| abstract |
To present an electrolyte material having a high softening temperature, which is useful for obtaining a polymer electrolyte fuel cell which can be operated at a high temperature and whereby a high output power can be obtained with little catalyst poisoning. 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 (which may contain 1 or 2 oxygen atoms), of which at least one carbon atom is contained in the main chain of the polymer, and an ionic group such as a sulfonic acid group which is bonded to the 5-membered ring directly or via a perfluoroalkylene group having a linear or branched structure; and the polymer has a softening temperature of at least 120° C. |