The effect of structural variations on aromatic polyethers for high-temperature PEM fuel cells

Three series of new aromatic polyether sulfones bearing phenyl, p‐tolyl or carboxyl side groups, respectively, and polar pyridine main chain groups were developed. Most of the polymeric materials presented high molecular weights and excellent solubility in common organic solvents. More importantly, they formed stable, self‐standing membranes that were thoroughly characterized in respect to their thermal, mechanical and oxidative stability, their phosphoric acid doping ability and ionic conductivity. Particularly, the copolymers bearing side p‐tolyl or carboxyl groups fulfill all necessary requirements for application as proton electrolyte membranes in high temperature fuel cells, which are glass transition temperatures higher than 220 °C, thermal stability up to 400 °C, oxidative stability, high doping levels (DLs) and proton conductivities of about 0.02 S/cm. Initial single fuel cell results at high temperatures, 160 °C or 180 °C, using a copolymer bearing p‐tolyl side groups with a relatively low DLs around 200 wt % and dry H2/Air feed gases, revealed efficient power generation with a current density of 0.5 A/cm2 at 500 mV. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 Aromatic polyethers comprised of pyridine main chain units and either phenyl, p‐tolyl or carboxyl side ones are presented aiming at high temperature PEMFC applications. The copolymers showed excellent film forming ability, mechanical and thermal properties as well as outstanding oxidative stability even after prolonged exposure under an oxidative environment. The copolymers can be readily doped with phosphoric acid, reaching high doping levels up to 450 wt %. The ionic conductivities obtained are around 0.02 S/cm at RT, while initial single fuel cell tests revealed efficient power output with a current density of 0.5 A/cm2 at 500 mV at elevated temperatures of 160 °C or 180 °C.