CA2274040C

CA2274040C - Chelating silicone

Info

Publication number: CA2274040C
Application number: CA 2274040
Authority: CA
Inventors: Michael A. Brook; Rodica S. Stan
Original assignee: McMaster University
Current assignee: McMaster University
Priority date: 1999-05-27
Filing date: 1999-05-27
Publication date: 2010-11-30
Anticipated expiration: 2019-05-27
Also published as: CA2274040A1

Abstract

The present invention provides a polymeric species comprising a hydrophilic component that is responsive to, and which can bind with, a variety of metals, and a hydrophobic component. The hydrophobic component may be any organometallic polymer with surface-active properties, preferably a silicone polymer with hydrophobic organic radicals bound to the silicon. The hydrophilic component is comprised of multiple binding sites for metals, clustered in segments on the silcone such that more than one ligand (or binding site) can cooperatively bind a metal centre.

Description

Chelating Silicones Background of the Invention A wide variety of applications require control of the interfacial properties.
Generally, for good performance it is necessary to stabilize interfaces. Some simple examples include the use of coupling agents to modify silica surfaces so that silica may be used to reinforce organic polymers, with which it is otherwise incompatible, and the use of surfactants to stabilize oils in water, such as in hair conditioner applications.
Silicones are among the most surface active materials known. They diffuse rapidly to interfaces and readily spread. Spreading of the silicone is facilitated by the incorporation of polar groups on the silicone backbone. Some of the most effective spreading compounds, particularly at solid/liquid/air surfaces, are the so-called superwetters (made by manufacturers including Witco and Dow Corning)' of the general structure (Me3SiO)2SiMe(CH2)3(OCH2CH2)õOZ, Z
= H, Me, OAc, etc. The stabilization of liquid-liquid interfaces, rather than simply the efficiency of wetting biphasic interfaces, is generally accomplished by the use of silicones bearing non-ionic hydrophilic groups. Common examples include derivatives of so-called silicone polyols;
silicones containing polyether sidechains. These are'useful in particular at stabilizing water/silicone interfaces as taught by US57076132 Iohic silicone copolymers can also be used to stabilize interfaces. US5124466 teaches that ammonium-modified silicone surfactants are useful in the stabilization of silicones emulsions in water.3 The surface active of silicones, whether cationic, zwitterionic or non-ionic, cannot be readily changed, although pH modifications may affect the'behaviour of some types of ammonium compounds. There are advantages in being able to change the surface activity of a surface active material so as to change the properties of systems; for instance, to flocculate emulsions on demand. pH sensitive materials of this are well known. Carboxylic acids and polymers derived from them (e.g., carbopol) change their ability to swell, water and to stabilize interfaces upon pH
changes that convert neutral carboxylic acids to carboxylates or vice-versa.
Silicones containing carboxylic acids are known, and change surface properties as a function of pH
as taught by US5447997.4 The properties of ionic surfactants may not only be changed by pH, but by the nature of the counterions. For example, carboxylates with monovalent counterions such as sodium swell well with water. By contrast, multivalent counterions in the same system, however, lead to ionic crosslinking and a reduction of swelling. At an interface, the surface activity of such materials will be affected similarly by the nature of the counterion.
Multidentate ligands bind metals very tightly. The classic example is EDTA
(ethylenediaminetetraacetic acid). This material, normally in its calcium, disodium salt form, is frequently found in food products. Any heavier metals coming into contact with the EDTA will complex to three of four of the carboxylic acid groups, displacing the sodium/calcium ions. The binding efficiencies of many metals and different oxidation states, to EDTA
and related derivatives are well known. Many patents exist in. which chelators have been added to a formulation.5 Multidentate ligands have also been bound to polymers. For instance, chelating groups similar to those mentioned above are used a supports in affinity chromatography. We describe in this invention surface active materials, based on silicone, which are able to sequester metal ions using complementary binding.

1 ., Summary of the Invention As described above, described within is a composition of a polymeric species containing two components; a hydrophilic component that is responsive to, and which can bind with, a variety of metals, and, a hydrophobic component. The hydrophobic, component can be an organometallic polymer with surface active properties. The preferred embodiment of the hydrophobic component is a silicone polymer. The hydrophobic nature of the silicone is provided by organic radicals bound to silicon, such as methyl. The hydrophilic component is comprised of multiple binding sites for metals, clustered in segments on the silicone such that more than one ligand (binding site) can cooperatively bind a metal centre. Such hydrophilic binding sites can include carboxylic acids and derivatives, amines, phosphines, alcohols, and unsaturated systems (7[
bonds) that are rendered hydrophilic by incorporation of other polar groups located nearby.
Description of the Invention In accordance with the present invention, a silicone polymer is modified by hydrophilic groups.
The silicone may have a linear structure of the general formula, R' R1 R' I
Si.~ SiN. Sim R- RMO II O n RNR

where R, R', R", R', R2 = H, alkoxy, alkyl, allyl,, ar yl, vinyl, propargyl, groups that can be covalently bound to the hydrophilic component and substituted versions of the preceding groups.
The molecule may be symmetric, or may have different substituents at each terminus, such as the general formula, R' R' A
RCS .,O+S 2 O n SiN

R" R2 J D Alternatively, the silicone may be a branched silicone polymer incorporating terminal, difunctional, trifunctional and tetrafunctional silanes, of general type Y
is O R' R' S y I I I' R. 1~.O+S,~O'Si~ Sim Sim I z O" J~ R" R
R" O "" O +Mf-R
Y Y

where R, R', R", Rt, R2, R3 = H, alkoxy, alkyl, allyl, aryl, vinyl, propargyl, groups that can be covalently bound to the hydrophilic component and substituted versions of the preceding groups and Y = SiXZ where z = 0-3 and X = R, R', R", R% R2, and/or W. The molecule may be symmetric, or may not any planes or axes of symmetry.
The hydrophilic component will comprise clusters of at least two groups that may act as ligands for metals. Such ligands may include, but are not limited to groups that possess exchangeable hydrogens (OH, NH, and less-exchangeable hydrogens SH, PH), neutral groups that are known to be good ligands for metals RR'R"N, RR'R"P, carbonyl groups, thiocarbonyl groups, alkenes, alkynes and other n-systems and ionic groups including carboxylates. The preferred embodiment of the invention utilizes clusters of carboxylic acids that may both change character as a result of pH changes and by binding metals with different coordination numbers; such metals may be charged or neutral. A general formula for the hydrophilic component, without limitation is, O
HO O
N
OH
OH

O
The invention comprises a combination of hydrophilic and hydrophobic components. Several general ways of combining the two distinct components are disclosed. The hydrophilic clusters may appear at the terminus of a silicone, as in the general formula, O
R' RI R' HO O
R- 0+12 s1~E N v 'OH
R" R~ R"
OH
0 , where E is a linker.
Alternatively, the hydrophilic clusters may appear at both termini of a linear silicone, as in the general formula, O O
0 OH R' R' R' HO 0 ~~ Sim LSim Sim N
HO E 1 O+L I O' n\ E 11 v 'OH
NH
R" R~ R".
HO OH
0 0 , where E is a linker.
Alternatively, the hydrophilic clusters may appear avarious sites along the backbone of a silicone chain, as in the general formula, Y
R' R3 0 R R' R"Si`\O O
~+n Si%I Si\
Rõ 0 \ O PM I 0+ 1R
O E R"
Y Y

HO

OH

HO , where E is a linker.

The linkers in the preceding general formula may consist, but is not limited to, organic functional groups such as esters, ethers, amines, amides, alkanes and derivatives thereof. One specific example is shown in example 1.

In an embodiment of the disclosure, there is also provided a polymer of the formula RR'R"SiO(R'R2SiO)nSi(R4R5)-W, wherein RR'R"SiO(R'R2SiO)nSi(R4R5) is a hydrophobic group, wherein n = 2 to 4000, and R, R', R", R', R2, R4 and R5 are independently H, alkoxy, alkyl, allyl, aryl, vinyl or propargyl groups, and wherein W is a hydrophilic group comprising at least two binding sites for metal.
In another embodiment, the at least two binding sites independently or simultaneously comprise an OH group, a COOH group, a SH group, a NH group, a PH
group, a carbonyl group, a thiocarbonyl group, a phosphine group, an amine group, an alkene group, an alkyne group, a conjugated alkene group, a conjugated alkyne group, an arene group or a carboxylate group.
In a further embodiment, the carboxylic acids are oriented to bind a mono-, di-, tri- or tetravalent, wherein the metal is neutral or formally charged, and the charged metal comprises a charge from +1 to +4.
In another embodiment, the group R in the hydrophobic group RR'R"SiO(R'R2SiO)nSi(R4R5) is replaced with W to give a hydrophobic group substituted with two hydrophilic groups and is of the formula W-(R'R")SiO(R' R2SiO)nSi(R4R5)-W.
In another embodiment of the disclosure, there is also provided a polymer comprising a hydrophobic group and a hydrophilic group, the hydrophobic group having the formula (RR'R"SiO)k(R' R2SiO)i(SiO4/2)m(R3SiO3/2)p, wherein k, I, m and p = 0 to 4000, and R, R', R", R', R2 and R3 are H, alkoxy, alkyl, allyl, aryl, vinyl or propargyl groups, and wherein at least one of R, R', R", R1, R2 and R3 is replaced with a group of the formula SiXZ, wherein z = 0 to 3, and X is H, alkoxy, alkyl, allyl, aryl, vinyl or propargyl groups, and wherein at least one of R, R', R", R1, R2 and R3 is replaced by a hydrophilic group comprising at least two binding sites for metal.

In another embodiment, the at least two binding sites independently or simultaneously comprise an OH group, a COOH group, a SH group, a NH group, a PH
group, a carbonyl group, a thiocarbonyl group, a phosphine group, an amine group, an alkene group, an alkyne group, a conjugated alkene group, a conjugated alkyne group, an arene group or a carboxylate group.
In a further embodiment, the carboxylic acids are oriented to bind a mono-, di-, tri- or tetravalent, wherein the metal is neutral or formally charged, and the charged metal comprises a charge from +1 to +4.
The behaviour of the hydrophilic/hydrophobic compounds may be changed by pH
and by the addition of metals with greater than one binding site. Thus, a neutral compound can be converted to an ionic species whose behaviour in turn can be modified by the addition of metals, as in the general scheme, ~0 ('OH R' R' R' HO"'U) IO
HO " v N E"S~\O Si\ Sim N_ R R2 O~n R,~ E OH
HO OH

increase pH

0 0 R' R1 R' HO 0 m N~
HON E-'Si1\ S1\ SiRõ
RõO+ R 2 O'" E

0 increase pH 0 O O R' R' R' O 0 0_N E~Si\ Si\ Sim R,~ N~
E
O+ 1 2 O 1 \v/~`0 R RN
0 O_ 0 multivalent metals 0 0 0 R' R~ R' 0 0 N S\ Si\ ~Si~
O E Rõ0 R2 0 Jn Rõ E O
' O-M' M-O

Examples Example 1: ; ._ A series of surface active polymers were prepared using silicones of different molecular weight.
Thus, amino-terminated linear silicones of molecular weights ranging from about 500 - 5000 (8 parts) were reacted with succinic anhydride (16 parts) in methylene chloride (3000 parts) to give carboxylic acid-terminated silicones after aqueous extraction first with water and then with IN
HC1 and drying with sodium sulfate.
Activation of the carboxyl groups on the silicones (2.5 parts) was performed by reaction with N-hydroxysuccinimide (5 parts) in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (5 parts) in 1,2-dimethoxyethane (220 parts). After removal of the solvents in vacuo, it was dissolved in methylene chloride (900 parts), washed with water, IN HCl and then dried over sodium sulfate.
The succinimidyl-terminated polydimethylsiloxane (65 parts) dissolved in 1,2-dimethoxyethane (150 parts) was vigorously stirred with N,V -bis(carboxymethyl)-L-lysine sodium salt (1.5 parts) dissolved in water (270 parts) overnight. The two layers were separated and the solvents were removed in vacuo from the bottom aqueous layer. The solid obtained was purified by dialysis against deionized water. Lyophilization led to the desired product as a white solid.
These compounds readily complexed metals including iron, copper and cobalt.
The most diagnotic characteristic of the complexed materials were the mass spectral molecular fragments showing components of the tricarboxylic acid, silicone and the metal.

HzN SIB SIB Sl NH
O+ O+1 z O O
O
-~-Icy O p HO H H OH
N +Si ~i 1 p O "

O (OH p DCC O N O

O O
O p N-O H H O-N
N~~Si~ Sim O'n ~.

O p O p O

N O
O
O
O
O p O ~N O_1-,~N
0 p-O O

N N
O p 0 R' R' i' N Sim Sim 1 Si R.. z O,^ R#' R

1 (a) Ananthapadmanabhan, K. P.; Goddard, E.' D. `Chandar P. Coll. Surf 1990, 44,28 1. (b) Zhu, S.; Miller, W. G.; Scriven, L. E.; Davis, H. T. Coll. SurfA. 1"4,90,79. (c) He, M.; Hill, R.
M.; Lin, Z.; Scriven, L. E.; Davis, H. T. J. Phys. Chem. 1993,97,8820. (d) Gentle, T. E.;
Snow, S. A. Langmuir 1995,11, 2905.
2 Hill, R.M., US5707613, Spontaneously formed clear silicone microemulsions, to Dow Corning Corporation, 1998.
3 Azechi; S.; Meguriya; N.; Tanaka; M. US5124466, Cationic silicone surfactant and method of its manufacture, to Shin-Etsu Chemical Company Limited 1992.
4 Raleigh, W. J.; Campagna, J. A.; Lucarelli, M. A. US5447997, Silicone polyether carboxylic acids, to General Electric Company, 1995.
Bolich, Jr., R. E.; Norton, M. J.; Russell, G. D. US5106609, Vehicle systems for use in cosmetic compositions, to Procter & Gamble Company, 1992.

Claims

1. A polymer of the formula RR'R"SiO(R1R2SiO)n Si(R4R5)-W, wherein RR'R"SiO(R1R2SiO)n Si(R4R) is a hydrophobic group, wherein n = 2 to 4000, W is a hydrophilic group comprising at least two binding sites for a metal, R is H, alkoxy, alkyl, allyl, aryl, vinyl, propargyl group or W, and R', R", R1, R2, R4 and R5 are independently H, alkoxy, alkyl, allyl, aryl, vinyl or propargyl groups.

2. The polymer according to claim 1, wherein the at least two binding sites independently or simultaneously comprise an OH group, a COOH group, a SH group, a NH group, a PH group, a carbonyl group, a thiocarbonyl group, a phosphine group, an amine group, an alkene group, an alkyne group, a conjugated alkene group, a conjugated alkyne group, an arene group or a carboxylate group.

3. The polymer according to claim 2, wherein the phosphine group has the formula RR'R"P, and R, R' and R" are independently as defined in claim 1.

4. The polymer according to claim 2, wherein the amine group has the formula RR'R"N, and R, R' and R" are independently as defined in claim 1.

5. The polymer according to claim 2, wherein the at least two binding sites comprise carboxylic acids.

6. The polymer according to claim 5, wherein the carboxylic acid comprises

7. The polymer according to claims 5 or 6, wherein the carboxylic acids are oriented to bind a mono-, di-, tri- or tetravalent metal atom.

8. The polymer according to claim 7, wherein the metal is neutral or formally charged.

9. The polymer according to claim 8, wherein the charged metal comprises a charge from +1 to +4.

10. The polymer according to any one of claims 1 to 9, wherein the group R in the hydrophobic group as defined in claim 1 is W to give a hydrophobic group substituted with two hydrophilic groups and is of the formula W-(R'R")SiO(R1R2SiO)n Si(R4R5)-W.

11. The polymer according to any one of claims 1 to 10, wherein the hydrophobic group and the hydrophilic group are joined by a linking group.

12. The polymer according to claim 11, wherein the linking group is an ester, ether, amine, amide or alkyl group.

13. A polymer comprising a hydrophobic group and a hydrophilic group, the hydrophobic group having the formula (RR'R"SiO)k(R1R2SiO)l(SiO4/2)m(R3SiO3/2)p, wherein k, l, m and p = 0 to 4000, and R, R', R", R1, R2 and R3 are H, alkoxy, alkyl, allyl, aryl, vinyl or propargyl groups, and wherein at least one of R, R', R", R1, R2 and R3 is replaced with a group of the formula SiX z, wherein z = 0 to 3, and X is H, alkoxy, alkyl, allyl, aryl, vinyl or propargyl groups, and wherein at least one of R, R', R", R1, R2 and R3 is replaced by a hydrophilic group comprising at least two binding sites for metal.

14. The polymer according to claim 13, wherein the at least two binding sites independently or simultaneously comprise an OH group, a COOH group, a SH group, a NH group, a PH group, a carbonyl group, a thiocarbonyl group, a phosphine group, an amine group, an alkene group, an alkyne group, a conjugated alkene group, a conjugated alkyne group, an arene group or a carboxylate group.

15. The polymer according to claim 13, wherein the phosphine group has the formula RR'R"P, and R, R' and R" are independently as defined in claim 13.

16. The polymer according to claim 13, wherein the amine group has the formula RR'R"N, and R, R' and R" are independently as defined in claim 13.

17. The polymer according to claim 13, wherein the at least two binding sites comprise carboxylic acids.

18. The polymer according to claim 17, wherein the carboxylic acid comprises

19. The polymer according to claims 17 or 18, wherein the carboxylic acids are oriented to bind a mono-, di-, tri- or tetravalent metal.

20. The polymer according to claim 19, wherein the metal is neutral or formally charged.

21. The polymer according to claim 20, wherein the charged metal comprises a charge from +1 to +4.

22. The polymer according to any one of claims 13 to 21, wherein the hydrophobic group and the hydrophilic group are joined by a linking group.

23. The polymer according to claim 22, wherein the linking group is an ester, ether, amine, amide or alkyl group.

24. A use of a polymer as claimed in any one of claims 1 to 23 for the chelation of metal.

25. The use according to claim 24 wherein the metal is iron, cobalt or copper.