High-Performance Anion Exchange Membranes and Methods of Making Same

Abstract

Anion exchange membranes may include a polymeric microporous substrate and a cross-linked anion exchange polymeric layer on the substrate. Anion exchange membranes may have a resistivity of less than about 1.5 Ohm-cm 2 and an apparent permselectivity of at least about 95%. The anion exchange membranes may be produced by a unique, two step process.

1 . A method of making an anion exchange membrane, comprising:
 mixing a tertiary amine monomer with a quaternization agent to produce a functional monomer;   mixing a cross-linking agent and a solvent with the functional monomer to form a monomeric solution; and   casting the monomeric solution on a polymeric microporous substrate to form the anion exchange membrane.   
     
     
         2 . The method of  claim 1 , wherein the tertiary amine monomer is selected from the group consisting of 1-vinylimidazole, 2-methyl-1-vinylimidazole, 9-vinylcarbazole, N-ethyl-2-vinylcarbazole, 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, and mixtures thereof. 
     
     
         3 . The method of  claim 2 , wherein the quaternization agent is selected from the group consisting of benzyl chloride, benzyl bromide, benzyl iodide, p-dichlorobenzene, m-dichlorobenzene, 1,4-dichloro-2-nitrobenzene, 3-(Benzyloxy)benzyl chloride, 4-(Benzyloxy)benzyl chloride 2-(Trifluoromethyl)-benzyl chloride, 3-(Trifluoromethyl)benzyl chloride, 4-(Trifluoromethyl)benzyl chloride, 1-chlorohexane, 1-chloropentane, 1-chlorobutane, 1-chloropropane, 1,6 dichlorohexane, 1,5-dichloropentane, 1,4-dichlorobutane, 1,3-dichloropropane, 1-bromohexane, 1-bromopentane, 1-bromobutane, 1-bromopropane, 1,6-dibromohexane, 1,5-dibromopentane, 1,4-dibromobutane, 1,3-dibromopropane, 1-iodohexane, 1-iodopentane, 1-iodobutane, 1-iodoopropane, 1-iodideethane, 1-iodidemethane, 1,6-diiodohexane, 1,5-diiodorpentane, 1,4-diiodobutane, 1,3-diiodopropane, and mixtures thereof. 
     
     
         4 . The method of  claim 3 , wherein the cross-linking agent is selected from the group consisting of vinylbenzyl chloride, m-divinylbenzene, ethyleneglycol-dimethacrylate, p-dichlorobenzene, m-dichlorobenzene, 1,4-dichloro-2-nitrobenzene, 1,6 dichlorohexane, 1,5-dichloropentane, 1,4-dichlorobutane, 1,3-dichloropropane, 1,6-dibromohexane, 1,5-dibromopentane, 1,4-dibromobutane, 1,3-dibromopropane, 1,6-dibromohexane, 1,5-dibromopentane, 1,4-dibromobutane, 1,3-dibromopropane, 1,4-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, Pentaerythritol triacrylate, divinyl benzene, (m- and p-mixture), trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ethoxylated (n) bisphenol A di(meth)acrylate (n=1.5, 2, 4, 6, 10, 30), ethoxylated (n) trimethylolpropanetri(meth)Acrylate (n=3,6,9,10,15,20), propoxylated(n) trimethylolpropane triacrylate (n=3,6), and mixtures thereof. 
     
     
         5 . The method of  claim 4 , wherein the solvent comprises dipropyleneglycol, n-propanol, 2-propanol, 1-methyl-2-pyrrolidinone, 1-butanol, and mixtures thereof. 
     
     
         6 . The method of  claim 5 , further comprising mixing a polymerization initiator with the monomer solution. 
     
     
         7 . The method of  claim 6 , wherein the polymerization initiator is selected from the group consisting of organic peroxides, 2,2′ azobis[2,[2-imdazolin-2-yl]-propane]dihydrochloride, α,α′-azoisobutyronitrile, 2,2′-azobis[2-methylpropioaminidine]dihydrochloride, 2,2′-azobis[2,[2-imdazolin-2-yl]-propane], dimethyl2,2′azobis[2-methylpropionate] and benzoyl peroxide. 
     
     
         8 . The method of  claim 7 , further comprising controlling polymerization with an inhibitor. 
     
     
         9 . The method of  claim 8 , wherein the polymerization inhibitor is selected from the group consisting of 4-methoxyphenol and 4-tert-butyl catechol. 
     
     
         10 . The method of  claim 9 , wherein the polymeric microporous substrate comprises at least one of polypropylene, high molecular weight polyethylene, ultrahigh molecular weight polyethylene, polyvinyl chloride, polyvinylidene difluoride, and polytetrafluoroethylene. 
     
     
         11 . The method of  claim 10 , wherein casting comprises applying heat at a temperature of about 0° C. to about 100° C., ultraviolet light at a wavelength of about 100 nm to about 400 nm, or ionizing radiation. 
     
     
         12 . An anion exchange membrane, comprising:
 a polymeric microporous substrate; and   a cross-linked anion exchange polymeric layer on the substrate,   the membrane having a resistivity of less than about 1.5 Ohm-cm 2  and an apparent permselectivity of at least about 95%.   
     
     
         13 . The anion exchange membrane of  claim 12 , wherein the cross-linked anion exchange polymeric layer comprises a copolymerization product of at least one quaternized tertiary amine monomer and at least one cross-linking agent. 
     
     
         14 . The anion exchange membrane of  claim 12 , wherein the cross-linked anion exchange polymeric layer comprises a copolymerization product of a two-step fabrication process. 
     
     
         15 . The ion exchange membrane of  claim 14 , wherein a thickness of the polymeric microporous substrate is between about 20 microns and about 255 microns. 
     
     
         16 . The ion exchange membrane of  claim 15 , wherein the thickness of the polymeric microporous substrate is less than about 155 microns. 
     
     
         17 . The ion exchange membrane of  claim 16 , wherein the thickness of the polymeric microporous substrate is less than about 55 microns. 
     
     
         18 . A fuel cell including at least one anion exchange membrane of  claim 12 . 
     
     
         19 . An electrochemical separation device, comprising:
 at least one anion exchange membrane having a resistivity of less than about 1.5 Ohm-cm 2  and an apparent permselectivity of at least about 95%.   
     
     
         20 . The electrochemical separation device of  claim 19 , wherein the electrochemical separation device comprises an electrodialysis cell. 
     
     
         21 . The electrochemical separation device of  claim 19 , wherein the electrochemical separation device comprises an electrodeionization cell. 
     
     
         22 . A desalination system, wastewater treatment system, onsite acid/base generation system, or water treatment system for the food and beverage industry including at least one electrochemical separation device of  claim 19 . 
     
     
         23 . The electrochemical separation device of  claim 19 , wherein the at least one anion exchange membrane is configured for ion selective removal of nitrate, sulfate, perchlorate, boron, silica or anionic selenium.