Reinforced anion exchange membrane and method for producing the same

Abstract

Disclosed herein are high-performance anion exchange membranes with excellent mechanical properties and a novel process for their manufacture. The membranes are useful for fuel cell or electrolysis applications due to their low ionic resistance and high durability under alkaline conditions. The membranes are fabricated by preparing an ionic polymer from two or more aromatic monomers and a trifluoromethyl ketone compound and impregnating the ionic polymer into a porous membrane substrate. The novel process for reinforced anion exchange membranes allows the membranes to be significantly thinner and more dimensionally stable in water than prior art commercially available membranes.

Description

[Technical Field]

[0001] The present disclosure provides an anion exchange membrane reinforced with a porous polymer support. In particular, the present disclosure provides an anion exchange membrane impregnated with an aryl ether-free polycyclic aromatic polymer having a random copolymer structure containing two or more aromatic ring components. [Background technology]

[0002] Anion exchange membranes (AEMs) are important components in electrochemical energy conversion devices such as fuel cells, electrolyzers, and flow batteries. They transport anions between electrodes while preventing reactant intermixing. For better device performance, AEMs should have low ionic resistance, long-term durability, and good mechanical properties.

[0003] Conventional AEM materials contain aryl ether-containing polyaromatic electrolytes due to their beneficial mechanical properties. The aryl ether groups in the polymers provide flexibility to the rigid polyaromatic structure, thereby providing greater strength to the AEM. However, the aryl ether groups are not chemically stable at high pH conditions due to the aryl ether cleavage reaction of quaternary polyaromatics, which impairs the long-term durability of the membrane. For this reason, other types of polymers have been developed (Patent Documents 1 and 2).

[0004] Regarding the ionic resistance of AEMs, membranes with higher ion exchange capacity (IEC) usually exhibit higher anion conductivity and lower ionic resistance. However, high IEC can also lead to membrane flooding, impairing its mechanical properties under high relative humidity conditions. Due to this trade-off between desirable properties, numerous reinforcement methods have been developed to simultaneously provide ion exchange membranes with good mechanical properties and high IEC. Reinforcement methods include forming pore-filled membranes, composite membranes with added fillers, and cross-linking between polymers within the pores of the support or with additives. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 10,435,504 [Patent Document 2] U.S. Patent No. 1,104,039 Summary of the Invention [Means for solving the problem]

[0006] The present disclosure provides a reinforced anion exchange membrane prepared by impregnating an ionic polymer into a porous membrane substrate, wherein the impregnated polymer is an aryl ether-free polyaromatic polymer having a random copolymer structure containing two or more aromatic ring components. The copolymer may be uncrosslinked or crosslinked. The latter may help confine the polymer within the pores of the porous substrate and prevent polymer leaching. The reinforced anion exchange membrane may be useful in electrochemical energy conversion devices, such as AEM fuel cells, AEM electrolyzers, and flow batteries. Currently, there are no membranes impregnated with a random copolymer using two or more different aromatic monomers, which are employed for aryl ether group-free quaternary polyaromatic monomers.

[0007] In some embodiments, the porous membrane substrate may be a thin film that is highly porous and has a continuous pore structure from one side to the other. The porous substrate is hydrophobic and does not swell in water. The porous substrate is preferably made of a material including high molecular weight polyethylene, ultra-high molecular weight polyethylene, polytetrafluoroethylene, expanded polytetrafluoroethylene, polypropylene, and combinations thereof. The thickness of the porous membrane substrate is about 200 microns or less.

[0008] Some embodiments of the present disclosure include a novel method for making a reinforced anion exchange membrane, which includes reacting two or more aromatic compounds with a trifluoromethyl ketone compound under acidic conditions to produce an aryl ether-free polycyclic aromatic polymer having a random copolymer structure containing two or more aromatic ring components, reacting the polymer with an amine to form an ionic polymer, dissolving the ionic polymer in a solvent to form a polymer solution, and impregnating a porous membrane substrate with the polymer solution to form the reinforced anion exchange membrane. [Brief explanation of the drawings]

[0009] [Figure 1] 1 illustrates an exemplary method for enhancing anion exchange membranes according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Some embodiments of the present disclosure include reinforced anion exchange membranes prepared by impregnating an ionic polymer into a porous membrane substrate, where the impregnated polymer is an aryl ether-free polyaromatic polymer based on a random copolymer structure containing two or more aromatic ring components. The polymer can be uncrosslinked or crosslinked, the latter of which confines the polymer within the pores of the porous membrane substrate and prevents leaching of the impregnated copolymer from the reinforced anion exchange membrane during operation in water. The reinforced anion exchange membrane may be useful in electrochemical energy conversion devices, such as AEM fuel cells, AEM electrolyzers, and flow batteries. The impregnated membranes of the present disclosure offer significantly improved mechanical (e.g., tensile) strength, chemical durability, and water management properties compared to currently available impregnated membranes.

[0011] In some embodiments, the impregnated ionic polymer has Formula I: [ka] (where Ar1, Ar2, Ar3, … and Ar n are different aryl groups that form a random copolymer, and Arn is between 2 and 20, each of a1, a2, a3, ... and an is independently 1 to 1,000,000; R1, R2, R3, … and R n (However, R n is 2 to 20) is [ka] Or a combination of these (where A is S, O, NH, SO 2、 A' comprises N, an alkyl group, or a combination thereof; X comprises a halide (e.g., Br); FG comprises NR3 + X - , NR3 + OH - , OH, NR2, SO3H, P(=O)(OH)2, CO2H, SO3 - M + , P(=O)(O - )22M + , CO2 - M + (M=Li, Na, K), linear polyquaternary ammonium groups, branched polyquaternary ammonium groups, or combinations thereof, and FG' is NR2 + X - , NR2 + OH - wherein R is an alkyl group (e.g., CH3 or CH2CH3), m is 0 to 20, and n is 0 to 20.) In one embodiment, a "random copolymer" is one that consists of two or more different monomers in a completely random order of repeat units.

[0012] Ar1, Ar2, Ar3, … and Ar n teeth, [ka] or a combination thereof (wherein R comprises an alkyl group (e.g., CH3 or CH2CH3), a halide (e.g., F), or a combination thereof; R' comprises H, an alkyl group (e.g., CH3 or CH2CH3), or a combination thereof; X comprises a halide; A comprises S, O, NH, SO2, an alkyl group (e.g., CH2 or CH2CH3), or a combination thereof; and n is 0 to 20).

[0013] The ionic polymer having two or more aromatic ring components is accommodated within the pores of the porous membrane substrate. In some embodiments, the porous substrate may be a highly porous thin film having a continuous pore structure from one side to the other. The porous substrate is hydrophobic and does not swell in water. The porous substrate preferably comprises a material selected from high molecular weight polyethylene, ultra-high molecular weight polyethylene, polytetrafluoroethylene, expanded polytetrafluoroethylene, or polypropylene. The thickness of the porous membrane substrate is preferably about 200 microns or less, more preferably less than about 50 microns. In some embodiments, the porous substrate has a porosity of more than 30%, preferably more than 70%. Preferred substrate membranes have pore sizes of 0.05 microns to 1.0 microns. In some embodiments, the pore-filled reinforced membrane contains more than 30% by weight, preferably more than 70% by weight, of the ionic polymer.

[0014] Some embodiments of the present disclosure include a novel method for making a reinforced anion exchange membrane, which includes reacting two or more aromatic compounds with a trifluoromethyl ketone compound under acidic conditions to produce an aryl ether-free polyaromatic polymer based on a random copolymer structure containing two or more aromatic ring components, reacting the polyaromatic with an amine to form an ionic polymer, dissolving the ionic polymer in a solvent to form a polymer solution, and impregnating a porous membrane substrate with the polymer solution to form the reinforced anion exchange membrane.

[0015] In some embodiments, R 1、 R 2、R 3、 …or R n teeth, [ka] It is partially crosslinked with a crosslinker selected from the group consisting of NHR2, N,N,N',N'-tetramethyl-1,6-hexanediamine, bis(2-dimethylaminoethyl) ether, diamines, multiamines, or combinations thereof, where R comprises H, an alkyl group (e.g., CH3 or CH2CH3), or combinations thereof, and n is 0 to 20. In some embodiments, the copolymer has a degree of crosslinking of 0% to 100%, or any subrange therebetween.

[0016] The cross-linking reaction occurs within the pores of the porous substrate, trapping the copolymer within the pores and preventing leaching of the impregnated copolymer from the reinforced anion exchange membrane during operation.

[0017] [Note] [Appendix 1] reacting two or more aromatic compounds with a trifluoromethyl ketone compound under acidic conditions to form a precursor copolymer; reacting the precursor copolymer with an amine to form an ionic polymer; dissolving the ionic polymer in a solvent to form a polymer solution; impregnating a porous membrane substrate with the polymer solution to form a reinforced anion exchange membrane; Including, Method for producing reinforced anion exchange membranes.

[0018] [Appendix 2] The aromatic compound is [ka] and combinations thereof, wherein R comprises an alkyl group (e.g., CH3 or CH2CH3), a halide (e.g., F), or a combination thereof; R' comprises H, an alkyl group (e.g., CH3 or CH2CH3), or a combination thereof; X comprises a halide; A comprises S, O, NH, SO2, an alkyl group (e.g., CH2 or CH2CH3), and a combination thereof; and n is 0 to 20.

[0019] [Appendix 3] The trifluoromethyl ketone compound is [ka] and combinations thereof (where A is S, O, NH, SO 2、 A' comprises N, an alkyl group, or a combination thereof; X is a halide (e.g., Br); and n is 0 to 20.

[0020] [Appendix 4] 2. The method of claim 1, wherein the amine is selected from the group consisting of trimethylamine, triethylamine, tripropylamine, tributylamine, triisobutylamine, tripentylamine, trihexylamine, N,N-diisopropylmethylamine, N-isopropyl-N-methyl-tert-butylamine, N-methylpiperidine, N-methylpyrrolidine, 1-ethylpyrrolidine, 1-butylpyrrolidine, 1,2,2,6,6-pentamethylpiperidine, diamines, multiamines, and combinations thereof.

[0021] [Appendix 5] The solvent is selected from the group consisting of toluene, tetrahydrofuran, dichloromethane, chloroform, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, nitrobenzene, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, methanol, ethanol, 1-propanol, 2-propanol, or a combination thereof.

[0022] [Appendix 6] 2. The method of claim 1, wherein the porous membrane substrate comprises a polymer selected from the group consisting of high molecular weight polyethylene, ultra-high molecular weight polyethylene, polytetrafluoroethylene, expanded polytetrafluoroethylene, polypropylene, or a combination thereof.

[0023] [Appendix 7] 2. The method of claim 1, wherein the porous membrane substrate has a thickness of less than about 200 microns.

[0024] [Appendix 8] 2. The method of claim 1, wherein the porous membrane substrate has a thickness of about 10 to 50 microns.

[0025] [Appendix 9] 2. The method of claim 1, wherein the ionic copolymer is based on Formula I. [ka] (However, Ar1, Ar n are different aryl groups forming a random copolymer, [ka] and combinations thereof, wherein R' comprises an alkyl group, a halide, or a combination thereof; n is 2 to 20; a1,… and a n each of which is independently from 10 to 1,000,000; R1,… and Rn Each of the [ka] (where x is between 0 and 20, FG is NR3 + X - , NR3 + OH - , OH, NR2, SO3H, P(=O)(OH)2, CO2H, SO3 - M + , P(=O)(O - )22M + , CO2 - M + (M=Li, Na, K), linear polyquaternary ammonium groups, branched polyquaternary ammonium groups, bridged polyquaternary ammonium groups, and combinations thereof; R is an alkyl group; and X is a halide.

[0026] [Appendix 10] a porous membrane substrate; an ionic polymer according to Formula I impregnated into the pores of the porous membrane substrate; A reinforced anion exchange membrane comprising: [ka] (where Ar1, Ar2, Ar3, … and Ar n are different aryl groups that form a random copolymer, and Ar n is between 2 and 20, each of a1, a2, a3, ... and an is independently 1 to 1,000,000; R1, R2, R3, … and R n (However, R n is 2 to 20) is [ka] Or a combination of these (where A is S, O, NH, SO 2、A' comprises N, an alkyl group, or a combination thereof; X comprises a halide (e.g., Br); FG comprises NR3 + X - , NR3 + OH - , OH, NR2, SO3H, P(=O)(OH)2, CO2H, SO3 - M + , P(=O)(O - )22M + , CO2 - M + (M=Li, Na, K), linear polyquaternary ammonium groups, branched polyquaternary ammonium groups, or combinations thereof, and FG' is NR2 + X - , NR2 + OH - wherein R is an alkyl group (e.g., CH3 or CH2CH3), m is 0 to 20, and n is 0 to 20.

[0027] [Appendix 11] Ar1, Ar2, Ar3, … and Ar n is, independently, [ka] and combinations thereof, wherein R comprises an alkyl group (e.g., CH3 or CH2CH3), a halide (e.g., F), or a combination thereof; R' comprises H, an alkyl group (e.g., CH3 or CH2CH3), or a combination thereof; X comprises a halide; A comprises S, O, NH, SO2, an alkyl group (e.g., CH2 or CH2CH3), and a combination thereof; and n is 0 to 20.

[0028] [Appendix 12] 10. The reinforced anion exchange membrane of claim 9, wherein the porous membrane substrate comprises a polymer selected from the group consisting of high molecular weight polyethylene, ultra-high molecular weight polyethylene, polytetrafluoroethylene, polypropylene, or a combination thereof.

[0029] [Appendix 13] 10. The reinforced anion exchange membrane of claim 9, wherein the thickness of the reinforced anion exchange membrane is about 200 microns or less.

[0030] [Appendix 14] 10. The reinforced anion exchange membrane according to claim 9, wherein the thickness of the reinforced anion exchange membrane is about 10 to 50 microns.

[0031] [Appendix 15] 10. The reinforced anion exchange membrane of claim 9, wherein the reinforced anion exchange membrane has an ion exchange capacity of about 0.5 to about 5.0 meq / g.

[0032] [Appendix 16] R 1、 R 2、 R 3、 …and R n Some of the [ka] 10. The reinforced anion exchange membrane of claim 9, wherein the membrane is crosslinked with a diamine selected from the group consisting of NHR2, N,N,N',N'-tetramethyl-1,6-hexanediamine, bis(2-dimethylaminoethyl)ether, diamines, multiamines, or combinations thereof, wherein R comprises H, an alkyl group (e.g., CH3 or CH2CH3), and combinations thereof, and n is 0 to 20.

[0033] [Appendix 17] a porous membrane substrate; an ionic polymer according to Formula II impregnated into the pores of the porous membrane substrate; A reinforced anion exchange membrane comprising: [ka] (where m and n are between 1 and 1,000,000.)

[0034] [Appendix 18] 17. The reinforced anion exchange membrane of claim 16, wherein the porous membrane substrate comprises a polymer selected from the group consisting of high molecular weight polyethylene, ultra-high molecular weight polyethylene, polytetrafluoroethylene, polypropylene, or a combination thereof.

[0035] [Appendix 19] 17. The reinforced anion exchange membrane of claim 16, wherein the thickness of the reinforced anion exchange membrane is about 200 microns or less.

[0036] [Appendix 20] 17. The reinforced anion exchange membrane according to claim 16, wherein the thickness of the reinforced anion exchange membrane is about 10 to 50 microns.

[0037] [Appendix 21] 17. The reinforced anion exchange membrane of claim 16, wherein the reinforced anion exchange membrane has an ion exchange capacity of about 0.5 to about 5.0 meq / g.

[0038] [Appendix 22] 2. The reinforced anion exchange membrane of claim 1, wherein the ionic copolymer is based on Formula I. [ka] (However, Ar1, Ar n are different aryl groups forming a random copolymer, [ka] and combinations thereof, wherein R' comprises an alkyl group, a halide, or a combination thereof; n is 2 to 20; a1,… and a n each of which is independently from 10 to 1,000,000; R1,… and Rn Each of the [ka] (where x is between 0 and 20, FG is NR3 + X - , NR3 + OH - , OH, NR2, SO3H, P(=O)(OH)2, CO2H, SO3 - M + , P(=O)(O - )22M + , CO2 - M + (M=Li, Na, K), linear polyquaternary ammonium groups, branched polyquaternary ammonium groups, bridged polyquaternary ammonium groups, and combinations thereof; R is an alkyl group; and X is a halide.

Claims

1. reacting two or more aromatic compounds with a trifluoromethyl ketone compound under acidic conditions to form a precursor copolymer; reacting the precursor copolymer with an amine to form an ionic polymer; dissolving the ionic polymer in a solvent to form a polymer solution; impregnating a porous membrane substrate with the polymer solution to form a reinforced anion exchange membrane; Including, Method for producing reinforced anion exchange membranes.

2. The aromatic compound is 【Chemistry 1】 and combinations thereof (wherein R is an alkyl group (e.g., CH ３ or CH ２ CH ３ ), halide (e.g., F), or combinations thereof, and R' is H, alkyl group (e.g., CH ３ or CH ２ CH ３ ), or a combination thereof, wherein X comprises a halide, and A comprises S, O, NH, SO ２ , alkyl groups (e.g., CH ２ or CH ２ CH ３ 2. The method of claim 1, wherein n is selected from the group consisting of:

3. The trifluoromethyl ketone compound is 【Chemistry 2】 and combinations thereof (where A is S, O, NH, SO ２、 A' comprises N, an alkyl group, or a combination thereof; X is a halide (e.g., Br); and n is 0 to 20.

4. 2. The method of claim 1, wherein the amine is selected from the group consisting of trimethylamine, triethylamine, tripropylamine, tributylamine, triisobutylamine, tripentylamine, trihexylamine, N,N-diisopropylmethylamine, N-isopropyl-N-methyl-tert-butylamine, N-methylpiperidine, N-methylpyrrolidine, 1-ethylpyrrolidine, 1-butylpyrrolidine, 1,2,2,6,6-pentamethylpiperidine, diamines, multiamines, and combinations thereof.

5. The solvent is selected from the group consisting of toluene, tetrahydrofuran, dichloromethane, chloroform, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, nitrobenzene, dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methyl-2-pyrrolidone, methanol, ethanol, 1-propanol, 2-propanol, or a combination thereof. The method of claim 1.

6. 10. The method of claim 1, wherein the porous membrane substrate comprises a polymer selected from the group consisting of high molecular weight polyethylene, ultra-high molecular weight polyethylene, polytetrafluoroethylene, expanded polytetrafluoroethylene, polypropylene, or a combination thereof.

7. The method of claim 1 , wherein the porous membrane substrate has a thickness of less than about 200 microns.

8. The method of claim 1, wherein the porous membrane substrate has a thickness of about 10 to 50 microns.

9. The method of claim 1 , wherein the ionic copolymer is according to Formula I: 【Transformation 3】 (However, Ar １ , Ar ｎ are different aryl groups forming a random copolymer, 【Chemistry 4】 and combinations thereof, wherein R′ comprises an alkyl group, a halide, or a combination thereof; n is 2 to 20; a １ , ... and a ｎ each is independently 10 to 1,000,000; R １ , ... and R ｎ Each of the 【Transformation 5】 (where x is between 0 and 20, FG is NR ３ ＋ X － , N.R. ３ ＋ OH － , O.H., N.R. ２ , S.O. ３ H, P (=O) (OH) ２ , CO ２ H, SO ３ － M ＋ , P(=O)(O － ) ２ 2M ＋ , CO ２ － M ＋ (M=Li, Na, K), linear polyquaternary ammonium groups, branched polyquaternary ammonium groups, bridged polyquaternary ammonium groups, and combinations thereof; R is an alkyl group; and X is a halide.

10. a porous membrane substrate; an ionic polymer according to Formula I impregnated into the pores of said porous membrane substrate; A reinforced anion exchange membrane comprising: 【Transformation 6】 (However, Ar １ , Ar ２ , Ar ３ , … and Ar ｎ are different aryl groups that form a random copolymer, and Ar ｎ is between 2 and 20, each of a1, a2, a3, ... and an independently ranges from 1 to 1,000,000; R １ , R ２ , R ３ , … and R ｎ (However, R ｎ is 2 to 20) is 【Transformation 7】 Or a combination thereof (where A is S, O, NH, SO ２、 A' comprises N, an alkyl group, or a combination thereof; X comprises a halide (e.g., Br); FG comprises NR ３ ＋ X － , N.R. ３ ＋ OH － , O.H., N.R. ２ , S.O. ３ H, P (=O) (OH) ２ , CO ２ H, SO ３ － M ＋ , P(=O)(O － ) ２ 2M ＋ , CO ２ － M ＋ (M=Li, Na, K), linear polyquaternary ammonium groups, branched polyquaternary ammonium groups, or combinations thereof; FG′ is NR ２ ＋ X － , N.R. ２ ＋ OH － wherein R is an alkyl group (e.g., CH ３ or CH ２ CH ３ ) wherein m is 0 to 20 and n is 0 to 20.

11. Ar １ , Ar ２ , Ar ３ , … and Ar ｎ is, independently, 【Transformation 8】 and combinations thereof (wherein R is an alkyl group (e.g., CH ３ or CH ２ CH ３ ), halide (e.g., F), or combinations thereof, and R' is H, alkyl group (e.g., CH ３ or CH ２ CH ３ ), or a combination thereof, wherein X comprises a halide, and A comprises S, O, NH, SO ２ , alkyl groups (e.g., CH ２ or CH ２ CH ３ 10. The reinforced anion exchange membrane of claim 9, wherein the anion exchange membrane is selected from the group consisting of:

12. 10. The reinforced anion exchange membrane of claim 9, wherein the porous membrane substrate comprises a polymer selected from the group consisting of high molecular weight polyethylene, ultra-high molecular weight polyethylene, polytetrafluoroethylene, polypropylene, or a combination thereof.

13. 10. The reinforced anion exchange membrane of claim 9, wherein the thickness of the reinforced anion exchange membrane is about 200 microns or less.

14. The reinforced anion exchange membrane of claim 9, wherein the thickness of the reinforced anion exchange membrane is about 10 to 50 microns.

15. 10. The reinforced anion exchange membrane of claim 9, wherein the reinforced anion exchange membrane has an ion exchange capacity of about 0.5 to about 5.0 meq / g.

16. R １、 R ２、 R ３、 …and R ｎ Some of the 【Chemistry 9】 NHR ２ , N,N,N',N'-tetramethyl-1,6-hexanediamine, bis(2-dimethylaminoethyl)ether, diamines, multiamines, or combinations thereof (wherein R is H, alkyl group (e.g., CH ３ or CH ２ CH ３ 10. The reinforced anion exchange membrane of claim 9, wherein the anion exchange membrane is crosslinked with a diamine selected from the group consisting of:

17. a porous membrane substrate; an ionic polymer according to Formula II impregnated into the pores of the porous membrane substrate; A reinforced anion exchange membrane comprising: 【Chemistry 10】 (where m and n are from 1 to 1,000,000.)

18. 17. The reinforced anion exchange membrane of claim 16, wherein the porous membrane substrate comprises a polymer selected from the group consisting of high molecular weight polyethylene, ultra-high molecular weight polyethylene, polytetrafluoroethylene, polypropylene, or a combination thereof.

19. 17. The reinforced anion exchange membrane of claim 16, wherein the thickness of the reinforced anion exchange membrane is about 200 microns or less.

20. 17. The reinforced anion exchange membrane of claim 16, wherein the thickness of the reinforced anion exchange membrane is about 10 to 50 microns.

21. 17. The reinforced anion exchange membrane of claim 16, wherein the reinforced anion exchange membrane has an ion exchange capacity of about 0.5 to about 5.0 meq / g.

22. The reinforced anion exchange membrane of claim 1 , wherein the ionic copolymer is based on Formula I: 【Chemistry 11】 (However, Ar １ , Ar ｎ are different aryl groups forming a random copolymer, 【Chemistry 12】 and combinations thereof, wherein R′ comprises an alkyl group, a halide, or a combination thereof; n is 2 to 20; a １ , ... and a ｎ each is independently 10 to 1,000,000; R １ , ... and R ｎ Each of the 【Chemistry 13】 (where x is between 0 and 20, FG is NR ３ ＋ X － , N.R. ３ ＋ OH － , O.H., N.R. ２ , S.O. ３ H, P (=O) (OH) ２ , CO ２ H, SO ３ － M ＋ , P(=O)(O － ) ２ 2M ＋ , CO ２ － M ＋ (M=Li, Na, K), linear polyquaternary ammonium groups, branched polyquaternary ammonium groups, bridged polyquaternary ammonium groups, and combinations thereof; R is an alkyl group; and X is a halide.

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