Fabrication and investigation of phosphoric acid doped imidazolium siloxane crosslinked poly(2,6‐dimethyl‐1,4‐phenylen oxide) for high temperature polymer electrolyte membranes

A series of high temperature polymer electrolyte membranes were fabricated based on imidazolium poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) using methylimidazole (MeIm) and triethoxysilylpropyldihydroimidazole (SiIm) as quaternization reagents via the S(N)2 nucleophilic substitution. Meanwhile SiIm was also employed as a crosslinking agent and the crosslinked Si-O-Si network was constructed through a hydrolysis procedure of SiIm in an acid medium. Compared with the PPO-100%MeIm membrane without the crosslinking structure, the imidazolium siloxane crosslinked PPO-x%SiIm-y%MeIm membranes exhibited increased acid doping contents, enhanced dimensional stabilities, improved mechanical properties and higher conductivities. The PPO-30%SiIm-70%MeIm/(198 wt% phosphoric acid) membrane displayed a conductivity of 0.08 S cm(-1) at 180 degrees C without humidifying and a tensile strength of 6.4 MPa at room temperature. (c) 2019 Society of Chemical Industry