Ion exchange membranes containing inorganic particles
View Patent ↗An ion exchange membrane and a method of making it. The membrane may be used, for example, in an electrodialysis module or electrochemical cell. The membrane comprises an ion exchange polymer and inorganic particles preferably linked to the ion exchange polymer. To make a membrane, inorganic particles are mixed into an ion exchange membrane pre-cursor. A polymerization initiator or catalyst is then added and the resulting mixture is placed in a form and cured. The inorganic particles may comprise, for example, an oxidized form of graphite such as graphite oxide. The ion exchange polymer may comprise an ionic monomer, containing a quaternary ammonium group for anion exchange or a sulfonate group for cation exchange, along with a crosslinking co-monomer containing polymerizable diacrylic functionalities. The membrane is self-supporting and can be made without a supporting fabric.
1. A method for making an ion exchange membrane comprising polymerizing an ionic monomer, and optionally another, second compound, in the presence of inorganic particles to form the ion exchange membrane, the monomer or second compound linking to the inorganic particles by a physical or chemical bond, wherein the monomer or second compound links to the inorganic particles by a C—O or N—O chemical bond, hydrogen bonding or π-π stacking, and wherein the monomer or second compound is selected from the group consisting of a) ethylenic monomers, b) polyepoxides, c) N-vinyl caprolactam, d) glycidyl methacrylate and e) a reaction product of dimethylaminopropylmethacrylamide (DMAPMA) and 1,4-cyclohexanedimethanol diglycidyl ether (CHDMDGE).
2. The method of claim 1 wherein the monomer is a reaction product of dimethylaminopropylmethacrylamide (DMAPMA) and 1,4-cyclohexanedimethanol diglycidyl ether (CHDMDGE) having one of the following structures:
wherein R is —[CH 2 —CH(OH)]—W—; R 1 is hydrogen or a C 1 -C 12 alkyl group; Z is oxygen or N—R 3 ; R 2 is —[CH 2 ] n —; R 3 is hydrogen or —[CH 2 ] m —CH 3 ; R 4 and R 5 are each, independently, —[CH 2 ] m —CH 3 ; X is selected from the group consisting of Cl, Br, I and acetate; W is a bridging group or atom; m is an integer from 0 to 20, and n is an integer from 1 to 20.
3. The method of claim 1 wherein the ionic monomer is polymerized along with a crosslinking co-monomer containing polymerizable diacrylic functionalities.
4. The method of claim 1 wherein the inorganic particles are added prior to a catalyst or initiator.
5. The method of claim 1 wherein the inorganic particles comprise an oxidized graphite derivative, a silicate or a zeolite.
6. The method of claim 1 wherein the inorganic particles comprise graphite oxide, graphene oxide or partially reduced graphene oxide.
7. The method of claim 1 comprising curing the polymer without a reinforcing fabric.
8. The method of claim 1 wherein the monomer has the following structure:
wherein R is —[CH 2 —CH(OH)]—W—; R 1 is hydrogen or a C 1 -C 12 alkyl group; Z is oxygen or N—R 3 ; R 2 is —[CH 2 ] n —; R 3 is hydrogen or —[CH 2 ] m —CH 3 ; R 4 and R 5 are each, independently, —[CH 2 ] m —CH 3 ; X is selected from the group consisting of Cl, Br, I and acetate; W is a bridging group or atom; m is an integer from 0 to 20, and n is an integer from 1 to 20.