Patent ID: 7799468

Claim:
An electrolyte material for polymer electrolyte fuel cells, which is made of a polymer containing repeating units based on a fluoromonomer having a radical polymerization reactivity, wherein the repeating units contain a 5-membered ring, of which at least one carbon atom is contained in the main chain of the polymer, and an ionic group which is bonded to the 5-membered ring directly or via a perfluoroalkylene group having a linear or branched structure; the ionic group is represented by the formula —(SO 2 X(SO 2 R f ) g ) − H + , wherein R f is a linear or branched perfluoroalkyl group, and X is an oxygen atom, a nitrogen atom or a carbon atom, provided that when X is an oxygen atom, g=0, when X is a nitrogen atom, g=1, and when X is a carbon atom, g=2; and the polymer has a softening temperature of at least 120° C.