Résumé
The properties of a new ether-linked polybenzimidazole (PBI) that can be directly sulfonated in solution have been associated with those of a polymeric phosphonic acid, with the aim of inducing proton conductivity at both lower (-SO3H groups) and higher (-PO3H2 functions) temperatures. Conductivity was determined up to 120 degrees C and at relative humidity values between 25 and 95% on dense interpenetrating network type membranes having 5-10 phosphonic acid groups/sulfonated PBI repeat unit. At 120 degrees C, the mixed functionality (-SO3H/-PO3H2) membrane has higher conductivity than the sulfonic or phosphonic acid functionalised membranes alone at relative humidity values below 80%, and the dependence of its conductivity at this temperature on RH is significantly lower than that of the sulfonated PBI membranes alone.