A polyarylene copolymer having a sulfonic acid group which has high proton conductivity and reduced swelling in hot water and reduced shrinkage in drying; a solid polymer electrolyte and a proton conductive membrane comprising the copolymer; and a membrane...

[Object] To provide a proton exchange membrane for a fuel cell having excellent proton conductivity, lower property of swelling with hot water, and excellent durability, as well as a block copolymer forming the proton exchange membrane, and a composition, ...