Annealing effect of highly sulfonated polyphenylsulfone polymer

• Alcohol solvent for hydrocarbon polymer electrolyte (SPPSU).
• Improvement of a stability of the SPPSU membrane using annealing processing.
• High proton conductivity for PEMFCs.

Sulfonated polyphenylsulfone (SPPSU) membranes were prepared using alcohol solvents such as isopropanol and 1-propanol in combination with a highly sulfonated PPSU polymer. A covalently crosslinked membrane was obtained after annealing at 180 °C without a crosslinker. The membrane was stable in water, and the thermal stability was higher than that of a synthesized SPPSU polymer. This higher stability was because of the crosslinking effect through the sulfonyl and/or phenyl groups of SPPSU. A high conductivity of 0.1 S/cm and power density of 471 mW/cm2 were obtained at 80 °C and relative humidity (RH) 100%.