Chemically modified anion exchange membrane and method of preparing the same
The present invention relates to a chemically modified anion exchange membrane and a method of preparing the same and, more particularly, an anion exchange membrane in which sulfonic acid groups in a perfluorinated sulfonic acid electrolyte membrane are substituted with anion conductive groups such as ammonium group, phosphonium group, imidazolium group, pyridinium group and sulfonium group, and a method of preparing an anion exchange membrane by chemically modifying sulfonic acid groups in a perfluorinated sulfonic acid electrolyte membrane.
1. A method of preparing an anion exchange membrane, comprising:
a) chlorinating sulfonic acid groups in a perfluorinated sulfonic acid electrolyte membrane;
b) introducing bridge groups to the chlorinated electrolyte membrane; and
c) substituting the chlorine groups in the bridge group-introduced electrolyte membrane with anion-conductive functional groups
selected from phosphonium group, imidazolium group, pyridinium group or sulfonium group.
2. The method of claim 1 , wherein the perfluorinated sulfonic acid electrolyte membrane is a perfluorinated sulfonic acid ionomer free-standing membrane or a reinforced composite membrane including porous supports.
3. The method of claim 2 , wherein the perfluorinated sulfonic acid ionomer is selected from the group consisting of poly(perfluorosulfonic acid)s, sulfonic acid-containing-copolymers composed of tetrafluoroethylene and fluorovinylether, and their mixtures thereof.
4. The method of claim 2 , wherein the porous supports of the reinforced composite membrane are selected from the group consisting of polytetrafluoroethylene, poly(vinyldifluoroethylene), polyethylene, polypropylene, poly(ethyleneterephthalate), polyimide and polyamide.
5. The method of claim 1 , wherein the chlorination is performed by treating the perfluorinated sulfonic acid electrolyte membrane with a solution including one or more compounds selected from the groups consisting of SOCl 2 , MeSO 2 Cl, PCl 5 , POCl 3 , and dichloromethane (DCM).
6. The method of claim 1 , wherein the introduction of bridge groups is performed by treating the chlorinated electrolyte membrane with a solution including chlorobenzene, bromobenzene, or their mixtures thereof.
7. The method of claim 1 , wherein the bridge group is phenyl group.
8. The method of claim 1 , wherein the substitution of chlorine groups with anion-conductive functional groups is to react the bridge group-introduced electrolyte membrane with a solution including one or more compounds selected from tris(2,4,6-trimethoxyphenyl)-phosphine, 1-methylimidazole, pyridine, 4-dimethylamino pyridine, dimethyl sulfide and methyl phenyl sulfide.
9. The method of claim 1 , wherein each of the chlorination, the introduction of bridge groups, and the substitution of chlorine groups with anion-conductive functional groups is performed at 10 to 130° C. for 30 seconds to 24 hours.
10. The method of claim 1 , further comprising washing and drying, after each of the chlorination, the introduction of bridge groups and the substitution with anion-conductive functional groups.