Novel sulfonated poly(ether ether ketone)/ polybenzimidazole blends for proton exchange membranes

A novel soluble polybenzimidazole with a pendant phenyl group (Ph-PBI) was successfully synthesized based on 4,4′-(1,4-phenylenedioxy-2-phenyl) dibenzoic acid and diaminobenzidine. A phenylated sulfonated poly(ether ether ketone) (Ph-SPEEK) with a similar chemical structure to Ph-PBI was selected as matrix. Ph-SPEEK/Ph-PBI membranes were produced by a solution method. The obtained blend membranes exhibited much higher thermal stability as well as oxidative stability and lower water uptake than the pristine Ph-SPEEK membrane. The proton conductivity of the blend membranes could be in the range of 0.0374–0.1456 S cm −1 at 100°C. As a result, the blend membranes also showed improved mechanical properties that may be related with the acid–base interactions between the two components.