Novel poly(aryl ether sulfone) copolymers containing 2.5-biphenylpyridine and tetramethyl biphenyl moieties were synthesized by polycondensation of 4-fluorophenyl sulfone with 2,5-(4',4 '' dihydroxy biphenyl)pyridine and tetramethyl biphenyl diol. Copolymers with different molecular weights and different monomer compositions were obtained. These copolymers exhibit excellent film-forming properties, mechanical integrity, and high modulus up to 250 degrees C, high glass transition temperatures (above 280 degrees C) as well as high thermal stability up to 400 degrees C. In addition to the above properties required for PEMFC application, this novel material shows high oxidative stability and doping ability, enabling proton conductivity in the range acid of 10(-2) S.cm(-1) above 130 degrees.