CATION-EXCHANGE POLYMER AND METHODS OF PRODUCTION

Abstract

The present disclosure provides a method of producing a cation exchange polymer, the method includes polymerizing an anionic monomer in the presence of a polymerizable crosslinker having a cationic functional group. A sufficient amount of anionic monomer is used to provide both the anionic charges necessary for cation exchange, and the anionic charges necessary to pair with the cationic functional groups in the crosslinker.

Claims

1. A method of producing a cation exchange polymer, the method comprising: polymerizing, in a water-based solution, an anionic monomer in the presence of a crosslinker having a cationic functional group; wherein the anionic monomer comprises at least one polymerizable functional group, and the cationic crosslinker comprises at least two polymerizable functional groups; wherein the anionic monomer and the cationic crosslinker are soluble in the water-based solution, and the amounts of anionic monomer and cationic crosslinker are such that there is a molar excess of anionic charges in the polymerized cation exchange polymer.

2. The method according to claim 1, wherein the anionic monomer and the crosslinker are polymerized in a molar ratio such that there are from about 3:1 to about 1.8:1 anionic charges to cationic charges.

3. The crosslinker according to claim 1, wherein the polymerizable functional groups are alkenyl-based functional groups, such as a vinyl-based functional group, an acrylate-based functional group, a methacrylate-based functional group, an acrylamide-based functional group, or a methacrylamide-based functional group.

4. The method according to claim 1, wherein the water-based solution is at least 50% water by weight, such as at least 80% water, at least 90%, at least 95%, or at least 99% water by weight.

5. The method according to claim 1, wherein the cationic crosslinker comprises at least one quaternary ammonium functional group, or at least one pyridinium-based functional group.

6. The method according to claim 5, wherein the cationic crosslinker has a chemical structure according to Formula (I):
P.sub.1Z.sub.1N.sup.+(R.sub.1)(R.sub.2)Z.sub.2P.sub.2 Formula (I) wherein P.sub.1 and P.sub.2 are each, independently, an alkenyl-based functional group; Z.sub.1 and Z.sub.2 are each, independently, an alkyl-based or aryl-based linker; and R.sub.1 and R.sub.2 are each, independently, an alkyl group, and preferably methyl.

7. The method according to claim 6, wherein P.sub.1 and P.sub.2 are independently selected from the group consisting of: ##STR00024##

8. The method according to claim 6, wherein Z.sub.1 and Z.sub.2 are independently selected from the group consisting of: optionally functionalized aryl; and C.sub.1-20 alkyl optionally substituted with hydroxyl.

9. The method according to claim 8, wherein the optionally functionalized aryl is ##STR00025##

10. The method according to claim 8, wherein the C.sub.1-20 alkyl optionally substituted with hydroxyl is: ethyl, propyl, or 2-hydroxy propyl.

11. The method according to claim 1, wherein the cationic crosslinker is: ##STR00026##

12. The method according to claim 1, wherein the cationic crosslinker has a structure according to Formula (II) or (Ill): ##STR00027##

13. The method according to claim 12, wherein the cationic crosslinker has the structure: ##STR00028## where x is an integer from 0 to 100.

14. The method according to claim 1, wherein the anionic monomer has a chemical structure according to Formula (IV):
P.sub.3Z.sub.3-Q Formula (IV) wherein P.sub.3 is an alkenyl functional group; Q is SO.sub.3.sup., OPO.sub.3.sup., or COO.sup.; and Z.sub.3 is an optionally functionalized alkyl-based linker, or an optionally functionalized aryl-based linker.

15. The method according to claim 14, wherein Q is SO.sub.3.

16. The method according to claim 14, wherein P.sub.3 is selected from the group consisting of: ##STR00029##

17. The method according to claim 14, wherein Z.sub.3 is aryl or C.sub.1-20 alkyl.

18. The method according to claim 17, wherein Z.sub.3 is: ##STR00030##

19. The method according to claim 1, wherein the anionic monomer is: 2-acrylamido-2-methyl-1-propanesulfonic acid, 4-vinyl benzenesulfonic acid, 2-sulfoethyl methacrylate, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate, or a salt thereof.

20. The method according to claim 1, wherein the anionic monomer has a molecular weight of less than 300 per anionic charge.

21. The method according to claim 1, wherein the polymerization is performed on a backing to generate a cation exchange membrane.

22. The method according to claim 1, wherein the polymerization is performed on a carbon electrode, such as to generate a non-faraday carbon electrode for use in an electrodialysis reversal stack.

23. A cation-exchange polymer made according to the method of claim 1.

24. A cation-exchange polymer comprising both cationic functional groups and anionic functional groups, wherein the anionic functional groups are in sufficient excess that the polymer has an ion exchange capacity of at least 1 meq/g.

25. The cation-exchange polymer according to claim 24, wherein the anionic functional group and the cationic functional group are present in a molar ratio from about 3:1 to 1.8:1, anionic charges to cationic charges.

26. The cation-exchange polymer according to claim 24, wherein the anionic functional group is derived from an anionic monomer having a molecular weight of less than 300 per anionic charge.

27. A cation-exchange membrane comprising a backing and the cation-exchange polymer according to claim 23.

28. A carbon electrode coated with the cation-exchange polymer according to claim 23.

Description

DETAILED DESCRIPTION

[0018] The singular forms a, an, and the include plural referents unless the context clearly dictates otherwise. The endpoints of all ranges reciting the same characteristic are independently combinable and inclusive of the recited endpoint. All references are incorporated herein by reference.

[0019] The modifier about used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., includes the tolerance ranges associated with measurement of the particular quantity).

[0020] Optional or optionally means that the subsequently described event, or circumstance may or may not occur, or that the subsequently identified material may or may not be present, and that the description includes instances where the event or circumstance occurs or where the material is present, and instances where the event or circumstance does not occur or the material is not present.

[0021] In the context of the present disclosure, a water based solution would be understood to refer to a reaction solution that is at least 50% water by weight. In some examples, the water-based solution is substantially only water. In some particular examples, the water-based solution is more than 80% water by weight, such as more than 90% water. In some further examples, the water-based solution is more than 95% water by weight. In other particular examples, the water-based solution is more than 99% water by weight. In some examples, the water-based solution does not include any additional solvents. The remaining portion of the water-based solution may be an organic solvent, such as N-methyl-2-pyrrolidone, propylene glycol, dipropylene glycol, 1-propanol, isopropyl alcohol, or any other water-miscible organic solvent. It should be understood that the purity of the water-based solution is determined excluding the reaction materials, such as the crosslinker, monomer, catalyst, and salts associated with any of the reaction materials.

[0022] In the context of the present disclosure, it should be understood that discussion of a range of values, such as at least 50% or from 70 to 90, is intended to include all of the ranges encompassed by the specifically disclosed range. For example, explicit disclosure of the range at least 50% is intended to also be a disclosure of the ranges: 50% to 60%, 70% to 100%, and 75% to 90%.

[0023] In the context of the present disclosure, optionally functionalized alkyl should be understood to encompass a linear or branched C.sub.1-20 alkyl; and optionally functionalized aryl should be understood to encompass a C.sub.5-20 aryl. An optional functionalization may be the replacement of one or more hydrogen atoms with any combination of: a halide, a heteroatom, an optionally functionalized alkyl, or an optionally functionalized aryl group. In particular examples, the optionally functionalized alkyl does not have more than 20 carbon atoms, including the carbon atoms in the optional functional groups. In particular examples, the optionally functionalized aryl does not have more than 20 carbon atoms, including the carbon atoms in the optional functional groups. The optional functionalization may be the replacement of one or more carbon atoms with a heteroatom. The optional functionalization may result in the alkyl or aryl group being a heteroalkyl or heteroaryl group. The optional functionalization of an alkyl or aryl group may include replacement of one or more hydrogen atoms, and the replacement of one or more carbon atoms.

[0024] An example of an optional functionalization of the alkyl or aryl group is the replacement of a carbon or hydrogen with, or the addition to the compound of, a non-charged functional group that increases the miscibility of the compound in water. An example of such a functionalization includes addition of an oxygen atom to result in: an ether bond, a hydroxyl group, or a heteroaryl compound. Another example of such a functionalization includes the addition of a nitrogen atom to result in a heteroaryl compound. The alkyl or aryl group may be functionalized with a plurality of functional groups. In view of the above, it should be understood that the term optionally functionalized alkyl in the context of a linking group includes, for example: C.sub.6H.sub.12; C.sub.3H.sub.6(CHOH)C.sub.2H.sub.4; C.sub.3H.sub.6OC.sub.3H.sub.6; and cyclic alkyl C.sub.6H.sub.8(OH).sub.2. Similarly, it should be understood that the term optionally functionalized aryl in the context of a linking group includes, for example: benzyl; 2-hydroxy benzyl; and 2-methylpyridine, where the two groups being linked are joined to the benzyl, 2-hydroxy benzyl, or 2-methylpyridine in place of hydrogen atoms.

[0025] In the context of the present disclosure, it should be understood that anionic monomer and monomer having an anionic group are equivalent, and both terms refer to both: (i) a monomer having a negative charge and a counter ion, such as 2-Acrylamido-2-methyl-1-propanesulfonate sodium salt, and (ii) a monomer having a neutral charge under one or more preparation conditions but a negative charge in the polymer under cation-exchange conditions, such as 2-Acrylamido-2-methyl-1-propanesulfonic acid.

[0026] Generally, the present disclosure provides a method where a molar excess of an anionic monomer is polymerized in the presence of a crosslinker having a cationic functional group to generate a polymer having sufficient anionic charges per gram for cation exchange. The amount of anionic monomer is selected to be sufficient to neutralize the cationic functional groups in the crosslinker, and provide the anionic charges necessary for the polymer to act as a cation-exchange polymer. The anionic equivalency (e.g. meq/gram) of the polymer is determined by the molar excess of the anionic charges. The molar excess is determined based on the moles of anionic charges vs. the moles of cationic charges.

[0027] A cationic crosslinker suitable for a method according to the present disclosure includes at least one cationic functional group and at least two polymerizable functional groups. In particular examples, the cationic crosslinker includes only one cationic functional group.

[0028] An anionic monomer suitable for a method according to the present disclosure includes at least one anionic functional group and at least one polymerizable functional group.

[0029] The polymerizable functional groups are all polymerizable under the same reaction conditions. The polymerizable functional group may be an alkenyl-based functional group, such as a vinyl-based functional group, an acrylate-based functional group, a methacrylate-based functional group, an acrylamide-based functional group, or a methacrylamide-based functional group. It should be understood that, in the context of the present disclosure, functional groups based on the noted chemical structures would include bonds to link the functional groups to the rest of the molecules. For example, a methacrylamide-based functional group refers at least to:

##STR00001##

The functional groups based on the noted chemical structures may include optional functionalization of the base chemical structure. For example, the term methacrylamide-based functional group also refers to compounds of formula:

##STR00002##

The C.sub.2-C.sub.12 alkyl is optionally functionalized.

[0030] The cationic and anionic functional groups are joined to their respective polymerizable functional groups by linkers, such as an optionally functionalized alkyl or optionally functionalized aryl group. The linker joining the cationic functional group to one of the polymerizable groups may be different from the linker joining the cationic functional group to the other polymerizable group.

[0031] In some examples, the cationic crosslinker has a chemical structure according to Formula (I): P.sub.1Z.sub.1N.sup.+(R.sub.1)(R.sub.2)Z.sub.2P.sub.2 where: P.sub.1 and P.sub.2 are each, independently, an alkenyl-based functional group; Z.sub.1 and Z.sub.2 are each, independently, an optionally functionalized alkyl-based linker or an optionally functionalized aryl-based linker; and R.sub.1 and R.sub.2 are each, independently, an optionally functionalized alkyl group, such as methyl.

[0032] P.sub.1 and P.sub.2 may be independently, for example: a vinyl-based functional group, an acrylate-based functional group, a methacrylate-based functional group, an acrylamide-based functional group, or a methacrylamide-based functional group. Particular examples of P.sub.1 and P.sub.2 include:

##STR00003##

[0033] Z.sub.1 and Z.sub.2 may be, for example, independently selected from the group consisting of: optionally functionalized aryl, such as

##STR00004##

and C.sub.1-20 alkyl optionally substituted with hydroxyl, such as ethyl, propyl, or 2-hydroxy propyl.

[0034] In specific examples, the cationic crosslinker may be:

##STR00005##

[0035] In other examples, the cationic crosslinker may be a compound as disclosed in U.S. Pat. No. 5,118,717 (incorporated herein by reference), such as a compound according to Formula (II):

##STR00006##

where R.sub.3 is an alkyloxy or an alkylimino group; and R.sub.4 is a benzyl or an alkyl group, and R.sub.5 and R.sub.6 are methyl or higher alkyl group (such as C.sub.2-C.sub.4 alkyl). In specific examples, the cationic crosslinker may be:

##STR00007##

[0036] In yet other examples, the cationic crosslinker be a compound as disclosed in U.S. Pat. No. 7,968,663 (incorporated herein by reference), such as a compound according to Formula (III)

##STR00008##

where R.sub.7 is hydrogen or a C.sub.1-C.sub.12 alkyl group; R.sub.8 is [CH.sub.2].sub.n; R.sub.9 is [CH.sub.2CH(OH)].sub.2X; R.sub.10 and R.sub.11 are each, independently, [CH.sub.2].sub.mCH.sub.3; W is oxygen or NR.sub.12 where R.sub.12 is hydrogen or [CH.sub.2]r-CH.sub.3; X is a bridging group or atom; m in each instance is an integer from 0 to 20; and n is an integer from 1 to 20. X may be a hydrocarbon group, an inorganic group or inorganic atom. X may be, for example: a C.sub.1-C.sub.30 alkyl group, C.sub.1-C.sub.30 alkyl ether group, C.sub.6-C.sub.30 aromatic group, C.sub.6-C.sub.30 aromatic ether group, or a siloxane. X may be, for example: a C.sub.1-C.sub.6 alkyl group, C.sub.1-C.sub.6 alkyl ether group, a C.sub.6-C.sub.10 aromatic group, or a C.sub.6-C.sub.10 aromatic ether group. X may be, for example: methyl, ethyl, propyl, butyl, isobutyl, phenyl, 1,2-cyclohexanedicarboxylate, bisphenol A, diethylene glycol, resorcinol, cyclohexanedimethanol, poly(dimethylsiloxane), 2,6-tolylene diisocyanate, 1,3-butadiene or dicyclopentadiene.

[0037] In specific examples, the cationic crosslinker may be:

##STR00009##

where x is an integer from 0 to 100.

[0038] Crosslinkers according to the present disclosure may be prepared by reacting, in water, a polymerizable tertiary amine with a polymerizable alkylating compound to result in a quaternary ammonium compound having two polymerizable functional groups. The polymerizable alkylating compound may include an epoxide and the alkylation may be performed under acidic conditions. The counter-ion of the produced cationic crosslinker may be exchanged though reaction with an anionic monomer. The resulting cationic crosslinker includes a cationic quaternary ammonium group linked to two polymerizable functional groups, and a counter-ion having a polymerizable functional group. The produced crosslinker may be mixed with additional anionic monomer, and a polymerizing initiator. A sufficient amount of anionic monomer may be added to result in a molar ratio from about 3:1 to about 1.8:1 (monomer:crosslinker).

[0039] An anionic monomer that may be used in a method according to the present disclosure may have chemical structure according to Formula (IV):

P.sub.3Z.sub.3-Q Formula (IV)

wherein

[0040] P.sub.3 is an alkenyl-based functional group;

[0041] Q is SO.sub.3.sup., OPO.sub.3.sup., or COO.sup.; and

[0042] Z.sub.3 is an optionally functionalized alkyl-based linker, or an optionally functionalized aryl-based linker.

[0043] P.sub.3 may be, for example: a vinyl-based functional group, an acrylate-based functional group, a methacrylate-based functional group, an acrylamide-based functional group, or a methacrylamide-based functional group. Particular examples of P.sub.3 include:

##STR00010##

[0044] Z.sub.3 may be, for example, aryl or C.sub.1-20 alkyl. In particular examples, Z.sub.3 is

##STR00011##

[0045] The anionic monomer, absent any counter-ion, may have a molecular weight of less than 300 per anionic charge. Specific examples of an anionic monomer which may be used in a method of the present disclosure include: 2-Acrylamido-2-methyl-1-propanesulfonate (AMPS), 4-vinylbenzenesulfonate, 2-sulfoethylmethacrylate, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate, and salts thereof.

[0046] Polymerizing initiators that may be used in methods according to the present disclosure include water-soluble azo-based initiators, such as 2,2-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044) and 2,2-Azobis(2-methylpropionamidine) dihydrochloride (V-50).

[0047] The mixture of cationic crosslinker, anionic monomer, and initiator may be cast on a backing and cured to initiate polymerization. The backing may be, for example, reinforcing material, such as a fabric, a felt, a microporous support (for example a micro- or ultra-filtration material), or a woven or nonwoven cloth. The backing may be made, for example, of polypropylene, polyester, polyacrylonitrile, polyvinyl chloride or polyamide. The thickness of the resulting membrane may be from about 0.1 mm to about 0.77 mm. The curing may include exposure of the reaction mixture to an elevated temperature, such as about 50 C. to about 120 C., and/or to a UV light. In particular methods, the curing includes increasing the temperature from room temperature to about 120 C. using multiple heating tables.

[0048] The non-polymerizable counter-ion of the cationic crosslinker may be the conjugate base of a strong acid, such as an acid having a pKa less than 1. Examples of such non-polymerizable counter-ions include Cl.sup., CH.sub.3SO.sub.3.sup., NO.sub.3.sup., HSO.sub.4.sup., and citrate.

ExamplesSummary

[0049] Specific examples are discussed in greater detail below. Table 1 is a summary of the reagents and amounts used in the discussed examples. GMA=glycidyl methacrylate; DMAPMA=N-[3-(dimethylamino)propyl]methacrylamide; DMAEMA=2-(dimethylamino)ethyl methacrylate; VBC=4-vinylbenzyl chloride; AMPS=2-acrylamido-2-methyl-1-propanesulfonic acid; and SSS=sodium 4-vinylbenzenesulfonate. AMPS 1 and SSS 1 refer to the AMPS and SSS compounds used as counter ions to the quaternary ammonium. AMPS 2 and SSS 2 refer to the AMPS and SSS compounds used as the source of excess anionic charges. In all of the examples, the total amount of anionic monomer present in a polymerization mixture is the sum of AMPS1 and AMPS2, or of SSS1 and SSS2.

TABLE-US-00001 TABLE 1 H.sub.2O GMA DMAPMA AMPS 1 AMPS 2 VA-044 Theoretical Example (g) (g) (g) (g) (g) (g) IEC (meq/g) 1 50 8.53 10.2 12.5 18.8 1 1.8 2 20.4 4.3 5.1 6.3 7.1 1 1.5 3 18.2 4.3 5.1 6.3 5.3 1 1.2 H.sub.2O GMA DMAPMA AMPS 1 AMPS 2 V-50 (g) (g) (g) (g) (g) (g) 4 18.2 4.3 5.1 6.3 5.3 1 1.2 5 18.2 4.3 5.1 6.3 5.3 1 1.2 H.sub.2O GMA DMAEMA AMPS 1 AMPS 2 VA-044 (g) (g) (g) (g) (g) (g) 6 23.1 4.3 4.71 6.3 9.4 1 1.8 7 20.6 4.3 4.71 6.3 6.9 1 1.5 H.sub.2O GMA DMAPMA SSS 1 SSS 2 V-50 (g) (g) (g) (g) (g) (g) 8 52.4 8.6 10.2 12.6 10.4 1 1.2 H.sub.2O GMA DMAPMA SSS 1 SSS 2 VA-044 (g) (g) (g) (g) (g) (g) 9 52.4 8.6 10.2 12.6 10.4 1 1.2 H.sub.2O GMA DMAPMA SSS 1 SSS 2 V-50 (g) (g) (g) (g) (g) (g) 10 46.7 8.6 10.2 12.6 10.4 1 1.2 H.sub.2O GMA DMAEMA SSS 1 SSS 2 V-50 (g) (g) (g) (g) (g) (g) 11 57 8.4 9.3 12.2 10.4 1 1.2 H.sub.2O VBC DMAPMA AMPS 1 AMPS 2 VA-044 (g) (g) (g) (g) (g) (g) 12 45 9.3 10.4 12.6 22.8 1 2

Example 1

[0050] Water (50 g) was added to a flask. DMAPMA (10.2 g) was added to the water with stirring. Hydrochloric acid (3.3 g of 33% HCl) was slowly added, maintaining the temperature below 60 C. using a water bath. GMA (8.53 g) was added to the solution and the temperature of the water bath was raised to about 55 C. The reaction was allowed to stir for about 1 hour, resulting in a crosslinker having a quaternary amine group of the following structure:

##STR00012##

[0051] AMPS (12.5 g) was added to the solution, resulting in a crosslinker according to the present disclosure. This AMPS is identified as AMPS 1 in Table 1. Additional AMPS (18.8 g) was added and allowed to dissolve. This additional AMPS is identified as AMPS 2 in Table 1.

[0052] The resulting mixture was allowed to cool to room temperature. VA-044 (1 g) was added as a polymerizing initiator. The mixture was cast on a backing to result in a membrane having thickness of about 0.6 mm, and cured in an oven at 80-90 C.

[0053] The resulting membrane has a water content of about 50% and an IEC of about 1.8 meq/g.

Example 2

[0054] Water (20.4 g) was added to a flask. DMAPMA (5.1 g) was added to the water with stirring. Hydrochloric acid (3.3 g of 33% HCl) was slowly added, maintaining the temperature below 60 C. using a water bath. GMA (4.3 g) was added to the solution and the temperature of the water bath was raised to about 55 C. The reaction was allowed to stir for about 1 hour, resulting in a crosslinker having a quaternary amine group of the following structure:

##STR00013##

[0055] AMPS (6.3 g) was added to the solution, resulting in a crosslinker according to the present disclosure. This AMPS is identified as AMPS 1 in Table 1. Additional AMPS (7.1 g) was added and allowed to dissolve. This additional AMPS is identified as AMPS 2 in Table 1.

[0056] The resulting mixture was allowed to cool to room temperature. VA-044 (1 g) was added as a polymerizing initiator. The mixture was cast on a backing to result in a membrane having thickness of about 0.6 mm, and cured in an oven at 80-90 C.

[0057] The resulting membrane has a water content of about 50% and an IEC of about 1.5 meq/g.

Example 3

[0058] Water (18.2 g) was added to a flask. DMAPMA (5.1 g) was added to the water with stirring. Methanesulfonic acid (2.8 g) was slowly added, maintaining the temperature below 60 C. using a water bath. GMA (4.3 g) was added to the solution and the temperature of the water bath was raised to about 55 C. The reaction was allowed to stir for about 1 hour, resulting in a crosslinker having a quaternary amine group of the following structure:

##STR00014##

[0059] AMPS (6.3 g) was added to the solution, resulting in a crosslinker according to the present disclosure. This AMPS is identified as AMPS 1 in Table 1. Additional AMPS (5.3 g) was added and allowed to dissolve. This additional AMPS is identified as AMPS 2 in Table 1.

[0060] The resulting mixture was allowed to cool to room temperature. VA-044 (1 g) was added as a polymerizing initiator. The mixture was cast on a backing to result in a membrane having thickness of about 0.6 mm, and cured in an oven at 80-90 C.

[0061] The resulting membrane has a water content of about 50% and an IEC of about 1.2 meq/g.

Example 4

[0062] Water (18.2 g) was added to a flask. DMAPMA (5.1 g) was added to the water with stirring. Methanesulfonic acid (2.8 g) was slowly added, maintaining the temperature below 60 C. using a water bath. GMA (4.3 g) was added to the solution and the temperature of the water bath was raised to about 55 C. The reaction was allowed to stir for about 1 hour, resulting in a crosslinker having a quaternary amine group of the following structure:

##STR00015##

[0063] AMPS (6.3 g) was added to the solution, resulting in a crosslinker according to the present disclosure. This AMPS is identified as AMPS 1 in Table 1. Additional AMPS (5.3 g) was added and allowed to dissolve. This additional AMPS is identified as AMPS 2 in Table 1. Sodium bicarbonate (4.7 g) was added to convert the AMPS 2 to its sodium form.

[0064] The resulting mixture was allowed to cool to room temperature. V-50 (1 g) was added as a polymerizing initiator. The mixture was cast on a backing to result in a membrane having thickness of about 0.6 mm, and cured in an oven at 80-90 C.

[0065] The resulting membrane has a water content of about 50% and an IEC of about 1.2 meq/g.

Example 5

[0066] Water (18.2 g) was added to a flask. DMAPMA (5.1 g) was added to the water with stirring. Methanesulfonic acid (2.8 g) was slowly added, maintaining the temperature below 60 C. using a water bath. GMA (4.3 g) was added to the solution and the temperature of the water bath was raised to about 55 C. The reaction was allowed to stir for about 1 hour, resulting in a crosslinker having a quaternary amine group of the following structure:

##STR00016##

[0067] AMPS (6.3 g) was added to the solution, resulting in a crosslinker according to the present disclosure. This AMPS is identified as AMPS 1 in Table 1. Additional AMPS (5.3 g) was added and allowed to dissolve. This additional AMPS is identified as AMPS 2 in Table 1. Sodium hydroxide (2.2 g) was added to convert the AMPS 2 to its sodium form.

[0068] The resulting mixture was allowed to cool to room temperature. V-50 (1 g) was added as a polymerizing initiator. The mixture was cast on a backing to result in a membrane having thickness of about 0.6 mm, and cured in an oven at 80-90 C.

[0069] The resulting membrane has a water content of about 50% and an IEC of about 1.2 meq/g.

Example 6

[0070] Water (23.1 g) was added to a flask. DMAEMA (4.71 g) was added to the water with stirring. Methanesulfonic acid (2.6 g) was slowly added, maintaining the temperature below 60 C. using a water bath. GMA (4.3 g) was added to the solution and the temperature of the water bath was raised to about 55 C. The reaction was allowed to stir for about 1 hour, resulting in a crosslinker having a quaternary amine group of the following structure:

##STR00017##

[0071] AMPS (6.3 g) was added to the solution, resulting in a crosslinker according to the present disclosure. This AMPS is identified as AMPS 1 in Table 1. Additional AMPS (9.4 g) was added and allowed to dissolve. This additional AMPS is identified as AMPS 2 in Table 1.

[0072] The resulting mixture was allowed to cool to room temperature. VA-044 (1 g) was added as a polymerizing initiator. The mixture was cast on a backing to result in a membrane having thickness of about 0.6 mm, and cured in an oven at 80-90 C.

[0073] The resulting membrane has a water content of about 50% and an IEC of about 1.8 meq/g.

Example 7

[0074] Water (20.6 g) was added to a flask. DMAEMA (4.71 g) was added to the water with stirring. Methanesulfonic acid (2.6 g) was slowly added, maintaining the temperature below 60 C. using a water bath. GMA (4.3 g) was added to the solution and the temperature of the water bath was raised to about 55 C. The reaction was allowed to stir for about 1 hour, resulting in a crosslinker having a quaternary amine group of the following structure:

##STR00018##

[0075] AMPS (6.3 g) was added to the solution, resulting in a crosslinker according to the present disclosure. This AMPS is identified as AMPS 1 in Table 1. Additional AMPS (6.9 g) was added and allowed to dissolve. This additional AMPS is identified as AMPS 2 in Table 1.

[0076] The resulting mixture was allowed to cool to room temperature. VA-044 (1 g) was added as a polymerizing initiator. The mixture was cast on a backing to result in a membrane having thickness of about 0.6 mm, and cured in an oven at 80-90 C.

[0077] The resulting membrane has a water content of about 50% and an IEC of about 1.5 meq/g.

Example 8

[0078] Water (52.4 g) was added to a flask. DMAPMA (8.6 g) was added to the water with stirring. Hydrochloric acid (6.6 g of 33% HCl) was slowly added, maintaining the temperature below 60 C. using a water bath. GMA (8.6 g) was added to the solution and the temperature of the water bath was raised to about 55 C. The reaction was allowed to stir for about 1 hour, resulting in a crosslinker having a quaternary amine group of the following structure:

##STR00019##

[0079] SSS (12.6 g) was added to the solution, resulting in a crosslinker according to the present disclosure. This SSS is identified as SSS 1 in Table 1. Additional SSS (10.4 g) was added and allowed to dissolve. This additional SSS is identified as SSS 2 in Table 1.

[0080] The resulting mixture was allowed to cool to room temperature. V-50 (1 g) was added as a polymerizing initiator. The mixture was cast on a backing to result in a membrane having thickness of about 0.6 mm, and cured in an oven at 80-90 C.

[0081] The resulting membrane has a water content of about 55% and an IEC of about 1.2 meq/g.

Example 9

[0082] Water (52.4 g) was added to a flask. DMAPMA (10.2 g) was added to the water with stirring. Hydrochloric acid (6.6 g of 33% HCl) was slowly added, maintaining the temperature below 60 C. using a water bath. GMA (8.6 g) was added to the solution and the temperature of the water bath was raised to about 55 C. The reaction was allowed to stir for about 1 hour, resulting in a crosslinker having a quaternary amine group of the following structure:

##STR00020##

[0083] SSS (12.6 g) was added to the solution, resulting in a crosslinker according to the present disclosure. This SSS is identified as SSS 1 in Table 1. Additional SSS (10.4 g) was added and allowed to dissolve. This additional SSS is identified as SSS 2 in Table 1.

[0084] The resulting mixture was allowed to cool to room temperature. VA-044 (1 g) was added as a polymerizing initiator. The mixture was cast on a backing to result in a membrane having thickness of about 0.6 mm, and cured in an oven at 80-90 C.

[0085] The resulting membrane has a water content of about 55% and an IEC of about 1.2 meq/g.

Example 10

[0086] Water (46.7 g) and N-methyl-2-pyrrolidone (NMP) (5.7 g) were added to a flask. DMAPMA (10.2 g) was added to the water and NMP solution with stirring. Hydrochloric acid (6.6 g of 33% HCl) was slowly added, maintaining the temperature below 60 C. using a water bath. GMA (8.6 g) was added to the solution and the temperature of the water bath was raised to about 55 C. The reaction was allowed to stir for about 1 hour, resulting in a crosslinker having a quaternary amine group of the following structure:

##STR00021##

[0087] SSS (12.6 g) was added to the solution, resulting in a crosslinker according to the present disclosure. This SSS is identified as SSS 1 in Table 1. Additional SSS (10.4 g) was added and allowed to dissolve. This additional SSS is identified as SSS 2 in Table 1.

[0088] The resulting mixture was allowed to cool to room temperature. V-50 (1 g) was added as a polymerizing initiator. The mixture was cast on a backing to result in a membrane having thickness of about 0.6 mm, and cured in an oven at 80-90 C.

[0089] The resulting membrane has a water content of about 55% and an IEC of about 1.2 meq/g.

[0090] The NMP was added to the water to increase the stability of the mixture.

Example 11

[0091] Water (57 g) was added to a flask. DMAEMA (9.3 g) was added to the water with stirring. Methanesulfonic acid (5.6 g) was slowly added, maintaining the temperature below 60 C. using a water bath. GMA (8.4 g) was added to the solution and the temperature of the water bath was raised to about 55 C. The reaction was allowed to stir for about 1 hour, resulting in a crosslinker having a quaternary amine group of the following structure:

##STR00022##

[0092] SSS (12.2 g) was added to the solution, resulting in a crosslinker according to the present disclosure. This SSS is identified as SSS 1 in Table 1. Additional SSS (10.4 g) was added and allowed to dissolve. This additional SSS is identified as SSS 2 in Table 1.

[0093] The resulting mixture was allowed to cool to room temperature. V-50 (1 g) was added as a polymerizing initiator. The mixture was cast on a backing to result in a membrane having thickness of about 0.6 mm, and cured in an oven at 80-90 C.

[0094] The resulting membrane has a water content of about 55% and an IEC of about 1.2 meq/g.

Example 12

[0095] Water (45 g) was added to a flask. DMAPMA (10.4 g) was added to the water with stirring. The temperature was raised to 40-42 C., and VBC (9.3 g) was added dropwise to the solution. The temperature of the reaction was maintained below 45 C. The reaction resulted in a crosslinker having a quaternary amine group of the following structure:

##STR00023##

[0096] The reaction was cooled to room temperature, and AMPS (12.6 g) was added to the solution, resulting in a crosslinker according to the present disclosure. This AMPS is identified as AMPS 1 in Table 1. Additional AMPS (22.8 g) was added and allowed to dissolve. This additional AMPS is identified as AMPS 2 in Table 1.

[0097] The resulting mixture was allowed to cool to room temperature. VA-044 (1 g) was added as a polymerizing initiator. The mixture was cast on a backing to result in a membrane having thickness of about 0.6 mm, and cured in an oven at 80-90 C.

[0098] The resulting membrane has a water content of about 45% and an IEC of about 2 meq/g.

[0099] In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the examples. However, it will be apparent to one skilled in the art that these specific details are not required. Accordingly, what has been described is merely illustrative of the application of the described examples and numerous modifications and variations are possible in light of the above teachings.

[0100] Since the above description provides examples, it will be appreciated that modifications and variations can be effected to the particular examples by those of skill in the art. Accordingly, the scope of the claims should not be limited by the particular examples set forth herein, but should be construed in a manner consistent with the specification as a whole.