Resilient anion exchange membranes prepared by polymerizing a composition

Abstract

A resilient anion exchange membrane including a homogeneous cross-linked ion-transferring polymer substantially filling pores and substantially covering surfaces of a porous substrate, wherein the resilient anion exchange membrane is prepared by polymerizing a composition including a quaternary ammonium cationic surfactant monomer, a crosslinking monomer including two or more ethylenic groups, a free radical initiator, and a solvent.

Claims

1. A resilient anion exchange membrane comprising a homogeneous cross-linked ion-transferring polymer substantially filling pores and substantially covering surfaces of a porous substrate; wherein the resilient anion exchange membrane is prepared by polymerizing a composition comprising: a quaternary ammonium cationic surfactant monomer having a chemical structure selected from formulae 1, 2, and 3 or its mixture: ##STR00005## wherein R.sub.1 is hydrogen or a methyl group, R.sub.2 is a C.sub.1-C.sub.4 alkylene group, R.sub.3 is a C.sub.1-C.sub.4 alkyl group, R.sub.4 is a C.sub.7-C.sub.22 alkyl group or a C.sub.7-C.sub.22 3-alkoxy-2-hydroxypropyl group, X.sup. is Cl.sup., Br.sup., I.sup. or acetate, and Z is O or NH; a crosslinking monomer comprising two or more ethylenic groups; a free radical initiator; and a solvent.

2. The resilient anion exchange membrane of claim 1, wherein the composition further comprises at least one hydrophilic cationic monomer selected from a group consisting of 3-acrylamidopropyl trimethylammonium chloride, 2-acryloyloxyethyl trimethylammonium chloride, 2-methacryloyloxyethyl trimethylammonium chloride, 3-methacryloylaminopropyl trimethylammonium chloride, and vinylbenzyl trimethylammonium chloride.

3. The resilient anion exchange membrane of claim 1, wherein the crosslinking monomer is selected from a group consisting of hexanediol diacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, pentaerythritol triacrylate, methylenebisacrylamide, and divinylbenzene.

4. The resilient anion exchange membrane of claim 1, wherein the free radical initiator is selected from a group consisting of -hydroxy ketones, benzoin ethers, benzil ketals, -dialkoxy acetophenones, -hydroxy alkylphenones, -amino alkylphenones, acylphosphine oxides, benzophenones/amines, thioxanthone/amines, and titanocenes.

5. The resilient anion exchange membrane of claim 4, wherein the free radical initiator is selected from a group consisting of 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxy-cyclohexyl-phenyl-ketone, benzophenone, and mixtures thereof.

6. The resilient anion exchange membrane of claim 4, wherein the free radical initiator is selected from a group consisting of 2,2-Azobis(2-methylpropionitrile), benzoyl peroxide, 1,7-bis(9-acridinyl)heptane, 2-hydroxy-[4-(2-hydroxypropoxy)phenyl]-2-methyl propanone, 4,4-bis(diethylamino)benzophenone, 4,4,4,4-methylidynetris(N,N-dimethylaniline), 2-hydroxy-2-methyl-1-(4-tert-butyl)phenyl propanone, 2-Benzyl-2-(dimethylamino)-4-morpholinobutyrophenone, 1-hydroxycyclohexyl phenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 4-methylbenzophenone, 4-phenylbenzophenone, 2-hydroxy-2-methyl-1-phenylpropanone, 2,2-bis-(2-chlorophenyl), 4,4,5,5-tetraphenyl-1,2-biimidazole, 2,2-Dimethyoxy-2-phenylacetophenone, 4-benzoyl-4-methyldiphenylsulphide, benzophenone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, methylbenzoylformate, methyl-o-benzoylbenzoate, 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide, ethyl(2,4,6-Trimethylbenzoyl)-phenyl phosphinate, and 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone.

7. The resilient anion exchange membrane of claim 1, wherein the solvent is selected from a group consisting of diethylene glycol, diethylene glycol methyl esters, 1,3-butanediol, ethanol, isopropanol, 1-butanol, N-methyl-2-pyrrolidone, dimethylacetamide, water, and mixtures thereof.

Description

DETAIL DESCRIPTION OF THE INVENTION

(1) To facilitate an understanding of the principles and features of the various embodiments of the invention, various illustrative embodiments are explained below. Although exemplary embodiments of the invention are explained in detail, it is to be understood that other embodiments are contemplated. Accordingly, it is not intended that the invention is limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, in describing the exemplary embodiments, specific terminology will be resorted to for the sake of clarity.

(2) It must also be noted that, as used in the specification and the appended claims, the singular forms a, an and the include plural references unless the context clearly dictates otherwise. For example, reference to a component is intended also to include composition of a plurality of components. References to a composition containing a constituent is intended to include other constituents in addition to the one named.

(3) Also, in describing the exemplary embodiments, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.

(4) Ranges may be expressed herein as from about or approximately or substantially one particular value and/or to about or approximately or substantially another particular value. When such a range is expressed, other exemplary embodiments include from the one particular value and/or to the other particular value.

(5) Similarly, as used herein, substantially free of something, or substantially pure, and like characterizations, can include both being at least substantially free of something, or at least substantially pure, and being completely free of something, or completely pure.

(6) By comprising or containing or including is meant that at least the named compound, element, particle, or method step is present in the composition or article or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if the other such compounds, material, particles, method steps have the same function as what is named.

(7) It is also to be understood that the mention of one or more method steps does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Similarly, it is also to be understood that the mention of one or more components in a composition does not preclude the presence of additional components than those expressly identified.

(8) The materials described as making up the various elements of the invention are intended to be illustrative and not restrictive. Many suitable materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of the invention. Such other materials not described herein can include, but are not limited to, for example, materials that are developed after the time of the development of the invention.

(9) The embodiments of the present disclosure pertain to resilient ion exchange membranes that have good chemical stability, good electrochemical properties, and improved mechanical stability in that they are flexible and resistant to the formation of stress lines, fractures, and the occurrence of cracking during use. The resilient ion exchange membranes disclosed herein relate to anion exchange membranes and to cation exchange membranes.

(10) Exemplary anion exchange membranes according to the present disclosure are prepared by polymerizing a composition containing at least a quaternary ammonium cationic surfactant monomer, onto the surfaces of and within the pores of a suitable porous substrate exemplified by woven fabrics, non-woven sheet materials, and microporous substrates.

(11) In an exemplary embodiment, the present invention is a resilient anion exchange membrane including a homogeneous cross-linked ion-transferring polymer substantially filling pores and substantially covering surfaces of a porous substrate, wherein the resilient anion exchange membrane is prepared by polymerizing a composition including a quaternary ammonium cationic surfactant monomer, a crosslinking monomer comprising two or more ethylenic groups, a free radical initiator, and a solvent.

(12) Suitable quaternary ammonium cationic surfactant monomers are exemplified by (meth)acryloxy or (meth)acrylamido monomers and their typical preparation processes have been described in U.S. Pat. Nos. 4,212,820, 4,918,228, and the reference of Macromolecules (1993) 26, 6121. Such (meth)acryloxy or (meth)acrylamido cationic surfactant monomers have the following formula:

(13) ##STR00001##
wherein R.sub.1 is hydrogen or a methyl group, Z is O or NH, R.sub.2 and R.sub.3 are C.sub.1-C.sub.4 alkyl groups, R.sub.4 is a hydrophobic group having a long alkyl group comprising 7-22 carbon atoms, and X.sup. is Cl.sup., Br.sup., I.sup. or acetate.

(14) Quaternary ammonium cationic surfactant monomers for anion exchange membranes according to one embodiment of the present disclosure may also be based on vinylbenzene or vinylpyridinium monomers. Exemplary processes for synthesis of vinylbenzene-based or vinylpyridinium-based cationic surfactant monomers have been disclosed in U.S. Pat. No. 4,469,873 and by Cochin et al. (1993, Photopolymerization of micelle-forming monomers. 1. Characterization of the systems before and after polymerization. Macromolecules 26, 5755-5764).

(15) Suitable vinylbenzyl cationic surfactant monomers are exemplified by the formula:

(16) ##STR00002##
wherein R.sub.3 is a C.sub.1-C.sub.4 alkyl group, R.sub.4 is a hydrophobic group having a long alkyl group comprising 7-22 carbon atoms, and X.sup. is Cl.sup., Br.sup., I.sup. or acetate.

(17) Suitable vinylpyridinium-based cationic surfactant monomers are exemplified by the formula:

(18) ##STR00003##
wherein R.sub.4 is a hydrophobic group having a long alkyl group comprising 7-22 carbon atoms, and X.sup. is Cl.sup., Br.sup., I.sup. or acetate.

(19) In one embodiment, these quaternary ammonium cationic surfactant monomers could be used optionally with one or more hydrophilic cationic monomers to prepare an exemplary anion exchange membrane of the present disclosure. Suitable hydrophilic cationic monomers are exemplified by 3-acrylamidopropyl trimethylammonium chloride, 2-acryloyloxyethyl trimethylammonium chloride, 2-methacryloyloxyethyl trimethylammonium chloride, 3-methacryloylaminopropyl trimethylammonium chloride, vinylbenzyl trimethylammonium chloride, and the like.

(20) Exemplary cation exchange membranes according to the present disclosure are prepared by polymerizing a composition containing at least a sulfonic anionic surfactant monomer onto the surface of and within the pores of a suitable porous substrate exemplified by woven fabrics, non-woven sheet materials, and microporous substrates.

(21) Suitable sulfonic anionic surfactant monomers are exemplified by (meth)acrylamido monomers and their general synthesis processes have been described in U.S. Pat. No. 3,506,707. These (meth)acrylamido sulfonic anionic surfactant monomers have the following formula:

(22) ##STR00004##
wherein R.sub.1 is hydrogen or a methyl group, R.sub.3 is hydrogen or a C.sub.1-C.sub.3 alkyl group, R.sub.4 is a hydrophobic group having a long alkyl group comprising 7-22 carbon atoms, and M.sup.+ is H.sup.+ or a salt ion.

(23) In another embodiment, these sulfonic anionic surfactant monomers could be used optionally with one or more hydrophilic anionic monomer to prepare an exemplary cation exchange membrane of the present disclosure. Suitable hydrophilic anionic monomers are exemplified by sodium 4-vinylbenzenesulfonate, 3-sulfopropyl acrylate potassium salt, and 2-acrylamido-2-methyl-1-propanesulfonic acid, and the like.

(24) According to one aspect, the porous substrate may comprise a woven fabric, a non-woven sheet material, or a microporous substrate.

(25) Suitable woven fabrics may be woven from strands selected from one or more of materials exemplified by polyester, PVC, LDPE, very-low-density polyethylene (VLDPE), polypropylene, polysulfone, nylon, nylon-polyamides. Suitable polyesters are exemplified by polyglycolide or polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), polyethylene adipate (PEA), polyhydroxyalkanoate (PHA), polyethylene teraphthalate (PET), polybutylene teraphthalate (PBT), polytrimethylene teraphthalate (PTT), polyethylene naphthalate (PEN), and VECTRAN, a fiber spun from a liquid crystal polymer formed by the polycondensation of 4-hydroxybenzoic acid and 6-hydroxynaphthalene-2-carboxylic acid (VECTRAN is a registered trademark of Kuraray Co. Ltd., Kurashiki City, Japan). PET is particularly suitable for producing a woven fabric matrix for the flexible ion exchange membrane of the present disclosure.

(26) Suitable non-woven sheet material may comprise sections of a single sheet comprising a material exemplified by polyester, PVC, LDPE, VLDPE, polypropylene, polysulfone, nylon, nylon-polyamides. Suitable polyesters are exemplified by polyglycolide or PGA, PLA, PCL, PEA, PHA, PET, PBT, PTT, and PEN. Also suitable is a sheet material that comprising two or more laminations of combinations of sheet material exemplified by PVC, LDPE, VLDPE, polypropylene, polysulfone, nylon, nylon-polyamides. Suitable polyesters are exemplified by polyglycolide or PGA, PLA, PCL, PEA, PHA, PET, PBT, PTT, and PEN.

(27) Suitable microporous sheet material may comprise sections of a single sheet microporous substrate comprising a material exemplified by polyester, PVC, LDPE, VLDPE, polypropylene, polysulfone, nylon, nylon-polyamides. Suitable polyesters are exemplified by polyglycolide or PGA, PLA, PCL, PEA, PHA, PET, PBT, PTT, and PEN.

(28) The exemplary resilient anion exchange membranes disclosed herein may be produced generally following the following steps. First, a suitable quaternary ammonium cationic surfactant monomer is provided. The selected quaternary ammonium cationic surfactant monomer may be sourced from a supplier or alternatively, it may be synthesized. The quaternary ammonium cationic surfactant monomer is dissolved in a suitable solvent to form a homogenous solution. A crosslinking monomer and a free radical initiator are then added and dissolved into the homogenous solution. It is optional, if so desired, to additionally dissolve one or more hydrophilic cationic monomers into the homogenous solution. The weight ratio of the quaternary ammonium cationic surfactant monomer to the hydrophilic cationic monomers is from about 30:1 to about 1:20, and preferably from about 20:1 to about 1:5. The homogenous solution is then applied onto a porous substrate such that the porous substrate is saturated with and impregnated with the homogenous solution. After excess homogenous solution is removed from the saturated porous substrate, the free radical initiator is stimulated to form free radicals and to initiate the polymerization. Anion exchange membranes are formed with the homogeneous crosslinked ion transferring polymers filling the pores and covering the surfaces of the porous substrate. The resulting membrane is then rinsed in water, and then converted into the chloride form by immersion in a sodium chloride (NaCl) solution.

(29) Suitable crosslinking monomers are exemplified by monomers having two or more ethylenic groups. Particularly suitable crosslinkers are hexanediol diacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, pentaerythritol triacrylate, methylenebisacrylamide, divinylbenzene, and the like.

(30) Suitable solvents for preparing the resilient anion exchange membranes of the present disclosure are exemplified by diethylene glycol, diethylene glycol methyl esters, 1,3-butanediol, dimethylacetamide, 1,3-butanediol, isopropanol, 1-butanol, N-methyl-2-pyrrolidone, dimethylacetamide, water, and mixtures thereof. The solvent content in the homogenous solution is preferably in a range of about 20% by weight to about 45% by weight.

(31) Suitable hydrophilic cationic monomers are exemplified by 3-acrylamidopropyl trimethylammonium chloride, 2-acryloyloxyethyl trimethylammonium chloride, 2-methacryloyloxyethyl trimethylammonium chloride, 3-methacryloylaminopropyl trimethylammonium chloride, vinylbenzyl trimethylammonium chloride, and the like.

(32) The exemplary resilient cation exchange membranes disclosed herein may be produced generally following the following steps. First, a suitable sulfonic anionic surfactant monomer is provided. The selected sulfonic anionic surfactant monomer may be sourced from a supplier or alternatively, it may be synthesized. The sulfonic anionic surfactant monomer is dissolved in a suitable solvent to form a homogenous solution. A crosslinking monomer and a free radical initiator are added and dissolved into the homogenous solution. It is optional, if so desired, to additionally dissolve one or more hydrophilic anionic monomers into the homogenous solution. The weight ratio of the sulfonic anionic surfactant monomer to the hydrophilic anionic monomers is from about 30:1 to about 1:20, and preferably from about 20:1 to about 1:5. The homogenous solution is then applied onto a porous substrate such that the porous substrate is saturated with and impregnated with the homogenous solution. After excess homogenous solution is removed from the saturated porous substrate, the free radical initiator is stimulated to form free radicals and to initiate the polymerization. Cation exchange membranes are formed with the homogeneous crosslinked ion-transferring polymers filling the pores and covering the surfaces of the porous substrate. The resulting membrane is then rinsed in water, and then converted into the sodium form by immersion in a sodium chloride (NaCl) solution.

(33) Suitable crosslinking monomers are exemplified by monomers having two or more ethylenic groups. Particularly suitable crosslinkers are hexanediol diacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, pentaerythritol triacrylate, methylenebisacrylamide, divinylbenzene, and the like.

(34) Suitable solvents for preparing the resilient cation exchange membranes of the present disclosure are exemplified by N,N-dimethylacetamide, N-methyl-2-pyrrolidone, water and mixtures thereof.

(35) Suitable hydrophilic anionic monomers are exemplified by sodium 4-vinylbenzenesulfonate, 3-sulfopropyl acrylate potassium salt, 2-acrylamido-2-methyl-1-propanesulfonic acid, and the like.

(36) Suitable free radical initiators for producing the anion exchange membranes and the cation exchange membranes of the present disclosure are exemplified by photoinitiators that release free radicals upon exposure to UV light and include among others -hydroxy ketones free radical initiators, benzoin ethers, benzil ketals, -dialkoxy acetophenones, -hydroxy alkylphenones, -amino alkylphenones, acylphophine oxides, benzophenons/amines, thioxanthone/amines, and titanocenes. Suitable -hydroxy ketone free radical initiators are exemplified by 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxy-cyclohexyl-phenyl-ketone, 1-hydroxy-cyclohexyl-phenyl-ketone:benzophenone, and mixtures thereof. Suitable free radical free radical initiators are exemplified by 2,2-Azobis(2-methylpropionitrile), benzoyl peroxide, 1,7-bis(9-acridinyl)heptane, 2-hydroxy-[4-(2-hydroxypropoxy)phenyl]-2-methyl propanone, 4,4bid(diethylamino)benzophenone, 4,4,4-methylidynetris(N,N-dimethylaniline), 2-hydroxy-2-methyl-1-(4-tert-butyl)phenyl propanone, 2-Benzyl-2-(dimethylamino)-4-morpholinobutyrophenone, 1-hydroxycyclohexyl phenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 4-methylbenzophenone, 4-phenylbenzophenone, 2-hydroxy-2-methyl-1-phenylpropanone, 2,2-bis-(2-chlorophenyl), 4,5,5-tetraphenyl-1,2biimidazole, 2,2-Dimethyoxy-2-phenylacetophenone, 4-benzoyl-4-methyldiphenylsulphide, benzophenone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, methylbenzoylformate, methyl-o-benzoylbenzoate, 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide, ethyl(2,4,6-Trimethylbenzoyl)-phenyl phosphinate, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, and mixtures thereof.

(37) The resilient ion exchange membranes produced by the process of the present disclosure comprise porous substrates impregnated with and covered by homogenous crosslinked ion-transferring polymers within, throughout, and about the substrates. The water content of the resilient ion exchange membranes can be adjusted to within selected target ranges by adjusting the percentages of the solvents in the homogenous solutions used to prepare the ion exchange membranes. The incorporation of ionic surfactant monomer with long hydrophobic alkyl groups for ion exchange membranes retains advantageous formulation process and also desired properties of the final ion exchange membranes: 1) The polarities of ionic surfactant monomers tuned compatible with any crosslinking monomer that minimum solvent content or no solvent is needed to form an initial homogenous monomer solution, making the final membrane with good ion-selective permeability; 2) Excellent mechanical property due to the incorporation of flexible alkyl groups; 3) Minimum osmotic swelling of ionic surfactant monomer units in the final membrane that crosslinking comonomer as less as 1-20 mol % of total monomer contents is needed to form resilient ion exchange membranes; 4) Tolerant to caustic degradation and chlorine oxidation;

(38) The present disclosure will be further illustrated in the following examples. However it is to be understood that these examples are for illustrative purposes only, and should not be used to limit the scope of the present disclosure in any manner.

EXAMPLE 1

Synthesis of cationic surfactant monomer N,N-dimethyl-N-dodecyl-N-(3-acrylamidopropyl) ammonium bromide

(39) N,N-dimethyl-N-dodecyl-N-(3-acrylamidopropyl) ammonium bromide was synthesized using the quaternerization reaction of N-(3-dimethylamonopropyl)acrylamide and bromododecane. In a vessel, N-(3-dimethylamonopropyl)acrylamide (31.2 g) was mixed with 1-bromododecane (74.7 g) at room temperature for 48 hours. Excess bromodecane was decanted and the transparent gel product was washed with diethyl ether and stored at cold temperature for membrane preparation.

EXAMPLE 2

Preparation of Anion Exchange Membrane

(40) N,N-dimethyl-N-dodecyl-N-(3-acrylamidopropyl) ammonium bromide (50.0 g) from Example 1 was first dissolved in diethylene glycol methyl ether (26.8 g). To this solution, crosslinking monomer hexanediol diacrylate (5.5 g) was added and stirred to form a homogenous solution. 2.5 g of a photoinitiator IRGACURE 2959 (IRGACURE is a registered trademark of Ciba Specialty Chemical Corp., Tarrytown, N.Y., USA, and has the chemical formula: 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone) was added and dissolved into the solution. The polymerizable solution was applied onto a woven polyester cloth made with SEFAR PET 1500 (SEFAR is a registered trademark of SEFAR Holdings AG Corp., Thal, Switzerland) wherein the woven polyester cloth has a mesh open of 151 m, open area of 53%, and a mesh thickness of 90 m. Excess solution was removed from the substrate by running a roller over the substrate with care being taken to exclude air bubbles from the substrate. The substrate impregnated with polymerizable solution was irradiated with UV light (wavelength 300-400 nm) for 8 minutes. The resulting homogenous membrane was rinsed thoroughly in water and was then placed in 10 wt % NaCl solution to convert the membrane into chloride form. The membrane has the following properties:

(41) Membrane thickness: 0.09 mm-0.10 mm

(42) Electrical resistance: 2.0-2.5 cm.sup.2

(43) Water content: 34 wt %

(44) Ion exchange capacity: 2.2 mmol per gram of dry resin

EXAMPLE 3

Preparation of Anion Exchange Membrane

(45) N,N-dimethyl-N-dodecyl-N-(3-acrylamidopropyl) ammonium bromide (50.0 g) from Example 1 was first dissolved in N,N-dimethylacetamide (50.0 g). To this solution were added and dissolved 10 g of the crosslinking monomer methylenebisacryamide and 3.3 g of the photoinitiator IRGACURE 2959. The polymerizable solution was applied onto a woven polyester cloth (SEFAR PET 1500, mesh open 151 m, open area of 53%, and mesh thickness of 90 m). Excess solution was removed from the substrate by running a roller over the substrate with care being taken to exclude air bubbles from the substrate. The substrate impregnated with polymerizable solution was then irradiated with UV light (wavelength 300-400 nm) for 8 minutes. The resulting homogenous membrane was rinsed thoroughly in water and was then placed in 10 wt % NaCl solution to convert the membrane into chloride form. The membrane has the following properties:

(46) Membrane thickness: 0.09 mm-0.10 mm

(47) Electrical resistance: 1.8-2.4 cm.sup.2

(48) Water content: 45 wt %

(49) Ion exchange capacity: 2.0 mmol per gram of dry resin

EXAMPLE 4

Preparation of Anion Exchange Membrane

(50) N,N-dimethyl-N-dodecyl-N-(3-acrylamidopropyl) ammonium bromide (50.0 g) from Example 1 was dissolved in diethylene glycol methyl ether (12.5 g). Hydrophilic monomer 3-methacryloylaminopropyl trimethylammonium chloride (26.8 g; MAPTAC) was dissolved in 1,3-butanediol (26.8). The MAPTAC/butanediol solution was mixed with the N,N-dimethyl-N-dodecyl-N-(3-acrylamidopropyl) ammonium bromide/diethylene glycol methyl ether solution into a homogeneous solution. To this solution were added and dissolved the crosslinking monomer hexanediol diacrylate (51.2 g) and the photoinitiator IRGACURE 2959 (3.0 g). The polymerizable solution was applied onto a woven polyester cloth (SEFAR PET 1500, mesh open 151 m, open area of 53%, and mesh thickness of 90 m). Excess solution was removed from the substrate by running a roller over the substrate with care being taken to exclude air bubbles from the substrate. The substrate impregnated with polymerizable solution was then irradiated with UV light (wavelength 300-400 nm) for 15 minutes. The resulting homogeneous membrane was rinsed thoroughly in water and was then placed in 10 wt % NaCl solution to convert the membrane into chloride form. The membrane has the following properties:

(51) Membrane thickness: 0.09 mm-0.10 mm

(52) Electrical resistance: 3.0-4.2 cm.sup.2

(53) Water content: 25 wt %

(54) Ion exchange capacity: 1.9 mmol per gram of dry resin

EXAMPLE 5

Synthesis of cationic surfactant monomer N,N-dimethyl-N-dodecyl-N-(3-methacrylamidopropyl) ammonium bromide

(55) A mixture of N-(3-dimethylamonfsopropyl) methacrylamide (51.3 g) and bromododecane (186.7 g) was reacted at room temperature for 48 hours. Excess bromodecane was decanted and the transparent gel product was washed with diethyl ether. The transparent gel product crystallizes as white solid upon cooling and was stored at cold temperature (about 4 C.).

EXAMPLE 6

Preparation of Anion Exchange Membrane

(56) N,N-dimethyl-N-dodecyl-N-(3-methacrylamidopropyl) ammonium bromide (50.0 g) from Example 5 was first dissolved in diethylene glycol methyl ether (21.4 g). To this solution, crosslink monomer ethylene glycol dimethacrylate (12.5 g) was added and mixed into a homogeneous solution. IRGACURE 2959 (2.5 g) was added and dissolved in the mixture. The polymerizable solution was applied onto a woven polyester cloth (SEFAR PET 1500, mesh open 151 m, open area of 53%, and mesh thickness of 90 m). Excess solution was removed from the substrate by running a roller over the substrate with care being taken to exclude air bubbles from the substrate. The impregnated substrate with polymerizable solution was irradiated with UV light (wavelength 300-400 nm) for 20 minutes. The resulting homogenous membrane was rinsed thoroughly in water and then placed in 10 wt % NaCl solution to convert the membrane into chloride form. The membrane has the following properties:

(57) Membrane thickness: 0.09 mm-0.10 mm

(58) Electrical resistance: 2.8-3.5 cm.sup.2

(59) Water content: 26 wt %

(60) Ion exchange capacity: 1.9 mmol per gram of dry resin

EXAMPLE 7

Synthesis of anionic surfactant monomer 2-acrylamido-dodecane sulfonic acid

(61) A 250-ml three-neck flask equipped with a stirrer, thermometer, and condenser was charged with acrylonitrile (16.2 g) and 1-dodecene (37.9 g). The solution was stirred under ice-salt bath. Fuming sulfuric acid (66 wt %, 35.7 g) was gradually added while the contents were maintained at less than about 5 C. The solution was then slowly raised to ambient room temperature and kept overnight. The precipitate product was filtered, washed with diethyl ether, and dried under vacuum.

EXAMPLE 8

Preparation of Cation Exchange Membrane

(62) 2-acrylamido-dodecane sulfonic acid (50.0 g) from Example 7 was dissolved in N,N-dimethylacetamide (26.9 g). To this solution was added and dissolved 5.2 g of the crosslinking monomer methylenebisacryamide. IRGACURE 2959 (2.5 g) was added and dissolved in the mixture. The polymerizable solution was applied onto a woven polyester cloth (SEFAR PET 1500, mesh open 151 m, open area of 53%, and mesh thickness of 90 m). Excess solution was removed from the substrate by running a roller over the substrate with care being taken to exclude air bubbles from the substrate. The substrate impregnated with polymerizable solution was irradiated with UV light (wavelength 300-400 nm) for 8 minutes. The resulting homogenous membrane was rinsed thoroughly in water and was then placed in 10 wt % NaCl solution to convert the membrane into sodium form. The membrane has the following properties:

(63) Membrane thickness: 0.09 mm-0.10 mm

(64) Electrical resistance: 1.5-2.4 cm.sup.2

(65) Water content: 35 wt %

(66) Ion exchange capacity: 2.9 mmol per gram of dry resin

EXAMPLE 9

Preparation of Cation Exchange Membrane

(67) 2-acrylamido-dodecane sulfonic acid (50.0 g) from Example 7 and hydrophilic monomer -acrylamido-2-methyl-1-propanesulfonic acid (20.0 g) were dissolved in N,N-dimethylacetamide (40.0 g). To this solution was added the crosslinking monomer hexanediol diacrylate (46.7 g). IRGACURE 2959 (3.2 g) was added and dissolved in the mixture. The polymerizable solution was applied onto a woven polyester cloth (SEFAR PET 1500, mesh open 151 m, open area of 53%, and mesh thickness of 90 m). Excess solution was removed from the substrate by running a roller over the substrate with care being taken to exclude air bubbles from the substrate. The substrate impregnated with polymerizable solution was irradiated with UV light (wavelength 300-400 nm) for 8 minutes. The resulting homogeneous membrane was rinsed thoroughly in water and was then placed in 10 wt % NaCl solution to convert the membrane into sodium form. The membrane has the following properties:

(68) Membrane thickness: 0.09 mm-0.10 mm

(69) Electrical resistance: 2.7-3.5 cm.sup.2

(70) Water content: 27 wt %

(71) Ion exchange capacity: 2.1 mmol per gram of dry resin

EXAMPLE 10

Synthesis of anionic surfactant monomer 2-acrylamido-hexadecane sulfonic acid

(72) A 250 ml three-neck flask equipped with a stirrer, thermometer, and condenser was charged with acrylonitrile (21.6 g) and 1-hexadecene (44.8 g). The solution was stirred under ice-salt bath. Fuming sulfuric acid (66 wt %, 35.7 g) was gradually added while the contents were maintained at less than about 5 C. The solution was then slowly raised to room temperature and kept overnight. The precipitate product was filtered, washed with diethyl ether, and dried under vacuum at room temperature.

EXAMPLE 11

Preparation of Cation Exchange Membrane

(73) 2-acrylamido-hexadecane sulfonic acid (50.0 g) from Example 10 was dissolved in N,N-dimethylacetamide (21.4 g). To this solution was added 3.8 g of the crosslinking monomer methylenebisacryamide. IRGACURE 2959 (2.2 g) was added and dissolved in the mixture. The polymerizable solution was applied onto a woven polyester cloth (SEFAR PET 1500, mesh open 151 m, open area of 53%, and mesh thickness of 90 m). Excess solution was removed from the substrate by running a roller over the substrate with care being taken to exclude air bubbles from the substrate. The substrate impregnated with polymerizable solution was irradiated with UV light (wavelength 300-400 nm) for 8 minutes. The resulting homogenous membrane was rinsed thoroughly in water and was then placed in 10 wt % NaCl solution to convert the membrane into sodium form. The membrane has the following properties:

(74) Membrane thickness: 0.09 mm-0.10 mm

(75) Electrical resistance: 2.4-3.0 cm.sup.2

(76) Water content: 30 wt %

(77) Ion exchange capacity: 2.4 mmol per gram of dry resin

EXAMPLE 12

Synthesis of cationic surfactant monomer N,N-dimethyl-N-(3-alkoxy-2-hydroxylpropyl)-N-(3-acrylamidopropyl) ammonium acetate

(78) Into a 250 ml flask were added 31.2 g of N-(3-dimethylamonopropyl)acrylamide and 42.4 g of isopropanol. The solution was stirred while the base of the flask was immersed in an ice-water bath. Acetic acid (12.0 g) was added and reacted in the solution ambient room temperature for one hour. 56.2 g of C.sub.12-C.sub.14 alkyl glycidyl ether (Dow Chemical Company, equivalent weight 280) were added slowly into the solution at room temperature, after which, the reaction mixture was heated and kept at 45 C. for 3 hours. The hydrophobic cationic monomer solution was stored at cold temperature for membrane preparation.

EXAMPLE 13

Preparation of Anion Exchange Membrane

(79) N,N-dimethyl-N-(3-alkoxy-2-hydroxylpropyl)-N-(3-acrylamidopropyl) ammonium acetate solution (50.0 g) from Example 12 was mixed with the crosslinking monomer hexanediol diacrylate (3.9 g) into a homogenous solution. IRGACURE 2959 (1.6 g) was added and dissolved in the mixture. The polymerizable solution was applied onto a woven polyester cloth (SEFAR PET 1500, mesh open 151 m, open area of 53%, and mesh thickness of 90 m). Excess solution was removed from the substrate by running a roller over the substrate with care being taken to exclude air bubbles from the substrate. The substrate impregnated with polymerizable solution was irradiated with UV light (wavelength 300-400 nm) for 8 minutes. The resulting homogenous membrane was rinsed thoroughly in water and then placed into a 10 wt % NaCl solution to convert the membrane into chloride form. The membrane has the following properties:

(80) Membrane thickness: 0.09 mm-0.10 mm

(81) Electrical resistance: 4.2-5.0 cm.sup.2

(82) Water content: 30 wt %

(83) Ion exchange capacity: 1.8 mmol per gram of dry resin

EXAMPLE 14

Synthesis of cationic surfactant monomer N,N-dimethyl-N-(3-alkoxy-2-hydroxylpropyl)-N-(3-methacrylamidopropyl) ammonium acetate

(84) Into a 250 ml flask were added 51.3 g of N-(3-dimethylamonopropyl)methacrylamide and 65.7 g of ethanol. The solution was stirred in an ice-water bath. Acetic acid (18.0 g) was then added and reacted in the solution at room temperature for one hour. 84.0 g of C.sub.12-C.sub.14 alkyl glycidyl ether (Dow chemical company, equivalent weight 280) was added slowly into the solution at room temperature, after which, the reaction mixture was heated and kept at 45 C. for 3 hours. The hydrophobic cationic monomer solution was stored at cold temperature for membrane preparation.

EXAMPLE 15

Preparation of Anion Exchange Membrane

(85) N,N-dimethyl-N-(3-alkoxy-2-hydroxylpropyl)-N-(3-methacrylamidopropyl) ammonium acetate solution (65.0 g) from Example 14 was mixed with the crosslinking monomer ethylene glycol dimethacrylate (7.2 g) into a homogenous solution. IRGACURE 2959 (2.2 g) was added and dissolved in the mixture. The polymerizable solution was applied onto a woven polyester cloth (SEFAR PET 1500, mesh open 151 m, open area of 53%, and mesh thickness of 90 m). Excess solution was removed from the substrate by running a roller over the substrate with care being taken to exclude air bubbles from the substrate. The substrate impregnated with polymerizable solution was irradiated with UV light (wavelength 300-400 nm) for 15 minutes. The resulting homogenous membrane was rinsed thoroughly in water and was then placed in 10 wt % NaCl solution to convert the membrane into chloride form. The homogenous membrane has the following properties:

(86) Membrane thickness: 0.09 mm-0.10 mm

(87) Electrical resistance: 4.2-5.0 cm.sup.2

(88) Water content: 30 wt %

(89) Ion exchange capacity: 1.8 mmol per gram of dry resin

EXAMPLE 16

Synthesis of cationic surfactant monomer N,N-dimethyl-N-dodecyl-N-(4-vinylbenzyl) ammonium chloride

(90) Into a 200 ml flask were added 29.8 g of 4-vinylbenzyl chloride and 50 g of N,N-dimethyldodecylamine. The reaction mixture was stirred at room temperature for 24 hours. The solid precipitate from the reaction was filtered, washed with diethyl ether, and dried under vacuum at room temperature.

EXAMPLE 17

Preparation of Anion Exchange Membrane

(91) N,N-dimethyl-N-dodecyl-N-(4-vinylbenzyl) ammonium chloride (50 g) from Example 16 was dissolved in N,N-dimethylacetamide (21.6 g). To this solution was added 5.5 g of the crosslinking monomer divinylbenzened and mixed to produce a homogenous solution. IRGACURE 2959 (2.3 g) was added into the mixture and dissolved. The polymerizable solution was applied onto a woven polyester cloth (SEFAR PET 1500, mesh open 151 m, open area of 53%, and mesh thickness of 90 m). Excess solution was removed from the substrate by running a roller over the substrate with care being taken to exclude air bubbles from the substrate. The substrate impregnated with polymerizable solution was irradiated with UV light (wavelength 300-400 nm) for 1 hour. The resulting homogenous membrane was rinsed thoroughly in water. The membrane has the following properties:

(92) Membrane thickness: 0.09 mm-0.10 mm

(93) Electrical resistance: 3.5-4.2 cm.sup.2

(94) Water content: 30 wt %

(95) Ion exchange capacity: 2.4 mmol per gram of dry resin

EXAMPLE 18

Synthesis of Cationic Surfactant Vinyl Pyridinium Based Quaternary Monomer

(96) 4-vinyl pyridine (31.5 g) was added into a 250-ml flask. The solution was stirred in an ice-water bath. Acetic acid (75.2 g) was added slowly and then the mixture was warmed to room temperature and the reaction allowed to proceed for 1 hour. Then, 84.0 g of C.sub.12-C.sub.14 alkyl glycidyl ether (Dow chemical company, equivalent weight 280) was added slowly into the solution at room temperature, after which, the reaction mixture was heated and kept at 45 C. for 3 hours. The hydrophobic cationic monomer solution was stored at cold temperature for membrane preparation.

EXAMPLE 19

Preparation of Anion Exchange Membrane

(97) Vinyl pyridinium-based quaternary monomer solution (30.0 g) from Example 18 was mixed with the crosslinking monomer divinylbenzene (2.4 g) until a homogenous solution was formed. IRGACURE 2959 (1.0 g) was added and dissolved in the mixture. The polymerizable solution was applied onto a woven polyester cloth (SEFAR PET 1500, mesh open 151 m, open area of 53%, and mesh thickness of 90 m). Excess solution was removed from the substrate by running a roller over the substrate with care being taken to exclude air bubbles from the substrate. The substrate impregnated with polymerizable solution was irradiated with UV light (wavelength 300-400 nm) for 1 hour. The resulting homogenous membrane was rinsed thoroughly in water and was then placed in 10 wt % NaCl solution to convert the membrane into chloride form. The homogenous membrane has the following properties:

(98) Membrane thickness: 0.09 mm-0.10 mm

(99) Electrical resistance: 4.0-4.7 cm.sup.2

(100) Water content: 30 wt %

(101) Ion exchange capacity: 2.0 mmol per gram of dry resin

EXAMPLE 20

Degradation of Ion Exchange Membranes

(102) The caustic stabilities of the ion exchange membranes made in Examples 3 (AEM) and 8 (CEM) were tested by soaking the membranes in 0.1 mol L.sup.1 sodium carbonate/3.0 mol L.sup.1 sodium chloride solution with pH 10.8 at 60 C. The membrane performances are summarized in Table 1 below. The permselectivity of the membrane was measured in solutions of 0.6 mol L.sup.1 sodium chloride solution vs. 0.02 mol L.sup.1 sodium chloride solution.

(103) TABLE-US-00001 TABLE 1 Performance of CEM* and AEM** stored under caustic conditions (pH 10.8) at 60 C. CEM from Example 8 AEM from Example 3 Storage Permse- Water Permse- Water Time Resistance lectivity Content Resistance lectivity Content 0 2.0 cm.sup.2 92.0% 35.0% 2.2 cm.sup.2 85.0% 45.2% 1 month 2.0 cm.sup.2 92.0% 34.2% 2.2 cm.sup.2 85.0% 44.3% 2 months 1.8 cm.sup.2 92.0% 35.6% 2.2 cm.sup.2 85.0% 45.0% *CEM = cation exchange membrane **AEM = anion exchange membrane

(104) Numerous characteristics and advantages have been set forth in the foregoing description, together with details of structure and function. While the invention has been disclosed in several forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions, especially in matters of shape, size, and arrangement of parts, can be made therein without departing from the spirit and scope of the invention and its equivalents as set forth in the following claims. Therefore, other modifications or embodiments as may be suggested by the teachings herein are particularly reserved as they fall within the breadth and scope of the claims here appended.