 2 g, 36.6 mmol, 1 eq.) was added to a round bottom flask containing N,N-dimethylformamide (50 mL) and heated until it dissolved. In a separate round bottom flask, carbonyldiimidazole (5.8 g, 36.6 mmol, 1 eq.), imidazole hydrochloride (9.6 g, 91 .5 mmol, 2.5 eq.), and 3-diethylaminopropylamine (6.4 mL, 40 mmol, 1.1 eq,) were added to N,N-dimethyformamide (100 mL). The solution was heated to 60^°C and magnetically stirred rapidly for 2 h. After 2 h, the hot dissolved starch was added to the round bottom flask containing the carbonyldiimidazole, imidazole hydrochloride, and 3- diethylaminopropylamine. At this point, more imidazole hydrochloride (5.7 g, 55 mmol, 1.5 eq.) was added. The solution was heated to 80^'C for approximately 72 h. The reaction was allowed to cool, and the starch was recovered via vacuum filtration. The starch was rinsed thoroughly with N,N-dimethylformamide (3 times), followed by rinsing with methanol (3 times). Functionalized starch (1.6919 g) was recovered and used as is for further experimentation (for example, see Figure 32).

[00503] Synthesis #2:

[00504] Starch (0.4 g, 7.3 mmol, 1 eq.) was added to a round bottom flask containing dimethylsulfoxide (40 ml.) and heated to 110^°C. In a separate round bottom flask, carbonyldiimidazole (1.4 g, 8.6 mmol, 1.2 eq.), imidazole hydrochloride (1.35 g, 13 mmol, 1.5 eq.), and 3-diethylaminopropylamine (1.3 ml_, 8.6 mmol, 1.2 eq,) were added to N,N- dimethyformamide (50 ml_). The solution was heated to 100^°C and stirred rapidly for 1 h. After 1 h, the hot dissolved starch was added to the round bottom flask containing the carbonyldiimidazole, imidazole hydrochloride, and 3-diethylaminopropylamine. The solution was heated at a constant at 110^°C for approximately 16 h. The reaction was allowed to cool, and the starch was recovered via vacuum filtration. The starch was rinsed thoroughly with dimethylformamide (3 times), followed by rinsing with methanol (3 times). Functionalized starch (0.12 g) was recovered and used as is for further experimentation (for example, see Figure 32).

[00505] A slight variation on the above experimental #2 entailed heating the reaction solution at a constant 50^°C as opposed to 100^°C; however, the starch was still preheated at 110^'C until fully dissolved. Without wishing to be bound by theory, it was considered that this modification would help slow amine oxidation, which would result in a loss of the amino functionality on the starch. It was found that, as another alternative, adding excess amine (3- diethylaminoproylamine) also helped.

[00506] Discussion:

[00507] It was observed that starch was not soluble in water at room temperature, but that it could be solubilized by boiling in water for a short period of time. Once solubilized into hot water, the resultant starch solution could be cooled and stored for a moderate period of time, though it was observed that the starch would eventually aggregate and precipitate out of water. [00508] Synthesis of a switchable starch, involving surface functionalization to comprise switchable moieties as defined above, was initially investigated to provide means for solubilizing starch without use of excessive heat: without being bound by theory, it was postulated that once the switchable starch was switched to its ionized form, in the presence of an aqueous solution and an ionizing trigger such as C0₂, that it would be more soluble in water at room temperature than non-functionalized starch.

[00509] EXAMPLE 4B: Synthesis of Switchable Cellulose, and Investigations into Their Use as Drying Agents

[00510] Synthetic method 1 :

[0051 1 ] Preparation of ethylformate-functionalized cellulose:

[00512] Cellulose fibers (Sigma-Aldrich, Sigmacell cellulose type 101 , high purified, fibers) were dried overnight at 1 10 ^°C in an oven. Dried cellulose was then used as is, with no other pre-treatments. Dried cellulose fiber (6.5 g) was added to a 250 mL round bottom flask and flame dried under vacuum. Using Schlenk techniques for inert conditions, diisopropylethylamine (1 .6 eq., 0.19 mol) and anhydrous dichloromethane (150 mL, alkene stabilized) were added to the round bottom flask. The round bottom flask was cooled in an ice bath for approximately 30 minutes, after which ethylchloroformate (1.5 eq., 0.18 mol) was added drop-wise via addition funnel to the cooled mixture. The solution was warmed to room temperature and allowed to react for 12 h. The cellulose fibres were recovered by vacuum filtration and washed thoroughly with ethanol, followed by multiple washings with distilled water. The washed particles were dried at 1 10 ^"C overnight, then stored under Ar<_g) until further use.

[00513] Representative preparation switchable-functionalized cellulose :

[00514] Ethylformate-functionalized cellulose (compound 2 of Figure 35; 1 g) was added to a 150 mL round bottom flask. Following a literature procedure [Kim, B., et al., Synthesis. 2012, 44, 42-5], tetrahydrofuran (THF; 80 mL) with 0.2 % H₂0 was added to the round bottom flask and stirred for 30 min. Potassium tert-butoxide (2.2 eq.) was added, turning the clear solution to a cloudy light yellow. A select amine (1 .1 eq.) was added to the reaction mixture, which was then left stirring overnight at room temperature (26 ^°C) exposed to air.

[00515] Representative procedure for testing switchable celluloses as drying agents: [00516] Solvent chosen to compare utility of switchable cellulose materials as drying agents was isobutanol, which was doped with 5 wt% H₂0. The switchable cellulose and 'wet' isobutanol solution was added to a vial, and C0₂ was bubbled through the solution for 1 h. The vial was then sealed and stirred for 15 h. The switchable cellulose was separated from the wet isobutanol solution via vacuum filtration; water content remaining in the isobutanol solution after filtration was analyzed via gas chromatography thermal conductivity detector (GC-TCD). Results are reported in Table 1 1.

[00517] There were a total of 5 amines prepared and tested via the procedures delineated above, each being assigned a title A1 - A5. A1 : 3-(dimethylamino)-1 -propylamine. A2: 3-(dibutylamino)-1-propylamine. A3: 3-(diethylamino)-1-propylamine. A4: 1 -(3- aminopropyl)imidazole. A5: N-(3-aminopropyl)piperidine. In the case of A1 , compound 3 of Figure 35 was formed.

[00518] Synthetic method 2:

[00519] Preparation of ethylformate-functionalized cellulose:

[00520] Cellulose fibers (Sigma-Aldrich, Sigmacell cellulose type 101 , high purified, fibers) were dried overnight at 1 10 ^°C in an oven. Dried cellulose was then used as is, with no other pre-treatments. Dried cellulose fiber (6.5 g) was added to a 250 mL round bottom flask and flame dried under vacuum. Using Schlenk techniques for inert conditions, diisopropylethylamine (1 .6 eq., 0.19 mol) and anhydrous dichloromethane (150 mL, alkene stabilized) were added to the round bottom flask. The round bottom flask was cooled in an ice bath for approximately 30 minutes, after which ethylchloroformate (1.5 eq., 0.18 mol) was added drop-wise via addition funnel to the cooled mixture. The solution was warmed to room temperature and allowed to react for 12 h. The cellulose fibers were recovered by vacuum filtration and washed thoroughly with ethanol, followed by multiple washings with distilled water. The washed particles were dried at 1 10 ^"C overnight, then stored under Ar<_g) until further use.

[00521 ] Preparation of switchable cellulose:

[00522] 3-(dimethylamino)-1-propylamine (DMAPA, 1 eq. 75.2 mmol) was added drop-wise under inert conditions to a cooled (ice bath, ca. 1 ^°C) suspension of sodium hydride (1 eq., 75.2 mmol) in tetrahydrofuran (40 mL). The ice bath was removed and the mixture was stirred rapidly while being allowed to warm to room temperature (ca. 26^°C) over the course of ca. 3 h. In a separate round bottom flask, the ethylformate-functionalized cellulose (2) was dried at 110^"C for 3 h and then stored temporarily under dynamic argon. The mixture of 3-(dimethylamino)propyl-1 -amine and sodium hydride (comprising sodium (3- aminopropyl) dimethylamine; compound 1 of Figure 36) was then transferred via cannula into the round bottom containing the ethylformate-functionalized cellulose (compound 2 of Figure 36) after 3h has passed. The resultant mixture was stirred rapidly at room

temperature overnight to yield (compound 3 of Figure 36). The reaction was neutralized using an ca. 1.3 eq. solution of ammonium chloride (in excess) in water. Functionalized cellulose (A1 - Method 2) was recovered using vacuum filtration. In order to deprotonate any of the cellulose protonated by the excess ammonium chloride, it was mixed overnight in a solution of tetramethylguanidine / tetrahydrofuran (1 :4 v/v). The functionalized cellulose (A1 -Method 2) was then rinsed with copious amounts of ethanol, followed by sonication for 20 minutes in 50 mL of ethanol (repeated three times). The functionalized cellulose (A1 - Method 2) was then dried in an oven at 110^°C for 4 h, after which it was characterized by FTIR: non-functionalized cellulose: 3242 cnr¹ (s, b), 2899 cnr¹ (m, b), 1651 cnr¹ (w, b), 1433- 1261 cnr¹ (m, b), 1 162-1059 cnr¹ (s, b), 896 cnr¹ (w, sh); functionalized cellulose: 3241 cnr¹ (s, b), 2921 cnr¹ (m, b),1616 cnr¹ (m, b), 1433-1261 cnr¹ (m, b), 1 162-1059 cnr¹ (s, b), 896 cnr¹ (w, sh), 750-850 (w, sh); m=medium, w=weak, s=strong, n=narrow, b=broad, sh=sharp.

[00523] Representative procedure for testing switchable celluloses as drying agents:

[00524] Solvent chosen to compare utility of switchable cellulose materials as drying agents was isobutanol, which was doped with 5 wt% H₂0. The switchable cellulose and 'wet' isobutanol solution was added to a vial, and CO2 was bubbled through the solution for 1 h. The vial was then sealed and stirred for 15 h. The switchable cellulose was separated from the wet isobutanol solution via vacuum filtration; water content remaining in the isobutanol solution after filtration was analyzed via gas chromatography thermal conductivity detector (GC-TCD). Results are reported in Table 12.

[00525] Discussion:

[00526] FT-IR analysis of A1 , Method 2 suggests functionalization of cellulose with 3- (dimethylamino)-l-propylamine was successful: the IR spectrum of A1 was different from the IP spectrum of non-functionalized cellulose, in that the peak at ~1600 cnr¹ was broader for A1 than non-functionalized cellulose, and is indicative of functionalization.

[00527] Synthetic method 3: [00528] 3-(Dibutylamino)-1 -propylamine (DBAPA, 1 eq. 75.2 mmol) was added drop- wise under inert conditions to a cooled (ice bath, ca. 1 ^°C) suspension of sodium hydride (1 eq., 75.2 mmol) in tetrahydrofuran (40 ml_). The ice bath was removed, and the mixture was stirred rapidly while being allowed to warm to room temperature (ca. 26^°C) over ca. 3 h. In a separate round bottom flask, ethylformate-functionalized cellulose (compound 2) was dried at 110^°C for 3 h, and then stored temporarily under dynamic argon. The mixture of 3- (dibutylamino)propyl-l -amine and sodium hydride (comprising sodium (3-aminopropyl) dibutylamine) was then transferred via cannula under inert conditions into the round bottom flask containing the ethylformate-functionalized cellulose after 3 h had passed. The resultant mixture was stirred rapidly at room temperature overnight to yield a butyl-amine

functionalized cellulose. The reaction was neutralized using ca. 1 .3 eq. solution of ammonium chloride (in excess) in water. Functionalized cellulose was recovered using vacuum filtration.

[00529] In order to deprotonate any of the functionalized cellulose protonated by excess ammonium chloride, it was stirred overnight in a solution of tetramethylguanidine / tetrahydrofuran (1 :4 v/v). The functionalized cellulose (A2 - Method 3) was then rinsed with copious amounts of ethanol, followed by sonication for 20 minutes in 50 mL of ethanol (repeated three times). The functionalized cellulose (A2 - Method 3) was then dried in an oven at 1 10^°C for 4 h, after which it was characterized by FT-IR: non-functionalized

cellulose: 3242 cnr¹ (s, b), 2899 cnr¹ (m, b), 1651 cnr¹ (w, b), 1433-1261 cnr¹ (m, b), 1 162- 1059 cnr¹ (s, b), 896 cnr¹ (w, sh); functionalized cellulose: 3241 cnr¹ (s, b), 2921 cnr¹ (m, b), 1616 cm^"1 (m, b), 1433-1261 cnr¹ (m, b), 1 162-1059 cnr¹ (s, b), 896 cnr¹ (w, sh), 750-850 cnr¹ (w, sh); functionalized cellulose exhibited an increased intensity in broad shifts in the following ranges: 1000-1200 cnr¹ (C-N stretch), 2800-3000 cnr¹ (potential carbamate ester N-H) and 3300-3500 cnr¹ (potential carbamate ester N-H); m=medium, w=weak,s=strong, n=narrow, b=broad, sh=sharp.

[00530] Representative procedure for testing switchable celluloses as drying agents:

Solvent chosen to compare utility of switchable cellulose materials as drying agents was isobutanol, which was doped with 5 wt% H₂0. The switchable cellulose and 'wet' isobutanol solution was added to a vial, and CO2 was bubbled through the solution for 1 h. The vial was then sealed and stirred for 15 h. The switchable cellulose was separated from the wet isobutanol solution via vacuum filtration; water content remaining in the isobutanol solution after filtration was analyzed via gas chromatography thermal conductivity detector (GC- TCD). For results, see A2 - Method 3, Table 33.

[00531 ] EXAMPLE 5: Functionalization of Filter Paper

[00532] Method 1 (Figure 13):

[00533] As described above, it has been postulated that the herein described switchable polysaccharides can find use as switchable filter papers. Though work is on going to investigate this application of switchable polysaccharides, a proof of principal experiment was undertaken to functionalize Whatman Type I filter paper with a long-chain (i.e. waxy) carboxylic acid via a CDI-mediated coupling, a demonstrative, non-limiting example of which is depicted in Figure 13.

[00534] The resultant functionalized filter paper was then analyzed by way of contact angle analysis via the sessile drop method (see Table 9); it was found that, following functionalization, the filter paper was hydrophobic, suggesting that the functionalization had been successful.

[00535] The present Example indicates that a switchable filter paper can be synthesized by functionalizing standard filter paper using an appropriate carboxylic acid functionalized with a switchable moiety, as described herein.

[00536] Method 2 (Figure 37):

[00537] A cellulosic substrate (whatman type 1 filter paper, 42.5 mm) was dried at 1 10 ^°C overnight and placed into a 250 ml_ round bottom flask and stored under Ar gas. In a separate round bottom flask, a solution of carbonyldiimidazole (5.14 mmol, 1 eq.) and 3- (dimethylamino)propionic acid hydrochloride (5.14 mmol, 1 eq.) in tetrahydrofuran (ca. 50 mL) was mixed rapidly for 4 h. A solution-containing compound 1 of Figure 37 was transferred into the round bottom flask containing the cellulosic substrate; the resultant mixture was left stirring under a dynamic flow of C0₂ overnight at room temperature (ca. 26^"C) [Vaidyanathan, R. et al., J. Org. Chem. 2004, 69, 2565-2568]. The substrate was rinsed with copious amounts of ethanol, followed by sonication for 20 minutes in 50 mL of ethanol (repeated three times). In order to activate the functionalized cellulose substrate by removing the hydrochloride salt of 1 of Figure 37, the substrate was mixed overnight in a solution of tetramethylguanidine / tetrahydrofuran (1 :4 v/v). The cellulosic substrate was then rinsed with copious amounts of ethanol, followed by sonication for 20 minutes in 50 mL of ethanol (repeated three times). The functionalized substrate was then dried in an oven at 1 10 ^°C for 4 h.

[00538] Method 3 (Figure 38):

[00539] A cellulosic substrate (whatman type 1 filter paper, 42.5 mm) was dried at 1 10 ^"C overnight and placed into a 250 mL round bottom flask and stored under argon. In a separate round bottom flask, a solution of carbonyldiimidazole (5.14 mmol, 1 eq.) and 3- (dimethylamino)propionic acid hydrochloride (5.14 mmol, 1 eq.) in tetrahydrofuran (ca. 50 mL) was mixed rapidly for 4 h. The solution containing compound 1 of Figure 38, as well as imidazole hydrochloride (mild acid catalyst; 25.7 mmol, 5 eq.), were added to the round bottom flask containing the cellulosic substrate. The resultant mixture was left mixing overnight at room temperature (ca. 26 ^°C). The substrate (compound 2 of Figure 38) was rinsed with copious amounts of ethanol, followed by sonication for 20 minutes in 50 mL of ethanol (repeated three times). In order to deprotonate the functionalized cellulose substrate by removing the hydrochloride salt of 1 of Figure 38, the substrate was mixed overnight in a solution of tetramethylguanidine / tetrahydrofuran (1 :4 v/v). The cellulosic substrate (compound 3 of Figure 38) was then rinsed with copious amounts of ethanol, followed by sonication for 20 minutes in 50 mL of ethanol (repeated three times). The functionalized substrate was then dried in an oven at 1 10 ^°C for 4 h.

[00540] Method 4 (Figure 39):

[00541 ] A cellulosic substrate (whatman type 1 filter paper, 42.5 mm) is dried at 1 10

^"C overnight and placed into a 250 mL round bottom flask and stored under argon. In a separate round bottom flask, a solution of carbonyldiimidazole (5.14 mmol, 1 eq.) and 3-

(dimethylamino)propionic acid hydrochloride (5.14 mmol, 1 eq.) in tetrahydrofuran (ca. 50 mL) was mixed rapidly overnight. Compound 1 of Figure 39 is isolated and treated with methyliodide (4eq.) in acetonitrile at room temperature (ca. 26 ^°C) and is stirred for 24 h.

The solvent is removed under vacuum to yield compound 2 of Figure 39. Compound 2 (1 eq.) is added to a round bottom flask containing the dried filter paper and triethylamine (1 eq.), and the solution is stirred at room temperature (ca. 26 ^°C) for 24 h. The substrate is rinsed with copious amounts of ethanol, followed by sonication for 20 minutes in 50 mL of ethanol (repeated three times). To deprotonate the functionalized cellulose substrate by removing the hydrochloride salt of compound 3 of Figure 39, the substrate is mixed overnight in a solution of tetramethylguanidine / tetrahydrofuran (1 :4 v/v). The cellulosic substrate is then rinsed with copious amounts of ethanol, followed by sonication for 20 minutes in 50 mL of ethanol (repeated three times). The functionalized substrate (compound 4 of Figure 39) is then dried in an oven at 110 ^"C for 4 h.

[00542] Method 5:

[00543] Grafting of switchable poly-[(dimethylamino)propyl]methacrylamide onto filter paper (attempt 1):

[00544] General materials list for grafting from on filter paper:

[00545] Ν,Ν-Diisopropylethylamine (DIPEA; Aldrich, 99%), 2-bromo-2-methylpropionyl bromide (BIBB; Aldrich, 98%), copper(l) bromide (Aldrich, 99.999%), N,N,N',N",N"- pentamethyldiethylenetriamine (PMDETA, Aldrich, 99%), N-[3-(dimethylamino)- propyl]methacrylamide (DMAPMAm, Aldrich, 99%), 4-dimethylaminopyridine (DMAP, Aldrich, 99%), ethylenediaminetetraacetic acid (EDTA, Aldrich, 98.5%), anhydrous tetrahydrofuran (THF, EMD chemicals, 99.9 %), anhydrous methanol (MeOH, EMD chemicals, 99.8%), aluminum oxide, activated basic Brockmann I (Aldrich, standard grade), N-(1 -napthyl)-N-phenylmethacrylamide (NPMAm, Aldrich, 98%), ethyl 2-bromo-2- methylpropionate (eBIBB, Aldrich, 98%).

[00546] A cellulosic substrate (fisherbrand filter paper, 9 cm diameter, type P8, 0.4163 g, 2.31 mmolcH20H) was dried at 110 ^°C overnight, torn into six pieces, placed into a 500 mL round bottom flask and stored under Argon. The round bottom flask containing the cellulosic substrate was charged with a solution of N,N-diisopropylethylamine (46 mmol) in

tetrahydrofuran (ca. 50 mL). The solution was cooled to approximately 0 ^°C with an ice water bath. To the cooled solution, 2-Bromo-2-methylpropionyl bromide (BIBB, 46 mmol), a known initiator for Atom Transfer Radical Polymerization (ATRP), was added drop-wise. Once drop-wise addition had completed, the solution remained in the ice bath for approximately 20 min, after which, the ice bath was removed, and the solution was left to equilibrate to room temperature, ca. 26 ^°C. This reaction was left overnight and ran for a total of 18 h. The resultant BIBB-functionalized filter paper was rinsed thoroughly with tetrahydrofuran, followed by methanol, and then dried at 1 10 ^°C overnight before subsequent usage.

[00547] The BIBB-functionalized filter paper was placed inside a 100 mL round bottom flask, the flask was charged with a stir bar, N,N- [(dimethylamino)propyl]methacrylamide (DMAPMAm, 205 mmol, 200 eq.) and N-(l -napthyl)- N-phenylmethacrylamide (NPMAm, 0.35 mmol, 1 .2 eq.) under argon. NPMAm is a UV active monomer, and if incorporated, the resultant co-polymer was expected to fluoresce under UV light (AMAX 220 nm). DMAPMAm was run through a basic alumina column to remove monomethyl ether of hydroquinone (MEHQ), a radical inhibitor. MEHQ was removed from DMAPMAm but not from NPMAm because it was considered that the amount of NPMAm used did not contain enough inhibitor to warrant removal (500-1000 ppm MEHQ in 100 mg NPMAm). It was understood that MEHQ would not inhibit the ATRP, only slightly retard rates of reaction. The flask was charged with 50 mL of anhydrous methanol, and degassed with argon via a needle for 1 h. In a separate round bottom flask, catalyst was prepared: copper(l)bromide (0.30 mmol, 1 eq.) was mixed with N,N,N',N",N"- pentamethyldiethylenetriamine (PMDETA, 0.60 mmol, 2 eq.) in 15 mL of anhydrous methanol under argon. The catalyst solution was degassed with argon via a needle for 0.5 h. The solution containing monomer and filter paper bound initiator was heated to 50 ^°C, and the catalyst solution was transferred into it via cannula under argon. Polymerization was left to occur, with stirring under argon, over the course of 3 days. The polymer-grafted filter paper was rinsed first with methanol to remove physisorbed compounds, followed by a 0.1 M solution of EDTA in water to remove left over copper catalyst. The washed polymer-grafted filter paper was then dried in a vacuum oven at 100 ^"C for 4 h.

[00548] Subsequent analysis by ATR-FTIR did not detect a difference between the polymerized filter paper and native substrate. Filter paper was not found to be hydrophobic, as it absorbed water. Without wishing to be bound by theory, it was considered that the BIBB reaction failed due in part to over heating of the fibers before functionalization.

[00549] Grafting of switchable poly-[(dimethylamino)propyl]methacrylamide onto filter paper (attempt 2):

[00550] A cellulosic substrate (whatman type 1 filter paper, 42.5 mm, 0.1240 g, 0.625 mmolcH20H) was rinsed thoroughly in acetone, followed by tetrahydrofuran. The cellulosic substrate was then sonicated in acetone for 30 min, followed by sonication in tetrahydrofuran for 30 min. The cellulosic substrate was then left in fresh tetrahydrofuran to soak for 4 h. In a 100 mL 2-neck round bottom flask, a solution of triethylamine (TEA, 2.2 eq., 1 .375 mmol, 0.1916 mL), 2-bromo-2-methylpropionyl bromide (BIBB, 2 eq., 1 .25 mmol, 0.154 mL) and a catalytic amount of 4-dimethylaminopyridine (DMAP, 0.01 eq., 0.0625 mmol, 7.6 mg) was prepared in 40 mL of tetrahydrofuran at room temperature. The cellulosic substrate was immersed into the solution and left overnight at room temperature (ca. 26 ^°C) to react under argon. The functionalized substrate was then rinsed and sonicated in tetrahydrofuran, followed by sonication in methanol. The functionalized substrate was left in dry methanol until it was ready to be polymerized under argon.

[00551 ] This procedure was slightly adapted from Calmark and Malmstrom, Journal of applied polymer science, 2006, 100, 4155-5162.

[00552] The resultant BIBB-functionalized filter paper was placed inside a 250 mL round bottom flask, this flask was charged with N,N-[(dimethylamino)propyl]methacrylamide (DMAPMAm, 300 eq. 186 mmol, 34 mL) and 100 mL of anhydrous methanol . A stir bar was added, and the flask was degassed with argon via a needle for 1 h. Radical inhibitor MEHQ was removed from DMAPMAm by flowing the monomer over basic alumina. In a separate flask, catalyst was prepared: copper(l)bromide (1 eq., 0.625 mmol, 90 mg) was mixed with N,N,N',N",N"-Pentamethyldiethylenetriamine (PMDETA, 2 eq., 1.2 mmol, 0.26 mL) in 15 mL of anhydrous methanol. The catalyst solution was degassed via needle with argon for 0.5 h. The solution containing the monomer and filter paper bound initiator was heated to 45 ^"C, and the catalyst solution was transferred into it via cannula under argon. Polymerization was left to occur, with stirring under argon, over the course of 34 h. The resultant polymer-grafted filter paper was sonicated for 20 min in fresh methanol (3x) to remove physisorbed polymer, excess monomer, ligand, and catalyst. The filter paper was sonicated in 0.1 M EDTA solution to remove physisorbed copper. Subsequent ATR-FTIR analysis, relative to native cellulose, suggested presence of polymer on the filter paper, with an amide peak at ~1640 cm ¹ (for example, see Figure 78). Two different spots on the above-described polymer- grafted filter paper were analyzed by ATR-FTIR, and a varying amide peak height at ~1640 cm ¹ was observed; this suggested that the polymer-grafting may not have occurred equally across the filter paper.

[00553] Grafting of switchable poly-[(dimethylamino)propyl]methacrylamide on filter paper (attempt 3):

[00554] A cellulosic substrate (whatman type 1 filter paper, 42.5 mm, 0.1240 g, 0.625 mmolcH20H) was rinsed thoroughly in acetone, followed by tetrahydrofuran. The cellulosic substrate was then sonicated in acetone for 30 min, followed by sonication in tetrahydrofuran for 30 min. The cellulosic substrate was then left in fresh tetrahydrofuran to soak for 4 h. In a

100 mL 2-neck round bottom flask, a solution of triethylamine (TEA, 2.2 eq., 1 .375 mmol,

0.1916 mL), 2-bromo-2-methylpropionyl bromide (BIBB, 2 eq., 1 .25 mmol, 0.154 mL), and a catalytic amount of 4-dimethylaminopyridine (DMAP, 0.01 eq., 0.0625 mmol, 7.6 mg) was prepared in 40 mL of tetrahydrofuran at room temperature under argon. The cellulosic substrate was immersed into the solution and left overnight at room temperature (ca. 26 ^°C) to react. The resultant functionalized substrate was then rinsed and sonicated in

tetrahydrofuran, followed by sonication in methanol. The functionalized substrate was left in dry methanol until it was ready to be polymerized.

[00555] This procedure was slightly adapted from Calmark and Malmstrom, Journal of applied polymer science, 2006, 100, 4155-5162.

[00556] The BIBB-functionalized filter paper was placed inside a 250 mL round bottom flask, the flask was charged with N,N-[(dimethylamino)propyl]methacrylamide (DMAPMAm, 300 eq. 186 mmol, 34 mL), ethyl 2-bromo-2-methylpropionate (eBIBB, 0.005 eq., 0.0031 mmol, 0.000455 mL) and 100 mL of anhydrous methanol under argon. Ethyl 2- bromo-2-methylpropionate was used as an ATRP initiator and served as a sacrificial initiator. A stir bar was added to the round bottom flask, and the flask was degassed with argon via a needle for 1 h. The radical inhibitor MEHQ was removed from DMAPMAm by flowing the monomer over basic alumina. In a separate flask, catalyst was prepared: copper(l)bromide (1 eq., 0.625 mmol, 90 mg) was mixed with Ν,Ν,Ν' ,Ν' ' ,Ν' ' - pentamethyldiethylenetriamine (PMDETA, 2 eq., 1 .2 mmol, 0.26 mL) in 15 mL of anhydrous methanol . The catalyst solution was degassed via needle with argon for 0.5 h. The solution containing the monomer, sacrificial initiator and filter paper-bound initiator was heated to 45 ^'C under argon, and the catalyst solution was transferred into it via cannula. Polymerization was left to occur, with stirring under argon, over the course of 34 h. The resultant polymer- grafted filter paper was sonicated for 20 min in fresh methanol (3x) to remove physisorbed polymer, excess monomer, ligand and catalyst. It was observed that the filter paper appeared white, with no colour from residual copper being noted. Subsequent ATR-FTIR analysis, relative to native cellulose, suggested presence of polymer on the filter paper, with an amide peak at ~1640 cm ¹ (for example, see Figure 78). Two different spots on the above-described polymer-grafted filter paper were analyzed by ATR-FTIR, and a varying amide peak height at ~1640 cm ¹ was observed; this suggested that the polymer-grafting may not have occurred equally across the filter paper.

[00557] Discussion: [00558] Water contact analysis of the switchable polymer-grafted filter paper from Attempts 2 and 3 showed that absorption of a water droplet was retarded by 2-4 seconds relative to native filter paper, which instantaneously absorbed water. This suggested that the surface of the filter paper had been rendered more hydrophobic relative to native cellulose. It has been considered that use of more hydrophobic polymeric amines, such as N,N- [(dibutylamino)propyl]methacrylamide, or a polymer synthesized from 2- (diisopropylamino)ethyl methacrylate (DIAEMA, Aldrich, 97%), may generate a relatively more hydrophobic filter paper material.

[00559] As such, it has been considered that the above-described switchable polymer-grafted filter paper is suitable for facilitating separation of hydrophobic materials from an aqueous mixture - and that switching the polymer On' in the presence of an acid gas (such as C0₂) will allow isolation of said hydrophobic materials from the surface of the filter paper.

[00560] EXAMPLE 6A: Synthesis and characterization of C0₂ responsive Chitosan-g- Poly(Diethylaminoethyl methacrylate).

[00561 ] Materials: Chitosan (CTS, Aldrich, degree of deacetylation of 85%), glycidyl methacrylate (GMA, Aldrich, 97%), hydroquinone (Fisher), acetic acid (Fisher, 99.7%), tetrahydrofuran (THF, ACP, 99+%), deuterium oxide (Cambridge Isotope Laboratories, D 99.9%). Styrene (St, Aldrich, 99+%) and 2-(Diethylamino)ethyl methacrylate (DEAEMA, Aldrich, 99%) were passed over a column containing basic aluminum oxide (Aldrich, - 150 mesh, 58 A) to remove the inhibitor and stored below 5°C prior to polymerization. Ν,Ν^'- dicyclohexylurea was purchased from Aldrich and used as received. SG 1 (N-tert-butyl-N-(1 - diethylphosphono-2,2-dimethylpropyl) nitroxide) (85%, kindly supplied by Arkema). N- Hydroxysuccinimide-BlocBuilder (NHS-BB) was synthesized from BlocBuilder (BB, N-(2- methylpropyl)-N-(1 -diethylphosphono-2,2-imethylpropyl)-0-(2-carboxylprop-2-yl)

hydroxylamine (BB, 99%, provided by Arkema) according to the reported procedure [J. Vinas, N. Chagneux, D. Gigmes, T. Trimaille, A. Favier and D. Bert , Polymer, 2008, 49, 3639-3647.], as follows: BB (5 g, 13.1 mmol) and N-hydroxysuccinimide (1 .81 g, 15.7 mmol) were dissolved in THF (20 mL) and deoxygenated by nitrogen bubbling for 15 min. Then, a degassed solution of N,N^'dicyclohexylcarbodiimide (3 g, 14.4 mmol) in THF (5 mL) was added. After stirring at 0°C for 1 .5 h, the precipitated Ν,Ν^'-dicyclohexylurea was removed by filtration and the filtrate volume was reduced under vacuum to one third and placed at -20°C for 2 h in order to precipitate the residual Ν,Ν^'-dicyclohexylurea. After filtration, the solution was concentrated under reduced pressure and precipitation was performed in pentane. The obtained solid was further washed with water to remove N-hydroxysuccinimide. After drying under vacuum, alkoxyamine 1 was obtained as a white powder. Nickel sulphate

(NiS0₄-6H₂0, Aldrich, 99%), concentrated nitric acid (Aldrich, 68.0-70%) and carbon dioxide gas (MEGS, bone dry 99.8%) were obtained for the equilibrium absorption studies.

[00562] Instrumentation: ¹H NMR spectroscopy was performed on an FT-NMR Bruker Avance 400 MHz spectrometer with a total of 256 scans, at room temperature using

D₂O/CH3COOH 0.4 M as solvent at 5 mg/mL. Fourier Transform Infrared (FT-IR)

spectroscopy was carried out on a Thermo Scientific. Thermogravimetric analysis (TGA) was performed using a TA Instruments Q500 TGA analyser by heating the sample using the following ramp: 10°C min ¹ from 30 to 75°C, held for 30 min at a plateau of 75°C, and 10 °C min^-1 to 600°C. Gel Permeation Chromatography (GPC) analysis was performed with a Waters 2690 Separation Module and Waters 410 Differential Refractometer with THF as the eluent. The column bank consisted of Waters Styragel HR (4.6x300 mm) 4, 3, 1 , and 0.5 separation columns at 40°C. pH measurements were completed with a Thermo Fisher Scientific Inc. Orion Star A21 1 Benchtop Meter. Agitation for equilibrium absorption studies was completed with a 120V, VWR International LLC. Standard Orbital shaker model 5000 (shaker table).

[00563] Synthesis of Chitosan-g-glycidyl methacrylate (CTS-g-GMA):

[00564] CTS-g-GMA was synthesized (see Figure 14) using a methodology published by Garcia-Valdez et a/. , which offered slight modifications over a previous report [O. Garcia-Valdez, R. Champagne-Hartley, E. Saldivar-Guerra, P. Champagne and M. F. Cunningham, Polymer Chemistry, 2015; O. Garcia-Valdez, R. Champagne-Hartley, E. SALDIVAR-GUERRA, P. Champagne and M. F. Cunningham, POLYMER-15-185, 2015; E. A. Elizalde-Pefia, N. Flores-Ramirez, G. Luna-Barcenas, S. R. Vasquez-Garcia, G.

Arambula- Villa, B. Garcia-Gaitan, J. G. Rutiaga-Quifiones and J. Gonzalez-Hernandez, European Polymer Journal, 2007, 43, 3963-3969]. Chitosan (1 .0 g) was dissolved in 100 mL of 0.4 M acetic acid solution (2.4 g, 2.28 mL in 100 mL of de-ionized water) in a 250 mL three neck round bottom flask under magnetic agitation using an egg-shaped stir bar (size: 1 .90 x 0.95 cm). After that, 5 mL of 0.05 M KOH (0.014g of KOH dissolved in 5mL of water) and 10 mL of 9.08 mM hydroquinone solution (0.01 g, 9.08*10 ⁵ mol in 10 mL of water) was added to the mixture. A mercury thermometer and a condenser were connected to the three neck round bottom flask while water at 5°C was circulated. Then the mixture was degassed under nitrogen for 30 minutes prior to be heated to 65^°C in an oil bath. When the chitosan solution reached 65°C, GMA (24.0 mmol, 3.53 g, 3.30 mL) was injected to the flask dropwise and the mixture was magnetically stirred for 2 hours under these conditions. The solvent was removed under vacuum and the product was washed twice with THF (~80 mL) and once with de-ionized water (~80 mL) and filtered under vacuum. CTS-g-GMA was analyzed by ¹H NMR.

[00565] CTS-g-GMA was synthesized by reaction of an epoxide group of GMA with a primary alcohol from CTS under acidic conditions (pH=3.8). Protection of the CTS amino groups was achieved by performing the reaction under acidic conditions, where the amino groups were protonated and thus, were not able to react with the epoxy group of the GMA. ¹H NMR for CTS-g-GMA (Figure 17) showed peaks at 3.09, 3.67, 3.83, and 4.52 ppm attributed to H2, H5-6, H3-6, and H1 respectively. Peaks at 4.24 ppm were attributed to protons H7, 8 of GMA, which were closest to CTS' ether linkage. Peaks at 5.71 and 6.1 1 ppm were attributed to vinyl protons H10, 1 1 protons of the GMA unit. Degree of functionalization of CTS with GMA was estimated to be 1 1 mol%, based on integral ratio between GMA's vinyl proton peak at 6.1 ppm and CTS' proton peak at 3.1 ppm.

[00566] Synthesis of Poly((Diethylamino)ethyl methacrylate) (PDEAEMA) via

Nitroxide mediated polymerization:

[00567] Polymerization of DEAEMA was completed using similar NMP methodology from previous publications [J. Nicolas, S. Brusseau and B. Charleux, Journal of Polymer Science Part A: Polymer Chemistry, 2010, 48, 34-47; J. Nicolas, C. Dire, L. Mueller, J. Belleney, B. Charleux, S. R. A. Marque, D. Bertin, S. Magnet and L. Couvreuer,

Macrmolecules, 2006, 39, 8274-8282] (Figure 15). In a 250 mL three neck round bottom flask, the un-inhibited DEAEMA (0.26 mol, 50 g, 47.57 mL), styrene (0.03 mol, 3.12 g, 3.47 mL), NHS-BlocBuilder® (0.0029 mol, 1.4038 g) and SG 1 (0.0003 mol, 0.1016 g, 0.1022 mL) were mixed magnetically using an egg-shaped stir bar (size: 1 .90 x 0.95 cm). A mercury thermometer and a condenser were connected to the three neck round bottom flask while water at 5°C was circulated. The mixture was degassed under nitrogen for 30 minutes. The mixture was maintained at 80^°C using an oil bath and stirred for 1 hour. After, PDEAEMA was precipitated in hexanes (250 mL) cooled with liquid nitrogen (300 mL), decanted, washed in THF (300 mL), re-precipitated in 250 mL of hexanes (cooled with liquid nitrogen) and decanted. Analysis was completed via GPC and TGA. [00568] PDEAEMA was synthesized via nitroxide-mediated polymerization.

Conversion of monomer into polymer (determined by gravimetry) was 53%. Molecular weight distribution of PDEAMEA obtained by GPC (Figure 18) was narrow, suggesting a well- controlled reaction. Average weight molecular weight (M_w) was 13316 g/mol, and number average molecular weight (M_n) was 9714 g/mol, which gave a dispersity index (D=M_W/M_n) of 1 .37.

[00569] Synthesis of CTS-g-GMA-PDEAEMA:

[00570] Grafting to synthesis was conducted using the following procedure (see Figure 16). In a 250 mL three neck round bottom flask, CTS-g-GMA (1 .2182 g) was dissolved in 100 mL of 0.1 M acetic acid (0.6 g, 0.57 mL in 100 mL of de-ionized water) solution. The pH of the solution was then adjusted to 5.0 using 50 mL of 1 .0 M KOH (0.2805 g in 50 mL of de-ionized water) solution. A mercury thermometer and a condenser were connected to the three neck round bottom flask while water at 5°C was circulated. The mixture was degassed for 30 minutes under a nitrogen atmosphere and heated to 90^°C. PDEAMEA (2.40 g) was dissolved in 60 mL of 0.1 M acetic acid (0.36 g, 0.342 mL in 100 mL of de-ionized water) solution and degassed for 30 minutes. When the CTS-g-GMA solution reached 90^°C, the polymer solution was added in a semi-batch manner: 20 mL every hour. The total reaction was 3 hours. After the reaction system was cooled in an ice bath, the solvent was removed under vacuum. The product was washed twice with THF (~80 mL), once with 0.1 M KOH (0.560 g in 100 mL of water) solution, once with de-ionized water (~80 mL) and vacuum dried. The product was analyzed via TGA and ¹H NMR.

[00571 ] Proposed mechanism of grafting PDEAEMA chains to CTS-g-GMA was based on thermal dissociation of SG1 from the polymer chain resulting in two radicals: a stable SG 1-nitroxide radical and a free radical at the end of the polymer chain; this chain- end radical reacted with the double bond of CTS-g-GMA before being deactivated by the SG 1 , covalently linking the polymer chain to CTS. Degree of functionalization of chitosan with PDEAEMA was determined by ¹H NMR, by the ratio of methyl group protons of the PDEAEMA to the CTS backbone chain, divided by a number-average degree of

polymerization of PDEMA in the polymer chain. It was determined that for every 100 CTS units, 2.7 chains of PDEAEMA were attached, which corresponds to 135 DEAEMA units for every 100 chitosan units.

[00572] ¹H-NMR spectra CTS-g-GMA-PDEAEMA (Figure 19) showed peaks of CTS previously discussed. Signals characteristically belonging to PDEAEMA (PDEAEMA methyl groups at 1.4 ppm, 3.21 and 3.45 ppm; signals attributed to six protons in a-position to the

PDEAEMA amino group) suggested the success of the 'grafting to' synthesis.

[00573] CTS-g-GMA-PDEAEMA was also analyzed by thermogravimetric analysis (TGA) (Figure 20). The TGA indicated that CTS backbone chains decompose between 250 and 350°C, and the PDEAEMA around 350 and 450°C, which confirmed presence of PDEAEMA covalently attached to CTS.

[00574] Ni(ll) Sorption Equilibrium Studies:

[00575] Equilibrium sorption studies were conducted using a combination of previously reported procedures [P. Champagne-Hartley, A Combined Passive System for the Treatment of Acid Mine Drainage, Ottawa, 2001 ; S. R. Popuri, Y. Vijaya, V. M. Boddu and K. Abburi, Bioresources Technology, 2009, 100, 194-199]. Stock solutions were diluted to the desired Ni(ll) concentrations of 50, 200, 500 and 1000 mg/L from nickel sulphate at ambient laboratory conditions. To a 250 mL beaker, 50 mg of a specific absorbent (e.g. switchable chitosan) and 100 mL of a desired stock solution were added. After recording an initial pH, the beakers were covered and agitated at 150 rpm on a shaker table. After a 24 hour contact period, a final pH of the samples was recorded. 10 mL samples were filtered using 0.2 pm PTFE syringe filters and acidified with two drops of concentrated nitric acid.

[00576] Trials that required pH adjustment via carbon dioxide were prepared by adding 50 mg of an absorbent and 100 mL of de-ionized water to a 250 mL beaker. After an initial pH reading, 1 hour of carbon dioxide gassing was completed and a final pH recorded. Nickel sulphate was added in an appropriate proportion to meet a desired initial concentration (50, 200, 500 or 1000 mg/L), and the solution stirred with a magnetic star bar (size: 2.5 cm x 0.8 cm) at 350 rpm for 15 minutes to complete dissolution. For metal analysis, an initial 5 mL sample was taken and acidified with two drops of nitric acid, and the beaker was agitated at 150 rpm for 24 hours. Final metal content was analyzed via a 10 mL sample acidified with two drops of nitric acid.

[00577] Metal concentrations were determined via ICP-OES analysis completed by Queen's University Analytical Services Unit.

[00578] For each absorbent, the unit equilibrium uptake capacity (q_e, mg/g) was calculated according to mass balance (Equation 5).

[00580] Where ^Lo and » were the initial and equilibrium metal concentrations (mg/L), m was the mass of absorbent (g) and V was the volume of solution (L).

[00581 ] Figure 22 depicts absorption capacities of CTS versus CTS-g-PDEAEMA without initial carbon dioxide gassing . Initial pH range for initial absorption trials was from 5.80 to 5.87. After the grafted material was removed, washed with de-ionized water, and placed in de-ionized water, initial pH readings were 8.57 to 8.94. After gassing with carbon dioxide for 1 hour, pH dropped to 5.47 to 5.63.

[00582] These results suggested that the synthesized CTS-g-GMA was not as a strong absorbent as pure CTS without carbon dioxide gassing. With 1 hour of carbon dioxide gassing, 25-82% of the absorbed metal was recovered off the grafted material. After regeneration, the grafted material's absorbance capacity was increased by 196-241 %, with it surpassing pure CTS at equilibrium nickel concentrations of approximately 300 mg/L.

Without wishing to be bound by theory, this increase in capacity was hypothesized to be attributed to residual charge on the grafted material that allowed for better dispersion and thus, improved interactions of dissolved nickel ions with the chelation sites on the material. It was considered that variation of the result trends may be attributed to natural variation of the natural biomaterial.

[00583] C0₂ Regeneration Studies:

[00584] After completing the equilibrium sorption studies and preparing the 10 mL sample for analysis, the remaining solution containing a grafted absorbent was filtered using Whatman 1 filter paper and washed de-ionized water (~20 ml_). The grafted absorbent was collected and placed in an Erlenmeyer flask containing 20.0 mL of de-ionized water. Initial pH was recorded, the vials were covered and carbon dioxide gas was bubbled into the solution. After 1 hour of gassing, the final pH was recorded, a 10 mL sample was collected, filtered using 0.2 μηι PTFE syringe filters and acidified with two drops of concentrated nitric acid. Again, metal concentrations were determined via ICP-OES analysis completed by Queen's University Analytical Services Unit. The remaining solution was filtered through using Whatman 1 filter paper and the grafted absorbent collected to air-dry overnight. [00585] Figure 23 depicts absorption capacities of CTS versus CTS-g-PDEAEMA with initial carbon dioxide gassing of the absorbent solution before addition of nickel . After gassing, initial pH dropped to 4.09-4.17 for pure CTS and 4.56-4.83 for the grafted material. Recovery of absorbed nickel from the grafted material after 1 hour of carbon dioxide gassing was 30-67%.

[00586] These results suggested that, with the exception of the trials that equilibrated at 50 mg Ni(ll)/L, pure CTS behaved as a better absorbent. However, the trend observed in the grafted material was not characteristic of an absorption isotherm, suggesting that the results were not conclusive. It has been hypothesized that again, natural variation of the material played a role in these inconsistencies, and that because the mass of absorbent used (50 mg) was relatively small, these effects were exacerbated.

[00587] C0₂ Switchability:

[00588] In order to demonstrate switchable capability of CTS-g-GMA-PDEAEMA, 0.5 g of CTS-g-GMA-PDEAEMA was put in 10 mL of de-ionized water in a 20 mL vial with an egg-shaped stir bar (size: 1.27 x 0.31 cm) and the vial was sealed with a rubber cap. Then carbon dioxide was bubbled through the vial via a 5 cm needle for 2 hours under magnetic stirring. Then nitrogen was bubbled to the vial through for 2 hours under magnetic stirring. Pictures (Figure 21) were taken before and after bubbling carbon dioxide. Before carbon dioxide gassing, the copolymer appeared suspendended in the water (Figure 21 (A)). After gassing with carbon dioxide for 2 hours, the material appeared visually swelled and more translucent (Figure 21 (B)). Regeneration of the material to its initial form was evident after gassing with nitrogen (Figure 21 (C)).

[00589] EXAMPLE 6B: Further Synthesis and Characterization of C0₂-Responsive Chitosans

[00590] To further develop purification processes with respect to removal of heavy metals from water, herein described materials were tested. It was considered that chitosan- based materials, which comprise primary amino- and hydroxyl-functional groups, and may be further functionalized to comprise other amino-functional groups, may be suitable for adsorbing metals. As such, functionalized chitosan-based materials were synthesized, characterized, and investigated for their metal-absorption capabilities. Without wishing to be bound by theory, it was considered that functionalizing these chitosan-based materials could result in an increase in absorption site density and/or change the type of adsorption site, and may result in an increase in selectivity.

[00591 ] Experimental:

[00592] Chitosan (CTS, Aldrich, deacetylation degree 85%), glycidyl methacrylate (GMA, Aldrich, 97%), hydroquinone (Fisher), acetic acid (Fisher, 99.7%), tetrahydrofuran (THF, ACP, 99%), acetonitrile (Aldrich, 99.8%), deuterium oxide (Cambridge Isotope Laboratories, D 99.9%), styrene (St, Aldrich, 99%), 2-(diethylamino)ethyl methacrylate (DEAEMA, Aldrich, 99%), 2-(dimethylamino)ethyl methacrilate (DMAEMA, Aldrich, 99%) purified on a column of basic alumina (Aldrich, 150 mesh, 58 A) for inhibitor removal and stored refrigerated before polymerization, SG 1 (N-tert-butyl-N-(1 -diethylphosno-2,2- dimethylpropyl) nitroxide) (85%, provided by Arkema), BlocBuilder (BB or Alkl, N-(2- methylpropyl)-N-(1 -diethylphosphono-2,2-imethylpropyl)-0-(2-carboxylprop-2-yl) hydroxyl- amine) (99%, provided by Arkema), nickel sulfate (NiS0₄'6H₂0, Aldrich, 99%), concentrated nitric acid (Aldrich, 68-70%) and dry carbon dioxide (MEGS, 99.8%) were used for test of nickel adsorption.

[00593] Instrumentation:

[00594] Determination of polymer molecular weights was performed by gel permeation chromatography (GPC) using a Waters 2690 Separation Module Water 410 Differential Refractometer, with THF as eluent. Columns used were Waters Styragel HR (4.6x300 mm) with 4, 3, 1 , 0.5 of separation at 40 °C. ¹H NMR were performed using a FT- NMR Bruker Avance 400 MHz, with a total of 256 scans, at room temperature, using a solvent of D₂0/CH₃COOH (0.4 M) with a concentration of 5 mg/mL. Thermogavimetric analysis tests (TGA) were performed using a TA Instrument Q500, with samples having the following thermal treatment: 10°C/min of 30 to 75°C, with a plateau 75°C for 15 minutes, and 10°C/min until 600°C. pH measurements were performed using a Thermo Fisher Scientific Inc. Orion Star A21 1 Benchtop Meter. Agitation for nickel adsorption tests were performed using a VWR International LLC Standard Orbital Shaker model 5000.

[00595] Synthesis of chitosan-g-glycidyl methacrylate (CTS-g-GMA):

[00596] CTS-g-GMA was synthesized via a procedure reported in the literature [Garcia-Valdez, R. Champagne-Hartley, E. Saldivar-Guerra, P. Champagne, M.F. Cunningham, Polymer Chemistry (2015) 6, 2827-2836]. Chitosan (2.0 g) was dissolved in 200 mL of 0.4 M acetic acid (4.56 mL of acetic acid in 200 mL of deionized water) in a 500 mL round bottom flask. The resulting solution was transferred to a 250 mL three-necked round bottom flask, to which a 10 mL solution of 0.05 M potassium hydroxide (KOH; 0.028 mL in 10 mL of deionized water) and a 20 mL solution of 18.16 mM of hydroquinone (0.02 g in 20 mL of deionized water) was added. This resultant solution was degassed with nitrogen for 30 minutes.

[00597] The reaction was carried out once at a constant temperature of 65 ^°C, and again at a constant temperature of 75 °C, to obtained different degrees of functionalization with GMA. GMA (48.0 mmol, 6.60 mL) was added to the three-neck round bottom flask dropwise. and the resultant mixture was magnetically stirred for 2 hours under these conditions. Solvent was removed under vacuum (rotary evaporator); following which 70 mL of acetonitrile was added to cause product precipitation, after which the solvent was decanted; and the precipitated product was washed twice with 30 mL of THF and filtered. The product, CTS-g-GMA, was analyzed by ¹H NMR (300MHz, D₂0, ppm) 6.1 (H, C=CH₂), 3.09. (H, HC-NH₂).

[00598] PDMAEMA and PDEAEMA synthesis via nitroxide mediated polymerization (NMP):

[00599] Monomers DEAEMA and DMAEMA were polymerized using NMP, a general procedure for which was as follows:

In a three-necked flask (250 mL), inhibitor-free monomer (50 g), styrene (3.27 g), Alkl / BB (1.0358 g), and SG1 (0.0799 g) were stirred magnetically and degassed with N2 for 30 minutes. The resultant reaction mixture had the following initial molar ratios: [styrene]/[monomer+styrene]=0.09, [SG1]/[Alkl] = 0.10. The mixture was stirred at 90 °C. In 20 min intervals, 2 mL of reaction mixture was collected to determine the product's avergae number molecular weight (Mn) and polydispersity; once a desired Mn was reached, the reaction was stopped (see Figures 74 and 75). The respective products, PDMAEMA and PDEAEMA, were each washed in THF, and characterized using GPC (Figures 74 and 75).

[00600] Synthesis of (CTS-g-GMA)-g-PDMAEMA and (CTS-g-GMA)-g-PDEAEMA:

[00601] A general procedure for synthesizing chitosan-grafted polymers was as follows: [00602] In a 250 mL three-necked round bottom flask, CTS-g-GMA (1 g) was dissolved in 100 mL of a 0.1 M acetic acid solution (0.57 mL in 100 mL of deionized water). pH of solution was adjusted to a value of 5.0 using a 1.0 M KOH solution (0.2805 g in 50 mL of deionized water), followed by degassing for 30 min with nitrogen and heating to 90 °C.

[00603] Without wishing to be bound by theory, amount of polymer needed to synthesize polymer-grafted product was approximated as follows:

[00604] One gram of chitosan was approximated to comprise 6.21x10 ³ mol of OH. Assuming, for example, a degree of GMA functionalization of 7%, then (x) is 0.07 (see Figures 74 and 75). As it is understood, reactions of grafting-to polymer with (CTS-g-GMA) result in polymer bonding to GMA; as such, it was considered that moles of GMA available to react with polymer was equal to moles OH per degree of functionalization of GMA: 6.21x10^~3 mol of OH * 0.07. Given that there is a one to one correspondence (polymer→GMA→OH), then the theoretical moles of polymer required for reaction equals 6.21x10 ³ mol of OH * 0.07. As Mn of the polymer was known, 1.5 times the theoretical amount of polymer was added to the reaction mixture.

[00605] As such, it was approximated that grafting a polymer to chitosan, when that polymer has a molecular weight of M_n = 10038 g/mol and 1.5 times the theoretical mass, would require dissolving 3.2726 g of polymer in 60 mL of a 0.1 M solution of acetic acid (0.57 mL in 100 mL of deionized water). Aliquiots (20 mL) of the resultant polymer solution were then added in 60 minute intervals to the three-necked round bottom flask, heated to 90 °C, and magnetically stirred. The reaction was carried out for 3 hours, and then quenched by placing the round bottom flask in an ice bath.

[00606] The resultant products were isolated and washed via the following general procedure: reaction solvent was removed under vacuum; product was washed with 100 mL of a 1 M KOH solution (5.61 1 g in 100 mL); wash solution was removed under vacuum in a rotary evaporator; product was washed again with 100 mL of distilled water; wash solution was again removed under vacuum in a rotary evaporator; product was washed twice with 50 mL of THF, which was decanted off each time; and, the product was dried on a glass surface to prevent sample loss during filtering. Products were analyzed by ¹H NMR (D₂0, δ ppm: PDMAEMA 1.05 (3H, -CCH₃), PDEAEMA 1.25 (3H, -CCH₃), chitosan 3.1 (1 H, -HCNH₂); Figure 76) and TGA (Figure 77).

[00607] Nickel adsorption tests: [00608] Procedure followed was in accordance with those reported in the literature [Champagne-Hartley, P. ; A Combined Passive System for the Treatment of Acid Mine Drainage; Ph.D. Thesis; Ottawa-Carleton Institute for Civil Engineering: Ottawa 2001 ;

Popuri, R,; Vijaya, Y.; Boddu, V.M.; Abburi, K, Bioresources Technology 2009, 100, 194-199; Madill, Evan A.W.; C0₂ Responsive Graft Modified Chitosan for Heavy Metal Recovery, ENCH 417 Thesis, 2015.]:

[00609] To a round bottom flask, 25 mg of adsorbent (chitosan, PDEAEMA,

PDMAEMA, CTS-g-PDEAEMA and CTS-g-PDMAEMA) and 50 mL of distilled water was added. Initial pH readings were taken, followed by a 1 -hour gasification with CO2, and then a final pH reading. Nickel sulfate was added in an appropriate proportion to achieve initial Ni concentrations of 50, 200, 500 and 1000 mg/L. The resultant solution was magnetically stirred for 10 minutes (full dilution was achieved) and a pH reading was taken. After, it stirred for 24 hours at 150 rpm on a shaking table. Nickel dsorption tests at different Ni

concentrations were performed in triplicate. After 24 hours of stirring, nickel content of each final solution was analyzed via 10 mL of sample being filtered through 0.2 μηη PTFE syringe filters, and acidified with two drops of concentrated nitric acid.

[00610] Nickel concentrations were determined with an inductively coupled plasma- optical emission spectrometer, Agilent ICP-OES in Analytical Services Unit, Queen's University. Equilibrium adsorption capacity (q_e, mg/g) was calculated by the following equation: q_e = (^) v

(a)

[0061 1 ] Where Co and Ce are initial concentrations of nickel and equilibrium concentration of nickel (after of 24 hours) respectively (mg/L), m is mass of adsorbent (g) and V is solution volume (L).

[00612] Results of nickel adsorption experiments were fitted to a Langmuir model, which assumes uniform energies of adsorption on a surface and not transmigration of adsorbate in the plane of a surface. [00613] Where qe and Ce are equilibrium concentrations of the adsorbent (mg/g) and liquid phase (mg/L), respectively. Qm and b are Langmuir constants that are related to adsorption capacity and adsorption energy, respectively. Langmuir isotherm assumes that adsorption occurs at specific sites on the adsorbent. Linear form of the Langmuir isotherm is given by the following expression:

[00614] Where Qe and b can be calculated from the intercept and slope of the linear graph, with Ce/qe versus Ce.

[00615] Results:

[00616] Figures 74 and 75 show Ni adsorption results of chitosan material (CTS-g- GMA)(x)-g-PDMAEMA) and (CTS-g-GMA) (x)-g-P(DEAEMA) respectively, where x indicates degree of insertion of GMA.

[00617] These results suggest that (CTS-g-GMA)(x)-g-PDMAEMA) adsorbed the highest concentration of nickel relative to (CTS-g-GMA) (x)-g-P(DEAEMA); and that, (CTS-g- GMA) (x)-g-P(DEAEMA) absorbed a higher concentration of nickel relative to unfunctionalized chitosan (see Table 32). Without wishing to be bound by theory, and in view of the results as illustrated by Figures 74 and 75, it was considered that both types of functionalized chitosan-based materials can be used for adsorbing high nickel concentrations (> 1000 ppm).

[00618] EXAMPLE 7: Modification of crystalline nanocellulose (CNC) with poly (diethylaminoethylmethacrylate) (PDEAEMA) combining nitroxide-mediated polymerization with grafting to approach, and free radical polymerization with grafting from approach.

[00619] Materials: Crystalline nanocellulose (CNC, from FP Innovations), glycidyl methacrylate (GMA, Aldrich, 97%), hydroquinone (Fisher), acetic acid (Fisher, 99.7%), tetrahydrofuran (THF, ACP, 99+%), deuterium oxide (Cambridge Isotope Laboratories, D 99.9%). Styrene (St, Aldrich, 99+%) and 2-(Diethylamino)ethyl methacrylate (DEAEMA, Aldrich, 99%) were passed over a column containing basic aluminum oxide (Aldrich, - 150 mesh, 58 A) to remove the inhibitor and stored below 5°C prior to polymerization. Ν,Ν^'- dicyclohexylurea and 2,2'-Azobis(2-methylpropionitrile) (AIBN, 98%) were purchased from Aldrich and used as received. SG 1 (N-tert-butyl-N-(1 -diethylphosphono-2,2-dimethylpropyl) nitroxide) (85%, kindly supplied by Arkema). N-Hydroxysuccinimide-BlocBuilder (NHS-BB) was synthesized from BlocBuilder (BB, N-(2-methylpropyl)-N-(1 -diethylphosphono-2,2- imethylpropyl)-0-(2-carboxylprop-2-yl) hydroxylamine (BB, 99%, provided by Arkema) according to the reported procedure [J. Vinas, N. Chagneux, D. Gigmes, T. Trimaille, A. Favier and D. Bert , Polymer, 2008, 49, 3639-3647] just as follows: BB (5 g, 13.1 mmol) and N-hydroxysuccinimide (1 .81 g, 15.7 mmol) were dissolved in THF (20 mL) and deoxygenated by nitrogen bubbling for 15 min. Then, a degassed solution of N,N^'dicyclohexylcarbodiimide (3 g, 14.4 mmol) in THF (5 mL) was added. After stirring at 0°C for 1.5 h, the precipitated Ν,Ν^'-dicyclohexylurea was removed by filtration and the filtrate volume was reduced under vacuum to one third and placed at -20°C for 2 h in order to precipitate the residual Ν,Ν^'-dicyclohexylurea. After filtration, the solution was concentrated under reduced pressure and precipitation was performed in pentane. The obtained solid was further washed with water to remove N-hydroxysuccinimide. After drying under vacuum, alkoxyamine was obtained as a white powder.

[00620] Instrumentation: CP/MAS ¹³C NMR spectra were recorded on a Bruker Avance 600 spectrometer operating at 150.91 MHz using a Bruker 5 mm CP/MAS probe. In a typical measurement, spinning rate was 12 kHz with a cross-polarization contact time of 3 ms and a repetition delay of 2 s. For all samples, number of scan was in excess of 1000 to guarantee sufficient signal-to-noise ratios. Thermogravimetric analysis (TGA) was performed using a TA Instruments Q500 TGA analyser by heating the sample using the following ramp: 10°C min-1 from 30 to 75°C, held for 30 min at a plateau of 75°C, and 10 °C min ¹ to 600°C. Gel Permeation Chromatography (GPC) analysis was performed with a Waters 2690 Separation Module and Waters 410 Differential Refractometer with THF as the eluent.

Column bank consisted of Waters Styragel HR (4.6x300 mm) 4, 3, 1 , and 0.5 separation columns at 40°C.

[00621 ] Functionalization of CNC with glycidyl methacrylate (CNC-g-GMA):

[00622] Functionalization of CNC with glycidyl methacrylate (CNC-g-GMA) is depicted in Figure 24, and was carried out following similar procedures previously reported [O. Garcia-Valdez, R. Champagne-Hartley, E. Saldivar-Guerra, P. Champagne and M. Cunningham, Polymer Chemistry, 2015]. CNC (1 .0 g) was dispersed in 100 mL of 0.4 M acetic acid solution (2.4 g, 2.28 mL in 100 mL of de-ionized water) solution in a 250 mL three neck round bottom flask under magnetic agitation using a Stir bar Egg-Shaped (size1 .90 x 0.95 cm). After that, 5 mL of 0.05 M KOH (0.014g of KOH dissolved in 5mL of water) and 10 ml. of 9.08 mM hydroquinone solution (0.01 g, 9.08*10 ⁵ mol in 10 mL of water) was added to the mixture. A mercury thermometer and a condenser were adapted to a three neck round bottom flask by which water at 5°C was circulated. Then the mixture was degassed under nitrogen for 30 minutes prior to be heated to 65^°C in an oil bath. When the CNC dispersion reached 65°C GMA (24.0 mmol, 3.53 g, 3.30 mL) was injected to the flask drop wise and the mixture was magnetically stirred for 2 hours under these conditions. The solvent was removed under vacuum and the product was washed twice with THF and once with de- ionized water and filtered. CNC-g-GMA was analyzed by TGA and ¹³C NMR CP-MAS.

[00623] After functionalization of CNC with GMA, CNC-g-GMA, due to its insolubility in common organic solvents, was analyzed only by CP/MAS ¹³C NMR; the respective spectra is shown in Figure 27. The spectra showed carbons C4 at 86~92 ppm, which indicated a crystalline region, while a 80-86 ppm signal indicated an amorphous region. For C6, 62.5-67.5 ppm and 58~65 ppm ranges indicated a crystalline region. C1 signal appeared at 105 ppm, while C2, C3, and C5 reside at 67~79 ppm. Around 170 ppm, a signal attributed to carbonyl (C=0) group from the GMA unit was observed, and at 15 ppm, a displacement attributed to a methyl group from GMA was observed.

[00624] Synthesis of Poly((Diethylamino)ethyl methacrylate) (PDEAEMA) via

Nitroxide mediated polymerization:

[00625] Polymerization of DEAEMA was completed using NMP methodology from previous publications [J. Nicolas, S. Brusseau and B. Charleux, Journal of Polymer Science Part A: Polymer Chemistry, 2010, 48, 34-47; J. Nicolas, C. Dire, L. Mueller, J. Belleney, B. Charleux, S. R. A. Marque, D. Bertin, S. Magnet and L. Couvreuer, Macrmolecules, 2006, 39, 8274-8282] (see Figure 15). In a 250 mL three neck round bottom flask, the un-inhibited DEAEMA (0.26 mol, 50 g, 47.57 mL), styrene (0.03 mol, 3.12 g, 3.47 mL), NHS- BlocBuilder® (0.0029 mol, 1 .4038 g) and SG 1 (0.0003 mol, 0.1016 g, 0.1022 mL) were mixed magnetically using a Stir bar Egg-Shaped (size1 .90 x 0.95 cm). A mercury thermometer and a condenser were adapted to a three neck round bottom flask by which water at 5°C was circulated. The mixture was degassed under nitrogen for 30 minutes. The mixture was stirred at 80^°C for 1 hour. After reaction time, PDEAEMA was precipitated in hexanes (250 mL) cooled with liquid nitrogen (300 mL), decanted, washed in THF (300 mL), re-precipitated in 250 mL of hexanes (cooled with liquid nitrogen) and decanted. Analysis was completed via GPC and TGA. [00626] PDEAEMA was synthesized via nitroxide-mediated polymerization.

Conversion of monomer into polymer (determined by gravimetry) was 53%. Molecular weight distribution of PDEAMEA obtained by GPC (Figure 18) was narrow, suggesting a well controlled reaction. Average weight molecular weight (M_w) was 13316 g/mol, and number average molecular weight (M_n) was 9714 g/mol, which gave a dispersity index (D=M_W/M_n) of 1 .37.

[00627] Modification of CNC with PDEAEMA combining nitroxide-mediated polymerization with grafting to approach:

[00628] Figure 25 depicts grafting PDEAEMA to CNC-g-GMA via NMP. In a 250 mL three neck round bottom flask, CNC-g-GMA (1 .0 g) was dispersed in 100 mL of DMSO. A mercury thermometer and a condenser were adapted to a three neck round bottom flask by which water at 5°C was circulated. The mixture was degassed for 30 minutes under a nitrogen atmosphere and heated to 90^°C. PDEAMEA (1 g) was dissolved in 60 mL of 1 ,4- dioxane and degassed for 30 minutes. The flask with the CNC-g-GMA dispersion was submerged in an oil bath at 95°C. When the CNC-g-GMA reached 90°C, the polymer solution was added in semi-batch manner to the system, 20 mL every hour. The total reaction was 3 hours. After the reaction system was cooled in an ice bath. The CNC-g-GMA- PDEAEMA dispersion was submitted to three centrifugation processes to separate it from the solvents and the remaining unreacted PDEAEMA. The product was washed twice with THF, and dried under vacuum. The product was analyzed using TGA and ¹³C NMR CP- MAS.

[00629] Mechanism of grafting PDEAEMA chains to CNC-g-GMA was previously proposed [O. Garcia-Valdez, R. Champagne-Hartley, E. SALDIVAR-GUERRA, P.

Champagne and M. F. Cunningham, POLYMER-15-185, 2015]. CNC-g-GMA-PDEAEMA was analyzed by TGA and CP/MAS ¹³C NMR to confirm presence of PDEAEMA covalently attached to CNC. The CP/MAS ¹³C NMR of CNC-g-GMA-PDEAEMA is depicted in Figure 28. The spectrum showed, besides characteristic signals of CNC-g-GMA previously discussed, new signals attributed to grafted PDEAEMA. At 20-22 ppm there was observed signals attributed to methyl groups from PDEAEMA and GMA; at 35-45 ppm signals attributed to methylene groups (-CH2-); and at 175 ppm, signal of the C=0 group from the methacrylate unit.

[00630] CNC-g-GMA-PDEAEMA was also analyzed by TGA. Figure 29 depicts a TGA corresponding thermogram for CNC, PDEAEMA and CNC-g-PDEAEMA. The thermogram of CNC (Figure 29 (A)) indicated its decomposition between 280 and 300°C. The thermogram of PDEAEMA (Figure 29 (B)) indicated the decomposition of the polymer between 320 and 450°C, and TGA for CNC-g-GMA-PDEAEMA (Figure 29 (C)) indicated decomposition of this new material between 300 and 450°C.

[00631 ] Modification of crystalline nanocellulose (CNC) with Poly(Diethylaminoethyl methacrylate) (PDEAEMA) combining and free radical polymerization (FRP) with grafting from approach:

[00632] Figure 26 depicts modified grafting of PDEAEMA to CNC-g-GMA via FRP. In a 250 mL three neck round bottom flask, CNC-g-GMA (0.45 g) was dispersed in 45 mL of DMSO. DEAEMA (4.5 g, 4.9 mL, and 0.0025 mol) and AIBN (0.17 g, 0.00125 mol) were added to three neck round bottom flask. A mercury thermometer and a condenser were adapted to a three neck round bottom flask by which water at 5°C was circulated. The mixture was degassed for 30 minutes under a nitrogen atmosphere prior to be heated to 80^°C for 3 hours. After the reaction system was cooled in an ice bath. The CNC-g-GMA- PDEAEMA dispersion was submitted to three centrifugation process in order to separate it from the solvents and the remaining unreacted PDEAEMA. The product was washed twice with THF, and dried under vacuum. The products were analyzed using TGA and ¹³C NMR CP-MAS.

[00633] In this case, CNC-GMA was copolymerized with DEAEMA via FRP, using AIBN as initiator. Also were used TGA and CP/MAS ¹³C NMR to confirm presence of PDEAEMA covalently attached to CNC. The CP/MAS ¹³C NMR of CNC-g-GMA-PDEAEMA is depicted in Figure 30, which indicated new signals attributed to grafted PDEAEMA. For example, at 20-22 ppm there was observed signals attributed to methyl groups from PDEAEMA and GMA; at 35-45 ppm there was observed signals attributed to methylene groups (-CH₂-); and at 175 ppm, the signal of the C=0 group from the methacrylate unit.

[00634] CNC-g-GMA-PDEAEMA obtained via free radical polymerization was also analyzed by TGA. Figure 31 depicts TGA corresponding thermogram for CNC, PDEAEMA and CNC-g-PDEAEMA. The thermogram of CNC (Figure 31 (A)) indicated its decomposition between 280 and 300°C. The thermogram of PDEAEMA (Figure 31 (B)) indicated decomposition of this polymer between 320 and 450°C, and TGA for CNC-g-GMA- PDEAEMA obtained via free radical polymerization (Figure 31 (C)) indicated decomposition of this new material between 300 and 450°C, which confirms that PDEAEMA is covalently attached to CNC backbone chain. [00635] EXAMPLE 8: Grafting switchable polymers from crystalline nanocellulose via nitroxide-mediated polymerization

[00636] Materials: Crystalline nanocellulose (CNC), provided by FPInnovations, was prepared at FPInnovations pilot plant (Pointe-Claire, QC) by sulfuric acid hydrolysis of a commercial bleached softwood Kraft pulp. BlocBuilder (N-(2-methylpropyl)-N-(1 - diethylphosphono-2,2-imethylpropyl)-0-(2- carboxylprop-2-yl) hydroxylamine (BB, 99%) was used as received from Arkema. 2-(Dimethylamino)ethyl methacrylate (DMAEMA, Aldrich, 99+%), 2-(Diethylamino)ethyl methacrylate (DEAEMA, Aldrich, 99+%) and 3- (Dimethylamino)propyl methacrylamide (DMAPMAm, Aldrich, 99+%) were passed over a column containing basic aluminum oxide (Aldrich, -150 mesh, 58 A) to remove the inhibitor and stored below 5°C prior to polymerization. Chloromethyl styrene (CMS, Aldrich 90%), and dimethyl sulfoxide (DMSO, Fisher, 99.9%) were used as received. All deionized (Dl) water (18.2 ΜΩ-cm resistivity) used in the experimental work was collected from a Direct-Q 3

Millipore ultrapure water system. SG 1 is (N-tert-butyl-N-(1-diethylphosphono-2,2- dimethylpropyl) nitroxide).

[00637] Synthesis of crystalline nanocellulose (CNC) - chloromethyl styrene (CMS), (CNC-CMS):

[00638] Chloromethyl styrene (CMS, 2.6 ml_, 18.5 mmol) was added dropwise to a 3 wt% solution of CNC (2 g) in DMSO (60 g) in the presence of solid sodium hydroxide at room temperature. The reaction was allowed to proceeded overnight before being precipitated with a minimal amount of ethanol. Styrene-functionalized CNC (CNC-CMS) was collected by centrifugation and thoroughly re-dispersed in Dl water. Centrifugation and re- dispersion were repeated again in water and twice with t-butanol. After the final sedimentation, the CNC-CMS was re-dispersed in a known quantity of t-butanol (~1 wt% CNC in t-butanol) before being used in the subsequent step.

[00639] Synthesis of Crystalline nanocellulose (CNC) - BlocBuilder (BB), (CNC-BB):

[00640] A solution of BB (4.68 g, 12.3 mmol) in 10 mL t-butanol was added to the CNC-CMS dispersion (100 mL) in a 2-neck round bottom flask with a condenser and was bubbled with N₂ for 30 minutes. The solution was introduced to an oil bath at 95°C under nitrogen and the reaction was allowed to reflux for 90 minutes before being removed from the oil bath. CNC-BB was collected by centrifugation and re-dispersed in ethanol, and this procedure was repeated 3 times. After the final sedimentation, a small portion of the CNC- BB was freeze-dried for characterization and the remaining CNC-BB particles were subjected to a solvent exchange with dimethylsulphoxide (DMSO) to yield a 5 wt% dispersion of CNC-BB in DMSO to be used for polymerization. Care was taken to ensure that the CNC modified particles were thoroughly cleaned and well dispersed, for both functionalization and characterization, via the sedimentation and solvent exchange method used.

[00641 ] Grafting poly((Dimethylamino)ethyl methacrylate) (PDMAEMA), poly((Diethylamino)ethyl methacrylate) (PDEAEMA), poly((Dimethylamino)propyl methacrylamide) (PDMAPMAm), from CNC surface via Nitroxide-mediated polymerization:

[00642] In a typical experiment, 19 g of monomer, either DMAEMA, DEAEMA or DMAPMAm, was added drop-wise to 5 g of a 5 wt% CNC-BB dispersion in DMSO while stirring under nitrogen in a 100 mL 3-neck round bottom flask affixed with a condenser. The flask was then submersed in an oil bath (time zero) at 90°C. Grafting-from polymerizations were conducted for 0.5 and 1 h. For polymerizations, 10 mol% of the total monomer concentration was styrene to enhance control over the polymerization. Products were cleaned using the same solvent exchange procedure described above, with tetrahydrofuran (THF) as the wash solvent. Washing process was repeated at least three times, after which products were dried under reduced pressure. All materials and precursors were analyzed by elemental analysis (CHN mode) in PerkinElmer 2400 Series II CHN Elemental Analyzer for the determination of carbon, hydrogen, and nitrogen content. FT-IR analyses were performed using an ATR FT-IR spectrometer (Bruker ALPHA FT-IR). ζ-potential was meseured in a dynamic light scattering instrument "Zetasizer Nano ZS" using a Universal 'dip' cell. See Figure 40.

[00643] Elemental analysis of starting materials and products is provided in Table 13. Elemental analysis was used to determine: a) N% (mass%), and therefore amount of BB on the surface of CNC-BB; and b) composition (mass%) of CNC modified with grafted polymer chains. With respect to the CNC-BB entry of Table 13, nitrogen content was attributed to presence of SG 1 moieties, which attached to CNC and allowed for graft polymerization. For the remaining entries of Table 13, nitrogen content was attributed to the presence of the SG 1 groups, and the tertiary amines of the corresponding grafted polymer chains. From the nitrogen content in every sample, an amount of grafted polymer was calculated (see Table 14), representing the mass % of switchable polymer and CNC in the material. [00644] Successful synthesis of CNC-g-PDMAEMA, CNC-g-PDEAEMA and CNC-g- PDMAPMAm was further determined by ATR-FT-IR. Figure 49 depicts FT-IR spectra of CNC, CNC-g-PDMAEMA, CNC-g-PDEAEMA and CNC-g-PDMAPMAm. The CNC spectrum depicts: OH signals at 3400 cm ¹, stretching vibrations (symmetrical and asymmetrical) from C-H bonds at 2875 cm ¹; bending from CH₂ groups at 1414 cm ¹; symmetrical deformation of CH3 groups at 1375 cm ¹; and, stretching vibrations of C-0 bonds between 1 160 and 1 150 cm ¹. Spectra for CNC CNC-g-PDMAEMA, CNC-g-PDEAEMA depicted: characteristic signals of CNC; and, signals corresponding to the grafted polymer (i.e., C=0 stretch at 1715 cm ¹, C-N stretch at 1 150 cm ¹, and C=C-H stretch from the styrene units). Spectrum for CNC-g-PDMAPMAm depicted characteristic signals of N-H stretch of the methacrylamide unit at 1600 cm ¹, and the C=0 stretch at 1650-1670 cm ¹.

[00645] Measurement of ζ-potential and pH under glycolic acid/NaOH environments of CNC-g-PDMAEMA, CNC-g-PDEAEMA and CNC-g-PDMAPMAm:

[00646] Measurement of ζ-potential and pH under glycolic acid/NaOH environments for each of CNC-g-PDMAEMA, CNC-g-PDEAEMA and CNC-g-PDMAPMAm was undertaken to determine their pH responsiveness. It was expected that at low pH (glycolic acid environment), tertiary amine groups from the grafted polymers would be protonated (indicated by a postive ζ-potential), and that at high pH (NaOH environment), tertiary amines would not be protonated (indicated by a negative ζ-potential).

[00647] General procedure:

[00648] Sample of either CNC-g-PDMAEMA, CNC-g-PDEAEMA or CNC-g-

PDMAPMAm (0.1 g), was poured into dionized water (10 mL) in a 50 mL beaker in the presence of magnetic bar and a pH-meter probe. Afterwards, controlled amounts of glycolic acid (GIAc; 0.5 M, 5 mL) were added until pH decreased and pH measurement was stable; the ζ-potential was then measured. After, controlled amounts of NaOH (0.5 M, 5 mL) were added to the resultant dispersion until pH increased and pH measurement was stable; then the ζ-potential was measured. This procedure was repeated 3 times.

[00649] ζ-potential and pH measurements for CNC-g-PDMAEMA are reported in

Table 15 and Figure 41 ; measurements for CNC-g-PDEAEMA are reported in Table 16 and Figure 42; and, measurements for CNC-g-PDMAPMAm are reported in Table 17 and Figure 43. The measurements of ζ-potential at various pH suggested that when pH was low, the switchable amine polymers were protonated (glycolic acid protonated such groups). This was evidenced by the increased, positive ζ-potential, which, when positive, indicates that a surface is protonated. When pH was high, the low, negative ζ-potential indicated that the switchable amine polymers were de-protonated; and that, thus, the CNC surface was not protonated. Without wishing to be bound by theory, it was considered that these results suggested the CNC-g-polymer were pH responsive.

[00650] Measurement of ζ-potentials at different pH values suggested that at low pH, switchable amine functionalities of the polymer-grafted CNCs were protonated (by glycolic acid), as indicated by the positive ζ-potentials. The measurements also suggested that at high pH, switchable amine functionalities were deprotonated, as indicated by the negative ζ- potentials. It was considered, therefor, that CNC-g-polymer materials were pH responsive.

[00651] Measurement of pH vs ζ-potential under CO2/N2 enviorements of CNC-g- PDEAEMA, CNC-g- PDMAEMA and CNC-g-PDMAPMAm:

[00652] Measurement of ζ-potential and pH under CO2/N2 for each of CNC-g- PDMAEMA, CNC-g-PDEAEMA and CNC-g-PDMAPMAm was undertaken to determine their CO₂/N₂ switchability. It was expected that in a C0₂ -based environment, tertiary amine groups from the grafted polymers would be switched On' or protonated (indicated by a postive ζ-potential), and that at in a N₂-based environment, tertiary amines would not be protonated (indicated by a negative ζ-potential).

[00653] General procedure:

[00654] Sample of either CNC-g-PDMAEMA, CNC-g-PDEAEMA or CNC-g-

PDMAPMAm (0.1 g), was poured into deionized water (10 mL) in a 50 mL 3-neck round bottom flask in the presence of magnetic bar and a pH-meter probe. Afterwards, C0₂ was bubbled to the flask until pH decreased and measurement was stable; then a sample was extracted from the flask via a needle and syringe to measure ζ-potential. Afterwards, N: was bubbled to the resultant dispersion until pH decreased and measurement was stable; then again sample was extracted from the flask to measure ζ-potential. This procedure was repeated 3 times. pH was measured with a pH-meter S470 SevenExcellence™ pH/Conductivity. ζ-potential was measured with a Zetasizer Nano ZS.

[00655] ζ-potential and pH measurements for CNC-g-PDMAEMA are reported in

Table 18 and Figure 44; measurements for CNC-g-PDEAEMA are reported in Table 19 and Figure 43; and, measurements for CNC-g-PDMAPMAm are reported in Table 20 and Figure 44. The measurements of ζ-potential at various pH suggested that when pH was low, the switchable amine polymers were protonated (CO2 in water protonated such groups). This was evidenced by the increased, positive ζ-potential, which, when positive, indicates that a surface is protonated. When pH was high, the low, negative ζ-potential indicated that the switchable amine polymers were de-protonated; and that, thus, the CNC surface was not protonated. Without wishing to be bound by theory, it was considered that these results suggested the CNC-g-polymer were CO2 responsive.

[00656] Measurement of ζ-potentials at different pH values suggested that in the presence of C0₂, switchable amine functionalities of the polymer-grafted CNCs were switched 'on' or protonated, as indicated by the positive ζ-potentials. The measurements also suggested that at in the presence of N₂, switchable amine functionalities were switched 'off' or deprotonated, as indicated by the negative ζ-potentials. It was considered, therefor, that CNC-g-polymer materials were C0₂ responsive.

The above analysis suggested that CNC surfaces were modified with graft polymers PDMAEMA, PDEAEMA and PDMAPMAm via nitroxide-mediated polymerization using a grafting-from approach yielding CNC-g-PDMAEMA, CNC-g-PDEAEMA and CNC-g- PDMAPMAm. pH and CO2 responsiveness was tested by measuring ζ-potential at different pH under different atmospheres (either glycolic acid/NaOH or C0₂/N₂). Responsiveness were considered reproducible, given that similar ζ-potentials were obtained under repeat conditions.

[00657] Table 1 . Zeta potential and Z-average size of native CNC (ca. 0.5 mg/mL dispersion) in response to continuous repeated C0₂/N₂ sparging cycles.

Number After C0₂ Sparging After N₂ Sparging of Cycles Zeta potential (mV) Zeta Potential (mV)

Cycle 1 -46.8 ± 2.4 -56.6 ± 1 .5

Cycle 2 -47.3 ± 0.9 -59.5 ± 2.1

Cycle 3 -47.9 ± 1 .3 55.7 ± 2.0

Number After C0₂ Sparging After N₂ Sparging of Cycles Z-average Size (nm) PDI (-) Z-average Size (nm) PDI (-)

Cycle 1 159 ± 1 0.460 151 ± 1 0.416

Cycle 2 133 ± 1 0.412 149 ± 2 0.418

Cycle 3 128 ± 3 0.385 143 ± 3 0.334 [00658] Table 2. Elemental analysis data for CNC-APIm and native CNC.

Sample %C %H %N %S

CNC-APIm #1^a 44.05 6.52 3.78 0.78

CNC-APIm #2^a 43.75 6.87 3.71 0.66

CNC-APIm

43.90 6.70 3.75 0.72 (Average)

Native CNC^b 42.28 6.86 0.01 0.78 aTwo CNC-APIm were prepared in two independent batches using identical recipes and experimental procedures. ^b It was anticipated that native CNC and CNC-APIm would have comparable %C and %H values due to a smaller percentage of surface atoms available for

functionalization (approx. 20-30%) versus atoms in the bulk.

[00659] Table 3. Z-average sizes of CNC-APIm (ca. 0.5 mg/mL dispersion) in response to continuous repeated C0₂/N₂ sparging cycles.

Number After C0₂ Sparging After N₂ Sparging of Cycles Z-average Size (nm) PDI (-) Z-average Size (nm)^a

Cycle 1 201 ± 1 0.390 > 10 microns

Cycle 2 21 1 ± 3 0.370 > 10 microns

Cycle 3 233 ± 4 0.427 > 10 microns

Cycle 4 252 ± 14 0.456 > 10 microns

Cycle 5 259 ± 9 0.443 > 10 microns

Cycle 6 358 ± 14 0.664 > 10 microns aRecorded on a Malvern Zetasizer Nano ZS instrument where measured size data were in range of tens of microns (CNC-APIm macroscopically visible aggregates formed upon N₂

sparging).

[00660] Table 4. Zeta potential and Z-average size of CNC-APIm in discarded supernatant (ca. 0.5 mg/mL dispersion) in response to continuous repeated C0₂/N₂ sparging cycles.

Number After C0₂ Sparging After N₂ Sparging of Cycles _Zeta potential (mV) Zeta potential (mV)

Cycle 1 45.3 ± 2.1 20.9 ± 4.0

Cycle 2 43.8 ± 0.8 15.7 ± 6.4 Cycle 3 43.2 ± 0.9 24.2 ± 4.1

After C0₂ Sparging After N₂ Sparging

Number

of Cycles Z-average Size (nm) PDI (-) Z-average Size (nm)³

Cycle 1 167 ± 1 0.31 1 > 10 microns

Cycle 2 176 ± 2 0.392 > 10 microns

Cycle 3 190 ± 6 0.406 > 10 microns

aRecorded on a Malvern Zetasizer Nano ZS instrument where the measured size data were in the range of tens of microns (CNC-APIm macroscopically visible aggregates formed upon

N₂ sparging).

[00661 ] Table 5. Time-dependent Z-average size and zeta potential changes of CNC- APIm (ca. 0.5 mg/mL dispersion) in response to CO2/N2 sparging cycles.

Z-average size and zeta potential changes in response to C0₂

Time Z-average Size (nm) PDI (-) Zeta potential (mV)

0 s > 10 microns³ / 20.9 ± 0.8

30 s 217 ± 1 0.384 58.8 ± 0.8

60 s 215 ± 1 0.376 57.9 ± 0.6

10 min 210 ± 4 0.366 57.0 ± 1 .4

Z-average size and zeta potential changes in response to N₂ following C0₂ stimulus

Time Z-average Size (nm) PDI (-) Zeta potential (mV)

0 s 210 ± 4 0.366 57.0 ± 1 .4

30 s 213 ± 1 0.372 58.2 ± 1 .4

2 min 217 ± 1 0.436 54.5 ± 0.4

3 min 220 ± 3 0.367 49.5 ± 1 .2

4 min 215 ± 2 0.384 48.3 ± 1 .4

5 min 208 ± 7 0.377 46.9 ± 0.3

6 min 30 s 349 ± 53 0.620 43.4 ± 1 .0

9 min > 10 microns³ / 35.9 ± 1 .7

20 min > 10 microns³ / 31 .7 ± 4.1

³Recorded on a Malvern Zetasizer Nano ZS instrument where measured size data of CNC- APIm macroscopically visible aggregates were in range of tens of microns. [00662] Table 6. Degree of protonation of HPIm calculated by different protons in different conditions measured by ¹H NMR (see Figure 3 for the assignment of different protons in HPIm).

Degree of protonation in different conditions³

Protons Original C0₂ Sparging (5 min) C0₂ + N₂ Sparging (5+30 min)

(%) (%) (%)

1 7.0 77 16

2 24.8 108 35

3 19 97 28

Average 17 94 26

aData were recorded on a Bruker Avance 400 NMR spectrometer at 25°C using 90% H₂0 +

^

10% D₂0 as solvent. The degree of protonation was calculated as: — xl00%, where

^ioo^—

δ , δ₁₀₀ , and £>₀ denote a specific chemical shift and chemical shifts at 100% (1 .0 M HCI) and 0% (1.0 M NaOH) degree of protonation, respectively. To check reproducibility, all NMR measurements were conducted at least in triplicate and differences for all repeated measurements were less than 5%. Only one set of data were used for the calculation in this table. The degree of protonation value is not exact.

[00663] Table 7. Mass of water absorbed by Cotton-APIm versus non-functionalized Cotton.

Initial Mass Final Mass Δ in Mass Average

Cotton type Standard Deviation

(g) (g) (g) (g)

Functionalized 0.14983 0.76271 0.61288 0.54548 0.05844

0.15219 0.66692 0.51473

0.14527 0.6541 0.50883

Non-

0.16277 0.52053 0.35776 0.33090 0.02425 functionalized

0.15891 0.48325 0.32434 0.1549 0.46551 0.31061 [00664] Table 8. Contact angle analysis via the sessile drop method for unfunctionalized cotton linen and functionalized Cotton-API m

[00665] Table 9. Contact angle analysis via the sessile drop method for native and functionalized (i.e. waxy) filter paper.

[00666] Table 10. Contact angle analysis via sessile drop method for unfunctionalized cotton linen and functionalized Linen-pDEAEMA via "grafting-from" method

[00667] Table 1 1. Investigation of switchable celluloses, prepared via synthetic method 1 , as drying agents.

[00668] Table 12. Investigation of switchable celluloses, prepared via synthetic method 2, as drying agents.

[00669] Table 13. Elemental analysis (C%, H%, N%) of switchable polymers grafted on crystalline nanocellulose via nitroxide-mediated polymerization

[00670] Table 14. Percent composition of switchable polymers grafted on crystalline nanocellulose via nitroxide-mediated polymerization

[00671 ] Table 15. ζ-potential and pH measurements for CNC-g-PDMAEMA in the presence of glycolic acid (GIAc) 0.5 M and NaOH 0.5 M.

[00672] Table 16. ζ-potential and pH measurements for CNC-g-PDEAEMA in the presence of glycolic acid (GIAc) 0.5 M and NaOH 0.5 M.

[00673] Table 17. ζ-potential and pH measurements for CNC-g-PDMAPMAm in the presence of glycolic acid (GIAc) 0.5 M and NaOH 0.5 M.

[00674] Table 18. ζ-potential and pH measurements for CNC-g-PDMAEMA in the presence of C0₂/N₂.

[00675] Table 19. ζ-potential and pH measurements for CNC-g-PDEAEMA in the presence of C0₂/N₂.

[00676] Table 20. ζ-potential and pH measurements for CNC-g-PDMAPMAm in the presence of C0₂/N₂.

[00677] Table 21 . Atomic and mass composition of bromine functionalized CNC by XPS analysis

[00678] Table 22. Elemental analysis of unmodified CNC, PDEAEMA#-g-CNC and PDMAEMA-g-CNC

a Remaining sample was assumed to be oxygen (O).

[00679] Table 23. Comparative CHNS analysis by elemental analysis in weight percent for CNC-CTP and native CNC

¹ Nitrogen readings were from nitrogenated impurities from functionalization reactions *Oxygen content was determined by difference. [00680] Table 24. Comparative elemental analysis of unmodified CNC, CNC-g- PDMAEMA by RAFT polymerization

aRemaining sample was assumed to be oxygen (O).

Table 25. Molarity of each ion in modified Bold's Basal Medium used for

Major element Ionic strength (mM)

NaN0₃ 5.88

MgS0₄-7H₂0 2.43

CaCI₂-2H₂0 1.02

NaCI 0.86

KOH 0.22

Na₂EDTA-2H₂0 0.1 1

ZnS0₄-7H₂0 0.01

MnCI₂-7H₂0 0.04

Na₂Mo0₄-2H₂0 0.01

CuS0₄-5H₂0 0.00

Co(N0₃)₂-6H₂0 0.00

Dl water 2.70

[00682] Table 26. Parameters used in Derjaguin-Landau-Verwey-Overbeek (DLVO) theory equations

[00683] Table 27. pH of microalgae solution under different APIm-modified CNC dose during three harvesting steps; dose was calculated based on the dry weights of microalgal biomass and APIm-modified CNC

[00684] Table 28. Harvesting performance at different pH conditions adjusted by HCI and NaOH to mimic C0₂/air-treated samples; dose was calculated based on the dry weights of microalgal biomass and APIm-modified CNC (see p values in Table 29)

[00685] Table 29. p values for the f-tests on HE, RE and RC using pH adjustment compared to C0₂/air treatment

[00686] Table 30. p values for t-tests on three performance indicators (HE, RE, and RC) with air and nitrogen

N₂

Flow rates

Indicators

(ml min ¹) 25 80 140

HE RE RC HE RE RC HE RE RC

HE 0.03

25 RE 0.03

RC 0.03

HE 0.06

Air 80 RE 0.06

RC 0.06

HE 0.10

140 RE 0.06

RC 0.05 Note: Shaded cells with p>0.05 and thus there is no statistical difference between two groups.

Table 31. p values for t-tests on three indicators (HE, RE, and RC) with th

[00688] Table 32. Ni adsorption results of chitosan material (CTS-g-GMA)(x)-g- PDMAEMA) and (CTS-g-GMA) (x)-g-P(DEAEMA) respectively, where x indicates degree of insertion of GMA

[00689] Table 33. delineates investigation of switchable celluloses, prepared synthetic method 3, as drying agents

[00690] Table 34. Contact angle analysis via the sessile drop method for unfunctionalized cotton linen and functionalized Linen-pDEAEMA via "grafting-from" method

[00691] All publications, patents and patent applications mentioned in this

Specification are indicative of the level of skill of those skilled in the art to which this invention pertains and are herein incorporated by reference to the same extent as if each individual publication, patent, or patent applications was specifically and individually indicated to be incorporated by reference.

[00692] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims

WE CLAIM:

1 . A composite material that is reversibly switchable between a first form and a second form, the composite material comprising a polysaccharide and at least one polysaccharide- supported switchable moiety attached to the polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with the first form of the composite material, and an ionized form associated with the second form of the composite material, wherein the switchable moiety comprises an amine, amidine, or guanidine.

2. The composite material of claim 1 , wherein the switchable moiety is an amine and the switchable moiety is bound to the polysaccharide via a linker XY; and

wherein the first form of the composite material has the structure of formula 1

(2);

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X, and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a Ci- Ci5 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X is a divalent linker moiety, or a multivalent linker moiety bonded to Y, or to the polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, each X is independently is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or two of R¹ and R², together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; wherein each X and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and

NR¹R² and N⁺R¹R² are each a switchable functional group, wherein R¹ and R² are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic, a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to C10 aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or R¹ and R², together with the atoms to which they are attached, are connected to form a cycle, or heterocycle, each of which may be substituted; or R² is repeat unit -(X-NR¹)_S-Z, wherein X and R¹ are as defined above, s is an integer between 1 and 10 000 wherein m x p x s is 10 000 or less, and Z is a monovalent moiety bonded to the switchable functional group, and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thiol, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted; wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; wherein each of [X(NR¹R²)_n]_m and [X(N⁺R¹R²)_n]_m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit is the same or different relative to other repeat units; and wherein, (a) if both of R¹ and R² are H, than X is a sterically hindered group or, (b) if one of R¹ and R² is H, then either (i) the other one of R¹ and R² is a sterically hindered group, or (ii) X is a sterically hindered group.

3. The composite material of claim 2, wherein the first form of the composite material has the structure of formula 1 a when Y is absent, p is 1 , and R² is repeat unit -(X-NR¹)s-Z,

the second form of the composite material has the structure of formula 2a,

4. The composite material of claim 2, wherein the first form of the composite material has the structure of formula 1 c when m is 1 ,

the second form of the composite material has the structure of formula 2c,

5. The composite material of claim 1 , wherein the switchable moiety is an amidine and the switchable moiety is bound to the polysaccharide via a linker XY; and

3c,

(4a) (4b) (4c); wherein:

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X, and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a Ci- Ci5 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X is a divalent linker moiety, or a multivalent linker moiety bonded to Y, or to the polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C1 -C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1 -C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, each X is independently is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or more of R³, R⁴, and R⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; wherein each X and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and

N=CR³NR⁴R⁵ , R³N=CN R⁴R⁵, R³N=CR⁴NR⁵, and (N=CR³N R⁴R⁵)⁺ , (R³N=CNR⁴R⁵)⁺, (R³N=CR⁴NR⁵)⁺ are each switchable functional groups, wherein R³, R⁴, and R⁵ are independently H , a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to C10 aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R³, R⁴, and R⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; or,

any one of R³, R⁴, and R⁵ is repeat unit -(X-N=CR³N R⁴)_S-Z, -(X-N=CN R⁴R⁵)_S-Z; or -(X-C=NR³NR⁴)s-Z, -(X-C=NNR⁴R⁵)s-Z; or -(X-NCR⁴=NR³)_S-Z, -(X-NR⁵CR⁴=N)_S-Z, -(X-N R⁵C=NR³)s-Z, wherein X and R³, R⁴, and R⁵ are as defined above, s is an integer between 1 and 10 000 wherein m x p x s is 10 000 or less, and Z is a monovalent moiety bonded to the switchable functional group, and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted; wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and wherein each of [X(N=CR³NR⁴R⁵)_n]_m, [X(R³N=CNR⁴R⁵)_n]_m, [X(R³N=CR⁴NR⁵)_n]_m, and [X((N=CR³NR⁴R⁵)⁺)n]m,

optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit is the same or different relative to other repeat units.

6. The composite material of claim 5, wherein the first form of the composite material has the structure of formula 3d, 3d', 3e, 3e', 3f, 3f, or 3f" when Y is absent, p is 1 , and R³, R⁴, or R⁵ is repeat unit -(X-N=CR³NR⁴)_S-Z, -(X-N=CNR⁴R⁵)_S-Z; or-(X-C=NR³NR⁴)_s-Z, -(X-C=NNR⁴R⁵)_S-Z; or -(X-NCR⁴=NR³)_s-Z, -(X-NR⁵CR⁴=N)_S-Z, -(X-NR⁵C=NR³)_S-Z,,

(3d) (3d') (3e)

7. The composite material of claim 5, wherein the first form of the composite material has the structure of formula 3g, 3h, or 3i when Y is absent, p is 1 , and m is 1 ,

(3g) (3h) (3i); and the second form of the com osite material has the structure of formula 4g, 4h, or 4i,

(4g); (4h); (4i).

8. The composite material of claim 1 , wherein the switchable moiety is a guanidine, and the switchable moiety is bound to the polysaccharide via a linker XY; and

wherein the first form of the composite material has the structure of formula 5a, 5b, 5c,

(5a); (5b); (5c); the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker XY has the structure of formula 6a, 6b, 6c,

(6a); (6b) ; (6c); and wherein: n is an integer 1 , 2 or 3; p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent;

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X, and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a Ci-

Ci5 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X is a divalent linker moiety, or a multivalent linker moiety bonded to Y, or to the polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, each X is independently is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or more of R⁶, R⁷, R⁸, R⁹ and R¹⁰, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; wherein each X and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and

N=CNR⁶R⁷NR⁸R⁹, R¹⁰N=CNR⁶NR⁸R⁹, R¹⁰N=CNR⁶R⁷NR⁹, and (N=CNR⁶R⁷NR⁸R⁹)⁺, (R¹⁰N=CNR⁶NR⁸R⁹)⁺, (R¹⁰N=CNR⁶R⁷NR⁹)⁺ are each switchable functional groups, wherein R⁶, R⁷, R⁸, R⁹ and R¹⁰ are independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C5 to C10 aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R⁶, R⁷, R⁸, R⁹ and R¹⁰, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; or,

any one of R⁶, R⁷, R⁸, R⁹ and R¹⁰ is repeat unit -(X-N=CNR⁶R⁷NR⁸)_S-Z,

-(X-N=CNR⁷NR⁸R⁹)s-Z, or -(X-NR⁶C=NNR⁸R⁹)_S-Z, -(X-NR⁶C=NR¹⁰NR⁸)_S-Z,

-(X-NC=NR¹⁰NR⁸R⁹)s-Z, wherein X and R⁶, R⁷, R⁸, R⁹ and R¹⁰ are as defined above, s is an integer between 1 and 10 000 wherein m x p x s is 10 000 or less, and Z is a monovalent moiety bonded to the switchable functional group, and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted; wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; wherein at least one of R⁶, R⁷, R⁸, R⁹ and R¹⁰ is an unsaturated functional group (e.g., aryl) or an an electron withdrawing group; and wherein each of [X(N=CNR⁶R⁷NR⁸R⁹)_n]_m, [X(R¹⁰N=CNR⁶NR⁸R⁹)_n]_m,

9. The composite material of claim 8, wherein the first form of the composite material has the structure of formula 5d, 5d', 5d", 5e, or 5e' when Y is absent, p is 1 , and R⁶, R⁷, R⁸, R⁹ or R¹⁰ is repeat unit -(X-N=CNR⁶R⁷NR⁸)_S-Z, -(X-N=CNR⁷NR⁸R⁹)_S-Z, or -(X-NR⁶C=NNR⁸R⁹)_S-Z, -(X-NR⁶C=NR¹⁰NR⁸)s-Z, -(X-NC=NR¹⁰NR⁸R⁹)_S-Z,

( '); (5d");

(5e) (5e'); and

the second form of the composite material has the structure of formula 6d, 6d', 6d", 6e, '

(6e) (6e').

10. The composite material of claim 8, wherein the first form of the composite material has the structure of formula 5f, 5g, or 5h when Y is absent, p is 1 , and m is 1 ,

(6f); (6g); (6h).

1 1 . The composite material of claim 1 , wherein the switchable moiety is a pyridine, switchable moiety is bound to the polysaccharide via a linker XY; and

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X, and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a Ci- Ci5 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X is a divalent linker moiety, or a multivalent linker moiety bonded to Y, or to the polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, each X is independently is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or more of R¹⁵ , together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; wherein each X and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyi ether, or siloxane moieties, or a combination thereof, within its linear or branched carbon chain, or at one of said chain's termini; and

is a switchable functional group, wherein R¹⁵ is

H, a Ci to Cio aliphatic group that is linear, branched, or cyclic, a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a Cs to Cio aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or any two of R¹⁵, together with the atoms to which they are attached, are connected to form a cycle, or heterocycle, each of which may be substituted; or

any one of R¹⁵ is repeat unit

, wherein X and R¹⁵ are as defined above, q' is integer 1 or 2, s is an integer between 1 and 10 000 wherein m x p x s is 10 000 or less, and Z is a monovalent moiety bonded to the switchable functional group, and is a hydrogen, a halogen, linear or branched C1-C15 alkyi, a C15-C30 alkyi, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thioether, a thioester, a dithioester, silyl alkyi ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted; wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and

wherein each of and ^moptionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit is the same or different relative to other repeat units.

12. The composite material of claim 1 1 , wherein the first form of the composite material has the structure of formula 7a when Y is absent is 1 and R¹⁵ is repeat unit

the second form of the composite material has the structure of formula 8a,

13. The composite material of claim 1 1 , wherein the first form of the composite material has the structure of formula 7b when Y is absent, p is 1 , and m is 1 ,

(7b); and

the second form of the composite material has the structure of formula 8b,

14. The composite material of claim 5, wherein the switchable moiety is bound to the polysaccharide via a linker XY; and

(9c); (9d); and

(10a); (10b);

(10c); (10d); and wherein: n is an integer 1 , 2 or 3; p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent;

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X, and is a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a Ci- Ci5 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X is a divalent linker moiety, or a multivalent linker moiety bonded to Y, or to the polysaccharide when Y is absent, and the switchable moiety; each X is independently a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a Ci₅-C₃₀ alkenylene, a C1-C15 alkynylene, a Ci₅-C₃₀ alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, each X is independently is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; or, each X, and one or more of R¹¹ , R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; wherein each X and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini;

R¹¹ , R¹², R¹³, and R¹⁴ are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to Ci₀ aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R¹¹ , R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a cycle or heterocycle, each of which may be substituted; or

any one of R¹¹ , R¹², R¹³, and R¹⁴ is repeat unit -(X-lm)s-Z, wherein X is as defined above, Im is an optionally substituted imidazole ring, s is an integer between 1 and 10 000 wherein m x p x s is 10 000 or less, and Z is a monovalent moiety bonded to the switchable functional group, and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, sulphide, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted; wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and wherein each of [X(lm)_n]_m and [X((lm)⁺)_n]_m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit is the same or different relative to other repeat units.

15. The composite material of claim 14, wherein the first form of the composite material has the structure of formula 9e, 9f, 9g, or 9h when Y is absent, p is 1 , and m is 1 ,

(10e); (10f);

(l og); (1 Oh).

16. The composite material of claim 15, wherein the first form of the composite material has the structure

and the second form of the e structure

17. The composite material of any one of claims 1 -16, wherein the polysaccharide comprises cellulose nanocrystal (CNC), cellulose, dextran, starch, chitin, chitosan, glycogen, pectin, arabinoxylan, or any combination or modification thereof.

18. The composite material of any one of claims 1 -16, wherein the polysaccharide is comprised within cotton, cotton linen, paper, flax, hemp jute, sisal, linen, or any combination or modification thereof.

19. The composite material of any one of claims 1 -18, wherein the first form of the composite material is neutral and hydrophobic, and the second form of the composite material is ionized and hydrophilic.

20. The composite material of any one of claims 1 -19, wherein the composite material converts to, or is maintained in, the second, ionized form when the switchable moiety is exposed to an ionizing trigger at an amount sufficient to maintain the switchable moiety in its ionized form; and, wherein the composite material converts to, or is maintained in, the first form when the ionizing trigger is removed or reduced to an amount insufficient to maintain the switchable moiety in its ionized form.

21 . The composite material of claim 20, wherein the ionizing trigger is an acid gas.

22. The composite material of claim 21 , wherein the acid gas is C0₂, COS, CS₂, or a combination thereof

23. The composite material of claim 20, wherein the ionizing trigger is removed or reduced by exposing the composite material to: (i) an at least partial vacuum; (ii) heat; (iii) a flushing inert gas (iv) a liquid substantially devoid of an ionizing trigger; or, (v) any combination thereof; in the presence or absence of agitation.

24. The composition material of claim 23, wherein the inert gas is l\ , Ar or air.

25. The composite material of claim 23, wherein exposing to heat is heating to≤ 60 °C,≤ 80 °C, or≤ 150 °C.

26. The composite material claim 20, wherein the ionizing trigger is a Bronsted acid sufficiently acidic to ionize the switchable moiety from its neutral form; or, any Bronsted base sufficiently basic to de-ionize the switchable moiety from its ionized form.

27. A method for switching a composite material of any one of claims 1 - 26 between its first form and second form, comprising: exposing the neutral composite material to (i) an aqueous liquid, or (ii) a nonaqueous liquid and water, to form a mixture, and exposing said mixture to an ionizing trigger, thereby protonating the switchable moiety and rendering the composite material ionized; and/or exposing the neutral composite material to an aqueous liquid comprising an ionizing trigger to form a mixture, wherein the liquid protonates the switchable moiety to render the composite material ionized; and optionally, separating the ionized composite material from the mixture.

28. A method for switching a composite material of any one of claims 1 - 26 between its second form and first form, comprising: exposing an ionized composite material to: (i) an at least partial vacuum; (ii) heat; (iii) a flushing inert gas; (iv) a liquid substantially devoid of an ionizing trigger; or, (v) any combination thereof; in the presence or absence of agitation, thereby expelling the ionizing trigger from the switchable moiety and rendering the composite material neutral; and optionally, separating the neutral composite material from the mixture.

29. The method of claims 27 or 28, wherein the ionizing trigger is a Bronsted acid, or an acid gas.

30. The method of claim 29, wherein the acid gas is C0₂, COS, CS₂, or a combination thereof.

31 . The method of claim 28, wherein the inert gas is N₂, Ar or air.

32. The method of claim 28, wherein exposing to heat is heating to≤ 60 °C,≤ 80 °C, or ≤ 150 °C.

33. Use of the composite material of any one of claims 1 -26, for manipulating and/or controlling dispersibility, for example, CNC dispersibility.

34. Use of the composite material of any one of claims 1 -26, as a separation membrane.

35. Use of the composite material of any one of claims 1 -26, for formation of a membrane comprising a chiral nematic liquid crystalline structure.

36. Use of the composite material of any one of claims 1 -26, as an absorbent or adsorbent.

37. Use of the composite material of any one of claims 1 -26, as a drying agent.

38. Use of the composite material of any one of claims 1 -26, as a flocculent.

39. Use of the composite material of any one of claims 1 -26, for water or wastewater treatment.

40. The use of claim 39, wherein water or wastewater treatment comprises removal of organic contaminants or metal contaminants.

41 . The use of claim 40, wherein the metal contaminant is nickel.

42. Use of the composite material of any one of claims 1 -26, for cleaning a surface.

43. Use of the composite material of any one of claims 1 -26, for formation of a switchable fabric.

44. Use of the composite material of any one of claims 1 -26, for formation of a switchable filter paper.

45. Use of the composite material of any one of claims 1 -26, for stabilizing an emulsion.

46. Use of the composite material of any one of claims 1 -26, as a switchable viscosity modifier.

47. Use of the composite material of any one of claims 1 -26, for use in chromatography.

48. Use of the composite material of any one of claims 1 -26, for use in algae harvesting and/or microalgae recovery.

49. A method, comprising

changing ionization of a composite material comprising a polysaccharide and a polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, wherein the switchable moiety comprises an amine, amidine or guanidine, and wherein said composite material has a first, neutral form and a second, ionized form, the step of changing ionization comprising:

50. The method of claim 49, additionally comprising the step of contacting the composite material in its second form with (i) an at least partial vacuum; (ii) heat; (iii) a flushing inert gas; (iv) a liquid substantially devoid of an ionizing trigger; or, (v) any combination thereof; in the presence or absence of agitation, thereby expelling the ionizing trigger from the switchable moiety and switching the composite material back to its first, neutral form.

51 . The method of claims 49 or 50, wherein the ionizing trigger is a Bronsted acid or an acid gas.

52. The method of claim 51 , wherein the acid gas is C0₂, COS, CS₂, or a combination thereof.

53. The method of claim 50, wherein the inert gas is N 2, Ar or air.

54. The method of claim 50, wherein exposing to heat is heating to≤ 60 °C,≤ 80 °C, or < 150 °C.

55. The method of any one of claims 49 - 54, wherein the composite material is a membrane (e.g., a separation membrane), an absorbent material, a drying agent, a flocculent, material for water or wastewater treatment, a fabric, a filter (e.g., filter paper), an emulsion stabilizer/destabilizer, a viscosity modifier, or a chromatography support or resin.

56. A composite material that is reversibly switchable between a first form and a second form, said composite material comprising a polysaccharide and polysaccharide-supported switchable moiety attached to said polysaccharide via a linker, the switchable moiety comprising a functional group that is switchable between a neutral form associated with said first form of said composite material, and an ionized form associated with said second form of the composite material, the switchable moiety comprising an amine, amidine, or guanidine;

(91); wherein: n is an integer 1 , 2 or 3; X is a divalent moiety bonded to the polysaccharide and the switchable moiety; X is independently a linear or branched C1-C15 alkylene, a C15-C30 alkylene, a C1-C15 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, each of which may be substituted; or, X is independently is a divalent cycle, or heterocycle, each of which may be substituted ; or, X, and one or more of R¹¹ , R¹², and R¹⁴, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted;

R^{1 1} , R¹², and R¹⁴ are each independently H, a Ci to C10 aliphatic group that is linear, branched , or cyclic; a C_nSi_m group where n and m are independently a number from 0 to 10 and n + m is a number from 1 to 10, a C5 to C10 aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring , each of which may be substituted; or, any combination of R^{1 1} , R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a cycle or heterocycle, each of which may be substituted; and, when the polysaccharide is a CNC, n is 1 , and X is -C(0)-NH-(CH2)3- or -CO2- NH-(CH₂)₃- then only two of R^{1 1} , R¹², or R¹⁴ is H.

57. The composite material of claim 1 , wherein the switchable moiety is an amine and the switchable moiety is bound to the polysaccharide via a linker ΧΎ; and

wherein the first form of the composite materi has the structure of formula I

(I); and the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via linker ΧΎ has the structure of formula I I

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X', and is a linear or branched C 1-C15 alkylene, a C15-C30 alkylene, a Ci- Ci5 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X' is independently a linear or branched C 1-C15 alkanetriyl, a C15-C30 alkanetriyl, a C1-C15 alkenetriyl, a C15-C30 alkenetriyl, a C1-C15 alkynetriyl, a C15-C30 alkynetriyl, an aryltriyl, a heteroaryltriyl, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X' is independently is a trivalent cycle, or heterocycle, each of which may be substituted; or, each X', and one or two of R¹ and R², together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted ; wherein each X' and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini;

NR¹R² and N⁺R¹R² are each a switchable functional group, wherein R¹ and R² are each independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic, a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C5 to C10 aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or R¹ and R², together with the atoms to which they are attached, are connected to form a cycle, or heterocycle, each of which may be substituted; and

Z is a monovalent moiety bonded to X', and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thiol, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted; wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; wherein each of [X'(NR¹R²)]_m and [X'(N⁺R¹R²)]_m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit in said chain is the same or different relative to other repeat units; and wherein, (a) if both of R¹ and R² are H, then X' is a sterically hindered group or, (b) if one of R¹ and R² is H, then either (i) the other one of R¹ and R² is a sterically hindered group, or (ii) X' is a sterically hindered group.

58. The composite material of claim 1 , wherein the switchable moiety is an amidine and the switchable moiety is bound to the polysaccharide via a linker ΧΎ; and

wherein the first form of the composite material has the structure of formula Ilia, lllb, or lllc,

(Ilia) (lllb) (lllc); and the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker ΧΎ has the structure of formula IVa, IVb, IVc,

(IVa) (IVb) (IVc); wherein:

E is O, S, or a combination thereof; Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X', and is a linear or branched C 1-C15 alkylene, a C15-C30 alkylene, a Ci- Ci5 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X' is independently a linear or branched C 1-C15 alkanetriyl, a C15-C30 alkanetriyl, a C1-C15 alkenetriyl, a C15-C30 alkenetriyl, a C1-C15 alkynetriyl, a C15-C30 alkynetriyl, an aryltriyl, a heteroaryltriyl, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X' is independently is a trivalent cycle, or heterocycle, each of which may be substituted; or, each X', and one or more of R³, R⁴, and R⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; wherein each X' and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini;

N=CR³NR⁴R⁵ , R³N=CNR⁴R⁵, R³N=CR⁴NR⁵, and (N=CR³NR⁴R⁵)⁺, (R³N=CNR⁴R⁵)⁺, (R³N=CR⁴NR⁵)⁺ are each switchable functional groups, wherein R³, R⁴, and R⁵ are independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to C10 aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R³, R⁴, and R⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; and

Z is a monovalent moiety bonded to X', and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thiol, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted; wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and wherein each of [X'(N=CR³NR⁴R⁵)]_m, [X'(R³N=CNR⁴R⁵)]_m, [X'(R³N=CR⁴NR⁵)]_m, and [X'(N=CR³NR⁴R⁵⁺)]_m, [X'(R³N=CNR⁴R⁵⁺)]_m, [X'(R³N=CR⁴NR⁵⁺)]_m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit in said chain is the same or different relative to other repeat units.

59. The composite material of claim 1 , wherein the switchable moiety is a guanidine, and the switchable moiety is bound to the polysaccharide via a linker ΧΎ; and

wherein the first form of the composite material has the structure of formula Va, Vb, Vc,

(Va); (Vb); (Vc); and the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysaccharide via a linker ΧΎ has the structure of formula Via, VIb, Vic,

(Via); (Vlb); (Vic) ; wherein: p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent;

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X', and is a linear or branched C 1-C15 alkylene, a C15-C30 alkylene, a Ci- Ci5 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X' is independently a linear or branched C 1-C15 alkanetriyl, a C15-C30 alkanetriyl, a C1-C15 alkenetriyl, a C15-C30 alkenetriyl, a C1-C15 alkynetriyl, a C15-C30 alkynetriyl, an aryltriyl, a heteroaryltriyl, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X' is independently is a trivalent cycle, or heterocycle, each of which may be substituted; or, each X', and one or more of R⁶, R⁷, R⁸, R⁹ and R¹⁰, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted ; wherein each X' and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini;

N=CNR⁶R⁷NR⁸R⁹, R¹⁰N=CNR⁶NR⁸R⁹, R¹⁰N=CNR⁶R⁷NR⁹, and (N=CNR⁶R⁷NR⁸R⁹)⁺, (R¹⁰N=CNR⁶NR⁸R⁹)⁺, (R¹⁰N=CNR⁶R⁷NR⁹)⁺ are each switchable functional groups, wherein R⁶, R⁷, R⁸, R⁹ and R¹⁰ are independently H, a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C₅ to Ci₀ aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R⁶, R⁷, R⁸, R⁹ and R¹⁰, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; and

Z is a monovalent moiety bonded to X', and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thiol, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted; wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; wherein at least one of R⁶, R⁷, R⁸, R⁹ and R¹⁰ is an unsaturated functional group (e.g., aryl) or an an electron withdrawing group; and wherein each of [X'(N=CNR⁶R⁷NR⁸R⁹)]_m, [X'(R¹⁰N=CNR⁶NR⁸R⁹)]_m, [X'(R¹⁰N=CNR⁶R⁷NR⁹)]_m, [X'(N=CNR⁶R⁷NR⁸R⁹)⁺]_m, [X'(R¹⁰N=CNR⁶NR⁸R⁹)⁺]_m,

60. The composite material of claim 1 , wherein the switchable moiety is a pyridine, and the switchable moiety is bound to the polysaccharide via a linker ΧΎ; and

wherein the first form of the composite material has the structure of formula VII,

the second form of the composite material comprising the ionized form of the switchable moiety bound to the polysacch structure of formula VIII,

(VIII),

wherein: o is an integer 1 , 2 or 3; p is an integer between 1 and 4, wherein when Y is absent, p is 1 ; m is an integer between 1 and 10 000, wherein m x p is 10 000 or less; or, m is an integer between 1 and 10 000 when Y is absent; E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X', and is a linear or branched C 1-C15 alkylene, a C15-C30 alkylene, a Ci- Ci5 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X' is independently a linear or branched C 1-C15 alkanetriyl, a C15-C30 alkanetriyl, a C1-C15 alkenetriyl, a C15-C30 alkenetriyl, a C1-C15 alkynetriyl, a C15-C30 alkynetriyl, an aryltriyl, a heteroaryltriyl, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X' is independently is a trivalent cycle, or heterocycle, each of which may be substituted; or, each X', and one and one or more of R¹⁵, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted; wherein each X' and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and

is a switchable functional group, wherein R¹⁵ h is

H , a Ci to C10 aliphatic group that is linear, branched, or cyclic, a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a C5 to C10 aryl group, or a heteroaryl group having 4 to 10 ring atoms, each of which may be substituted; or any two of R¹⁵, together with the atoms to which they are attached, are connected to form a cycle, or heterocycle, each of which may be substituted; and

wherein each of

and optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit in said chain is the same or different relative to other repeat units.

61 . The composite material of claim 1 , wherein the switchable moiety is bound to the polysaccharide via a linker X'Y; and

(IXa); (IXb);

(IXc); (IXd); and the second form of the composite material comprising the ionized form of the switchable iety bound to the polysaccharide via a linker ΧΎ has the structure of formula Xa, Xb, Xc, or

(Xa); (Xb);

(Xc) ; (Xd);

E is O, S, or a combination thereof;

Y is absent, or a divalent linker moiety, or a multivalent linker moiety bonded to the polysaccharide and X', and is a linear or branched C 1-C15 alkylene, a C15-C30 alkylene, a Ci- Ci5 alkenylene, a C15-C30 alkenylene, a C1-C15 alkynylene, a C15-C30 alkynylene, an arylene, a heteroarylene, a thiol, a silane, or a siloxane, or is a corresponding multivalent moiety thereof, each of which may be substituted; or, Y is a divalent or multivalent cycle, or heterocycle, each of which may be substituted; each X' is independently a linear or branched C 1-C15 alkanetriyl, a C15-C30 alkanetriyl, a C1-C15 alkenetriyl, a Cis-C₃o alkenetriyl, a C1-C15 alkynetriyl, a Cis-C₃o alkynetriyl, an aryltriyl, a heteroaryltriyl, a thiol, a silane, or a siloxane, each of which may be substituted; or, each X' is independently is a trivalent cycle, or heterocycle, each of which may be substituted; or, each X', and one or more of R¹¹ , R¹², R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a heterocycle, which may be substituted ; wherein each X' and Y optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini;

R^{1 1} , R^{1 2}, R^{1 3}, and R¹⁴ are each independently H , a Ci to C10 aliphatic group that is linear, branched, or cyclic; a C_qSi_r group where q and r are independently a number from 0 to 10 and q + r is a number from 1 to 10, a Cs to Ci o aryl group, or a heteroaryl group having from 4 to 10 carbon atoms in the aromatic ring, each of which may be substituted; or, any combination of R^{1 1} , R^{1 2}, R¹³, and R¹⁴, together with the atoms to which they are attached, are connected to form a cycle or heterocycle, each of which may be substituted;

Z is a monovalent moiety bonded to X', and is a hydrogen, a halogen, linear or branched C1-C15 alkyl, a C15-C30 alkyl, a C1-C15 alkenyl, a C15-C30 alkenyl, a C1-C15 alkynyl, a C15-C30 alkynyl, an aryl, a heteroaryl, a thiol, a silane, an alkoxyamine, a ketone, a carbamate ester, a carbonate diester, a cycle, a heterocycle, an ether, an ester, an alkoxyamines, a thiol, a thioether, a thioester, a dithioester, silyl alkyl ether, or a siloxane, or a combination thereof, each of which may be substituted; or, Z is a monovalent cycle, or heterocycle, each of which may be substituted; wherein Z optionally comprises one or more halogen, amine, amide, amidine, guanidine, carbonyl, ketone, carbamate ester, carbonate diester, cycle, heterocycle, ether, ester, alkoxyamines, sulphide, thiol, thioether, thioester, dithioester, silane, silyl alkyl ether, or siloxane moieties, or a combination thereof, within its linear or branched_carbon chain, or at one of said chain's termini; and wherein, each of [X'(lm)]_m and [X'(lm)⁺]_m optionally comprises a chain of repeat units that is linear or branched, wherein each repeat unit in said chain is the same or different relative to other repeat units, wherein Im is an optionally substituted imidazole ring.

62. The composite material of any one of claims 57-61 , wherein the polysaccharide is cellulose nanocrystal (CNC), cellulose, dextran, starch, chitin, chitosan, or any combination thereof.

63. The composite material of any one of claims 57-61 , wherein the polysaccharide is within cotton, cotton linen, paper, flax, hemp jute, sisal, linen, or any combination thereof.

64. The composite material of any one of claims 57-63, wherein the first form of the composite material is neutral and hydrophobic, and the second form of the composite material is ionized and hydrophilic.

65. The composite material of any one of claims 57-64, wherein the composite material converts to, or is maintained in, the second, ionized form when the switchable moiety is exposed to an ionizing trigger at an amount sufficient to maintain the switchable moiety in its ionized form; and, wherein the composite material converts to, or is maintained in, the first form when the ionizing trigger is removed or reduced to an amount insufficient to maintain the switchable moiety in its ionized form.

66. The composite material of claim 65, wherein the ionizing trigger is an acid gas.

67. The composite material of claim 66, wherein the acid gas is C0₂, COS, CS₂, or a combination thereof

68. The composite material of claim 65, wherein the ionizing trigger is removed or reduced by exposing the composite material to: (i) an at least partial vacuum; (ii) heat; (iii) a flushing inert gas (iv) a liquid substantially devoid of an ionizing trigger; or, (v) any combination thereof; in the presence or absence of agitation.

69. The composition material of claim 68, wherein the inert gas is l\ , Ar or air.

70. The composite material of claim 68, wherein exposing to heat is heating to≤ 60 °C,≤ 80 °C, or≤ 150 °C.

71 . The composite material claim 65, wherein the ionizing trigger is a Bronsted acid sufficiently acidic to ionize the switchable moiety from its neutral form; or, any Bronsted base sufficiently basic to de-ionize the switchable moiety from its ionized form.

72. A method for switching a composite material of any one of claims 57-71 between its first form and second form, comprising: exposing the neutral composite material to (i) an aqueous liquid, or (ii) a nonaqueous liquid and water, to form a mixture, and exposing said mixture to an ionizing trigger, thereby protonating the switchable moiety and rendering the composite material ionized; and/or exposing the neutral composite material to an aqueous liquid comprising an ionizing trigger to form a mixture, wherein the liquid protonates the switchable moiety to render the composite material ionized; and optionally, separating the ionized composite material from the mixture.

73. A method for switching a composite material of any one of claims 57-71 between its second form and first form, comprising: exposing an ionized composite material to: (i) an at least partial vacuum; (ii) heat; (iii) a flushing inert gas; (iv) a liquid substantially devoid of an ionizing trigger; or, (v) any combination thereof; in the presence or absence of agitation, thereby expelling the ionizing trigger from the switchable moiety and rendering the composite material neutral; and optionally, separating the neutral composite material from the mixture.

74. The method of claims 72 or 73 wherein the ionizing trigger is a Bronsted acid, or an acid gas.

75. The method of claim 74, wherein the acid gas is C0₂, COS, CS₂, or a combination thereof.

76. The method of claim 73, wherein the inert gas is N 2, Ar or air.

77. The method of claim 73, wherein exposing to heat is heating to≤ 60 °C,≤ 80 °C, or ≤ 150 °C.

78. Use of the composite material of any one of claims 57-71 , for manipulating and/or controlling dispersibility, for example, CNC dispersibility.

79. Use of the composite material of any one of claims 57-71 , as a separation membrane.

80. Use of the composite material of any one of claims 57-71 , for formation of a membrane comprising a chiral nematic liquid crystalline structure.

81 . Use of the composite material of any one of claims 57-71 , as an absorbent or adsorbent.

82. Use of the composite material of any one of claims 57-71 , as a drying agent.

83. Use of the composite material of any one of claims 57-71 , as a flocculent.

84. Use of the composite material of any one of claims 57-71 , for water or wastewater treatment.

85. The use of claim 84, wherein water or wastewater treatment comprises removal of organic contaminants or metal contaminants.

86. The use of claim 85, wherein the metal contaminant is nickel.

87. Use of the composite material of any one of claims 57-71 , for cleaning a surface.

88. Use of the composite material of any one of claims 57-71 , for formation of a switchable fabric.

89. Use of the composite material of any one of claims 57-71 , for formation of a switchable filter paper.

90. Use of the composite material of any one of claims 57-71 , for stabilizing an emulsion.

91 . Use of the composite material of any one of claims 57-71 , as a switchable viscosity modifier.

92. Use of the composite material of any one of claims 57-71 , for use in chromatography.

93. Use of the composite material of any one of claims 57-71 , for use in algae harvesting and/or microalgae recovery.