Acid functionalized poly(arylene ether)s for proton-conducting membranes

4,4′-Difluorobenzophenone and 4,4′-difluoro-diphenylsulfone were sulfonated successfully using fuming sulfuric acid (∼50% SO3). These monomers and hydroquinone 2-potassium sulfonate were converted to poly(arylene ether)s by nucleophilic displacement polycondensation with different bisphenols in the presence of potassium carbonate in NMP or in DMSO. The polymers obtained by displacement exhibit high molar masses with weight average molecular weights up to 1.84 × 105 g mol−1 in GPC. The chemical structures of the polymers were confirmed by spectroscopy and elemental analysis. The resulting acid functionalized poly(arylene ether)s are amorphous with glass transition temperatures between 175 and 248 °C, and the Tgʹs taken as maximum in the tan δ curve of the DMTA measurements are in good agreement with calorimetry results. The acid functionalized polymers exhibit acceptable thermal stability, i.e., a 5% weight loss occurred between 310 and 324 °C in TGA under synthetic air. The mechanical properties of these polymers indicate ductile mechanical behavior with an elongation at break up to 230%. Water uptakes of films cast from the polymers are between 39 and 49% (w/w), which corresponds to 8.8–10.0 molecules of H2O per sulfonic acid group. Ion exchange capacity was also determined by titration.