More studies on the sulfonated poly(phenylene oxide)+imidazole Brønsted acid–base polymer electrolyte membrane

Abstract In this article, we report the synthesis of a serious of proton-conducting polymer electrolytes made of sulfonated poly(phenylene oxide) (SPPO) and imidazole (Im) by tuning the mixing ratios. The samples were labeled by their mole composition as SPPO- x Im, where x is the molar ratio of Im to SPPO repeat unit. These membranes were studied by means of Thermogravimetric-differential thermal analysis (TG-DTA) and scanning electronic microscope (SEM) and investigation of activation energies of the SPPO- x Im at different relative humidity was also performed. TG-DTA curves reveal these SPPO- x Im composite materials had the high thermal stability. The proton conductivity of SPPO- x Im composite material increased with the temperature, and the highest proton conductivity of SPPO- x Im composite materials was found to be 6.92×10 −3  S/cm at 200 °C under 33% relative humidity (RH) with a “mixing rate” where x =2.