Novel proton conducting polybenzimidazole (PBI) membranes

New proton conducting polymeric materials based on sulfonated polybenzimidazoles (sPBI) have been prepared and characterized. Polybenzimidazoles are among the best thermo and chemically stable polymers, and can become good proton conductors when sulfonic acid groups are included into their chemical structures. The original approach of this work consists in the development of new sulfonated monomers that enable an excellent control on the final ionic conducting polymer. Indeed, it allows to tune the extent of sulfonation, the position of the sulfonic acid in the polymer structure, and the organization of sulfonated units in the polymer chain. sPBI membranes with ion exchange capacity (IEC) ranging from 0 to 3.8 meqH + /g have been prepared. Low sulfonated membranes exhibit outstanding resistance toward oxidation, but low conductivity. On the other hand, highly sulfonated ones have good conductivity (up to 1.9E-2 S/cm at Tamb) but low stability. A good balance of these properties is found for IEC values around 3 meqH + /g.