Patent ID: 8182949

Claim:
A polymer electrolyte membrane comprising as a main ingredient a block copolymer (P) that has been subjected to cross-linking treatment, wherein: the block copolymer (P) comprises, as its constituents, a vinyl alcoholic polymer block (A) and a polymer block (B) having ion-conducting groups; and the block copolymer (P) is: a block polymer represented by the following general formula (I) wherein polymer block (A) comprises monomer repeating units l and m, the relation between l and m is m/(l+m)≧0.80, polymer block (B) comprises monomer repeating units n, the relation among l, m and n is 0.01≦n/(l+m+n)≦R 1 represents a hydrogen atom or a methyl group, X represents a phenylene group or naphthylene group respectively optionally substituted with a methyl group, Y represents a sulfonyloxy group, a phosphonyloxy group or a carbonyloxy group and M represents a hydrogen atom, an ammonium ion or an alkali metal ion; or a block copolymer represented by the following general formula (II) wherein polymer block (A) comprises monomer repeating units l and m, the relation between l and m is m/(l+m)≧0.80, polymer block (B) comprises monomer repeating units n, the relation among l, m and n is 0.01≦n/(l+m+n)≦0.50, R 1 represents a hydrogen atom or a methyl group, Y represents a sulfonyloxy group, a phosphonyloxy group or a carbonyloxy group and M represents a hydrogen atom, an ammonium ion or an alkali metal ion.