Brønsted acid–base polymer electrolyte membrane based on sulfonated poly(phenylene oxide) and imidazole

The Brønsted acid–base polymer electrolyte membrane was prepared by entrapping imidazole in sulfonated poly(phenylene oxide) at the molar ratio of Im/SPPO = 2:1. The hybrid showed a high thermal stability up to 200 °C and peroxide tolerance. Differential scanning calorimetry shows that glass transition temperature is 232 °C. The conductivity increases with temperature exceeding 10−3 S/cm above 120 °C and a high conductivity of 6.9 × 10−3 S/cm was obtained at 200 °C under 33% RH conditions.