Proton conducting polymer membranes: synthesis & characterization of novel sulfonated polyimides

A new synthetic route to prepare the sulfonated monomer ((2,2’-bis(4-sulfobenzyloxy)benzidine), was developed. This and related compounds were characterized by 1H and 13C NMR, FTIR and EA. This new synthetic route provides access to a variety of new sulfonated monomers and polymers, which in turn facilitates studies of structure-property relationships of proton conducting membranes. A series of novel membranes were prepared from the sulfonated polymer. This series of novel sulfonated polyimide membranes possesses higher hydrolytic stability than those prepared from polyimides in which the sulfonate groups are attached directly to the polyimide main chain, yet their proton conductivity is similar. The polymers were also characterized by nuclear magnetic resonance, differential scanning calorimetry, thermogravimetric analysis and in a fuel cell.