Thermal crosslinking of aromatic polyethers bearing pyridine groups for use as high temperature polymer electrolytes

New aromatic polyethers containing main chain polar pyridine groups, as well as crosslinkable side chain double bonds, have been synthesized employing various comonomersʹ ratios affording soluble high molecular weight copolymers. The new copolymers were characterized and thereafter subjected to thermal curing above the glass transition temperature without the use of crosslinking agent that successfully led to their crosslinked analogs. The properties of the crosslinked materials in respect to their potential use as high temperature polymer electrolytes were thoroughly investigated. All materials exhibit excellent film forming properties and advanced chemical and physicochemical properties with high oxidative stability, mechanical integrity, high glass transition temperatures (Tg even above 330 °C) and thermal stability up to 400 °C. The doping ability in phosphoric acid was decreased compared to the non-crosslinked copolymers. Despite the moderate phosphoric acid doping levels, in-situ conductivity reached values above 5×10−2 S cm−1. Polarization curves were obtained at temperatures up to 220 °C demonstrating their feasibility to be used as electrolytes for high temperature PEM fuel cells.