What is claimed is:
1 . A cationic copolymer comprising the divalent monomer units:
wherein:
each Ar 1 independently represents phenylene;
each L independently represents a direct bond or
wherein each R 1 independently represents an alkyl group having 1 to 4 carbon atoms, and each R 2 independently represents an alkylene group having from 1 to 6 carbon atoms, and each Z− represents a non-interfering monovalent anion;
each Ar 2 independently represents an optionally substituted divalent aryl ring, with the proviso that if L represents a direct bond, then Ar 2 represents an optionally substituted cationic divalent aryl ring accompanied by Z−;
each R 3 represents a methyl group; and
each D independently represents a direct bond or the group represented by
wherein each R 4 is methyl, Z− represents a non-interfering monovalent anion, adjacent D and L are not both direct bonds, and wherein if L is a direct bond, then D is the group represented by
wherein the ratio of moles of monomer unit a) to the sum of the moles of monomer units b) and c) is 1:1 to 4:1, wherein for at least some of monomer units b), at least some Ar 1 are p-phenylene and wherein, for at least some of monomer units b), each L independently represents
2 . The cationic copolymer of claim 1 , wherein each R 1 is methyl, R 2 is methylene and Ar 2 is phenylene.
3 . The cationic copolymer of claim 2 , wherein Ar 2 is p-phenylene.
4 . A curable membrane precursor composition comprising:
i) the cationic copolymer of claim 2 ; and ii) a free-radical initiator.
5 . A membrane composition comprising an at least partially cured curable membrane composition according to claim 4 .
6 . A curable membrane precursor composition comprising:
i) the cationic copolymer of claim 1 ; and ii) a free-radical initiator.
7 . A membrane composition comprising an at least partially cured curable membrane composition according to claim 6 .
8 . An electrochemical device comprising:
an anode; a cathode; and a membrane positioned between the anode and cathode, wherein the membrane comprises the membrane composition of claim 7 .
9 . A membrane composition comprising an at least partially cured curable membrane composition according to claim 1 .