Synthesis and study of pyridine-containing sulfonated polybenzimidazole multiblock copolymer for proton exchange membrane fuel cells

To improve the chemical stability and acid doping levels of proton exchange membranes, a series of sulfonated polybenzimidazole multiblock copolymers containing pyridine rings (sPBI40-b-PyPBI5-b-PIx) was synthesized. All the copolymers exhibited excellent solubility. The proton exchange membranes were prepared using a solvent casting method. All the membranes were characterized by thermal stability, a tension test, chemical stability, dimensional stability, PA-doping ability, and proton conductivity. All of the membranes had good thermal stability, mechanical properties, and dimensional stability. The proton conductivity of sPBI40-b-PyPBI5-b-PI5 (ion exchange capacity, IEC = 1.83 mmol g−1) was 0.018 S cm−1 at 105 °C and 100% relative humidity. The proton conductivity of the sPBI40-b-PyPBI5-b-PI5 membrane with the highest PA uptake (199.8%) reached 0.23 S cm−1 at 180 °C. The high doping level and the proton conductivity were due to the pyridine group which increased the basicity of the copolymer. The chemical stability of the membranes, which was also a consequence of introducing the pyridine group, was better than that of sPBI-b-PI which does not have a pyridine group. This series of block copolymers have a promising application in proton exchange membranes.