CA3103620A1 - Bacterial cellulose gels, process for producing and methods of use - Google Patents
Bacterial cellulose gels, process for producing and methods of use Download PDFInfo
- Publication number
- CA3103620A1 CA3103620A1 CA3103620A CA3103620A CA3103620A1 CA 3103620 A1 CA3103620 A1 CA 3103620A1 CA 3103620 A CA3103620 A CA 3103620A CA 3103620 A CA3103620 A CA 3103620A CA 3103620 A1 CA3103620 A1 CA 3103620A1
- Authority
- CA
- Canada
- Prior art keywords
- cellulose
- aerogel
- disclosed
- gels
- film
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims description 74
- 230000008569 process Effects 0.000 title claims description 46
- 229920002749 Bacterial cellulose Polymers 0.000 title claims description 28
- 239000005016 bacterial cellulose Substances 0.000 title claims description 28
- 239000000499 gel Substances 0.000 title abstract description 108
- 229920002678 cellulose Polymers 0.000 claims abstract description 149
- 239000001913 cellulose Substances 0.000 claims abstract description 149
- 239000004964 aerogel Substances 0.000 claims abstract description 128
- 239000002131 composite material Substances 0.000 claims abstract description 26
- 239000002073 nanorod Substances 0.000 claims abstract description 23
- 239000002086 nanomaterial Substances 0.000 claims description 57
- 239000000463 material Substances 0.000 claims description 46
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 46
- 239000002904 solvent Substances 0.000 claims description 38
- 239000006185 dispersion Substances 0.000 claims description 32
- 239000000203 mixture Substances 0.000 claims description 30
- 239000003795 chemical substances by application Substances 0.000 claims description 19
- 241000894006 Bacteria Species 0.000 claims description 16
- 229920001046 Nanocellulose Polymers 0.000 claims description 16
- 230000005291 magnetic effect Effects 0.000 claims description 15
- 238000001035 drying Methods 0.000 claims description 14
- 239000002074 nanoribbon Substances 0.000 claims description 13
- 239000001257 hydrogen Substances 0.000 claims description 12
- 229910052739 hydrogen Inorganic materials 0.000 claims description 12
- 241000589216 Komagataeibacter hansenii Species 0.000 claims description 10
- 239000001963 growth medium Substances 0.000 claims description 10
- 241001136169 Komagataeibacter xylinus Species 0.000 claims description 9
- 235000002837 Acetobacter xylinum Nutrition 0.000 claims description 6
- 239000000654 additive Substances 0.000 claims description 6
- 230000000996 additive effect Effects 0.000 claims description 6
- 235000015097 nutrients Nutrition 0.000 claims description 3
- 239000000017 hydrogel Substances 0.000 abstract description 48
- 239000004973 liquid crystal related substance Substances 0.000 abstract description 38
- -1 ribbons Substances 0.000 abstract description 34
- 230000003287 optical effect Effects 0.000 abstract description 29
- 239000000835 fiber Substances 0.000 abstract description 13
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 38
- 239000002121 nanofiber Substances 0.000 description 35
- 229920003217 poly(methylsilsesquioxane) Polymers 0.000 description 33
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 26
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 24
- 229920001296 polysiloxane Polymers 0.000 description 23
- 230000003098 cholesteric effect Effects 0.000 description 20
- 239000002159 nanocrystal Substances 0.000 description 20
- 230000005540 biological transmission Effects 0.000 description 19
- 239000012071 phase Substances 0.000 description 19
- VVJKKWFAADXIJK-UHFFFAOYSA-N Allylamine Chemical compound NCC=C VVJKKWFAADXIJK-UHFFFAOYSA-N 0.000 description 18
- 239000007788 liquid Substances 0.000 description 18
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 17
- 239000000523 sample Substances 0.000 description 17
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 15
- 239000010410 layer Substances 0.000 description 14
- 230000004048 modification Effects 0.000 description 14
- 238000012986 modification Methods 0.000 description 14
- 229920000642 polymer Polymers 0.000 description 14
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 12
- 239000000377 silicon dioxide Substances 0.000 description 12
- 238000004132 cross linking Methods 0.000 description 11
- 239000002245 particle Substances 0.000 description 11
- 239000000243 solution Substances 0.000 description 11
- 229920002201 Oxidized cellulose Polymers 0.000 description 10
- 125000002091 cationic group Chemical group 0.000 description 10
- 229940107304 oxidized cellulose Drugs 0.000 description 10
- 238000000352 supercritical drying Methods 0.000 description 10
- 229920000742 Cotton Polymers 0.000 description 9
- 238000001879 gelation Methods 0.000 description 9
- 239000003960 organic solvent Substances 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 8
- 230000000670 limiting effect Effects 0.000 description 8
- 238000005259 measurement Methods 0.000 description 8
- 238000010438 heat treatment Methods 0.000 description 7
- 238000009413 insulation Methods 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 7
- 230000003647 oxidation Effects 0.000 description 7
- 238000007254 oxidation reaction Methods 0.000 description 7
- 239000002243 precursor Substances 0.000 description 7
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- 239000007864 aqueous solution Substances 0.000 description 6
- 230000001580 bacterial effect Effects 0.000 description 6
- AIXAANGOTKPUOY-UHFFFAOYSA-N carbachol Chemical group [Cl-].C[N+](C)(C)CCOC(N)=O AIXAANGOTKPUOY-UHFFFAOYSA-N 0.000 description 6
- 239000001768 carboxy methyl cellulose Substances 0.000 description 6
- 239000000725 suspension Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- VPJXQGSRWJZDOB-UHFFFAOYSA-O 2-carbamoyloxyethyl(trimethyl)azanium Chemical compound C[N+](C)(C)CCOC(N)=O VPJXQGSRWJZDOB-UHFFFAOYSA-O 0.000 description 5
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 5
- 239000004965 Silica aerogel Substances 0.000 description 5
- 239000002253 acid Substances 0.000 description 5
- 150000007942 carboxylates Chemical group 0.000 description 5
- 238000001246 colloidal dispersion Methods 0.000 description 5
- 239000008367 deionised water Substances 0.000 description 5
- 230000005684 electric field Effects 0.000 description 5
- 230000005670 electromagnetic radiation Effects 0.000 description 5
- 238000003384 imaging method Methods 0.000 description 5
- 239000011159 matrix material Substances 0.000 description 5
- 230000001404 mediated effect Effects 0.000 description 5
- 239000012528 membrane Substances 0.000 description 5
- 239000002105 nanoparticle Substances 0.000 description 5
- 239000011148 porous material Substances 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- 238000004626 scanning electron microscopy Methods 0.000 description 5
- 238000010008 shearing Methods 0.000 description 5
- 238000002834 transmittance Methods 0.000 description 5
- 241000589220 Acetobacter Species 0.000 description 4
- 229920003043 Cellulose fiber Polymers 0.000 description 4
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 4
- 229920001131 Pulp (paper) Polymers 0.000 description 4
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 4
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 4
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 4
- 230000001413 cellular effect Effects 0.000 description 4
- 108010040093 cellulose synthase Proteins 0.000 description 4
- 238000009833 condensation Methods 0.000 description 4
- 230000005494 condensation Effects 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- 238000001125 extrusion Methods 0.000 description 4
- 239000012530 fluid Substances 0.000 description 4
- 230000003993 interaction Effects 0.000 description 4
- BFXIKLCIZHOAAZ-UHFFFAOYSA-N methyltrimethoxysilane Chemical compound CO[Si](C)(OC)OC BFXIKLCIZHOAAZ-UHFFFAOYSA-N 0.000 description 4
- 239000002070 nanowire Substances 0.000 description 4
- 230000000737 periodic effect Effects 0.000 description 4
- 238000001878 scanning electron micrograph Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000006557 surface reaction Methods 0.000 description 4
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical compound [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 description 3
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 3
- JGFZNNIVVJXRND-UHFFFAOYSA-N N,N-Diisopropylethylamine (DIPEA) Chemical compound CCN(C(C)C)C(C)C JGFZNNIVVJXRND-UHFFFAOYSA-N 0.000 description 3
- 238000003917 TEM image Methods 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 230000002378 acidificating effect Effects 0.000 description 3
- 239000007900 aqueous suspension Substances 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 238000001446 dark-field microscopy Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 230000002209 hydrophobic effect Effects 0.000 description 3
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 3
- 238000000386 microscopy Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 150000003384 small molecules Chemical class 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 238000001931 thermography Methods 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- 238000004627 transmission electron microscopy Methods 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- STLICVZWECVJDT-UHFFFAOYSA-N 1-(4-hexylcyclohexyl)-4-isothiocyanatobenzene Chemical compound C1CC(CCCCCC)CCC1C1=CC=C(N=C=S)C=C1 STLICVZWECVJDT-UHFFFAOYSA-N 0.000 description 2
- GODZNYBQGNSJJN-UHFFFAOYSA-N 1-aminoethane-1,2-diol Chemical compound NC(O)CO GODZNYBQGNSJJN-UHFFFAOYSA-N 0.000 description 2
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 2
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 2
- 239000002202 Polyethylene glycol Substances 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 2
- 238000005903 acid hydrolysis reaction Methods 0.000 description 2
- 238000000149 argon plasma sintering Methods 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- 239000003637 basic solution Substances 0.000 description 2
- 239000011324 bead Substances 0.000 description 2
- 239000004202 carbamide Substances 0.000 description 2
- 239000002134 carbon nanofiber Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000012512 characterization method Methods 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 230000005294 ferromagnetic effect Effects 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 238000004108 freeze drying Methods 0.000 description 2
- 230000006870 function Effects 0.000 description 2
- 238000007306 functionalization reaction Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 230000005661 hydrophobic surface Effects 0.000 description 2
- 239000002609 medium Substances 0.000 description 2
- 125000000956 methoxy group Chemical group [H]C([H])([H])O* 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 230000006855 networking Effects 0.000 description 2
- 230000037361 pathway Effects 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- IYDGMDWEHDFVQI-UHFFFAOYSA-N phosphoric acid;trioxotungsten Chemical compound O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.OP(O)(O)=O IYDGMDWEHDFVQI-UHFFFAOYSA-N 0.000 description 2
- 238000004375 physisorption Methods 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 229920001223 polyethylene glycol Polymers 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 230000002829 reductive effect Effects 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- JHJLBTNAGRQEKS-UHFFFAOYSA-M sodium bromide Chemical compound [Na+].[Br-] JHJLBTNAGRQEKS-UHFFFAOYSA-M 0.000 description 2
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 2
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 239000007858 starting material Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 230000003319 supportive effect Effects 0.000 description 2
- KAEZRSFWWCTVNP-UHFFFAOYSA-N (4-methoxyphenyl)-(4-methoxyphenyl)imino-oxidoazanium Chemical compound C1=CC(OC)=CC=C1N=[N+]([O-])C1=CC=C(OC)C=C1 KAEZRSFWWCTVNP-UHFFFAOYSA-N 0.000 description 1
- YUYXUPYNSOFWFV-UHFFFAOYSA-N 4-(4-hexoxyphenyl)benzonitrile Chemical compound C1=CC(OCCCCCC)=CC=C1C1=CC=C(C#N)C=C1 YUYXUPYNSOFWFV-UHFFFAOYSA-N 0.000 description 1
- GPGGNNIMKOVSAG-UHFFFAOYSA-N 4-(4-octoxyphenyl)benzonitrile Chemical compound C1=CC(OCCCCCCCC)=CC=C1C1=CC=C(C#N)C=C1 GPGGNNIMKOVSAG-UHFFFAOYSA-N 0.000 description 1
- RDISTOCQRJJICR-UHFFFAOYSA-N 4-(4-pentoxyphenyl)benzonitrile Chemical compound C1=CC(OCCCCC)=CC=C1C1=CC=C(C#N)C=C1 RDISTOCQRJJICR-UHFFFAOYSA-N 0.000 description 1
- FURZYCFZFBYJBT-UHFFFAOYSA-N 4-(4-pentylcyclohexyl)benzonitrile Chemical compound C1CC(CCCCC)CCC1C1=CC=C(C#N)C=C1 FURZYCFZFBYJBT-UHFFFAOYSA-N 0.000 description 1
- 239000005212 4-Cyano-4'-pentylbiphenyl Substances 0.000 description 1
- HHPCNRKYVYWYAU-UHFFFAOYSA-N 4-cyano-4'-pentylbiphenyl Chemical group C1=CC(CCCCC)=CC=C1C1=CC=C(C#N)C=C1 HHPCNRKYVYWYAU-UHFFFAOYSA-N 0.000 description 1
- 206010003497 Asphyxia Diseases 0.000 description 1
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 1
- PTHCMJGKKRQCBF-UHFFFAOYSA-N Cellulose, microcrystalline Chemical compound OC1C(O)C(OC)OC(CO)C1OC1C(O)C(O)C(OC)C(CO)O1 PTHCMJGKKRQCBF-UHFFFAOYSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 239000004986 Cholesteric liquid crystals (ChLC) Substances 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- 239000005183 N-(4-Methoxybenzylidene)-4-butylaniline Substances 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- 238000001069 Raman spectroscopy Methods 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 239000005708 Sodium hypochlorite Substances 0.000 description 1
- 229920002125 Sokalan® Polymers 0.000 description 1
- 241000656145 Thyrsites atun Species 0.000 description 1
- 241000251555 Tunicata Species 0.000 description 1
- 229920001807 Urea-formaldehyde Polymers 0.000 description 1
- 239000003377 acid catalyst Substances 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 150000003973 alkyl amines Chemical class 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- 125000000129 anionic group Chemical group 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000008346 aqueous phase Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 238000009529 body temperature measurement Methods 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000000339 bright-field microscopy Methods 0.000 description 1
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 1
- 229910052794 bromium Inorganic materials 0.000 description 1
- 239000000872 buffer Substances 0.000 description 1
- 229940006005 carbamoylcholine Drugs 0.000 description 1
- 150000001720 carbohydrates Chemical class 0.000 description 1
- 150000001732 carboxylic acid derivatives Chemical group 0.000 description 1
- 229920002301 cellulose acetate Polymers 0.000 description 1
- 230000007073 chemical hydrolysis Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 230000003750 conditioning effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000000502 dialysis Methods 0.000 description 1
- 238000000113 differential scanning calorimetry Methods 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- IVJISJACKSSFGE-UHFFFAOYSA-N formaldehyde;1,3,5-triazine-2,4,6-triamine Chemical compound O=C.NC1=NC(N)=NC(N)=N1 IVJISJACKSSFGE-UHFFFAOYSA-N 0.000 description 1
- SLGWESQGEUXWJQ-UHFFFAOYSA-N formaldehyde;phenol Chemical compound O=C.OC1=CC=CC=C1 SLGWESQGEUXWJQ-UHFFFAOYSA-N 0.000 description 1
- ZZUFCTLCJUWOSV-UHFFFAOYSA-N furosemide Chemical compound C1=C(Cl)C(S(=O)(=O)N)=CC(C(O)=O)=C1NCC1=CC=CO1 ZZUFCTLCJUWOSV-UHFFFAOYSA-N 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000008103 glucose Substances 0.000 description 1
- 239000006481 glucose medium Substances 0.000 description 1
- 239000011121 hardwood Substances 0.000 description 1
- 238000003306 harvesting Methods 0.000 description 1
- 235000003642 hunger Nutrition 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 230000003301 hydrolyzing effect Effects 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 238000004433 infrared transmission spectrum Methods 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 239000012774 insulation material Substances 0.000 description 1
- 239000003446 ligand Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 230000002535 lyotropic effect Effects 0.000 description 1
- FEIWNULTQYHCDN-UHFFFAOYSA-N mbba Chemical compound C1=CC(CCCC)=CC=C1N=CC1=CC=C(OC)C=C1 FEIWNULTQYHCDN-UHFFFAOYSA-N 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- DBOAVDSSZWDGTH-UHFFFAOYSA-N n-(4-butylphenyl)-1-(4-ethoxyphenyl)methanimine Chemical compound C1=CC(CCCC)=CC=C1N=CC1=CC=C(OCC)C=C1 DBOAVDSSZWDGTH-UHFFFAOYSA-N 0.000 description 1
- 239000002114 nanocomposite Substances 0.000 description 1
- 239000002064 nanoplatelet Substances 0.000 description 1
- 239000002077 nanosphere Substances 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 238000000879 optical micrograph Methods 0.000 description 1
- 125000000962 organic group Chemical group 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 239000005022 packaging material Substances 0.000 description 1
- 230000036961 partial effect Effects 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 229920001568 phenolic resin Polymers 0.000 description 1
- 235000011007 phosphoric acid Nutrition 0.000 description 1
- 150000003016 phosphoric acids Chemical class 0.000 description 1
- 239000011120 plywood Substances 0.000 description 1
- 238000001907 polarising light microscopy Methods 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- ODGAOXROABLFNM-UHFFFAOYSA-N polynoxylin Chemical compound O=C.NC(N)=O ODGAOXROABLFNM-UHFFFAOYSA-N 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 1
- 125000001436 propyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 239000002096 quantum dot Substances 0.000 description 1
- 125000001453 quaternary ammonium group Chemical group 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000001338 self-assembly Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229920002545 silicone oil Polymers 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 239000004984 smart glass Substances 0.000 description 1
- UKLNMMHNWFDKNT-UHFFFAOYSA-M sodium chlorite Chemical compound [Na+].[O-]Cl=O UKLNMMHNWFDKNT-UHFFFAOYSA-M 0.000 description 1
- 229960002218 sodium chlorite Drugs 0.000 description 1
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 description 1
- 239000012064 sodium phosphate buffer Substances 0.000 description 1
- 239000011122 softwood Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 238000000527 sonication Methods 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 230000037351 starvation Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 230000002123 temporal effect Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- LFQCEHFDDXELDD-UHFFFAOYSA-N tetramethyl orthosilicate Chemical compound CO[Si](OC)(OC)OC LFQCEHFDDXELDD-UHFFFAOYSA-N 0.000 description 1
- 125000003396 thiol group Chemical group [H]S* 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
- 239000003053 toxin Substances 0.000 description 1
- 231100000765 toxin Toxicity 0.000 description 1
- 108700012359 toxins Proteins 0.000 description 1
- 238000000411 transmission spectrum Methods 0.000 description 1
- PISDRBMXQBSCIP-UHFFFAOYSA-N trichloro(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane Chemical compound FC(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)CC[Si](Cl)(Cl)Cl PISDRBMXQBSCIP-UHFFFAOYSA-N 0.000 description 1
- 238000001392 ultraviolet--visible--near infrared spectroscopy Methods 0.000 description 1
- 238000001429 visible spectrum Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2201/00—Foams characterised by the foaming process
- C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
- C08J2201/05—Elimination by evaporation or heat degradation of a liquid phase
- C08J2201/0504—Elimination by evaporation or heat degradation of a liquid phase the liquid phase being aqueous
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2205/00—Foams characterised by their properties
- C08J2205/02—Foams characterised by their properties the finished foam itself being a gel or a gel being temporarily formed when processing the foamable composition
- C08J2205/026—Aerogel, i.e. a supercritically dried gel
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
- C08J2301/02—Cellulose; Modified cellulose
-
- C—CHEMISTRY; METALLURGY
- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
- C12P19/00—Preparation of compounds containing saccharide radicals
- C12P19/04—Polysaccharides, i.e. compounds containing more than five saccharide radicals attached to each other by glycosidic bonds
Landscapes
- Chemical & Material Sciences (AREA)
- Polymers & Plastics (AREA)
- Materials Engineering (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
- Micro-Organisms Or Cultivation Processes Thereof (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Preparation Of Compounds By Using Micro-Organisms (AREA)
Abstract
Disclosed are cellulose-based flexible gels containing cellulose nanorods, ribbons, fibers, and the like, and cellulose-enabled inorganic or polymeric composites, wherein the gels have tunable optical, thermal, and mechanical properties. The disclosed gels can be in the form of hydrogels, organogels, liquid-crystal (LC) gels, and aerogels.
Description
BACTERIAL CELLULOSE GELS, PROCESS FOR PRODUCING
AND METHODS OF USE
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. Application No. 16/017,319, entitled BACTERIAL CELLULOSE GELS, PROCESS FOR PRODUCING AND METHODS OF
USE and filed June 25, 2018. This application also claims the benefit of U.S.
Provisional Application No. 62/684,661, entitled NANOCELLULOSE BIOFILMS FOR INSULATING
AND STRUCTURAL GELS and filed June 13, 2018. The entire contents of these applications are hereby incorporated herein by reference in their entirety.
FEDERALLY SPONSORED RESEARCH
This discovery was made with Government support under grant DMR-1410735 awarded by the U.S. National Science Foundation and under grant DE-AR0000743 awarded .. by the U.S. Department of Energy. The Government has certain rights in the invention.
FIELD
Disclosed are cellulose-based flexible gels containing cellulose nanorods, ribbons, fibers, and the like, and cellulose-enabled inorganic or polymeric composites, wherein the gels have tunable optical, heat transfer, and stiffness properties. The disclosed gels are in the form of hydrogels, organogels, liquid-crystal (LC) gels, and aerogels. Further disclosed are highly transparent and flexible cellulose nanofiber-polysiloxane composite aerogels featuring enhanced mechanical robustness, tunable optical anisotropy, and low thermal conductivity. Further disclosed are gels comprising cellulosic material derived from bacteria and processes for preparing bacterial cellulose gels and methods of use.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 shows the schematic of fabrication procedures of cellulose-enabled ordered gels (a) cellulose nanomaterials aqueous dispersion, (b) hydrogel, (c) organogel (d) aerogel, and (e) liquid crystal gel.
Figure 2 shows transmission electron microscopy (TEM) images of cellulose nanorods, nanofibers, nanoribbons from different sources: (a) cellulose nanorods from cotton, (b) cellulose nanowires from cotton, (c) cellulose nanowires from wood pulp, and (d) cellulose nanoribbons from bacterial cellulose.
Figure 3 shows photographs of nematic cellulose (a) hydrogel, (b) organogel, (c) aerogel, (d) nematogel, and (e) scanning electron microscopy (SEM) image of the ordered aerogel. The scale bar is 1 cm.
Figure 4 shows photographs of cholesteric (a) cellulose-silica composition, (b) silica aerogel, (c) silica nematogel, and (d) SEM image of the ordered silica aerogel. The scale bar is 5 mm.
Figure 5 is a schematic representation of a spectrometer assembly that can be used for haze measurements at diffuse illumination and unidirectional viewing.
Figure 6 describes a general schematic of one embodiment for the fabrication of the disclosed aerogels.
Figure 7 shows the optical pathway of a typical pump-and-probe measurement system.
Figure 8 discloses the components of a hot box apparatus: a metering box (simulating interior temperature) on one side of the window specimen; a controlled guard box surrounding the metering box; a climate chamber box (simulating exterior temperature) on the other side; and the specimen frame providing specimen support & insulation.
Figures 9A-9C depict various TEMPO-oxidized cellulose nanoparticle modifying agents.
Figure 9A depicts surface modification by allylamine. Figure 9B depicts surface modification by a 2-(carbamoyloxy)-N,N,N-trimethylethanaminium adduct. Figure 9C depicts surface modification by example a methoxy polyethylene glycol amine (mPEG-amine).
Figure 10 depicts the disclosed process for forming polymethylsilsesquioxane (PMSQ) network cellulosic hydrogels, organogels and aerogels process in general.
Figure 11 is a photograph showing the optical transparency of a hydrogel formed from the disclosed process.
Figure 12 is a photograph showing the optical transparency of an organogel formed from the disclosed process.
Figure 13 is photograph showing the optical transparency of an aerogel formed from the disclosed process wherein the surface modifying agent is allylamine.
Figure 14 is a photograph of an aerogel formed by the disclosed process wherein the surface modifying agent is an m-PEG-amine having an average molecular weight of 5000 daltons.
Figure 15 is a photograph of an aerogel formed by the disclosed process wherein the surface modifying agent is carbamoylcholine chloride.
Figure 16 depicts that the carbamoylcholine chloride-capped TOCN-PMSQ aerogels exhibit hydrophobic surface characteristics.
AND METHODS OF USE
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. Application No. 16/017,319, entitled BACTERIAL CELLULOSE GELS, PROCESS FOR PRODUCING AND METHODS OF
USE and filed June 25, 2018. This application also claims the benefit of U.S.
Provisional Application No. 62/684,661, entitled NANOCELLULOSE BIOFILMS FOR INSULATING
AND STRUCTURAL GELS and filed June 13, 2018. The entire contents of these applications are hereby incorporated herein by reference in their entirety.
FEDERALLY SPONSORED RESEARCH
This discovery was made with Government support under grant DMR-1410735 awarded by the U.S. National Science Foundation and under grant DE-AR0000743 awarded .. by the U.S. Department of Energy. The Government has certain rights in the invention.
FIELD
Disclosed are cellulose-based flexible gels containing cellulose nanorods, ribbons, fibers, and the like, and cellulose-enabled inorganic or polymeric composites, wherein the gels have tunable optical, heat transfer, and stiffness properties. The disclosed gels are in the form of hydrogels, organogels, liquid-crystal (LC) gels, and aerogels. Further disclosed are highly transparent and flexible cellulose nanofiber-polysiloxane composite aerogels featuring enhanced mechanical robustness, tunable optical anisotropy, and low thermal conductivity. Further disclosed are gels comprising cellulosic material derived from bacteria and processes for preparing bacterial cellulose gels and methods of use.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 shows the schematic of fabrication procedures of cellulose-enabled ordered gels (a) cellulose nanomaterials aqueous dispersion, (b) hydrogel, (c) organogel (d) aerogel, and (e) liquid crystal gel.
Figure 2 shows transmission electron microscopy (TEM) images of cellulose nanorods, nanofibers, nanoribbons from different sources: (a) cellulose nanorods from cotton, (b) cellulose nanowires from cotton, (c) cellulose nanowires from wood pulp, and (d) cellulose nanoribbons from bacterial cellulose.
Figure 3 shows photographs of nematic cellulose (a) hydrogel, (b) organogel, (c) aerogel, (d) nematogel, and (e) scanning electron microscopy (SEM) image of the ordered aerogel. The scale bar is 1 cm.
Figure 4 shows photographs of cholesteric (a) cellulose-silica composition, (b) silica aerogel, (c) silica nematogel, and (d) SEM image of the ordered silica aerogel. The scale bar is 5 mm.
Figure 5 is a schematic representation of a spectrometer assembly that can be used for haze measurements at diffuse illumination and unidirectional viewing.
Figure 6 describes a general schematic of one embodiment for the fabrication of the disclosed aerogels.
Figure 7 shows the optical pathway of a typical pump-and-probe measurement system.
Figure 8 discloses the components of a hot box apparatus: a metering box (simulating interior temperature) on one side of the window specimen; a controlled guard box surrounding the metering box; a climate chamber box (simulating exterior temperature) on the other side; and the specimen frame providing specimen support & insulation.
Figures 9A-9C depict various TEMPO-oxidized cellulose nanoparticle modifying agents.
Figure 9A depicts surface modification by allylamine. Figure 9B depicts surface modification by a 2-(carbamoyloxy)-N,N,N-trimethylethanaminium adduct. Figure 9C depicts surface modification by example a methoxy polyethylene glycol amine (mPEG-amine).
Figure 10 depicts the disclosed process for forming polymethylsilsesquioxane (PMSQ) network cellulosic hydrogels, organogels and aerogels process in general.
Figure 11 is a photograph showing the optical transparency of a hydrogel formed from the disclosed process.
Figure 12 is a photograph showing the optical transparency of an organogel formed from the disclosed process.
Figure 13 is photograph showing the optical transparency of an aerogel formed from the disclosed process wherein the surface modifying agent is allylamine.
Figure 14 is a photograph of an aerogel formed by the disclosed process wherein the surface modifying agent is an m-PEG-amine having an average molecular weight of 5000 daltons.
Figure 15 is a photograph of an aerogel formed by the disclosed process wherein the surface modifying agent is carbamoylcholine chloride.
Figure 16 depicts that the carbamoylcholine chloride-capped TOCN-PMSQ aerogels exhibit hydrophobic surface characteristics.
2
3 Figures 17A-17C are transmission electron microscopy (TEM) micrographs of the disclosed aerogels at various magnifications. Figure 17A shows that the colloidal dispersions consist of mostly individualized TOCNs, each of diameter D5 nm and length Lc=1-Figures 17B and 17C are scanning electron microscopy (SEM) that depict the well-defined and .. uniform-diameter 10-15 nm nanofibers that are formed by polysiloxane.
Figure 18 shows the visible transmission of a disclosed aerogel.
Figure 19 shows the haze coefficient of a disclosed aerogel.
Figure 20 depicts that the PMSQ matrix causes TOCN-PMSQ aerogels to exhibit strong absorption at a wavelength of 6-20 lam that is mainly due to the Si-0 bond.
Figure 21 shows the measured thermal conductivity of a TOCN-PMSQ aerogel versus sample porosity.
Figure 22 depicts the comparison of thermal conductivity between an aerogel formed from carbamoylcholine chloride modified nanocellulose (quaternary-amine) and an allylamine modified aerogel.
Figure 23 depicts the compression stress-strain relation for a TOCN-PMSQ
aerogel with 0.06 wt.% of TOCN.
Figure 24A and Figure 24B depict the reorientation of an A. hansenii bacterium using the infrared laser beam of a laser trap.
Figure 25 is a photograph of dark field microscopy showing an A. hansenn bacterium producing a cellulose fiber.
Figure 26 shows A. xylinum bacteria producing cellulose fibers.
Figure 27A and Figure 27B show the effect on cellulose fibril thickness when 1.5%
sodium carboxymethyl cellulose is added to A. xyhnurn. In Figure 27A the cellulose fibril is visible. In Figure 27B the thickness of the fibril is greatly reduced such that the fibril is invisible .. in the photograph.
Figure 28 is a depiction of an Acetobacter cell showing multiple cellulose synthase enzymes extruding cellulose fibrils from the cellular membrane. As the fibrils lengthen hydrogen bonding between adjacent strands cause the fibrils to coalesce and form ribbons.
Figure 29 is a depiction of an Acetobacter cell showing multiple cellulose synthase enzymes extruding cellulose fibrils from the cellular membrane. In this iteration, carboxymethyl cellulose is added to the growth media resulting in hydrogen bonds not forming the fibrils into ribbons of fiber.
Figure 30A and Figure 30B show an example of the disclosed aerogel biofilms.
Figure 31A and Figure 31B are thermal imaging photographs comparing a standard polysiloxane polymer with a gel formed by the disclosed process.
DETAILED DESCRIPTION
As used herein, a "gel" is understood to be a substantially dilute cross-linked system that exhibits no flow when in the steady state. The primary constituent of the gel is the ambient fluid surrounding it, whose form can be a liquid or gas. Prefixes such as "aero,"
"organo," "hydro," and variations are understood to indicate the ambient fluid in the cross-linked gel matrix and primary component of the gel material.
The disclosed gels contain cellulosic nanocomposites that are aligned in ordered liquid crystal phases. As such, the disclosed gels allow the formulator to adjust the optical transmissivity of the gel, thereby configuring the optical properties of the gel to range from opaque to transparent.
In addition, the properties can be adjusted to interact with a wide range of the electromagnetic spectra, for example, from the visible spectrum to infrared spectrum. In one embodiment, the thermal conductivity of the gel can be adjusted. The bulk properties of the disclosed gels, for example the level of stiffness or flexibility can be adjusted by the choice of the constituent cellulosic material, for example, nanorods, ribbons, fibers, and the like, as well as, the concentration of these materials in the resulting gels.
As used herein, a "film" and variations indicate non-porous lamellae ranging in thickness from about 10 nm to 1 mm and arbitrary lateral extent.
As used herein the term "cross-section" means width and the terms are used interchangeably. The disclosed cellulosic nanomaterials have a width from about 10 nm to about 500 nm. The length of the nanomaterials is at least ten times the width.
The term "composition" as used herein refers to the disclosed cellulose nanomaterial aqueous dispersions, hydrogels, organogels, aerogels, and liquid crystal gels.
The compositions can be a single layer of material comprising nanomaterials or the composition can be formed from two or more distinct layers wherein each layer consists of only one material.
As a non-limiting example, one layer can consist of an ordered nematic cellulosic gel onto which a second layer of aligned cholesteric cellulose film is applied thereto. This layering thereby forms a unified composite material with distinct layers.
The term "hydrogel" as used herein represents a network of cellulosic material as a colloidal gel dispersed in a carrier. In one embodiment the carrier is water.
In another embodiment the carrier is a mixture of a water compatible (miscible) organic solvent. The cellulosic material can be crosslinked or non-crosslinked.
Figure 18 shows the visible transmission of a disclosed aerogel.
Figure 19 shows the haze coefficient of a disclosed aerogel.
Figure 20 depicts that the PMSQ matrix causes TOCN-PMSQ aerogels to exhibit strong absorption at a wavelength of 6-20 lam that is mainly due to the Si-0 bond.
Figure 21 shows the measured thermal conductivity of a TOCN-PMSQ aerogel versus sample porosity.
Figure 22 depicts the comparison of thermal conductivity between an aerogel formed from carbamoylcholine chloride modified nanocellulose (quaternary-amine) and an allylamine modified aerogel.
Figure 23 depicts the compression stress-strain relation for a TOCN-PMSQ
aerogel with 0.06 wt.% of TOCN.
Figure 24A and Figure 24B depict the reorientation of an A. hansenii bacterium using the infrared laser beam of a laser trap.
Figure 25 is a photograph of dark field microscopy showing an A. hansenn bacterium producing a cellulose fiber.
Figure 26 shows A. xylinum bacteria producing cellulose fibers.
Figure 27A and Figure 27B show the effect on cellulose fibril thickness when 1.5%
sodium carboxymethyl cellulose is added to A. xyhnurn. In Figure 27A the cellulose fibril is visible. In Figure 27B the thickness of the fibril is greatly reduced such that the fibril is invisible .. in the photograph.
Figure 28 is a depiction of an Acetobacter cell showing multiple cellulose synthase enzymes extruding cellulose fibrils from the cellular membrane. As the fibrils lengthen hydrogen bonding between adjacent strands cause the fibrils to coalesce and form ribbons.
Figure 29 is a depiction of an Acetobacter cell showing multiple cellulose synthase enzymes extruding cellulose fibrils from the cellular membrane. In this iteration, carboxymethyl cellulose is added to the growth media resulting in hydrogen bonds not forming the fibrils into ribbons of fiber.
Figure 30A and Figure 30B show an example of the disclosed aerogel biofilms.
Figure 31A and Figure 31B are thermal imaging photographs comparing a standard polysiloxane polymer with a gel formed by the disclosed process.
DETAILED DESCRIPTION
As used herein, a "gel" is understood to be a substantially dilute cross-linked system that exhibits no flow when in the steady state. The primary constituent of the gel is the ambient fluid surrounding it, whose form can be a liquid or gas. Prefixes such as "aero,"
"organo," "hydro," and variations are understood to indicate the ambient fluid in the cross-linked gel matrix and primary component of the gel material.
The disclosed gels contain cellulosic nanocomposites that are aligned in ordered liquid crystal phases. As such, the disclosed gels allow the formulator to adjust the optical transmissivity of the gel, thereby configuring the optical properties of the gel to range from opaque to transparent.
In addition, the properties can be adjusted to interact with a wide range of the electromagnetic spectra, for example, from the visible spectrum to infrared spectrum. In one embodiment, the thermal conductivity of the gel can be adjusted. The bulk properties of the disclosed gels, for example the level of stiffness or flexibility can be adjusted by the choice of the constituent cellulosic material, for example, nanorods, ribbons, fibers, and the like, as well as, the concentration of these materials in the resulting gels.
As used herein, a "film" and variations indicate non-porous lamellae ranging in thickness from about 10 nm to 1 mm and arbitrary lateral extent.
As used herein the term "cross-section" means width and the terms are used interchangeably. The disclosed cellulosic nanomaterials have a width from about 10 nm to about 500 nm. The length of the nanomaterials is at least ten times the width.
The term "composition" as used herein refers to the disclosed cellulose nanomaterial aqueous dispersions, hydrogels, organogels, aerogels, and liquid crystal gels.
The compositions can be a single layer of material comprising nanomaterials or the composition can be formed from two or more distinct layers wherein each layer consists of only one material.
As a non-limiting example, one layer can consist of an ordered nematic cellulosic gel onto which a second layer of aligned cholesteric cellulose film is applied thereto. This layering thereby forms a unified composite material with distinct layers.
The term "hydrogel" as used herein represents a network of cellulosic material as a colloidal gel dispersed in a carrier. In one embodiment the carrier is water.
In another embodiment the carrier is a mixture of a water compatible (miscible) organic solvent. The cellulosic material can be crosslinked or non-crosslinked.
4 The term "organogel" as used herein is a gel wherein the aqueous phase of a precursor hydrogel has had substantially all of the water removed and replaced by a water compatible solvent. Non-limiting examples of compatible solvents include methanol, ethanol, propanol and isopropanol. In one embodiment, the disclosed organogels have a two-dimensional cross-linked network. In another embodiment the disclosed organogels have a three-dimensional crosslinked network.
The term "aerogel" as used herein refers to a gel derived from the further processing of a disclosed organogel as described herein.
The term "liquid crystal gel" refers to the compositions derived from the further processing of the disclosed organogels as described herein.
The term "nanomaterial" refers to the disclosed cellulosic material. The width of these materials is in the nanometer range, whereas the length of the cellulosic material can vary from nanometer length to micrometer. The terms "nanomaterial," "cellulosic material" and "cellulosic nanomaterial" are used interchangeably throughout the present disclosure.
The term "nematic" as used herein refers to a composition wherein the disclosed cellulosic materials possess long-range orientational order. In addition, the cellulosic materials are free to flow and their center of mass positions are randomly distributed, but still maintain their long-range directional order. The disclosed nematic compositions are uniaxial: they have one axis that is longer and preferred, with the other two being equivalent.
The term "cholesteric" as used herein refers to a composition with a helical structure and which is therefore chiral. The disclosed cholesteric compositions are organized in layers with no positional ordering within layers, but a director axis which varies with layers. The variation of the director axis can be periodic in nature. If present, the period of this variation (the distance over which a full rotation of 360 is completed) is known as the pitch, which can be adjusted by the formulator, and the degree of pitch determines the wavelength of electromagnetic radiation which is reflected.
The abbreviation "TOCN" as used throughout the specification means "TEMPO-oxidized cellulose nanofibers."
The term "low molecular weight compounds comprising a cationic moiety" means a compound that has a moiety that can react with an oxidized cellulose carboxyl group in addition to a separate cationic moiety. Non-limiting examples of units that can react with an oxidized cellulose carboxyl group include hydroxyl group, an amino group, a thiol group, and the like. A
non-limiting example of a cationic moiety includes a quaternary ammonium group.
The term "aerogel" as used herein refers to a gel derived from the further processing of a disclosed organogel as described herein.
The term "liquid crystal gel" refers to the compositions derived from the further processing of the disclosed organogels as described herein.
The term "nanomaterial" refers to the disclosed cellulosic material. The width of these materials is in the nanometer range, whereas the length of the cellulosic material can vary from nanometer length to micrometer. The terms "nanomaterial," "cellulosic material" and "cellulosic nanomaterial" are used interchangeably throughout the present disclosure.
The term "nematic" as used herein refers to a composition wherein the disclosed cellulosic materials possess long-range orientational order. In addition, the cellulosic materials are free to flow and their center of mass positions are randomly distributed, but still maintain their long-range directional order. The disclosed nematic compositions are uniaxial: they have one axis that is longer and preferred, with the other two being equivalent.
The term "cholesteric" as used herein refers to a composition with a helical structure and which is therefore chiral. The disclosed cholesteric compositions are organized in layers with no positional ordering within layers, but a director axis which varies with layers. The variation of the director axis can be periodic in nature. If present, the period of this variation (the distance over which a full rotation of 360 is completed) is known as the pitch, which can be adjusted by the formulator, and the degree of pitch determines the wavelength of electromagnetic radiation which is reflected.
The abbreviation "TOCN" as used throughout the specification means "TEMPO-oxidized cellulose nanofibers."
The term "low molecular weight compounds comprising a cationic moiety" means a compound that has a moiety that can react with an oxidized cellulose carboxyl group in addition to a separate cationic moiety. Non-limiting examples of units that can react with an oxidized cellulose carboxyl group include hydroxyl group, an amino group, a thiol group, and the like. A
non-limiting example of a cationic moiety includes a quaternary ammonium group.
5 In one aspect of the present disclosure are compositions comprising cellulosic nanoribbons that are aligned together and on which orientation can be adjusted by the formulator. The disclosed nanoribbons have aspect ratios from about 1:100 to about 1:1000. In one aspect, the disclosed nanoribbons can be used to form a nematic flexible gel.
These cellulose-based flexible gels can comprise cellulose ribbons, fibers, and other constituent-particle structures having in one embodiment aspect ratios of about 1:1000. These flexible gels are formed from linking the cellulose particle networks within the material. The original cellulose solvent which is used for the formation of the gel network can be retained or replaced to yield a variety of gel types, for example, hydrogels, alcogels, aerogels, and liquid-crystal gels. The use of the disclosed cellulosic material to form the gel network allows the formulator to adjust the flexibility of the gels.
The aspect ratios allow for a greater degree of flexibility or rigidity depending upon the selection of cellulosic nanomaterial. In addition, the cellulose particles can be ordered through chemical and mechanical means to yield a lyotropic liquid crystalline dispersion with ordered phases. The ordering can be preserved during the cross-linking process to form various ordered gels, non-limiting examples of which are given above. Figure 1 illustrates the fabrication procedure of cellulosic ordered gels.
In addition to flexibility, the optical transmissivity of the disclosed gels can be adjusted to range from opaque to transparent. The degree of opaqueness or transparency can also be matched of any wavelength or range of wavelength in the electromagnetic spectrum.
These results can be obtained by adjusting the various properties of the disclosed composites, i.e., density of cellulosic nanomaterial or size distribution. Also, the addition of adjunct ingredients such as liquid crystal materials can be used to tune the optical properties of the disclosed composites.
A further property which can be tailored to the needs of the formulator is the degree of thermal resistance displayed by the gels. Several factors enable the adjustment of the thermal resistive properties: (1) the intrinsically low thermal conductivity of cellulose, (2) the rarefication of fluid within the cellulose network thereby regulating the thermal convection, and (3) the thermal conductivity and convection properties of the fluids which comprise the cellulose-gel network.
In another aspect of the present disclosure are compositions comprising cellulosic nanorods that are aligned and on which orientation can be adjusted by the formulator. The disclosed nanoribbons have aspect ratios from about 1:10 to about 1:100. In one aspect, the disclosed nanorods can be used to form compositions with a cholesteric phase.
In one embodiment the disclosed nanocrystals form ordered films that can be ordered into a cholesteric phase in the film to form a periodic structure whose pitch and pitch gradient are
These cellulose-based flexible gels can comprise cellulose ribbons, fibers, and other constituent-particle structures having in one embodiment aspect ratios of about 1:1000. These flexible gels are formed from linking the cellulose particle networks within the material. The original cellulose solvent which is used for the formation of the gel network can be retained or replaced to yield a variety of gel types, for example, hydrogels, alcogels, aerogels, and liquid-crystal gels. The use of the disclosed cellulosic material to form the gel network allows the formulator to adjust the flexibility of the gels.
The aspect ratios allow for a greater degree of flexibility or rigidity depending upon the selection of cellulosic nanomaterial. In addition, the cellulose particles can be ordered through chemical and mechanical means to yield a lyotropic liquid crystalline dispersion with ordered phases. The ordering can be preserved during the cross-linking process to form various ordered gels, non-limiting examples of which are given above. Figure 1 illustrates the fabrication procedure of cellulosic ordered gels.
In addition to flexibility, the optical transmissivity of the disclosed gels can be adjusted to range from opaque to transparent. The degree of opaqueness or transparency can also be matched of any wavelength or range of wavelength in the electromagnetic spectrum.
These results can be obtained by adjusting the various properties of the disclosed composites, i.e., density of cellulosic nanomaterial or size distribution. Also, the addition of adjunct ingredients such as liquid crystal materials can be used to tune the optical properties of the disclosed composites.
A further property which can be tailored to the needs of the formulator is the degree of thermal resistance displayed by the gels. Several factors enable the adjustment of the thermal resistive properties: (1) the intrinsically low thermal conductivity of cellulose, (2) the rarefication of fluid within the cellulose network thereby regulating the thermal convection, and (3) the thermal conductivity and convection properties of the fluids which comprise the cellulose-gel network.
In another aspect of the present disclosure are compositions comprising cellulosic nanorods that are aligned and on which orientation can be adjusted by the formulator. The disclosed nanoribbons have aspect ratios from about 1:10 to about 1:100. In one aspect, the disclosed nanorods can be used to form compositions with a cholesteric phase.
In one embodiment the disclosed nanocrystals form ordered films that can be ordered into a cholesteric phase in the film to form a periodic structure whose pitch and pitch gradient are
6 adjustable for broad-band Bragg reflection of incident electromagnetic radiation. In another embodiment the resulting ordered gels are obtained because of the small relative aspect ratios of the cellulose nanorods or similar nanomaterials that comprise the nanocrystals. Nanorods result in the formation of different phases than other nanomaterials, i.e., nanofibers. Because of this fact broad-band reflection is enabled in ordered cellulose gels that are formed from cellulose structures with aspect ratios of about 1:10 to about 1:100.
As such, the mechanical flexibility, optical transmissivity, and thermal resistance can be configured by tuning the same parameters described nanofibers, except that those parameters now refer specifically to cellulose nanorods or other geometrically anisotropic cellulose structures.
A further aspect of the present disclosure relates to composite structures comprising lamellae that are formed from the disclosed aerogels or liquid crystal gels.
Composite structures with lamellae can be formed from the disclosed compositions that comprise nanofiber-like cellulosic materials (nematic phase) or from nanorod-like cellulosic materials (cholesteric phase).
These composite structures comprise a plurality of layers.
In a still further aspect of the present disclosure are composite structures wherein an amount of the cellulosic nanomaterial is replaced with one or more adjunct materials which can affect the alignment of the composite nanomaterials. In one embodiment a portion of the cellulosic nanomaterial is replaced with liquid crystals. As such, the nematic phase or cholesteric phase gels can have the liquid phase substituted by other anisotropic organic or inorganic materials. In one embodiment silica is introduced into the hydrogel. In another embodiment liquid crystal material, for example, 1-(trans-4-hexylcyclohexyl)-4-isothiocyanatobenzene can replace the carrier of the hydrogel. In another embodiment, after the incorporation and alignment of non-cellulosic materials, the cellulose can be partially or totally removed, by chemical means, to yield gels and films with partial or total cellulose substitution.
In a yet further aspect of the present disclosure are lamellae which comprise the disclosed composite structures. According to this aspect the lamellae are formed from two or more distinct layers wherein each layer comprises different materials. The cellulosic nanomaterials that comprise each layer can further serve as a template and can be substituted partially or totally by other materials such as silica or other polymers.
Further disclosed are methods for the preparation of the composite structures.
Exemplary methods can include providing a mixture of a growth medium, bacteria, and an additive that reduces an extent of (e.g., hydrogen) bonding between cellulose fibrils;
forming a pellicle of bacterial cellulose; exchanging water contained in the pellicle with a solvent; and drying the pellicle to remove the solvent to form an aerogel. The additive can reduce hydrogen bonding
As such, the mechanical flexibility, optical transmissivity, and thermal resistance can be configured by tuning the same parameters described nanofibers, except that those parameters now refer specifically to cellulose nanorods or other geometrically anisotropic cellulose structures.
A further aspect of the present disclosure relates to composite structures comprising lamellae that are formed from the disclosed aerogels or liquid crystal gels.
Composite structures with lamellae can be formed from the disclosed compositions that comprise nanofiber-like cellulosic materials (nematic phase) or from nanorod-like cellulosic materials (cholesteric phase).
These composite structures comprise a plurality of layers.
In a still further aspect of the present disclosure are composite structures wherein an amount of the cellulosic nanomaterial is replaced with one or more adjunct materials which can affect the alignment of the composite nanomaterials. In one embodiment a portion of the cellulosic nanomaterial is replaced with liquid crystals. As such, the nematic phase or cholesteric phase gels can have the liquid phase substituted by other anisotropic organic or inorganic materials. In one embodiment silica is introduced into the hydrogel. In another embodiment liquid crystal material, for example, 1-(trans-4-hexylcyclohexyl)-4-isothiocyanatobenzene can replace the carrier of the hydrogel. In another embodiment, after the incorporation and alignment of non-cellulosic materials, the cellulose can be partially or totally removed, by chemical means, to yield gels and films with partial or total cellulose substitution.
In a yet further aspect of the present disclosure are lamellae which comprise the disclosed composite structures. According to this aspect the lamellae are formed from two or more distinct layers wherein each layer comprises different materials. The cellulosic nanomaterials that comprise each layer can further serve as a template and can be substituted partially or totally by other materials such as silica or other polymers.
Further disclosed are methods for the preparation of the composite structures.
Exemplary methods can include providing a mixture of a growth medium, bacteria, and an additive that reduces an extent of (e.g., hydrogen) bonding between cellulose fibrils;
forming a pellicle of bacterial cellulose; exchanging water contained in the pellicle with a solvent; and drying the pellicle to remove the solvent to form an aerogel. The additive can reduce hydrogen bonding
7 between the fibrils in the grown medium (e.g., carboxymethyl cellulose) and/or be a molecule that provides steric hinderance for bonding between the fibrils. Exemplary additive can include short molecules that makes hydrogen bonds with cellulose fibrils (nanofibers) as they are created. The additive can be charged or uncharged oligomers that can adsorb to cellulose through hydrogen .. bonds or other interactions"
CELLULOSE NANOMATERIALS
The disclosed cellulose nanomaterials can have a variety of shapes and cross-sectional geometries that depend upon the nanomaterial's natural source and the process used to produce the particles. A disclosed cellulose nanomaterial can have a shape that is a rod, fiber, ribbon, whisker, and the like.
The disclosed cellulose nanomaterials can be obtained by chemical or mechanical treatment of a variety of natural sources, for example, cotton, soft wood pulp, hard wood pulp, tunicate and bacterial cellulose and the like. Typically, nanorods and nanofibers can be obtained from multiple sources, for example, cotton and bacterial cellulose.
In one embodiment, the disclosed nanocellulose can have a length from about 10 p.m to 100 p.m with cross sections from about 10 nm to 50 nm. In another embodiment, the disclosed nanocellulose can have a length from about 1 p.m to 10 p.m with cross sections from about 3 nm to 10 nm. In a yet another embodiment, the disclosed nanocellulose can have a length from about 100 nm to 1 p.m with cross sections from about 3 nm to 10 nm. Figure 2 shows TEM micrographs of cellulose particles with characteristic length scales of the aforementioned embodiments: (a) cellulose nanorods of 10 nm X 200 nm depends upon the chemical treatment from cotton, (b) cellulose nanowires of 7 nm X 800 nm from cotton, (c) cellulose nanowires of 4.8 nm X l[tm from wood pulp, and (d) cellulose nanoribbons of 10 nm X 50 nm X 10 lam from bacterial cellulose.
The cellulose nanomaterials can be obtained by chemical hydrolysis of natural cellulose by sulfuric acid, hydrochloric acid, etc. or by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation.
ALIGNMENT METHODS
The cellulose nanomaterials can be aligned by linear or circular shearing for nematic or cholesteric ordering, respectively. Nematic ordering of the disclosed cellulose nanofibers is shown in Figure 1(b). In one embodiment, the cellulose nanomaterial dispersion can be confined between glass plates in a mold such that, when a shear stress is applied from the plates in the specified direction, individual nanocellulose particles align to form a singular director alignment
CELLULOSE NANOMATERIALS
The disclosed cellulose nanomaterials can have a variety of shapes and cross-sectional geometries that depend upon the nanomaterial's natural source and the process used to produce the particles. A disclosed cellulose nanomaterial can have a shape that is a rod, fiber, ribbon, whisker, and the like.
The disclosed cellulose nanomaterials can be obtained by chemical or mechanical treatment of a variety of natural sources, for example, cotton, soft wood pulp, hard wood pulp, tunicate and bacterial cellulose and the like. Typically, nanorods and nanofibers can be obtained from multiple sources, for example, cotton and bacterial cellulose.
In one embodiment, the disclosed nanocellulose can have a length from about 10 p.m to 100 p.m with cross sections from about 10 nm to 50 nm. In another embodiment, the disclosed nanocellulose can have a length from about 1 p.m to 10 p.m with cross sections from about 3 nm to 10 nm. In a yet another embodiment, the disclosed nanocellulose can have a length from about 100 nm to 1 p.m with cross sections from about 3 nm to 10 nm. Figure 2 shows TEM micrographs of cellulose particles with characteristic length scales of the aforementioned embodiments: (a) cellulose nanorods of 10 nm X 200 nm depends upon the chemical treatment from cotton, (b) cellulose nanowires of 7 nm X 800 nm from cotton, (c) cellulose nanowires of 4.8 nm X l[tm from wood pulp, and (d) cellulose nanoribbons of 10 nm X 50 nm X 10 lam from bacterial cellulose.
The cellulose nanomaterials can be obtained by chemical hydrolysis of natural cellulose by sulfuric acid, hydrochloric acid, etc. or by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation.
ALIGNMENT METHODS
The cellulose nanomaterials can be aligned by linear or circular shearing for nematic or cholesteric ordering, respectively. Nematic ordering of the disclosed cellulose nanofibers is shown in Figure 1(b). In one embodiment, the cellulose nanomaterial dispersion can be confined between glass plates in a mold such that, when a shear stress is applied from the plates in the specified direction, individual nanocellulose particles align to form a singular director alignment
8 across the confined dispersion. In another embodiment, the nanocellulose suffers unidirectional alignment under extrusion from a sufficiently small diameter nozzle, syringe, or similar device.
With extrusion alignment, no confining plates are needed such that the aligned dispersion takes the form of a narrow bead, with linear extent much greater than its cross-sectional extent, which rests on a supportive substrate or other structure. In yet another embodiment, the helical axis of cellulose nanorods in cholesteric phase can be aligned by anticlockwise circular shearing during the evaporation of the dispersion.
The disclosed cellulose nanomaterials can also be aligned by magnetic or electric fields.
In one embodiment, the magnetic anisotropy of cellulose nanomaterial's relative permeability can be exploited to cause uniform alignment of nanocrystals. Under sufficiently strong magnetic fields (about 1 T), uniform alignment of nanocrystals perpendicular to the magnetic field is achieved through the magnetic interaction of the induced magnetic dipole moments of the cellulose nanomaterial with the applied magnetic field. In another embodiment, an oscillating electric field can also be used to align the cellulose nanomaterials with their long axis along the electric field.
ORDERED HYDROGELS
The alignment of the disclosed cellulose nanomaterial dispersions can be preserved by its conversion to a hydrogel, example embodiments which are shown in Figure 1(b) and Figure 3(a).
The extent of cross-linking of the cellulose nanomaterial establishes the degree to which uniform ordering is preserved in the dispersion. For example, a low level of crosslinking provides a weaker gelation. Conversely a greater degree of cross-linking yields firmer gelation.
Gelation is accomplished by the addition of an acid, photoacid generator and exposure to light, alcohol, or other cationic exchange reagent to a uniformly ordered cellulose nanomaterial dispersion. In one embodiment, hydrochloric, acetic, nitric, sulfuric, and phosphoric acids can be added to instigate gelation. In another embodiment, Ca2+ can be added to provide cross-linking.
ORDERED ORGANOGELS
The disclosed ordered hydrogels can be transformed into organogels, as shown in Figure 1(c) and Figure 3(b) using a solvent exchange procedure. For example, a hydrogel can be gently shaken while immersed in an ethanol-filled bath followed by replacing the solvent at regular intervals. In this way, the water is sequentially removed from the matrix and replaced with ethanol. Other organic solvents can substitute for ethanol. Non-limiting examples of other solvents include methanol, ethanol, isopropanol, butanol, hexane, acetone, dichloromethane, dimethylformamide (DMF), dimethylsulfoxide (DMSO), and toluene.
With extrusion alignment, no confining plates are needed such that the aligned dispersion takes the form of a narrow bead, with linear extent much greater than its cross-sectional extent, which rests on a supportive substrate or other structure. In yet another embodiment, the helical axis of cellulose nanorods in cholesteric phase can be aligned by anticlockwise circular shearing during the evaporation of the dispersion.
The disclosed cellulose nanomaterials can also be aligned by magnetic or electric fields.
In one embodiment, the magnetic anisotropy of cellulose nanomaterial's relative permeability can be exploited to cause uniform alignment of nanocrystals. Under sufficiently strong magnetic fields (about 1 T), uniform alignment of nanocrystals perpendicular to the magnetic field is achieved through the magnetic interaction of the induced magnetic dipole moments of the cellulose nanomaterial with the applied magnetic field. In another embodiment, an oscillating electric field can also be used to align the cellulose nanomaterials with their long axis along the electric field.
ORDERED HYDROGELS
The alignment of the disclosed cellulose nanomaterial dispersions can be preserved by its conversion to a hydrogel, example embodiments which are shown in Figure 1(b) and Figure 3(a).
The extent of cross-linking of the cellulose nanomaterial establishes the degree to which uniform ordering is preserved in the dispersion. For example, a low level of crosslinking provides a weaker gelation. Conversely a greater degree of cross-linking yields firmer gelation.
Gelation is accomplished by the addition of an acid, photoacid generator and exposure to light, alcohol, or other cationic exchange reagent to a uniformly ordered cellulose nanomaterial dispersion. In one embodiment, hydrochloric, acetic, nitric, sulfuric, and phosphoric acids can be added to instigate gelation. In another embodiment, Ca2+ can be added to provide cross-linking.
ORDERED ORGANOGELS
The disclosed ordered hydrogels can be transformed into organogels, as shown in Figure 1(c) and Figure 3(b) using a solvent exchange procedure. For example, a hydrogel can be gently shaken while immersed in an ethanol-filled bath followed by replacing the solvent at regular intervals. In this way, the water is sequentially removed from the matrix and replaced with ethanol. Other organic solvents can substitute for ethanol. Non-limiting examples of other solvents include methanol, ethanol, isopropanol, butanol, hexane, acetone, dichloromethane, dimethylformamide (DMF), dimethylsulfoxide (DMSO), and toluene.
9 ORDERED AEROGELS OR FILMS
The disclosed cellulose aerogels or films herein can be produced from the disclosed nano-structured organogel herein above. Example aerogels are shown in Figure 1(d) and Figure 3(c).
The resulting cellulose nanomaterial aerogel is porous having a skeleton of about 0.1-99.9% of cellulose nanocrystals and a porosity of from about 0.01 to about 99.99%. In one embodiment the porosity is from about 97% to about 99%.
Aerogels comprising a low percentage of of nanocellulosic material results aerogels having a high degree of transparency, for example, from about 1% to about 50%
by weight of the aerogel. Aerogels comprising from about 50% to about 90% by weight of nanocellulosic material results aerogels having a high degree translucent scattering.
To prevent deformation and crumbling of aerogels during the drying due to surface tension and capillary pressure in the ambient atmosphere, supercritical drying, freeze drying, or ambient drying with a low surface-tension solvent are used to remove liquid solvent from cellulose nanocrystal composites while maintaining the disclosed liquid crystalline structure, such as nematic or cholesteric liquid crystalline ordering.
As disclosed previously herein, the resulting monolithic cellulose nanomaterial film is a solid material with 100% cellulose composition. Ambient drying is used to remove liquid solvent.
ORDERED LIQUID-CRYSTAL GELS
The disclosed cellulose LC gels herein can be produced from the disclosed nano-structured organogel. The organic solvent is replaced with LC by solvent exchange. For the case of LC gels, the LC functions as the gel's solvent. Figure 1(e) portrays a schematic representation of LC gels while Figure 3(d) portrays an LC gel whose LC solvent is in the nematic phase.
The disclosed compositions can comprise any LC that will serve as solvents for the gels. Non-limiting examples of nematic LCs include: 1-(trans-4-hexylcyclohexyl)-4-isothiocyanatobenzene;
4'-(hexyloxy)-4-biphenylcarbonitrile; 4'-(octyloxy)-4-biphenyl-carbonitrile; 4'-(pentyloxy)-4-biphenylcarbonitrile; 4'-hepty1-4-biphenylcarbonitrile; 4'-hexy1-4-biphenylcarbonitrile; 4'-octy1-4-biphenylcarbonitrile; 4'-penty1-4-biphenylcarbonitrile;
4,4'-azoxyanisole; 4-isothiocyanatophenyl 4-pentylbicy cl o [2.2.2] octane-1 -carboxyl ate ;
4-(trans-4-pentylcy clohexyl)benzonitrile; 4-methoxycirmamic acid; N-(4-ethoxy benzylidene)-4-butylaniline; and N-(4-methoxybenzylidene)-4-butylaniline.
CELLULOSE-TEMPLATED ORDERED INORGANIC GELS OR FILMS
Inorganic nanomaterials can be incorporated into the heretofore disclosed ordered gels or films using cellulose nanomaterials as a template. As a non-limiting example, Figure 4 demonstrates cellulose-enabled cholesteric (a) cellulose-silica film composition, (b) silica aerogel, and (c) silica LC gel whose solvent is LC in its nematic phase. An SEM image of the ordered silica aerogel is displayed in Figure 4(d). At the final processing stage, the cellulose nanomaterials can be removed to obtain inorganic gels or films. Alternatively, inorganic/cellulose composite gels or films are formed without etching the cellulose nanomaterials. As one non-limiting example, the inorganic gels or films are made of silica, organo-silica, titanium dioxide, aluminum oxide, rare earth oxides, etc. The weight concentration of inorganic nanomaterial in the inorganic/cellulose composites can range from about 1% to about 99%.
CELLULOSE-TEMPLATED ORDERED POLYMERIC GELS OR FILMS
Polymers can be incorporated into the heretofore disclosed ordered gels or films using cellulose nanomaterials as a template. At the final processing stage, the cellulose nanomaterials can be removed to obtain polymeric gels or films. Alternatively, polymeric/cellulose composites gels or films are formed without etching the cellulose nanomaterials. As one non-limiting example, the polymeric gels or films are made of phenol-formaldehyde, melamine-formaldehyde, urea-formaldehyde, poly(acrylic acid), polyester, etc. The weight concentration of polymeric nanomaterial in the polymeric/cellulose composites can range from about 1% to 99%.
SURFACE FUNCTIONALIZATION ORDERED GELS
The surface properties of the disclosed gels can be modified by functionalizing the surface of the cellulosic network. The disclosed aerogels having no surface functionalization are hydrophilic and can dissolve or shrink its total volume upon contacting with water. Surface .. modifiers, for example, dimethyloctadecyl [3-(trimethoxysily1) propyl]
ammonium chloride (DMOAP) and trichloro(1H,1H,2H,2H-perfluoro-octyl)silane can be added to the hydrogel before conversion to an aerogel. This type of surface modification provides a hydrophobic aerogel that is stable upon exposure to water.
ORDERED COLLOIDAL DISPERSIONS WITHIN GELS
Colloidal particles having lengths ranging from about 1 nm to 10 p.m can be homogeneously dispersed within the gels. In one embodiment the colloids can include gold and silver plasmonic nanoparticles such as rods, triangular platelets, and triangular frames;
ferromagnetic nanoparticles such as ferromagnetic nanoplatelets; quantum dots such as nano-spheres, -cubes, -rods, and the like. The colloidal particles are introduced into the cellulose before cross-linking occurs. Cross-linking, through interaction with the colloidal surface ligands, binds the colloidal inclusions to the ordered cellulosic network as described previously herein. Any of the disclosed gels can contain one or more types of colloidal particles.
The disclosed gels have a thickness from about 1 lam to about 10 cm. In one embodiment the thickness varies from about 10 lam to about 1 cm. In another embodiment the thickness varies from about 100 lam to about 10 cm. In a further embodiment the thickness varies from about 50 lam to about 1 cm. In still further embodiment the thickness varies from about 1 cm to about 10 cm. In a yet another embodiment the thickness varies from about 10 lam to about 100 cm. In a yet still further embodiment the thickness varies from about 500 lam to about
The disclosed cellulose aerogels or films herein can be produced from the disclosed nano-structured organogel herein above. Example aerogels are shown in Figure 1(d) and Figure 3(c).
The resulting cellulose nanomaterial aerogel is porous having a skeleton of about 0.1-99.9% of cellulose nanocrystals and a porosity of from about 0.01 to about 99.99%. In one embodiment the porosity is from about 97% to about 99%.
Aerogels comprising a low percentage of of nanocellulosic material results aerogels having a high degree of transparency, for example, from about 1% to about 50%
by weight of the aerogel. Aerogels comprising from about 50% to about 90% by weight of nanocellulosic material results aerogels having a high degree translucent scattering.
To prevent deformation and crumbling of aerogels during the drying due to surface tension and capillary pressure in the ambient atmosphere, supercritical drying, freeze drying, or ambient drying with a low surface-tension solvent are used to remove liquid solvent from cellulose nanocrystal composites while maintaining the disclosed liquid crystalline structure, such as nematic or cholesteric liquid crystalline ordering.
As disclosed previously herein, the resulting monolithic cellulose nanomaterial film is a solid material with 100% cellulose composition. Ambient drying is used to remove liquid solvent.
ORDERED LIQUID-CRYSTAL GELS
The disclosed cellulose LC gels herein can be produced from the disclosed nano-structured organogel. The organic solvent is replaced with LC by solvent exchange. For the case of LC gels, the LC functions as the gel's solvent. Figure 1(e) portrays a schematic representation of LC gels while Figure 3(d) portrays an LC gel whose LC solvent is in the nematic phase.
The disclosed compositions can comprise any LC that will serve as solvents for the gels. Non-limiting examples of nematic LCs include: 1-(trans-4-hexylcyclohexyl)-4-isothiocyanatobenzene;
4'-(hexyloxy)-4-biphenylcarbonitrile; 4'-(octyloxy)-4-biphenyl-carbonitrile; 4'-(pentyloxy)-4-biphenylcarbonitrile; 4'-hepty1-4-biphenylcarbonitrile; 4'-hexy1-4-biphenylcarbonitrile; 4'-octy1-4-biphenylcarbonitrile; 4'-penty1-4-biphenylcarbonitrile;
4,4'-azoxyanisole; 4-isothiocyanatophenyl 4-pentylbicy cl o [2.2.2] octane-1 -carboxyl ate ;
4-(trans-4-pentylcy clohexyl)benzonitrile; 4-methoxycirmamic acid; N-(4-ethoxy benzylidene)-4-butylaniline; and N-(4-methoxybenzylidene)-4-butylaniline.
CELLULOSE-TEMPLATED ORDERED INORGANIC GELS OR FILMS
Inorganic nanomaterials can be incorporated into the heretofore disclosed ordered gels or films using cellulose nanomaterials as a template. As a non-limiting example, Figure 4 demonstrates cellulose-enabled cholesteric (a) cellulose-silica film composition, (b) silica aerogel, and (c) silica LC gel whose solvent is LC in its nematic phase. An SEM image of the ordered silica aerogel is displayed in Figure 4(d). At the final processing stage, the cellulose nanomaterials can be removed to obtain inorganic gels or films. Alternatively, inorganic/cellulose composite gels or films are formed without etching the cellulose nanomaterials. As one non-limiting example, the inorganic gels or films are made of silica, organo-silica, titanium dioxide, aluminum oxide, rare earth oxides, etc. The weight concentration of inorganic nanomaterial in the inorganic/cellulose composites can range from about 1% to about 99%.
CELLULOSE-TEMPLATED ORDERED POLYMERIC GELS OR FILMS
Polymers can be incorporated into the heretofore disclosed ordered gels or films using cellulose nanomaterials as a template. At the final processing stage, the cellulose nanomaterials can be removed to obtain polymeric gels or films. Alternatively, polymeric/cellulose composites gels or films are formed without etching the cellulose nanomaterials. As one non-limiting example, the polymeric gels or films are made of phenol-formaldehyde, melamine-formaldehyde, urea-formaldehyde, poly(acrylic acid), polyester, etc. The weight concentration of polymeric nanomaterial in the polymeric/cellulose composites can range from about 1% to 99%.
SURFACE FUNCTIONALIZATION ORDERED GELS
The surface properties of the disclosed gels can be modified by functionalizing the surface of the cellulosic network. The disclosed aerogels having no surface functionalization are hydrophilic and can dissolve or shrink its total volume upon contacting with water. Surface .. modifiers, for example, dimethyloctadecyl [3-(trimethoxysily1) propyl]
ammonium chloride (DMOAP) and trichloro(1H,1H,2H,2H-perfluoro-octyl)silane can be added to the hydrogel before conversion to an aerogel. This type of surface modification provides a hydrophobic aerogel that is stable upon exposure to water.
ORDERED COLLOIDAL DISPERSIONS WITHIN GELS
Colloidal particles having lengths ranging from about 1 nm to 10 p.m can be homogeneously dispersed within the gels. In one embodiment the colloids can include gold and silver plasmonic nanoparticles such as rods, triangular platelets, and triangular frames;
ferromagnetic nanoparticles such as ferromagnetic nanoplatelets; quantum dots such as nano-spheres, -cubes, -rods, and the like. The colloidal particles are introduced into the cellulose before cross-linking occurs. Cross-linking, through interaction with the colloidal surface ligands, binds the colloidal inclusions to the ordered cellulosic network as described previously herein. Any of the disclosed gels can contain one or more types of colloidal particles.
The disclosed gels have a thickness from about 1 lam to about 10 cm. In one embodiment the thickness varies from about 10 lam to about 1 cm. In another embodiment the thickness varies from about 100 lam to about 10 cm. In a further embodiment the thickness varies from about 50 lam to about 1 cm. In still further embodiment the thickness varies from about 1 cm to about 10 cm. In a yet another embodiment the thickness varies from about 10 lam to about 100 cm. In a yet still further embodiment the thickness varies from about 500 lam to about
10 cm.
The transmissivity of the disclosed gels relates to the amount of electromagnetic radiation that is blocked from passing through the gel. 0% transmission results in an opaque material which allows no transmission. 100% transmission results in a material that is transparent to electromagnetic radiation. The disclosed gels can have a transmission of from 0% to 100%. In one embodiment the gels have a transmission of from about 5% to about 15%. In another embodiment the gels have a transmission of from about 25% to about 50%. In a further embodiment the gels have a transmission of from about 95% to 100%. In a still further embodiment the gels have a transmission of from about 15% to about 35%. In a yet further embodiment the gels have a transmission of from about 50% to about 75%. In a yet another embodiment the gels have a transmission of from about 25% to about 75%.
The disclosed gels and composite materials can have a thermal conductivity of from about 10-3 W/(m.K) to about 10 W/(m.K). In another embodiment the thermal conductivity is from about 10-2 W/(m.K) to about 10 W/(m.K). In a further embodiment the thermal conductivity is from about 10-1 W/(m.K) to about 10 W/(m.K). In a still further embodiment the thermal conductivity is from about 10-3 W/(m.K) to about 1 W/(m.K). In yet further embodiment the thermal conductivity is from about 10' W/(m.K) to about 1 W/(m.K). In yet another embodiment the thermal conductivity is from about 1 W/(m.K) to about 10 W/(m.K).
The relative emissivity value of the disclosed gels ranges from about 10' to 0.99.
The disclosed gels and composites can have a bulk modulus of from about 1 Pa to about 106 Pa. In one embodiment the modulus is from about 10 Pa to about 105 Pa. In another embodiment the modulus is from about 102 Pa to about 106 Pa. In a further embodiment the modulus is from about 103 Pa to about 105 Pa. In a still further embodiment the modulus is from about 10 Pa to about 103 Pa. In a yet further embodiment the modulus is from about 1 Pa to about 10 Pa. In a yet another embodiment the modulus is from about 104 Pa to about 106 Pa.
Procedures Cellulosic starting material for the disclosed gels can be derived from a variety of sources.
The surface-sulfuricated cellulose particles (Figure 1(a) and Figure 2) that are suspended in water can be prepared by sulfuric acid-mediated oxidation of the natural cellulose.
The surface-carboxylated cellulose nanofibers and nanoribbons that are suspended in water can be prepared by 2,2,6,6- tetramethyl-l-piperidinyloxy (TEMPO)-mediated oxidation of the natural cellulose.
The dispersions of these nanomaterials spontaneously form a thermodynamically stable cholesteric (for cellulose nanorods) or nematic (for cellulose nanofibers or nanoribbons) liquid crystal phase that can be transformed into a hydrogel (Figure 1(b) and Figure 3(a)) with a similarly ordered spatial organization of cellulose particles.
Cellulosic starting material for the disclosed aerogels can be biosynthesized by Acetobacter xylinum, Acetobacter hansenii or other examples of bacterial strains utilizing, for example, glucose as a carbon source. As one example, Acetobacter xylinum can be cultivated in a glucose medium for 1-3 weeks under static conditions to produce cellulose pellicles. To remove bacterial cell debris, bacterial cellulose can be boiled in a 1 wt. % NaOH
aqueous solution for 2 hours, followed by washing with water and neutralization with 0.2 % acetic acid.
Natural cellulose material obtained in this way can easily be disintegrated into individual nanocrystals by a controlled TEMPO mediated oxidation. For example, 2 g of bacterial cellulose was suspended in water (150 mL) containing TEMPO (0.025 g) and NaBr (0.25 g).
A 1.8 M
NaC10 solution (4 mL) was added, and the pH of the suspension was maintained at 10 by adding 0.5 M NaOH. When no more decrease in pH was observed, the reaction was finished. The pH is then adjusted to 7 by adding 0.5M HC1. The TEMPO-oxidized products were cellulose nano-rods of controlled 4-10 nm diameter and 1000-3000 nm length, which were then thoroughly washed with water by filtration and stored at 4 C.
Cellulose nanocrystals can also be synthesized by sulfuric acid hydrolysis method from natural cellulose. The aqueous suspension of such cellulose nanocrystals above the critical concentration (-3-6 wt. %) self-assemble into liquid crystalline structures-chiral nematic phase, which shows periodic helicoidal structures with a pitch that can be controlled in the range 5-70 pm. This structure can strongly reflect electromagnetic radiation of the wavelength comparable with the pitch, which simultaneously serves as a high efficiency low-emissivity structure by tuning the pitch to be appropriate range. The disclosed films can have a pre-designed gradient of cholesteric pitch in helicoidally ordered nanocrystal self-assembly and achieve broadband infrared selective reflection and low-emissivity (compare to the red infrared emission curve taken from solicitation) while being transparent in the visible spectral range and also transmitting solar radiation (blue curve) in near-IR range.
The concentration of the liquid crystalline cellulose nanocrystal dispersions was then adjusted to 3 wt.% and used in preliminary studies. The chiral nematic liquid crystalline order of the nanocrystals was then poured into a mold and the orientation of the helix could be aligned uniformly perpendicular to the film plane using a circular shearing or magnetic field. The polarizing optical micrograph shown in Figure 4(c) was obtained for a sample with the helical axis aligned in the horizontal direction, providing a side view of the periodic helicoidal structure of the chiral nematic liquid crystal. In the design and fabrication of AIR
FILMs, this helical axis will be set orthogonal to the plane of the film and along the normal to the window (Figure 2) which will be achieved using the process of circular shearing (see, Park J.H.
et al. "Macroscopic control of helix orientation in films dried from cholesteric liquid-crystalline cellulose nanocrystal suspensions", ChemPhysChem. 15, 1477-1484,2014).
After cellulose nanomaterial preparation from one or multiple sources the cellulose nanomaterial can be dispersed in water and aligned by the following methods.
First, the aqueous suspension of cellulose nanorods above the critical concentration (about 0.1-4%) self-assemble into a liquid crystalline phase with nematic or cholesteric ordering. Second, in order to induce uniform alignment across the entire dispersion, linear or circular shearing can be used for nematic or cholesteric phases, respectively. Specifically, the dispersion can be confined between glass plates in a mold such that, when a shear stress is applied from the plates in the specified direction (along a line or through a rotation), individual nanomaterial directors align to form a singular director alignment across the confined dispersion. As an alternate but complementary approach to dispersion alignment, the nanocrystals suffer uniform alignment under extrusion from a sufficiently small diameter nozzle, syringe, or similar device. With extrusion alignment, no confining plates are needed such that the aligned dispersion takes the form of a narrow bead, with linear extent much greater than cross-sectional extent, which rests on a supportive substrate or other structure. Additionally, the magnetic anisotropy of cellulose nanomaterial's relative permeability can be exploited to cause uniform alignment of nanocellulose.
Under sufficiently strong magnetic fields (about 100 mT), uniform alignment of nanocrystals is achieved through the magnetic interaction of the induced magnetic dipole moments of the cellulose nanomaterial with the applied magnetic field. (An oscillating electric field can be used to align nanocellulose with its long axis along the electric field.) The aligned cellulose nanomaterial dispersion can be cross-linked to convert into a hydrogel while preserving its ordering. The extent of cross-linking of chains of cellulose nanomaterials establishes the degree to which uniform ordering is preserved in the dispersion.
That is, for loosely cross-linked cellulose nanomaterials, weak gelation results. Conversely, strong cross-linking yields firm gelation. Gelation results from the addition of an acid, a photoacid generator and exposure to light, an alcohol, or another cationic exchange mechanism to the uniformly ordered cellulose nanomaterial dispersion. Alternatively, the cellulose nanorods, inorganic/cellulose nanorods, or polymeric/cellulose nanorods can self-assemble into cholesteric phase by evaporation.
The nanocellulose-based ordered hydrogel was transformed into organogels (Figure 1(c) and Figure 3(b)) by shaking the cellulose-nanomaterial hydrogel gently in an organic-solvent-filled bath while replacing the solvent regularly in order to prompt the replacement of water in the hydrogel by the organic solvent. As one example, twice per day for an extent of three days ethanol was replaced to facilitate total solvent exchange.
The disclosed cellulose aerogels (Figure 1(d) and Figure 3(c)) can be produced from the disclosed nano-structured organogel herein above. The resulting cellulose nanocrystal aerogel is a porous material with a skeleton of about 0.1-99.9% cellulose nanocrystals and a porosity of about 0.1-99.9%. To prevent deformation and crumbling of aerogels during the drying stage due to surface tension and capillary pressure in the ambient atmosphere, supercritical drying, freeze drying, or ambient drying low-surface tension solvent are used to remove liquid solvent from cellulose nanocrystal composites while maintaining the disclosed liquid crystalline structure, such as nematic or cholesteric liquid crystalline ordering.
The disclosed cellulose LC gels (Figure 1(e) and Figure 3(d)) can be produced from an ordered nano-structured organogel, in which an organic solvent completely miscible with LC is chosen. The organogel is placed in a bath of LC above the boiling point of the organic solvent so that the organic solvent is replaced with LC, which functions as the gel's replacement solvent.
The disclosed cellulose-templated ordered inorganic and polymeric gels or films can be produced by mixing cellulose nanomaterials with silica precursors or prepolymer and drying the composites in the ambient environment. Then the cellulose nanomaterials will be removed either by acidic (for silica aerogel) or basic (for polymeric aerogel) treatment to form a hydrogel. The hydrogel can be further transferred into organogel, aerogel, and LC gel based on the methods described above.
Example 1: Ordered gels made from cellulose nanorods Colloidal suspensions of cellulose nanocrystals (CNCs) composed of cellulose nanorods were prepared by controlled sulfuric acid hydrolysis of cotton fibers, according to the method described by Revol and co-workers (J. F. Revol, H. Bradford, J. Giasson, R. H.
Marchessault, D.
G. Gray, Int. I Biol. Macromol. 14, 170 (1992)). During this process, disordered or paracrystalline regions of cellulose are preferentially hydrolyzed, whereas crystalline regions, which have a higher resistance to acid, remain intact. 7 g of cotton was added to 200 g of 65 wt% sulfuric acid and stirred at 45 C in a water bath for up to several hours until the cellulose had fully hydrolyzed.
The mixture was sonicated occasionally, which was found to help degrade the amorphous cellulose regions. The suspensions of cellulose were then centrifuged at 9000 rpm for 10 min and .. re-dispersed in deionized water 6 times to remove the excess sulfuric acid.
The resulting precipitate was placed into a dialysis tubing (MWCO 12000-14000, Thermo Fisher Scientific Inc.) in de-ionized water for three days until the water pH remained constant. The dimensions of CNCs are about 5-10 nm in cross-section and, on average, 100-300 nm in length. Then 3 wt% CNCs solution was cast in a mold and evaporated under ambient conditions to obtain an aerogel.
Example 2: Ordered gels made from cellulose nanofibers or nanoribbons Cellulose nanofibers (CNF's) with the dimension of 4.8 nm by several micrometers were synthesized following the literature (T. Saito, M. Hirota, N. Tamura, S.
Kimura, H. Fukuzumi, L.
Hew( and A. Isogai, Biomacromolecules, 10, 1992 (2009)). Briefly, cellulose based bleached coffee filter (1 g) was suspended in 0.05 M sodium phosphate buffer (90 mL, pH
6.8) dissolving 16 mg of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and 1.13 g of 80% sodium chlorite in an airtight flask. The 2 M sodium hypochlorite solution (0.5 mL, 1.0 mmol) was diluted to 0.1 M with the same 0.05 M buffer used as the oxidation medium and was added at one step to the flask. The flask was immediately stoppered, and the suspension was stirred at 500 rpm and 60 C for 96 hours. After cooling the suspension to room temperature, the TEMPO-oxidized cellulose was thoroughly washed with water by filtration. Then 0.1-1.0 vol.%
CNFs aqueous dispersion was poured into a mold, aligned by a shear force, and several drops of 1 M HC1 solution was added to form a hydrogel after 2 hours. The hydrogel was immersed into ethanol for 2 days for solvent exchange to form an organogel. To form a liquid-crystal gel, the organogel was immersed in a bath of liquid crystal 4-cyano-4'-pentylbiphenyl at 90 C for 12 hours. Subsequent cooling to room temperature after solvent exchange caused the LC to enter its expected nematic phase. The aerogel was formed by critical point drying of the organogel.
Example 3: Ordered gels made from cellulose-nanorods-templated silica CNCs were synthesized according the method in Example 1. Then 5 mL of 3 wt%
CNCs dispersion was mixed with 10-754 of silica precursor tetramethyl orthosilicate and stirred for 1 hour. Then the composites were cast into a Petri dish and dried over 1-2 days.
The CNCs were then removed by pyrolysis method (e.g. 540 C for 20 hours) or keeping in 16%
sodium hydroxide solution for 16 hours. The silica hydrogel was formed and can be further transferred into organogel by solvent exchange and aerogel by critical point drying or ambient drying.
Example 4: Ordered gels made from cellulose-nanorods-templated polymer CNCs were synthesized according the method in Example 1. Then 5 mL of 3 wt%
CNCs dispersion was mixed with 10-75 mg of water-soluble preformed polymer and stirred for 10 min.
Then the composites were casted into a Petri dish and dried over 1-2 days. The film was then cured at polymerization temperature for 24 hours. The CNCs were then removed by 16% sodium hydroxide solution for 16 hours. The polymer hydrogel was formed and can be further transferred into organogel by solvent exchange and aerogel by critical point drying or ambient drying.
The light scattered upon passing through aerogels can produce a hazy appearance, which can result in the reduction of contrast of objects viewed through the film.
Haze measurements can be performed using a hazemeter or spectrometer. Figure 5 describes an apparatus developed and adapted to measure the quality of the disclosed aerogels. The apparatus in Figure 5 has the advantage of conducting haze measurements that also provides diagnostic data on the origins of the haze.
The typical setup includes an integrating sphere where the measured film is placed against the sphere entrance port. The surface of the interior of the integrating sphere is highly reflecting throughout the visible wavelengths obtained from light sources. The light entering the integrating sphere is reflected from the surface towards the tested film. Then the light transmitted through the film is focused and directed to a photodetector. A photodetector in the spectrophotometer setup is computer driven and values for transmission and haze can be automatically calculated. The haze can be determined as haze = 100x(TiTt), where Tt is a total transmittance depending on intensity of incident light & total light transmitted by the film & Kt is diffuse transmittance depending on light scattered by a measuring setup & the film.
Characterization of the Morphology of Nanocellulose Gels Sound proofing characterization can be conducted by imaging of nanoparticles using TEM
and SEM. Figure 6 outlines a procedure for probing of the pore size, surface area, and structural properties of cholesteric cellulose-based aerogels under different preparation conditions. The ordering of nanocrystals on large scales will be probed using 3D imaging techniques such as Fluorescence Confocal Polarizing Microscopy (FCPM), Coherent Anti Stokes Raman Scattering Polarizing Microscopy (CARS-PM), and Three.-Photon Excitation -Fluorescence Polarizing Microscopy (.3PEF-PM). In addition, the monitoring of the disclosed liquid clystal and aerogel uniformity in lateral directions can be accomplished by using conventional dark-field, bright-field, and polarizing optical microscopy. Visible- and infrared-range spectroscopy can also be utilized.
The other properties of the disclosed aerogels include mechanical properties (both as-prepared aerogels and encapsulated, ready-to-install films), as well as soundproofing and condensation resistance of the films installed on sint2,1e-pane windows.
Measurement of Aerogel Thennophysieal Properties Prior to the application of films onto a window the thermophysical properties (for example, thermal conductivity, heat capacity) are characterized by the optical pump-and-probe method in order to determine the type of film that is suitable for the specific application. This procedure uses a femtosecond laser to construct a high temporal resolution temperature measurement system. Figure 7 shows the optical pathway of a typical pump-and-probe measurement system. In the optical pump and probe method, sub-picosecond (ps) time resolution is made possible by splitting the ultrafast sub-ps laser pulse output into an intense heating pulse, i.e., a "pump" beam, and a weaker "probe" beam, and controlling the optical path length difference of the pump and probe beam through a mechanical delay stage. The decay of the temperature rise is measured by the reflected energy of the probe pulse series. The thermal conductivity can then be deduced by fitting the temperature decay curves.
Condensation Resistance After determining the thermal conductivity of a disclosed aerogel, films can be applied atop of a window to determine the thermal insulation and condensation resistance performance, following the current standards of ASTM C1363-11 and ASTM C1199-14. This test method establishes principles for design of a hot box apparatus & requirements for the determination of the steady-state thermal performance of windows when exposed to controlled laboratory conditions. The window thermal insulation and condensation performance is represented by the overall heat transfer coefficient, U. Figure 8 discloses the components of a hot box apparatus: a metering box (simulating interior temperature) on one side of the window specimen; a controlled guard box surrounding the metering box; a climate chamber box (simulating exterior temperature) on the other side; and the specimen frame providing specimen support and insulation.
The walls of the hot box are insulated panels of plywood adhered to either side of a solid layer of XPS insulation. The space conditioning system used in the meter box employs hydronic cooling and electric resistance heating. The meter box cooling is measured using high precision thermocouples in combination with a precision flow meter to accurately quantify the heat removed from the meter box. Heat is added into the meter box via PID-controlled electric heaters.
Precision resistor circuits are employed to measure the heat added into the meter box. A constant and precise temperature can be maintained and the total heat addition/removal can be measured.
The hot box employs an insulated guard box surrounds the meter box and a hydronic guard loop is installed over the outside surface of the meter box. The guard box minimizes the influence of temperature changes in the lab. The liquid guard loop further ensures the outside surface of the meter box remains at a constant temperature. An insulated baffle separates the air space from the mixing chamber of the meter box. The baffle panels are constructed using thermal insulation material. For a1mx 1m test window sample, at least 25 calibrated precision thermocouples are used to measure temperatures on the baffle surface, 25 corresponding points in the air stream and at least 25 points on the interior surface of the test window specimen. Air drawn through the meter box baffle space at velocities representative of convection in real world conditions. DC powered axial draw-through circulation fans, at the top and bottom of the baffle, are used to ensure smooth flow along the surface of the wall sample in the direction that convection would occur.
The climate box has the same dimensions and construction as the guard box. The climate side air baffles are constructed using the same materials and methods as the air baffles in the meter box. Heat is added to/removed from the climate box via four fan coils which are connected to a liquid chiller and a hydronic heater. Electric resistance heaters permit fine tuning of the temperatures and ensure that temperatures remain close to the set point for the duration of the test.
The climate box has the capacity to run a range of realistic outdoor temperatures, from -30 C to 60 C. This enables the tested window assembly to remain undisturbed when tested from cold to hot climate conditions. Overall heat transfer coefficient is:
u - _________________________________________ A- (Tmeter Tchmate where Q is the time rate of net heat flow through the meter box opening, W; A
is meter box opening area, m2; Tmeter and Taimate are temperatures of meter box and climate box, respectively.
Cellulose-Polysiloxane Hybrid Aerogels Further disclosed are transparent cellulose-polysiloxane hybrid hydrogels, organogels and aerogels and a process for preparing the disclosed transparent cellulose-polysiloxane hybrid transparent cellulose-polysiloxane hybrid hydrogels, organogels and aerogels.
Disclosed is a cellulose-polysiloxane hybrid aerogel, comprising:
a) a cellulosic matrix; and b) a polysiloxane surface network Without wishing to be limited by theory, these characteristics are achieved by strictly controlling the dimensions of nanofibers and the homogeneous gel skeleton networks that they form, which can be tuned to form orientationally ordered liquid crystal (LC) states. In the gel fabrication process, an optimized acid/base catalyzed sol-gel reaction in a surfactant-based solution is used to form a polymethylsilsesquioxane (PMSQ) surface network.
Cellulose nanofibers having a uniform diameter are first surface functionalized. This functionalization can employ small charged molecules or polymer grafting resulting in increased cellulose nanofiber stability. Subsequently, these nanofibers are crosslinked with PMSQ fibers.
In addition to their high optical transparency, super thermal insulation, flexibility and mechanical robustness, the disclosed hybrid aerogels can be made optically isotropic or anisotropic, depending on the intended use by the formulator. In the case of anisotropic aerogels, they can be fabricated starting from the LC states of colloidal dispersions of nanofibers. The resulting compositions can have practical applications as they result can result in devices having optical polarization, thereby the ability to control visible light polarization while providing simultaneous thermal insulation.
Disclosed herein is a process for preparing polymethylsilsesquioxane (PMSQ) network cellulosic aerogels, comprising:
a) contacting an aqueous dispersion of cellulose with an oxidizing system that oxidizes the C6 hydroxyl units of cellulose to carboxylate units to form an aqueous solution of oxidized cellulose nanofibers;
b) reacting the oxidized cellulose nanofibers with a surface modifying agent to form an aqueous solution of surface modified cellulose nanofibers;
c) contacting the surface modified cellulose nanofibers with polymethylsilsesquioxane (PMSQ) to form an aqueous polysiloxane precursor;
d) hydrolyzing the polysiloxane precursor in the presence of an acid catalyst to form a PMSQ network cellulosic hydrogel;
e) exchanging the water contained in the hydrogel with a volatile solvent to form an organogel; and f) removing the volatile solvent to form an aerogel.
In one embodiment the oxidizing system comprises:
a) an admixture of 2,2,6,6-Tetramethy 1piperidi n- 1-yl)ox-y1 (TEMPO) and N
aC 10 .
Modifying Agents In one embodiment the surface modifying agent is chosen from C1-C6 linear or branched, saturated or unsaturated alkylamine low molecular weight compounds comprising a cationic moiety, oligomers or polymers.
The C1-C6 linear or branched, saturated or unsaturated alkylamines react with the cellulose carboxyl units under the conditions of the present process to form a carboxylate-quaternary ammonium complex, for example, as depicted in Figure 9A. One example of this embodiment comprises the use of allylamine as the modifying agent.
Another embodiment comprises the use of an oligomer or polymer as the modifying agent.
In one iteration m-PEG-amines having an average molecular weight of from about 2000 to about 10,000 daltons are used to modify the surface of the oxidized cellulose nanofibers. In one non-limiting example of this iteration the modifying agent is an m-PEG amine having an average .. molecular weight of 5000 daltons. For example, the m-PEG amine depicted in Figure 9C wherein the index n is approximately 112. Any oligomer or polymer that can covalently bond to the surface carboxylates of the oxidized nanofibers can be used to modify the cellulosic surface.
A further embodiment comprises a modifying unit that is a low molecular weight compound comprising a cationic moiety. The molecular weight of compounds of this type are .. less than about 400 g/mol. A non-limiting example of this embodiment is depicted in Figure 9B
wherein the use of a carbamoylcholine salt is the modifying agent. The salt can be chlorine, bromine and the like.
General Procedure In order for spontaneous nematic ordering of the nanofibers to occur, the nanocellulose concentration must be above the critical concentration. This behavior provides a unique opportunity for the formulator to impart LC ordering at low TOCN volume fractions which provides a means for obtaining the disclosed optical anisotropy and other properties.
Raw cellulosic material obtained from natural sources is used to form the disclosed hydrogels, organogels and aerogels. For example, cotton, grains, paper products made from .. natural sources and the like. The cellulosic material is first oxidized at the C6 saccharide carbons thereby oxidizing the ¨CH2OH moieties to carboxylate moieties, ¨COOH.
The oxidized cellulosic material is then treated with a modifying agent, which allows the cellulose nanofibers in the hydrogel to remain aligned and non-reactive to the subsequent treatment with the networking agent. Next, following treatment with the modifying agent, the nanofibers are treated with methyltrimethoxysilane (networking agent) which is hydrolyzed under acidic conditions to form a polysiloxane network over the hydrogel. Gelation results in a highly-transparent monolithic hydrogel of functionalized TOCNs, cross-linked by an isotropic, bicontinuous polysiloxane nanofibrous network.
The water is removed from the hydrogel by exchange with a volatile organic solvent to .. form the corresponding organogel. The resulting organogel exhibits both an isotropic and liquid-crystalline arrangement, which can be controlled by regulating the surface-modified TOCN
concentration. These orientationally ordered self-assembled structures are locked in place by the formation of the polysiloxane network. The disclosed process preserves the small and uniform cross-sections of individual fibers and their network and, consequently, assures low light scattering.
The corresponding aerogel is formed by drying of the organogel, which can be shaped to the needs of the formulator. In addition to mechanical flexibility and robustness, many practical aerogel applications can require a high degree of hydrophobicity (for example, to assure that these aerogels are stable under ambient conditions and in humid environments).
Example 5: PMSQ Network Cellulosic Aerogels The disclosed cellulose nanofibers are produced through the oxidation of native cellulose by selectively modifying the C6 primary hydroxyl groups on the surface of native cellulose to carboxylate groups catalyzed by TEMPO under mild pH aqueous conditions. The nanofibers with a diameter of 4.8 nm and micrometer-scale lengths are stabilized in a basic solution by the Coulombic repulsion of their anionic carboxylate moieties, which overpower their tendency to form hydrogen bonds. As a result, the aqueous TOCN dispersions are highly transparent. To eliminate the strong light scattering originating from bundling and clustering of TOCNs which are uncontrollably crosslinked by direct hydrogel bonds, as often observed in polymeric fibrous aerogels, we instead cross-link TOCNs with polysiloxane. This technique precludes the direct contacts between TOCNs and thereby generates a uniform nanofibrous network that exhibits small scattering cross-sectional areas. Hydrolysis of the polysiloxane precursor is acid-catalyzed.
However, even under mildly acidic conditions and dilute concentrations, TOCNs tend to form a gel-like phase due to the hydrogen bonding between carboxylic acid functional groups. To stably disperse TOCNs in polysiloxane precursor solutions, we implement various TOCN
surface functionalization schemes, as illustrated in Figures 9A-9C.
The TEMPO-mediated oxidation of cellulose produces a large density of carboxylic groups (-0.8 mmol/g) on the surface of nanofibrillated cellulose that is available for surface modification. This provides a means for altering the physical adsorption properties of the cellulose nanoparticles by covalently bonding either low molecular weight cationic molecules or polymeric chains to the surface thereby resulting in stabilized TOCNs by either electrostatic repulsion or steric hindrance.
In one embodiment as depicted in Figure 9A this modification is affected by physisorption of one or more polyelectrolytic monomers, in this example allylamine, to the anionic carboxylate groups of the oxidized cellulose. This process does not significantly affect the cross-sectional diameter of the TOCN's because of the size of the low molecular weight of the cationic small molecule.
In another embodiment as depicted in Figure 9B the surface functionalization can be accomplished by reaction of the carboxyl groups with a cationic-amine comprising adduct.
Figure 9B depicts the reaction of 2-(carbamoyloxy)-N,N,N-trimethylethanaminium (choline carbamate) with the TOCN's. This reaction introduces another form of cationic charge electrostatic repulsion In a further embodiment as depicted in Figure 9C the surface of the TOCN's are modified by reaction with a polymeric material, in this example a methoxy polyethylene glycol amine (mPEG-amine). Grafting of a polymer of this type provides a means for improving colloidal-TOCN stabilization.
The functionalization of the TOCN's produces cellulosic matrices that are stable to treatment with polysiloxane in the subsequent step of the disclosed process.
Figure 10 depicts the process in general. Oxidized and surface modified cellulose nanofibers as an aqueous suspension are represented by the long-aligned fibers and the differently shaded dots represent water molecules and molecules of PMSQ (far left figure).
The center figure represents Steps (c) and (d) of the process above wherein the nanofibers are first contacted with PMSQ then the PMSQ is hydrolyzed to form a PMSQ network cellulosic hydrogel.
The resultant of Steps (e) and (f) is depicted in the figure on the far right, the resulting aerogel. The resulting transparent surface-modified TOCNs' aqueous colloidal dispersions can exhibit LC ordering, depending upon the volume fraction of the nanofibers in the colloidal dispersion. In addition, .. these solutions can exhibit birefringence when they are observed between cross polarizers as depicted in Figure 10.
Surface modification of TOCN
1. Cationic Surface Physisorption.
The surface of the TEMPO-oxidized cellulose nanofibers was then functionalized by physical adsorption of allylamine onto the nanofibers. 500 mg of 0.2 wt.%
nanofiber aqueous solution was diluted by 2 mL of distilled and deionized water and combined with 10 mg of allylamine. The mixture was stirred overnight and dialyzed for 2 days in a deionized water bath across a cellulose acetate membrane with a cutoff molecular weight of 12,000-14,000 g/mol to obtain the desired allylamine-TOCNs.
2. Charged Small Molecule Modification An aqueous TOCN dispersion (500 mg of 0.38 wt.%) was diluted with 2 mL of deionized water followed by the addition of 24 mg of Hbis(dimethylamino)methylene1-1H-1,2,3-triazolo[4,5-blpyridinium 3-oxid hexafluorophosphate (HATU), 20 [IL of N,N-diisopropyl-ethylamine (DIPEA) and 50 mg carbamoylcholine chloride and 404 dimethylformamide (DMF).
The mixture was stirred for 2 days and dialyzed for another 2 days affording the desired dispersed surface modified nanofibers.
3. Oligomer/polymer Modification An aqueous TOCN dispersion (500 mg of 0.2 wt.%) was diluted with 2 mL of DI
water and followed by mixing with 28 mg of HATU, 204 of DIPEA, 18 mg mPEG-amine (MW=5000) and 404 DMF. The mixture was stirred for 2 days and then dialyzed for another 2 days to finally obtain mPEG-TOCNs. All of the functionalized TOCN dispersions were concentrated by a rotary evaporator to the desired concentration.
Preparation of PMSQ Network Cellulosic Hydrogels The disclosed PMSQ network cellulosic hydrogels were fabricated by cross-linking functional TOCNs with polysiloxane. For example, and in general, cetyltrimethylammonium bromide (0.4g)(CTAB) and 3.0 g of urea were dissolved in 8 mL of deionized (DI) water with sonication until the sol became homogeneous. To this solution is added 2 mL of a functionalized surface modified TOCN at differing concentrations, 1-5 mL of methyltrimethoxysilane (MTMS) and 0.01 mmol acetic acid under vigorous stirring. After stirring each sample for 30 minutes at room temperature, the sol was degassed in a vacuum oven and then transferred into a polystyrene petri dish with a diameter of 5 cm, sealed for gelation and allowed to age for 3 days in a 60 C
furnace to form the desired hydrogels.
Preparation of PMSQ Network Cellulosic Aerogels The hydrogels formed above were taken from the petri dish and immersed in DI
water for 24 hours to remove the urea and residual CTAB. This was followed by solvent exchange with isopropanol, which was replaced every 12 hours, at 60 C for 2 days. Finally, CO2 supercritical drying at 38 C under 8.6 MPa was conducted to obtain dried aerogel samples in a critical point dryer. This provided aerogels having bulk densities ranging from 30-200 mg/cm3 depending upon the amount of MTMS added to the functionalized surface modified cellulose in the above step. In one embodiment an aerogel having a density of 69 mg/cm3 promotes optimal optical transmission and mechanical flexibility. In one iteration of the disclosed process no stress is introduced to TOCN-PMSQ aerogel during processing.
Figure 11 is a photograph showing the optical transparency of a hydrogel formed from the disclosed process. This hydrogel is a highly-transparent monolithic hydrogel cross-linked by an isotropic, bicontinuous polysiloxane nanofibrous network as described herein. The hydrogel is contained within the outlined dotted area. Figure 12 is a photograph showing the optical transparency of an organogel formed from the disclosed process. The organogel is contained within the outlined dotted area. Figure 13 is photograph showing the optical transparency of an aerogel formed from the disclosed process wherein the surface modifying agent is allylamine.
The aerogel is contained within the circle. Figure 14 is a photograph of an aerogel formed by the disclosed process wherein the surface modifying agent is an m-PEG-amine having an average molecular weight of 5000 daltons. The circular aerogel is positioned on top of a copy of text. AS
can be seen in the photograph the aerogel is transparent in that neither the color nor the text is distorted. Figure 15 is a photograph of an aerogel formed by the disclosed process wherein the surface modifying agent is carbamoylcholine chloride. The circular aerogel is positioned on top of a copy of text. The aerogel is transparent in that neither the color nor the text is distorted.
As depicted in Figure 16 the carbamoylcholine chloride -capped TOCN-PMSQ
aerogels exhibit hydrophobic surface characteristics with a typical contact angle of 148 , largely due to the presence of hydrophobic methyl groups on the polysiloxane fibers within the nanostructured aerogels. An advantage of the disclosed process is that there is no need for post-synthetic hydrophobization treatment when the disclosed gels are used for hydrophobic applications.
The disclosed aerogels were analyzed for both their optical and electron imaging and spectra characteristics. For both polarized and unpolarized brightfield optical microscopic imaging, an Olympus BX-51 polarizing optical microscope was equipped with 10 x, 20 x, and 50 x air objectives with a numerical aperture NA = 0.3-0.9 and a 0.5x tube lens mounted right before a CCD camera Spot 14.2 ColorMosaic (Diagnostic Instruments, Inc.).
Transmission spectra were studied using a spectrometer USB2000-FLG (Ocean Optics) mounted on the microscope. For light transmittance and haze measurements of aerogels, a UV-VIS-NIR
spectrometer, ranging from 190 nm to 3200 nm, (UV-3101pc, from Shimadzu) equipped with a LabSphere brand integrating sphere attachment was employed. Haze is defined as the ratio of diffuse transmission to total transmission, where diffuse transmission is defined as transmitted light varying by greater than or equal to a 5 separation from the direction of incident light.
Infrared transmission spectra from wavenumbers 400 cm-1 to 4000 cm-1 (wavelengths 2.5 lam ¨ 25 lam) were recorded on a Fourier-transform infrared spectroscopy (FTIR) spectrometer (Nicolet AVATAR
from Thermo) equipped with an integrating sphere (NIR IntegratIR, from Pike).
Photographs of samples were taken using a digital camera. IR thermographs were obtained by an IR camera (T630sc, from FUR). TEM images were obtained using a CM100 microscope (from FEI Philips) at 80 kV. The TOCN samples were negatively stained with phosphotungstic acid to increase imaging contrast: 2 L of the sample is dropcasted on the formvar coated copper grid, allowed to settle for drying and then dipped into the stain solution (aqueous 2 wt.%
phosphotungstic acid).
The porous morphology of TOCN-PMSQ was characterized using an SEM using a Hitachi Su3500 and Carl Zeiss EVO MA 10 system. For this, freshly cut surfaces of the TOCN-PMSQ
aerogels were sputtered with a thin layer of gold and observed under SEM at a low voltage of 5kV
(as optimized to avoid the distortion of the aerogel samples).
Figures 17A-17C are transmission electron microscopy (TEM) micrographs of the disclosed aerogels at various magnifications. Figure 17A shows that the colloidal dispersions consist of mostly individualized TOCNs, each of diameter D5 nm and length Lc=1-Figures 17B and 17C are scanning electron microscopy (SEM) that depict the well-defined and uniform-diameter 10-15 nmnanofibers that are formed by polysiloxane treatment and individually dispersed TOCNs fibers within the aerogels as well as a narrow pore-size distribution of their resulting porous network. The depicted aerogel samples exhibit 3D bicontinuous network-like structures, in which both the smooth gel skeletons and the pores are interconnected without aggregation or clustering. The example depicted in Figures 17A-C have a bulk density pb that is calculated to be 69 mg/cm3 by weight/volume ratio of the sample. The porosity, defined as c=(1-pb/ps)x100%, is then determined to be 694.9%, where ps is the skeletal density taken to be 1.35 g/cm3. The average pore size for this particular example is calculated to be approximately 100 nm, consistent with the value observed directly from the SEM images. The mesoscale morphology of the 2.0-mm thick QA-capped TOCN-PMSQ composite aerogel with ultrathin fibers and uniform pore size distribution yields hydrogels and organogels with very high light transmission greater than 90% and aerogels with visible transmission close to 90% at 600 nm as depicted in Figure 18.
The exampled aerogel's haze coefficient, defined as the ratio of diffuse transmittance and total light transmittance, was determined to equal to 8.4%. Figure 19 is characterized following the ASTM D1003 standard using an integrating sphere setup when integrated across the visible range (390-700 nm), shown in Figure Si. The PMSQ matrix causes TOCN-PMSQ
aerogels to exhibit strong absorption at a wavelength of 6-20 lam, which is mainly due to the Si-0 bonds in Figure 20. This provides the formulator the opportunity to separately control transmission of visible and infrared light, in embodiments wherein control of solar gain and emissivity are important, i.e., in smart-window applications.
The disclosed aerogels were analyzed for their thermal, mechanical, and durability characteristics. The thermal conductivity is measured by measuring both the heat capacity and thermal diffusivity of the aerogel samples. The heat capacity of aerogel is measured by differential scanning calorimetry (DSC 204 Fl Phoenix, Netzsch). The thermal diffusivity of aerogel is characterized by a laser flash apparatus (LFA 457, Netzsch). Briefly, an optical source instantaneously heats one side of the material and the temperature increment on the other side of the material is recorded by infrared thermography for facile, noninvasive temperature sensing. To prevent the direct heating of the detector by laser light, the top and the bottom of the aerogel were covered with highly conductive carbon tape to prevent the laser from penetrating through the sample. The thermal conductivity of the aerogel can be calculated by subtracting the contribution of carbon tape from the effective thermal conductivity of the sandwich structure, which was determined by performing measurements for samples of different thickness. The Instron 5965 material-test system was used to probe the mechanical properties and determine stress-strain relationships. The mechanical properties shown in Figure 4f were measured with TOCN-PMSQ
aerogel samples with 0.25 vol.% QA-capped TOCN cut into rectangular strips of 20 mmx 6 mmxl mm. Aerogel durability testing was performed under a 500 Watt mercury lamp (Sun System 5, from Sunlight Supply Inc.) and in a Tenney environmental test chambers held at 80 C and 80%
relative humidity for 24 hours.
Figure 21 shows the measured thermal conductivity of a TOCN-PMSQ aerogel versus sample porosity. Figure 22 depicts the comparison of thermal conductivity between an aerogel formed from carbamoylcholine chloride modified nanocellulose (quaternary-amine) and an allylamine modified aerogel. Figure 23 depicts the compression stress-strain relation for a TOCN-PMSQ aerogel with 0.06 wt.% of TOCN.
Bacterial Cellulose Disclosed herein are cellulose (e.g., nanocellulose) biofilms derived from bacterial cellulose. The disclosed biofilms are suitable for use in preparing insulating and structural gels.
Non-limiting examples of cellulose producing bacteria that can be used to provide the disclosed biofilms include Acetobacter hansenii and Acetobacter xylinum.
The bacterial biofilms are formed in situ as depicted in, for example, Figures 6, 9A-9C, and 10. The resulting cellulose gels may be orientationally ordered¨e.g., using an oil, such as silicone oil and/or using an exterior stimulus, such as an infrared laser beam. Using an infrared laser beam as a laser trap the bacteria can be moved, re-orientated and positioned adjacent to one another such that the resulting fibrils of cellulosic material can coalesce with one another.
The disclosed cellulosic gels can be orientationally ordered because of their alignment as they are being formed because of hydrogen bonding between fibrils. This results in the fibrils forming ribbons. In addition, by modification of the growth nutrients, the number density of the fibrils in a bundle, hence, the ribbons can be determined by the formulator.
In addition, modification of the bacterial culture can result in a change in the fibril diameter.
Therefore, modifications to the growth media and to the nutrient composition, as well as, a change in bacterium species, can be used to tune the resultant gel to be transparent or opaque, flexible or stiff, thermally insulating or conducting, and fragile or load-bearing. Resultant gels can be further chemically treated to tune material and thermal properties of the invention, such as crosslinking density, material composition, and hydrophobicity. Colloidal inclusions can be introduced into the resultant gel to tune optical, thermal, magnetic, and electric properties of the gel.
Figure 24A and Figure 24B depict the reorientation of an A. hansenii bacterium using the infrared laser beam of a laser trap. The laser trap can be used to move a bacterium to a position in the growth media that provides easier harvesting of the pellicles or alternatively to determine the density of the pellicles. Figure 25 is a photograph of dark field microscopy showing an A.
hansenii bacterium producing a cellulose fiber. The cellulosic material is visible because the various single strands of cellulose have coalesced into a ribbon. This is depicted schematically in Figure 28. Figure 26 shows A. xylinum bacteria producing cellulose fibers.
Figure 27A and Figure 27B show the effect on cellulose fibril thickness when 1.5%
sodium carboxymethyl cellulose (CMC) is added to A. xylinum. In Figure 27A the cellulose fibril is visible. In Figure 27B the thickness of the fibril is greatly reduced such that the fibril is no longer visible/resolvable in the photograph. This is depicted schematically in Figure 29.
Once the pellicle is formed, the bacteria can by killed using any suitable technique, such as use of a basic solution, starvation, UV light, heat, toxins, plasma or other radiative treatment, asphyxiation, or the like.
Example 6 Bacterial cellulose derived from A. hansenii is used in this example. The bacterial cellulose pellicles are purified by first washing in 70 C lwt% NaOH aqueous solution for ¨4 hours, to kill any remaining bacteria. The pellicles are then transferred to 70 C or room temperature DI water to remove excess NaOH and reduce the ionic strength back to that near of pure DI water. Heating to 70 C speeds up the process, but the process can be done at room temperature (RT) as well. The pellicle is washed 2 additional times in pure DI
water (at RT or with mild heating, e.g., to 70 C), for a total of 3x DI water rinses. Then the pellicle is transferred into pure isopropanol (IPA) and allowed to solvent exchange. This solvent exchange from water to IPA can be done at RT or 60 C, depending on the urgency and speed desired.
The pellicle is then placed into a fresh bath of IPA, to further dilute any remaining water in the solvent exchange bath. The number of times the pellicle is washed with fresh IPA depends on the pellicle thickness.
For example, thin pellicles can require only need 2 total IPA baths to sufficiently remove water, whereas thicker pellicles can require 3-5 exchange cycles in IPA. After the water/IPA solvent exchange is complete, the pellicle is dried via conventional critical point drying (CPD) techniques (using liquid CO2, same as drying the aerogel). Once at the CO2 critical point, the pressure is bled off at ¨50PSI/min., and a bacteria cellulose aerogel is obtained.
Figure 28 is a depiction of an Acetobacter cell showing multiple cellulose synthase enzymes extruding cellulose fibrils from the cellular membrane. As the fibrils lengthen hydrogen bonding between adjacent strands cause the fibrils to coalesce and form ribbons.
Figure 29 is a depiction of an Acetobacter cell showing multiple cellulose synthase enzymes extruding cellulose fibrils from the cellular membrane. In this iteration, carboxymethyl cellulose (CMC) is added to the growth media resulting in hydrogen bonds not forming the fibrils into ribbons of fiber.
Figure 30A and Figure 30B demonstrate to optical and mechanical properties of the disclosed aerogels prepared from bacterial cellulose. In Figure 30A the aerogel is opaque whereas Figure 30B depicts the flexibility of the corresponding aerogel.
Example 7 Bacterial cellulose derived from A. hansenii wherein 1.5% carboxymethyl cellulose was added to the culture media was used in this example. The bacterial cellulose pellicles are purified by first washing in 70 C 1 wt% NaOH aqueous solution for ¨4 hours, to kill any remaining bacteria. The pellicles are then transferred to 70 C or room temperature DI
water to remove excess NaOH and reduce the ionic strength back to that near of pure DI water.
Heating to 70 C
speeds up the process, but the process can be done at room temperature (RT) as well. The pellicle is washed 2 additional times in pure DI water (at RT or with mild heating, e.g., to 70 C), for a total of 3x DI water rinses. Then the pellicle is transferred into pure isopropanol (IPA) and allowed to solvent exchange. This solvent exchange from water to IPA can be done at RT
or 60 C, depending on the urgency and speed desired. The pellicle is then placed into a fresh bath of IPA, to further dilute any remaining water in the solvent exchange bath. The number of times the pellicle is washed with fresh IPA depends on the pellicle thickness. For example, thin pellicles can require only need 2 total IPA baths to sufficiently remove water, whereas thicker pellicles can require 3-5 exchange cycles in IPA. After the water/IPA solvent exchange is complete, the pellicle is dried via conventional critical point drying (CPD) techniques (using liquid CO2, same as drying the aerogel). Once at the CO2 critical point, the pressure is bled off at ¨50PSI/min.
The thermal conductivity of the disclosed bacterial cellulosic gels can be measured by known processes (See, Hayase et al., App. Materials & Interfaces 6, 9466 (2014) and Zu et al., Chem. Mater. 30, 2759 (2018). Figure 31A and Figure 31B are thermal imaging photographs comparing a standard polysiloxane polymer, Figure 31A, with a gel formed by the disclosed process, Figure 31B. The patch of bacterial cellulosic aerogel is cold relative to the surrounding heated surface.
While particular embodiments of the present disclosure have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the disclosure. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this disclosure.
The transmissivity of the disclosed gels relates to the amount of electromagnetic radiation that is blocked from passing through the gel. 0% transmission results in an opaque material which allows no transmission. 100% transmission results in a material that is transparent to electromagnetic radiation. The disclosed gels can have a transmission of from 0% to 100%. In one embodiment the gels have a transmission of from about 5% to about 15%. In another embodiment the gels have a transmission of from about 25% to about 50%. In a further embodiment the gels have a transmission of from about 95% to 100%. In a still further embodiment the gels have a transmission of from about 15% to about 35%. In a yet further embodiment the gels have a transmission of from about 50% to about 75%. In a yet another embodiment the gels have a transmission of from about 25% to about 75%.
The disclosed gels and composite materials can have a thermal conductivity of from about 10-3 W/(m.K) to about 10 W/(m.K). In another embodiment the thermal conductivity is from about 10-2 W/(m.K) to about 10 W/(m.K). In a further embodiment the thermal conductivity is from about 10-1 W/(m.K) to about 10 W/(m.K). In a still further embodiment the thermal conductivity is from about 10-3 W/(m.K) to about 1 W/(m.K). In yet further embodiment the thermal conductivity is from about 10' W/(m.K) to about 1 W/(m.K). In yet another embodiment the thermal conductivity is from about 1 W/(m.K) to about 10 W/(m.K).
The relative emissivity value of the disclosed gels ranges from about 10' to 0.99.
The disclosed gels and composites can have a bulk modulus of from about 1 Pa to about 106 Pa. In one embodiment the modulus is from about 10 Pa to about 105 Pa. In another embodiment the modulus is from about 102 Pa to about 106 Pa. In a further embodiment the modulus is from about 103 Pa to about 105 Pa. In a still further embodiment the modulus is from about 10 Pa to about 103 Pa. In a yet further embodiment the modulus is from about 1 Pa to about 10 Pa. In a yet another embodiment the modulus is from about 104 Pa to about 106 Pa.
Procedures Cellulosic starting material for the disclosed gels can be derived from a variety of sources.
The surface-sulfuricated cellulose particles (Figure 1(a) and Figure 2) that are suspended in water can be prepared by sulfuric acid-mediated oxidation of the natural cellulose.
The surface-carboxylated cellulose nanofibers and nanoribbons that are suspended in water can be prepared by 2,2,6,6- tetramethyl-l-piperidinyloxy (TEMPO)-mediated oxidation of the natural cellulose.
The dispersions of these nanomaterials spontaneously form a thermodynamically stable cholesteric (for cellulose nanorods) or nematic (for cellulose nanofibers or nanoribbons) liquid crystal phase that can be transformed into a hydrogel (Figure 1(b) and Figure 3(a)) with a similarly ordered spatial organization of cellulose particles.
Cellulosic starting material for the disclosed aerogels can be biosynthesized by Acetobacter xylinum, Acetobacter hansenii or other examples of bacterial strains utilizing, for example, glucose as a carbon source. As one example, Acetobacter xylinum can be cultivated in a glucose medium for 1-3 weeks under static conditions to produce cellulose pellicles. To remove bacterial cell debris, bacterial cellulose can be boiled in a 1 wt. % NaOH
aqueous solution for 2 hours, followed by washing with water and neutralization with 0.2 % acetic acid.
Natural cellulose material obtained in this way can easily be disintegrated into individual nanocrystals by a controlled TEMPO mediated oxidation. For example, 2 g of bacterial cellulose was suspended in water (150 mL) containing TEMPO (0.025 g) and NaBr (0.25 g).
A 1.8 M
NaC10 solution (4 mL) was added, and the pH of the suspension was maintained at 10 by adding 0.5 M NaOH. When no more decrease in pH was observed, the reaction was finished. The pH is then adjusted to 7 by adding 0.5M HC1. The TEMPO-oxidized products were cellulose nano-rods of controlled 4-10 nm diameter and 1000-3000 nm length, which were then thoroughly washed with water by filtration and stored at 4 C.
Cellulose nanocrystals can also be synthesized by sulfuric acid hydrolysis method from natural cellulose. The aqueous suspension of such cellulose nanocrystals above the critical concentration (-3-6 wt. %) self-assemble into liquid crystalline structures-chiral nematic phase, which shows periodic helicoidal structures with a pitch that can be controlled in the range 5-70 pm. This structure can strongly reflect electromagnetic radiation of the wavelength comparable with the pitch, which simultaneously serves as a high efficiency low-emissivity structure by tuning the pitch to be appropriate range. The disclosed films can have a pre-designed gradient of cholesteric pitch in helicoidally ordered nanocrystal self-assembly and achieve broadband infrared selective reflection and low-emissivity (compare to the red infrared emission curve taken from solicitation) while being transparent in the visible spectral range and also transmitting solar radiation (blue curve) in near-IR range.
The concentration of the liquid crystalline cellulose nanocrystal dispersions was then adjusted to 3 wt.% and used in preliminary studies. The chiral nematic liquid crystalline order of the nanocrystals was then poured into a mold and the orientation of the helix could be aligned uniformly perpendicular to the film plane using a circular shearing or magnetic field. The polarizing optical micrograph shown in Figure 4(c) was obtained for a sample with the helical axis aligned in the horizontal direction, providing a side view of the periodic helicoidal structure of the chiral nematic liquid crystal. In the design and fabrication of AIR
FILMs, this helical axis will be set orthogonal to the plane of the film and along the normal to the window (Figure 2) which will be achieved using the process of circular shearing (see, Park J.H.
et al. "Macroscopic control of helix orientation in films dried from cholesteric liquid-crystalline cellulose nanocrystal suspensions", ChemPhysChem. 15, 1477-1484,2014).
After cellulose nanomaterial preparation from one or multiple sources the cellulose nanomaterial can be dispersed in water and aligned by the following methods.
First, the aqueous suspension of cellulose nanorods above the critical concentration (about 0.1-4%) self-assemble into a liquid crystalline phase with nematic or cholesteric ordering. Second, in order to induce uniform alignment across the entire dispersion, linear or circular shearing can be used for nematic or cholesteric phases, respectively. Specifically, the dispersion can be confined between glass plates in a mold such that, when a shear stress is applied from the plates in the specified direction (along a line or through a rotation), individual nanomaterial directors align to form a singular director alignment across the confined dispersion. As an alternate but complementary approach to dispersion alignment, the nanocrystals suffer uniform alignment under extrusion from a sufficiently small diameter nozzle, syringe, or similar device. With extrusion alignment, no confining plates are needed such that the aligned dispersion takes the form of a narrow bead, with linear extent much greater than cross-sectional extent, which rests on a supportive substrate or other structure. Additionally, the magnetic anisotropy of cellulose nanomaterial's relative permeability can be exploited to cause uniform alignment of nanocellulose.
Under sufficiently strong magnetic fields (about 100 mT), uniform alignment of nanocrystals is achieved through the magnetic interaction of the induced magnetic dipole moments of the cellulose nanomaterial with the applied magnetic field. (An oscillating electric field can be used to align nanocellulose with its long axis along the electric field.) The aligned cellulose nanomaterial dispersion can be cross-linked to convert into a hydrogel while preserving its ordering. The extent of cross-linking of chains of cellulose nanomaterials establishes the degree to which uniform ordering is preserved in the dispersion.
That is, for loosely cross-linked cellulose nanomaterials, weak gelation results. Conversely, strong cross-linking yields firm gelation. Gelation results from the addition of an acid, a photoacid generator and exposure to light, an alcohol, or another cationic exchange mechanism to the uniformly ordered cellulose nanomaterial dispersion. Alternatively, the cellulose nanorods, inorganic/cellulose nanorods, or polymeric/cellulose nanorods can self-assemble into cholesteric phase by evaporation.
The nanocellulose-based ordered hydrogel was transformed into organogels (Figure 1(c) and Figure 3(b)) by shaking the cellulose-nanomaterial hydrogel gently in an organic-solvent-filled bath while replacing the solvent regularly in order to prompt the replacement of water in the hydrogel by the organic solvent. As one example, twice per day for an extent of three days ethanol was replaced to facilitate total solvent exchange.
The disclosed cellulose aerogels (Figure 1(d) and Figure 3(c)) can be produced from the disclosed nano-structured organogel herein above. The resulting cellulose nanocrystal aerogel is a porous material with a skeleton of about 0.1-99.9% cellulose nanocrystals and a porosity of about 0.1-99.9%. To prevent deformation and crumbling of aerogels during the drying stage due to surface tension and capillary pressure in the ambient atmosphere, supercritical drying, freeze drying, or ambient drying low-surface tension solvent are used to remove liquid solvent from cellulose nanocrystal composites while maintaining the disclosed liquid crystalline structure, such as nematic or cholesteric liquid crystalline ordering.
The disclosed cellulose LC gels (Figure 1(e) and Figure 3(d)) can be produced from an ordered nano-structured organogel, in which an organic solvent completely miscible with LC is chosen. The organogel is placed in a bath of LC above the boiling point of the organic solvent so that the organic solvent is replaced with LC, which functions as the gel's replacement solvent.
The disclosed cellulose-templated ordered inorganic and polymeric gels or films can be produced by mixing cellulose nanomaterials with silica precursors or prepolymer and drying the composites in the ambient environment. Then the cellulose nanomaterials will be removed either by acidic (for silica aerogel) or basic (for polymeric aerogel) treatment to form a hydrogel. The hydrogel can be further transferred into organogel, aerogel, and LC gel based on the methods described above.
Example 1: Ordered gels made from cellulose nanorods Colloidal suspensions of cellulose nanocrystals (CNCs) composed of cellulose nanorods were prepared by controlled sulfuric acid hydrolysis of cotton fibers, according to the method described by Revol and co-workers (J. F. Revol, H. Bradford, J. Giasson, R. H.
Marchessault, D.
G. Gray, Int. I Biol. Macromol. 14, 170 (1992)). During this process, disordered or paracrystalline regions of cellulose are preferentially hydrolyzed, whereas crystalline regions, which have a higher resistance to acid, remain intact. 7 g of cotton was added to 200 g of 65 wt% sulfuric acid and stirred at 45 C in a water bath for up to several hours until the cellulose had fully hydrolyzed.
The mixture was sonicated occasionally, which was found to help degrade the amorphous cellulose regions. The suspensions of cellulose were then centrifuged at 9000 rpm for 10 min and .. re-dispersed in deionized water 6 times to remove the excess sulfuric acid.
The resulting precipitate was placed into a dialysis tubing (MWCO 12000-14000, Thermo Fisher Scientific Inc.) in de-ionized water for three days until the water pH remained constant. The dimensions of CNCs are about 5-10 nm in cross-section and, on average, 100-300 nm in length. Then 3 wt% CNCs solution was cast in a mold and evaporated under ambient conditions to obtain an aerogel.
Example 2: Ordered gels made from cellulose nanofibers or nanoribbons Cellulose nanofibers (CNF's) with the dimension of 4.8 nm by several micrometers were synthesized following the literature (T. Saito, M. Hirota, N. Tamura, S.
Kimura, H. Fukuzumi, L.
Hew( and A. Isogai, Biomacromolecules, 10, 1992 (2009)). Briefly, cellulose based bleached coffee filter (1 g) was suspended in 0.05 M sodium phosphate buffer (90 mL, pH
6.8) dissolving 16 mg of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and 1.13 g of 80% sodium chlorite in an airtight flask. The 2 M sodium hypochlorite solution (0.5 mL, 1.0 mmol) was diluted to 0.1 M with the same 0.05 M buffer used as the oxidation medium and was added at one step to the flask. The flask was immediately stoppered, and the suspension was stirred at 500 rpm and 60 C for 96 hours. After cooling the suspension to room temperature, the TEMPO-oxidized cellulose was thoroughly washed with water by filtration. Then 0.1-1.0 vol.%
CNFs aqueous dispersion was poured into a mold, aligned by a shear force, and several drops of 1 M HC1 solution was added to form a hydrogel after 2 hours. The hydrogel was immersed into ethanol for 2 days for solvent exchange to form an organogel. To form a liquid-crystal gel, the organogel was immersed in a bath of liquid crystal 4-cyano-4'-pentylbiphenyl at 90 C for 12 hours. Subsequent cooling to room temperature after solvent exchange caused the LC to enter its expected nematic phase. The aerogel was formed by critical point drying of the organogel.
Example 3: Ordered gels made from cellulose-nanorods-templated silica CNCs were synthesized according the method in Example 1. Then 5 mL of 3 wt%
CNCs dispersion was mixed with 10-754 of silica precursor tetramethyl orthosilicate and stirred for 1 hour. Then the composites were cast into a Petri dish and dried over 1-2 days.
The CNCs were then removed by pyrolysis method (e.g. 540 C for 20 hours) or keeping in 16%
sodium hydroxide solution for 16 hours. The silica hydrogel was formed and can be further transferred into organogel by solvent exchange and aerogel by critical point drying or ambient drying.
Example 4: Ordered gels made from cellulose-nanorods-templated polymer CNCs were synthesized according the method in Example 1. Then 5 mL of 3 wt%
CNCs dispersion was mixed with 10-75 mg of water-soluble preformed polymer and stirred for 10 min.
Then the composites were casted into a Petri dish and dried over 1-2 days. The film was then cured at polymerization temperature for 24 hours. The CNCs were then removed by 16% sodium hydroxide solution for 16 hours. The polymer hydrogel was formed and can be further transferred into organogel by solvent exchange and aerogel by critical point drying or ambient drying.
The light scattered upon passing through aerogels can produce a hazy appearance, which can result in the reduction of contrast of objects viewed through the film.
Haze measurements can be performed using a hazemeter or spectrometer. Figure 5 describes an apparatus developed and adapted to measure the quality of the disclosed aerogels. The apparatus in Figure 5 has the advantage of conducting haze measurements that also provides diagnostic data on the origins of the haze.
The typical setup includes an integrating sphere where the measured film is placed against the sphere entrance port. The surface of the interior of the integrating sphere is highly reflecting throughout the visible wavelengths obtained from light sources. The light entering the integrating sphere is reflected from the surface towards the tested film. Then the light transmitted through the film is focused and directed to a photodetector. A photodetector in the spectrophotometer setup is computer driven and values for transmission and haze can be automatically calculated. The haze can be determined as haze = 100x(TiTt), where Tt is a total transmittance depending on intensity of incident light & total light transmitted by the film & Kt is diffuse transmittance depending on light scattered by a measuring setup & the film.
Characterization of the Morphology of Nanocellulose Gels Sound proofing characterization can be conducted by imaging of nanoparticles using TEM
and SEM. Figure 6 outlines a procedure for probing of the pore size, surface area, and structural properties of cholesteric cellulose-based aerogels under different preparation conditions. The ordering of nanocrystals on large scales will be probed using 3D imaging techniques such as Fluorescence Confocal Polarizing Microscopy (FCPM), Coherent Anti Stokes Raman Scattering Polarizing Microscopy (CARS-PM), and Three.-Photon Excitation -Fluorescence Polarizing Microscopy (.3PEF-PM). In addition, the monitoring of the disclosed liquid clystal and aerogel uniformity in lateral directions can be accomplished by using conventional dark-field, bright-field, and polarizing optical microscopy. Visible- and infrared-range spectroscopy can also be utilized.
The other properties of the disclosed aerogels include mechanical properties (both as-prepared aerogels and encapsulated, ready-to-install films), as well as soundproofing and condensation resistance of the films installed on sint2,1e-pane windows.
Measurement of Aerogel Thennophysieal Properties Prior to the application of films onto a window the thermophysical properties (for example, thermal conductivity, heat capacity) are characterized by the optical pump-and-probe method in order to determine the type of film that is suitable for the specific application. This procedure uses a femtosecond laser to construct a high temporal resolution temperature measurement system. Figure 7 shows the optical pathway of a typical pump-and-probe measurement system. In the optical pump and probe method, sub-picosecond (ps) time resolution is made possible by splitting the ultrafast sub-ps laser pulse output into an intense heating pulse, i.e., a "pump" beam, and a weaker "probe" beam, and controlling the optical path length difference of the pump and probe beam through a mechanical delay stage. The decay of the temperature rise is measured by the reflected energy of the probe pulse series. The thermal conductivity can then be deduced by fitting the temperature decay curves.
Condensation Resistance After determining the thermal conductivity of a disclosed aerogel, films can be applied atop of a window to determine the thermal insulation and condensation resistance performance, following the current standards of ASTM C1363-11 and ASTM C1199-14. This test method establishes principles for design of a hot box apparatus & requirements for the determination of the steady-state thermal performance of windows when exposed to controlled laboratory conditions. The window thermal insulation and condensation performance is represented by the overall heat transfer coefficient, U. Figure 8 discloses the components of a hot box apparatus: a metering box (simulating interior temperature) on one side of the window specimen; a controlled guard box surrounding the metering box; a climate chamber box (simulating exterior temperature) on the other side; and the specimen frame providing specimen support and insulation.
The walls of the hot box are insulated panels of plywood adhered to either side of a solid layer of XPS insulation. The space conditioning system used in the meter box employs hydronic cooling and electric resistance heating. The meter box cooling is measured using high precision thermocouples in combination with a precision flow meter to accurately quantify the heat removed from the meter box. Heat is added into the meter box via PID-controlled electric heaters.
Precision resistor circuits are employed to measure the heat added into the meter box. A constant and precise temperature can be maintained and the total heat addition/removal can be measured.
The hot box employs an insulated guard box surrounds the meter box and a hydronic guard loop is installed over the outside surface of the meter box. The guard box minimizes the influence of temperature changes in the lab. The liquid guard loop further ensures the outside surface of the meter box remains at a constant temperature. An insulated baffle separates the air space from the mixing chamber of the meter box. The baffle panels are constructed using thermal insulation material. For a1mx 1m test window sample, at least 25 calibrated precision thermocouples are used to measure temperatures on the baffle surface, 25 corresponding points in the air stream and at least 25 points on the interior surface of the test window specimen. Air drawn through the meter box baffle space at velocities representative of convection in real world conditions. DC powered axial draw-through circulation fans, at the top and bottom of the baffle, are used to ensure smooth flow along the surface of the wall sample in the direction that convection would occur.
The climate box has the same dimensions and construction as the guard box. The climate side air baffles are constructed using the same materials and methods as the air baffles in the meter box. Heat is added to/removed from the climate box via four fan coils which are connected to a liquid chiller and a hydronic heater. Electric resistance heaters permit fine tuning of the temperatures and ensure that temperatures remain close to the set point for the duration of the test.
The climate box has the capacity to run a range of realistic outdoor temperatures, from -30 C to 60 C. This enables the tested window assembly to remain undisturbed when tested from cold to hot climate conditions. Overall heat transfer coefficient is:
u - _________________________________________ A- (Tmeter Tchmate where Q is the time rate of net heat flow through the meter box opening, W; A
is meter box opening area, m2; Tmeter and Taimate are temperatures of meter box and climate box, respectively.
Cellulose-Polysiloxane Hybrid Aerogels Further disclosed are transparent cellulose-polysiloxane hybrid hydrogels, organogels and aerogels and a process for preparing the disclosed transparent cellulose-polysiloxane hybrid transparent cellulose-polysiloxane hybrid hydrogels, organogels and aerogels.
Disclosed is a cellulose-polysiloxane hybrid aerogel, comprising:
a) a cellulosic matrix; and b) a polysiloxane surface network Without wishing to be limited by theory, these characteristics are achieved by strictly controlling the dimensions of nanofibers and the homogeneous gel skeleton networks that they form, which can be tuned to form orientationally ordered liquid crystal (LC) states. In the gel fabrication process, an optimized acid/base catalyzed sol-gel reaction in a surfactant-based solution is used to form a polymethylsilsesquioxane (PMSQ) surface network.
Cellulose nanofibers having a uniform diameter are first surface functionalized. This functionalization can employ small charged molecules or polymer grafting resulting in increased cellulose nanofiber stability. Subsequently, these nanofibers are crosslinked with PMSQ fibers.
In addition to their high optical transparency, super thermal insulation, flexibility and mechanical robustness, the disclosed hybrid aerogels can be made optically isotropic or anisotropic, depending on the intended use by the formulator. In the case of anisotropic aerogels, they can be fabricated starting from the LC states of colloidal dispersions of nanofibers. The resulting compositions can have practical applications as they result can result in devices having optical polarization, thereby the ability to control visible light polarization while providing simultaneous thermal insulation.
Disclosed herein is a process for preparing polymethylsilsesquioxane (PMSQ) network cellulosic aerogels, comprising:
a) contacting an aqueous dispersion of cellulose with an oxidizing system that oxidizes the C6 hydroxyl units of cellulose to carboxylate units to form an aqueous solution of oxidized cellulose nanofibers;
b) reacting the oxidized cellulose nanofibers with a surface modifying agent to form an aqueous solution of surface modified cellulose nanofibers;
c) contacting the surface modified cellulose nanofibers with polymethylsilsesquioxane (PMSQ) to form an aqueous polysiloxane precursor;
d) hydrolyzing the polysiloxane precursor in the presence of an acid catalyst to form a PMSQ network cellulosic hydrogel;
e) exchanging the water contained in the hydrogel with a volatile solvent to form an organogel; and f) removing the volatile solvent to form an aerogel.
In one embodiment the oxidizing system comprises:
a) an admixture of 2,2,6,6-Tetramethy 1piperidi n- 1-yl)ox-y1 (TEMPO) and N
aC 10 .
Modifying Agents In one embodiment the surface modifying agent is chosen from C1-C6 linear or branched, saturated or unsaturated alkylamine low molecular weight compounds comprising a cationic moiety, oligomers or polymers.
The C1-C6 linear or branched, saturated or unsaturated alkylamines react with the cellulose carboxyl units under the conditions of the present process to form a carboxylate-quaternary ammonium complex, for example, as depicted in Figure 9A. One example of this embodiment comprises the use of allylamine as the modifying agent.
Another embodiment comprises the use of an oligomer or polymer as the modifying agent.
In one iteration m-PEG-amines having an average molecular weight of from about 2000 to about 10,000 daltons are used to modify the surface of the oxidized cellulose nanofibers. In one non-limiting example of this iteration the modifying agent is an m-PEG amine having an average .. molecular weight of 5000 daltons. For example, the m-PEG amine depicted in Figure 9C wherein the index n is approximately 112. Any oligomer or polymer that can covalently bond to the surface carboxylates of the oxidized nanofibers can be used to modify the cellulosic surface.
A further embodiment comprises a modifying unit that is a low molecular weight compound comprising a cationic moiety. The molecular weight of compounds of this type are .. less than about 400 g/mol. A non-limiting example of this embodiment is depicted in Figure 9B
wherein the use of a carbamoylcholine salt is the modifying agent. The salt can be chlorine, bromine and the like.
General Procedure In order for spontaneous nematic ordering of the nanofibers to occur, the nanocellulose concentration must be above the critical concentration. This behavior provides a unique opportunity for the formulator to impart LC ordering at low TOCN volume fractions which provides a means for obtaining the disclosed optical anisotropy and other properties.
Raw cellulosic material obtained from natural sources is used to form the disclosed hydrogels, organogels and aerogels. For example, cotton, grains, paper products made from .. natural sources and the like. The cellulosic material is first oxidized at the C6 saccharide carbons thereby oxidizing the ¨CH2OH moieties to carboxylate moieties, ¨COOH.
The oxidized cellulosic material is then treated with a modifying agent, which allows the cellulose nanofibers in the hydrogel to remain aligned and non-reactive to the subsequent treatment with the networking agent. Next, following treatment with the modifying agent, the nanofibers are treated with methyltrimethoxysilane (networking agent) which is hydrolyzed under acidic conditions to form a polysiloxane network over the hydrogel. Gelation results in a highly-transparent monolithic hydrogel of functionalized TOCNs, cross-linked by an isotropic, bicontinuous polysiloxane nanofibrous network.
The water is removed from the hydrogel by exchange with a volatile organic solvent to .. form the corresponding organogel. The resulting organogel exhibits both an isotropic and liquid-crystalline arrangement, which can be controlled by regulating the surface-modified TOCN
concentration. These orientationally ordered self-assembled structures are locked in place by the formation of the polysiloxane network. The disclosed process preserves the small and uniform cross-sections of individual fibers and their network and, consequently, assures low light scattering.
The corresponding aerogel is formed by drying of the organogel, which can be shaped to the needs of the formulator. In addition to mechanical flexibility and robustness, many practical aerogel applications can require a high degree of hydrophobicity (for example, to assure that these aerogels are stable under ambient conditions and in humid environments).
Example 5: PMSQ Network Cellulosic Aerogels The disclosed cellulose nanofibers are produced through the oxidation of native cellulose by selectively modifying the C6 primary hydroxyl groups on the surface of native cellulose to carboxylate groups catalyzed by TEMPO under mild pH aqueous conditions. The nanofibers with a diameter of 4.8 nm and micrometer-scale lengths are stabilized in a basic solution by the Coulombic repulsion of their anionic carboxylate moieties, which overpower their tendency to form hydrogen bonds. As a result, the aqueous TOCN dispersions are highly transparent. To eliminate the strong light scattering originating from bundling and clustering of TOCNs which are uncontrollably crosslinked by direct hydrogel bonds, as often observed in polymeric fibrous aerogels, we instead cross-link TOCNs with polysiloxane. This technique precludes the direct contacts between TOCNs and thereby generates a uniform nanofibrous network that exhibits small scattering cross-sectional areas. Hydrolysis of the polysiloxane precursor is acid-catalyzed.
However, even under mildly acidic conditions and dilute concentrations, TOCNs tend to form a gel-like phase due to the hydrogen bonding between carboxylic acid functional groups. To stably disperse TOCNs in polysiloxane precursor solutions, we implement various TOCN
surface functionalization schemes, as illustrated in Figures 9A-9C.
The TEMPO-mediated oxidation of cellulose produces a large density of carboxylic groups (-0.8 mmol/g) on the surface of nanofibrillated cellulose that is available for surface modification. This provides a means for altering the physical adsorption properties of the cellulose nanoparticles by covalently bonding either low molecular weight cationic molecules or polymeric chains to the surface thereby resulting in stabilized TOCNs by either electrostatic repulsion or steric hindrance.
In one embodiment as depicted in Figure 9A this modification is affected by physisorption of one or more polyelectrolytic monomers, in this example allylamine, to the anionic carboxylate groups of the oxidized cellulose. This process does not significantly affect the cross-sectional diameter of the TOCN's because of the size of the low molecular weight of the cationic small molecule.
In another embodiment as depicted in Figure 9B the surface functionalization can be accomplished by reaction of the carboxyl groups with a cationic-amine comprising adduct.
Figure 9B depicts the reaction of 2-(carbamoyloxy)-N,N,N-trimethylethanaminium (choline carbamate) with the TOCN's. This reaction introduces another form of cationic charge electrostatic repulsion In a further embodiment as depicted in Figure 9C the surface of the TOCN's are modified by reaction with a polymeric material, in this example a methoxy polyethylene glycol amine (mPEG-amine). Grafting of a polymer of this type provides a means for improving colloidal-TOCN stabilization.
The functionalization of the TOCN's produces cellulosic matrices that are stable to treatment with polysiloxane in the subsequent step of the disclosed process.
Figure 10 depicts the process in general. Oxidized and surface modified cellulose nanofibers as an aqueous suspension are represented by the long-aligned fibers and the differently shaded dots represent water molecules and molecules of PMSQ (far left figure).
The center figure represents Steps (c) and (d) of the process above wherein the nanofibers are first contacted with PMSQ then the PMSQ is hydrolyzed to form a PMSQ network cellulosic hydrogel.
The resultant of Steps (e) and (f) is depicted in the figure on the far right, the resulting aerogel. The resulting transparent surface-modified TOCNs' aqueous colloidal dispersions can exhibit LC ordering, depending upon the volume fraction of the nanofibers in the colloidal dispersion. In addition, .. these solutions can exhibit birefringence when they are observed between cross polarizers as depicted in Figure 10.
Surface modification of TOCN
1. Cationic Surface Physisorption.
The surface of the TEMPO-oxidized cellulose nanofibers was then functionalized by physical adsorption of allylamine onto the nanofibers. 500 mg of 0.2 wt.%
nanofiber aqueous solution was diluted by 2 mL of distilled and deionized water and combined with 10 mg of allylamine. The mixture was stirred overnight and dialyzed for 2 days in a deionized water bath across a cellulose acetate membrane with a cutoff molecular weight of 12,000-14,000 g/mol to obtain the desired allylamine-TOCNs.
2. Charged Small Molecule Modification An aqueous TOCN dispersion (500 mg of 0.38 wt.%) was diluted with 2 mL of deionized water followed by the addition of 24 mg of Hbis(dimethylamino)methylene1-1H-1,2,3-triazolo[4,5-blpyridinium 3-oxid hexafluorophosphate (HATU), 20 [IL of N,N-diisopropyl-ethylamine (DIPEA) and 50 mg carbamoylcholine chloride and 404 dimethylformamide (DMF).
The mixture was stirred for 2 days and dialyzed for another 2 days affording the desired dispersed surface modified nanofibers.
3. Oligomer/polymer Modification An aqueous TOCN dispersion (500 mg of 0.2 wt.%) was diluted with 2 mL of DI
water and followed by mixing with 28 mg of HATU, 204 of DIPEA, 18 mg mPEG-amine (MW=5000) and 404 DMF. The mixture was stirred for 2 days and then dialyzed for another 2 days to finally obtain mPEG-TOCNs. All of the functionalized TOCN dispersions were concentrated by a rotary evaporator to the desired concentration.
Preparation of PMSQ Network Cellulosic Hydrogels The disclosed PMSQ network cellulosic hydrogels were fabricated by cross-linking functional TOCNs with polysiloxane. For example, and in general, cetyltrimethylammonium bromide (0.4g)(CTAB) and 3.0 g of urea were dissolved in 8 mL of deionized (DI) water with sonication until the sol became homogeneous. To this solution is added 2 mL of a functionalized surface modified TOCN at differing concentrations, 1-5 mL of methyltrimethoxysilane (MTMS) and 0.01 mmol acetic acid under vigorous stirring. After stirring each sample for 30 minutes at room temperature, the sol was degassed in a vacuum oven and then transferred into a polystyrene petri dish with a diameter of 5 cm, sealed for gelation and allowed to age for 3 days in a 60 C
furnace to form the desired hydrogels.
Preparation of PMSQ Network Cellulosic Aerogels The hydrogels formed above were taken from the petri dish and immersed in DI
water for 24 hours to remove the urea and residual CTAB. This was followed by solvent exchange with isopropanol, which was replaced every 12 hours, at 60 C for 2 days. Finally, CO2 supercritical drying at 38 C under 8.6 MPa was conducted to obtain dried aerogel samples in a critical point dryer. This provided aerogels having bulk densities ranging from 30-200 mg/cm3 depending upon the amount of MTMS added to the functionalized surface modified cellulose in the above step. In one embodiment an aerogel having a density of 69 mg/cm3 promotes optimal optical transmission and mechanical flexibility. In one iteration of the disclosed process no stress is introduced to TOCN-PMSQ aerogel during processing.
Figure 11 is a photograph showing the optical transparency of a hydrogel formed from the disclosed process. This hydrogel is a highly-transparent monolithic hydrogel cross-linked by an isotropic, bicontinuous polysiloxane nanofibrous network as described herein. The hydrogel is contained within the outlined dotted area. Figure 12 is a photograph showing the optical transparency of an organogel formed from the disclosed process. The organogel is contained within the outlined dotted area. Figure 13 is photograph showing the optical transparency of an aerogel formed from the disclosed process wherein the surface modifying agent is allylamine.
The aerogel is contained within the circle. Figure 14 is a photograph of an aerogel formed by the disclosed process wherein the surface modifying agent is an m-PEG-amine having an average molecular weight of 5000 daltons. The circular aerogel is positioned on top of a copy of text. AS
can be seen in the photograph the aerogel is transparent in that neither the color nor the text is distorted. Figure 15 is a photograph of an aerogel formed by the disclosed process wherein the surface modifying agent is carbamoylcholine chloride. The circular aerogel is positioned on top of a copy of text. The aerogel is transparent in that neither the color nor the text is distorted.
As depicted in Figure 16 the carbamoylcholine chloride -capped TOCN-PMSQ
aerogels exhibit hydrophobic surface characteristics with a typical contact angle of 148 , largely due to the presence of hydrophobic methyl groups on the polysiloxane fibers within the nanostructured aerogels. An advantage of the disclosed process is that there is no need for post-synthetic hydrophobization treatment when the disclosed gels are used for hydrophobic applications.
The disclosed aerogels were analyzed for both their optical and electron imaging and spectra characteristics. For both polarized and unpolarized brightfield optical microscopic imaging, an Olympus BX-51 polarizing optical microscope was equipped with 10 x, 20 x, and 50 x air objectives with a numerical aperture NA = 0.3-0.9 and a 0.5x tube lens mounted right before a CCD camera Spot 14.2 ColorMosaic (Diagnostic Instruments, Inc.).
Transmission spectra were studied using a spectrometer USB2000-FLG (Ocean Optics) mounted on the microscope. For light transmittance and haze measurements of aerogels, a UV-VIS-NIR
spectrometer, ranging from 190 nm to 3200 nm, (UV-3101pc, from Shimadzu) equipped with a LabSphere brand integrating sphere attachment was employed. Haze is defined as the ratio of diffuse transmission to total transmission, where diffuse transmission is defined as transmitted light varying by greater than or equal to a 5 separation from the direction of incident light.
Infrared transmission spectra from wavenumbers 400 cm-1 to 4000 cm-1 (wavelengths 2.5 lam ¨ 25 lam) were recorded on a Fourier-transform infrared spectroscopy (FTIR) spectrometer (Nicolet AVATAR
from Thermo) equipped with an integrating sphere (NIR IntegratIR, from Pike).
Photographs of samples were taken using a digital camera. IR thermographs were obtained by an IR camera (T630sc, from FUR). TEM images were obtained using a CM100 microscope (from FEI Philips) at 80 kV. The TOCN samples were negatively stained with phosphotungstic acid to increase imaging contrast: 2 L of the sample is dropcasted on the formvar coated copper grid, allowed to settle for drying and then dipped into the stain solution (aqueous 2 wt.%
phosphotungstic acid).
The porous morphology of TOCN-PMSQ was characterized using an SEM using a Hitachi Su3500 and Carl Zeiss EVO MA 10 system. For this, freshly cut surfaces of the TOCN-PMSQ
aerogels were sputtered with a thin layer of gold and observed under SEM at a low voltage of 5kV
(as optimized to avoid the distortion of the aerogel samples).
Figures 17A-17C are transmission electron microscopy (TEM) micrographs of the disclosed aerogels at various magnifications. Figure 17A shows that the colloidal dispersions consist of mostly individualized TOCNs, each of diameter D5 nm and length Lc=1-Figures 17B and 17C are scanning electron microscopy (SEM) that depict the well-defined and uniform-diameter 10-15 nmnanofibers that are formed by polysiloxane treatment and individually dispersed TOCNs fibers within the aerogels as well as a narrow pore-size distribution of their resulting porous network. The depicted aerogel samples exhibit 3D bicontinuous network-like structures, in which both the smooth gel skeletons and the pores are interconnected without aggregation or clustering. The example depicted in Figures 17A-C have a bulk density pb that is calculated to be 69 mg/cm3 by weight/volume ratio of the sample. The porosity, defined as c=(1-pb/ps)x100%, is then determined to be 694.9%, where ps is the skeletal density taken to be 1.35 g/cm3. The average pore size for this particular example is calculated to be approximately 100 nm, consistent with the value observed directly from the SEM images. The mesoscale morphology of the 2.0-mm thick QA-capped TOCN-PMSQ composite aerogel with ultrathin fibers and uniform pore size distribution yields hydrogels and organogels with very high light transmission greater than 90% and aerogels with visible transmission close to 90% at 600 nm as depicted in Figure 18.
The exampled aerogel's haze coefficient, defined as the ratio of diffuse transmittance and total light transmittance, was determined to equal to 8.4%. Figure 19 is characterized following the ASTM D1003 standard using an integrating sphere setup when integrated across the visible range (390-700 nm), shown in Figure Si. The PMSQ matrix causes TOCN-PMSQ
aerogels to exhibit strong absorption at a wavelength of 6-20 lam, which is mainly due to the Si-0 bonds in Figure 20. This provides the formulator the opportunity to separately control transmission of visible and infrared light, in embodiments wherein control of solar gain and emissivity are important, i.e., in smart-window applications.
The disclosed aerogels were analyzed for their thermal, mechanical, and durability characteristics. The thermal conductivity is measured by measuring both the heat capacity and thermal diffusivity of the aerogel samples. The heat capacity of aerogel is measured by differential scanning calorimetry (DSC 204 Fl Phoenix, Netzsch). The thermal diffusivity of aerogel is characterized by a laser flash apparatus (LFA 457, Netzsch). Briefly, an optical source instantaneously heats one side of the material and the temperature increment on the other side of the material is recorded by infrared thermography for facile, noninvasive temperature sensing. To prevent the direct heating of the detector by laser light, the top and the bottom of the aerogel were covered with highly conductive carbon tape to prevent the laser from penetrating through the sample. The thermal conductivity of the aerogel can be calculated by subtracting the contribution of carbon tape from the effective thermal conductivity of the sandwich structure, which was determined by performing measurements for samples of different thickness. The Instron 5965 material-test system was used to probe the mechanical properties and determine stress-strain relationships. The mechanical properties shown in Figure 4f were measured with TOCN-PMSQ
aerogel samples with 0.25 vol.% QA-capped TOCN cut into rectangular strips of 20 mmx 6 mmxl mm. Aerogel durability testing was performed under a 500 Watt mercury lamp (Sun System 5, from Sunlight Supply Inc.) and in a Tenney environmental test chambers held at 80 C and 80%
relative humidity for 24 hours.
Figure 21 shows the measured thermal conductivity of a TOCN-PMSQ aerogel versus sample porosity. Figure 22 depicts the comparison of thermal conductivity between an aerogel formed from carbamoylcholine chloride modified nanocellulose (quaternary-amine) and an allylamine modified aerogel. Figure 23 depicts the compression stress-strain relation for a TOCN-PMSQ aerogel with 0.06 wt.% of TOCN.
Bacterial Cellulose Disclosed herein are cellulose (e.g., nanocellulose) biofilms derived from bacterial cellulose. The disclosed biofilms are suitable for use in preparing insulating and structural gels.
Non-limiting examples of cellulose producing bacteria that can be used to provide the disclosed biofilms include Acetobacter hansenii and Acetobacter xylinum.
The bacterial biofilms are formed in situ as depicted in, for example, Figures 6, 9A-9C, and 10. The resulting cellulose gels may be orientationally ordered¨e.g., using an oil, such as silicone oil and/or using an exterior stimulus, such as an infrared laser beam. Using an infrared laser beam as a laser trap the bacteria can be moved, re-orientated and positioned adjacent to one another such that the resulting fibrils of cellulosic material can coalesce with one another.
The disclosed cellulosic gels can be orientationally ordered because of their alignment as they are being formed because of hydrogen bonding between fibrils. This results in the fibrils forming ribbons. In addition, by modification of the growth nutrients, the number density of the fibrils in a bundle, hence, the ribbons can be determined by the formulator.
In addition, modification of the bacterial culture can result in a change in the fibril diameter.
Therefore, modifications to the growth media and to the nutrient composition, as well as, a change in bacterium species, can be used to tune the resultant gel to be transparent or opaque, flexible or stiff, thermally insulating or conducting, and fragile or load-bearing. Resultant gels can be further chemically treated to tune material and thermal properties of the invention, such as crosslinking density, material composition, and hydrophobicity. Colloidal inclusions can be introduced into the resultant gel to tune optical, thermal, magnetic, and electric properties of the gel.
Figure 24A and Figure 24B depict the reorientation of an A. hansenii bacterium using the infrared laser beam of a laser trap. The laser trap can be used to move a bacterium to a position in the growth media that provides easier harvesting of the pellicles or alternatively to determine the density of the pellicles. Figure 25 is a photograph of dark field microscopy showing an A.
hansenii bacterium producing a cellulose fiber. The cellulosic material is visible because the various single strands of cellulose have coalesced into a ribbon. This is depicted schematically in Figure 28. Figure 26 shows A. xylinum bacteria producing cellulose fibers.
Figure 27A and Figure 27B show the effect on cellulose fibril thickness when 1.5%
sodium carboxymethyl cellulose (CMC) is added to A. xylinum. In Figure 27A the cellulose fibril is visible. In Figure 27B the thickness of the fibril is greatly reduced such that the fibril is no longer visible/resolvable in the photograph. This is depicted schematically in Figure 29.
Once the pellicle is formed, the bacteria can by killed using any suitable technique, such as use of a basic solution, starvation, UV light, heat, toxins, plasma or other radiative treatment, asphyxiation, or the like.
Example 6 Bacterial cellulose derived from A. hansenii is used in this example. The bacterial cellulose pellicles are purified by first washing in 70 C lwt% NaOH aqueous solution for ¨4 hours, to kill any remaining bacteria. The pellicles are then transferred to 70 C or room temperature DI water to remove excess NaOH and reduce the ionic strength back to that near of pure DI water. Heating to 70 C speeds up the process, but the process can be done at room temperature (RT) as well. The pellicle is washed 2 additional times in pure DI
water (at RT or with mild heating, e.g., to 70 C), for a total of 3x DI water rinses. Then the pellicle is transferred into pure isopropanol (IPA) and allowed to solvent exchange. This solvent exchange from water to IPA can be done at RT or 60 C, depending on the urgency and speed desired.
The pellicle is then placed into a fresh bath of IPA, to further dilute any remaining water in the solvent exchange bath. The number of times the pellicle is washed with fresh IPA depends on the pellicle thickness.
For example, thin pellicles can require only need 2 total IPA baths to sufficiently remove water, whereas thicker pellicles can require 3-5 exchange cycles in IPA. After the water/IPA solvent exchange is complete, the pellicle is dried via conventional critical point drying (CPD) techniques (using liquid CO2, same as drying the aerogel). Once at the CO2 critical point, the pressure is bled off at ¨50PSI/min., and a bacteria cellulose aerogel is obtained.
Figure 28 is a depiction of an Acetobacter cell showing multiple cellulose synthase enzymes extruding cellulose fibrils from the cellular membrane. As the fibrils lengthen hydrogen bonding between adjacent strands cause the fibrils to coalesce and form ribbons.
Figure 29 is a depiction of an Acetobacter cell showing multiple cellulose synthase enzymes extruding cellulose fibrils from the cellular membrane. In this iteration, carboxymethyl cellulose (CMC) is added to the growth media resulting in hydrogen bonds not forming the fibrils into ribbons of fiber.
Figure 30A and Figure 30B demonstrate to optical and mechanical properties of the disclosed aerogels prepared from bacterial cellulose. In Figure 30A the aerogel is opaque whereas Figure 30B depicts the flexibility of the corresponding aerogel.
Example 7 Bacterial cellulose derived from A. hansenii wherein 1.5% carboxymethyl cellulose was added to the culture media was used in this example. The bacterial cellulose pellicles are purified by first washing in 70 C 1 wt% NaOH aqueous solution for ¨4 hours, to kill any remaining bacteria. The pellicles are then transferred to 70 C or room temperature DI
water to remove excess NaOH and reduce the ionic strength back to that near of pure DI water.
Heating to 70 C
speeds up the process, but the process can be done at room temperature (RT) as well. The pellicle is washed 2 additional times in pure DI water (at RT or with mild heating, e.g., to 70 C), for a total of 3x DI water rinses. Then the pellicle is transferred into pure isopropanol (IPA) and allowed to solvent exchange. This solvent exchange from water to IPA can be done at RT
or 60 C, depending on the urgency and speed desired. The pellicle is then placed into a fresh bath of IPA, to further dilute any remaining water in the solvent exchange bath. The number of times the pellicle is washed with fresh IPA depends on the pellicle thickness. For example, thin pellicles can require only need 2 total IPA baths to sufficiently remove water, whereas thicker pellicles can require 3-5 exchange cycles in IPA. After the water/IPA solvent exchange is complete, the pellicle is dried via conventional critical point drying (CPD) techniques (using liquid CO2, same as drying the aerogel). Once at the CO2 critical point, the pressure is bled off at ¨50PSI/min.
The thermal conductivity of the disclosed bacterial cellulosic gels can be measured by known processes (See, Hayase et al., App. Materials & Interfaces 6, 9466 (2014) and Zu et al., Chem. Mater. 30, 2759 (2018). Figure 31A and Figure 31B are thermal imaging photographs comparing a standard polysiloxane polymer, Figure 31A, with a gel formed by the disclosed process, Figure 31B. The patch of bacterial cellulosic aerogel is cold relative to the surrounding heated surface.
While particular embodiments of the present disclosure have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the disclosure. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this disclosure.
Claims (28)
1. An aerogel, comprising bacterial cellulose.
2. The aerogel according to claim 1, wherein the aerogel has a thermal conductivity of from about 10-3W/(m.K) to about 10 W/(m.K).
3. The aerogel according to claim 1, wherein the aerogel comprises nanocellulose.
4. The aerogel according to claim 1, wherein the aerogel has a bulk modulus of from about 1 Pa to about 106 Pa.
5. The aerogel according to claim 1, wherein the bacterial cellulose is obtained from cellulose producing bacteria.
6. The aerogel according to claim 5, wherein the bacterial cellulose is obtained from Acetobacter hansenii, Acetobacter xylinum, or mixtures thereof
7. A film comprising bacterial cellulose nanomaterials.
8. The film according to claim 7, wherein the film has a thickness from about 1 p.m to about 10 cm.
9. The film according to claim 7, wherein the film has a bulk modulus of from about 1 Pa to about 106Pa.
10. The aerogel according to claim 7, wherein the bacterial cellulose is obtained from cellulose producing bacteria.
11. The film according to claim 7, wherein the bacterial cellulose is obtained from Acetobacter hansenii, Acetobacter xylinum or mixtures thereof
12. The film according to claim 7, wherein the nanomaterials comprise nanoribbons of cellulosic material.
13. The film according to claim 7, wherein the film comprises fibrils of cellulosic material.
14. The film according to claim 7, wherein the film comprises a layer comprising aligned nanoribbons of cellulosic material.
15. The film according to claim 14, wherein the nanoribbons have an aspect ratio from about 1:100 to about 1:1000.
16. The film according to claim 7, wherein the film comprises a layer comprising aligned nanorods of cellulosic material.
17. The film according to claim 16, wherein the nanorods have an aspect ratio from about 1:10 to about 1:100.
18. A composite structure comprising a film according to any of claims 7-17.
19. A process, comprising:
a) providing a mixture of a growth medium, bacteria, and possibly an additive that reduces an extent of bonding between cellulose fibrils;
b) forming a pellicle of bacterial cellulose;
c) exchanging water contained in the pellicle with a solvent; and d) drying the pellicle to remove the solvent to form an aerogel.
a) providing a mixture of a growth medium, bacteria, and possibly an additive that reduces an extent of bonding between cellulose fibrils;
b) forming a pellicle of bacterial cellulose;
c) exchanging water contained in the pellicle with a solvent; and d) drying the pellicle to remove the solvent to form an aerogel.
20. The process of claim 19, further comprising a step of treating the pellicle of bacterial cellulose to provide a bacteria-free pellicle.
21. The process according to claim 19, wherein the additive reduces hydrogen bonding between the fibrils in the bacteria growth medium.
22. The process according to claim 21, wherein the agent comprises a molecule that provides steric hinderance for bonding between the fibrils.
23. The process according to claim 19, wherein the bacterial cellulose is obtained from cellulose producing bacteria.
24. The process according to claim 19, wherein the bacterial cellulose is obtained from Acetobacter hansenii, Acetobacter xylinum, or mixtures thereof
25. The process according to claim 19, further comprising a step of manipulating a density of fibrils by modifying one or more of a growth medium and a nutrient composition within the growth medium.
26. The process of claim 19, further comprising a step of aligning nanocellulose material within a dispersion.
27. The process of claim 26, wherein the step of aligning comprises applying a shear stress to the dispersion.
28. The process of claim 26, wherein the step of aligning comprises applying one or more of an electric and a magnetic field to the dispersion.
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US201862684661P | 2018-06-13 | 2018-06-13 | |
US62/684,661 | 2018-06-13 | ||
US16/017,319 | 2018-06-25 | ||
US16/017,319 US20190055373A1 (en) | 2017-01-11 | 2018-06-25 | Bacterial cellulose gels, process for producing and methods of use |
PCT/US2019/037122 WO2019241603A1 (en) | 2018-06-13 | 2019-06-13 | Bacterial cellulose gels, process for producing and methods of use |
Publications (1)
Publication Number | Publication Date |
---|---|
CA3103620A1 true CA3103620A1 (en) | 2019-12-19 |
Family
ID=68842354
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA3103620A Pending CA3103620A1 (en) | 2018-06-13 | 2019-06-13 | Bacterial cellulose gels, process for producing and methods of use |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP3807349A4 (en) |
JP (1) | JP7536297B2 (en) |
CN (1) | CN112930366A (en) |
AU (2) | AU2019287564B2 (en) |
CA (1) | CA3103620A1 (en) |
WO (1) | WO2019241603A1 (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11612852B2 (en) * | 2020-05-28 | 2023-03-28 | Palo Alto Research Center Incorporated | Tunable, rapid uptake, aminopolymer aerogel sorbent for direct air capture of CO2 |
JP7559456B2 (en) | 2020-09-17 | 2024-10-02 | 東洋製罐グループホールディングス株式会社 | Coating solution containing cellulose nanocrystals containing anionic functional groups |
CN112662015B (en) * | 2020-12-24 | 2022-09-02 | 中国科学技术大学 | Flame-retardant nano-cellulose composite aerogel with oriented structure and preparation method thereof |
CN113402741B (en) * | 2021-07-05 | 2022-05-06 | 湖南工业大学 | Rare earth modified fiber reinforced polylactic acid and preparation method thereof |
JP2023175309A (en) * | 2022-05-30 | 2023-12-12 | 日信化学工業株式会社 | Cellulose-siloxane composite particles, method for producing the same, and cosmetic |
WO2024009622A1 (en) * | 2022-07-05 | 2024-01-11 | Sony Group Corporation | Structure, method of manufacturing structure, and heat insulating material |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0832798B2 (en) * | 1985-04-16 | 1996-03-29 | 工業技術院長 | High mechanical strength molding material containing bacterial cellulose |
US20080220333A1 (en) * | 2004-08-30 | 2008-09-11 | Shoichiro Yano | Lithium Ion Conductive Material Utilizing Bacterial Cellulose Organogel, Lithium Ion Battery Utilizing the Same and Bacterial Cellulose Aerogel |
US7968646B2 (en) * | 2007-08-22 | 2011-06-28 | Washington State University | Method of in situ bioproduction and composition of bacterial cellulose nanocomposites |
GB0916031D0 (en) * | 2009-09-14 | 2009-10-28 | Univ Nottingham | Cellulose nanoparticle aerogels,hydrogels and organogels |
US8772003B2 (en) * | 2010-05-24 | 2014-07-08 | Nympheas International Biomaterial Corp. | Bacterial cellulose film and uses thereof |
US10150848B2 (en) * | 2014-07-31 | 2018-12-11 | Case Western Reserve University | Polymer cellulose nanocrystal composite aerogels |
SE539714C2 (en) * | 2016-03-11 | 2017-11-07 | Innventia Ab | Method of producing shape-retaining cellulose products, and shape-retaining cellulose products therefrom |
US11180627B2 (en) * | 2017-01-11 | 2021-11-23 | The Regents Of The University Of Colorado, A Body Corporate | Cellulose enabled orientationally ordered flexible gels |
-
2019
- 2019-06-13 JP JP2020569102A patent/JP7536297B2/en active Active
- 2019-06-13 CA CA3103620A patent/CA3103620A1/en active Pending
- 2019-06-13 WO PCT/US2019/037122 patent/WO2019241603A1/en unknown
- 2019-06-13 AU AU2019287564A patent/AU2019287564B2/en active Active
- 2019-06-13 EP EP19819280.9A patent/EP3807349A4/en active Pending
- 2019-06-13 CN CN201980054456.7A patent/CN112930366A/en active Pending
-
2024
- 2024-08-23 AU AU2024216318A patent/AU2024216318A1/en active Pending
Also Published As
Publication number | Publication date |
---|---|
AU2019287564A1 (en) | 2021-02-04 |
EP3807349A4 (en) | 2022-03-23 |
AU2019287564A8 (en) | 2022-07-28 |
AU2024216318A1 (en) | 2024-09-12 |
AU2019287564B2 (en) | 2024-05-23 |
EP3807349A1 (en) | 2021-04-21 |
JP7536297B2 (en) | 2024-08-20 |
CN112930366A (en) | 2021-06-08 |
WO2019241603A1 (en) | 2019-12-19 |
WO2019241603A9 (en) | 2021-03-04 |
JP2021533213A (en) | 2021-12-02 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US20240158601A1 (en) | Bacterial cellulose gels, process for producing and methods for use | |
US12129353B2 (en) | Cellulose-enabled orientationally ordered flexible gels | |
AU2019287564B2 (en) | Bacterial cellulose gels, process for producing and methods of use | |
Liu et al. | Flexible transparent aerogels as window retrofitting films and optical elements with tunable birefringence | |
Tran et al. | Understanding the self‐assembly of cellulose nanocrystals—toward Chiral photonic materials | |
He et al. | Biomimetic optical cellulose nanocrystal films with controllable iridescent color and environmental stimuli-responsive chromism | |
Chu et al. | Free-standing optically switchable chiral plasmonic photonic crystal based on self-assembled cellulose nanorods and gold nanoparticles | |
Hynninen et al. | Inverse thermoreversible mechanical stiffening and birefringence in a methylcellulose/cellulose nanocrystal hydrogel | |
Pirzada et al. | Hybrid silica–PVA nanofibers via sol–gel electrospinning | |
Saha et al. | Photonic properties and applications of cellulose nanocrystal films with planar anchoring | |
Shopsowitz et al. | Free-standing mesoporous silica films with tunable chiral nematic structures | |
Bruckner et al. | Enhancing self-assembly in cellulose nanocrystal suspensions using high-permittivity solvents | |
Hu et al. | Distinct chiral nematic self-assembling behavior caused by different size-unified cellulose nanocrystals via a multistage separation | |
Sui et al. | Multi-responsive nanocomposite membranes of cellulose nanocrystals and poly (N-isopropyl acrylamide) with tunable chiral nematic structures | |
Bumbudsanpharoke et al. | Study of humidity-responsive behavior in chiral nematic cellulose nanocrystal films for colorimetric response | |
Azzam et al. | Adjustment of the chiral nematic phase properties of cellulose nanocrystals by polymer grafting | |
Wijesena et al. | Shape-stabilization of polyethylene glycol phase change materials with chitin nanofibers for applications in “smart” windows | |
Zhang et al. | Chemoselectivity of pristine cellulose nanocrystal films driven by carbohydrate–carbohydrate interactions | |
Meng et al. | Chiral cellulose nanocrystal humidity-responsive iridescent films with glucan for tuned iridescence and reinforced mechanics | |
Santos et al. | Optical sensor platform based on cellulose nanocrystals (CNC)–4′-(hexyloxy)-4-biphenylcarbonitrile (HOBC) bi-phase nematic liquid crystal composite films | |
Verma et al. | Cellulose nanocrystals for environment-friendly self-assembled stimuli doped multisensing photonics | |
Ivanova et al. | Cellulose nanocrystal-templated tin dioxide thin films for gas sensing | |
Zhao et al. | Iridescent chiral nematic papers based on cellulose nanocrystals with multiple optical responses for patterned coatings | |
Wei et al. | Cellulose Nanocrystal-based Liquid Crystal Structures and the Unique Optical Characteristics of Cellulose Nanocrystal Films. | |
Hamad | Photonic and semiconductor materials based on cellulose nanocrystals |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
EEER | Examination request |
Effective date: 20240612 |