New amphiphilic block copolymers composed of thermally and chemically stable poly(arylene sulfone ether ketone) and sulfonated poly(styrene-co-acrylonitrile) were successfully synthesized through two-step polymerization, condensation polymerization followed by controlled radical polymerization, for application to proton exchange membrane fuel cells. The morphological structures of membranes were investigated as functions of the hydrophilic chain length and the degree of sulfonation (DS), and were related to the proton conductivity of the membranes. Because of their inherent high thermal stability and well-connected hydrophilic channel, the newly synthesized membranes show high proton conductivity at relatively low DS and a continuous increase in proton conductivity above 90
C. They also exhibit good thermal and oxidative stability......