Novel proton exchange membrane for fuel cell developed from blends of polybenzimidazole with fluorinated polymer

Search of thermo-chemically and mechanically stable PEM with high proton conducting ability for the use in high temperature fuel cell motivated us to develop PEM from the blend of polybenzimidazole (PBI) with poly(vinylidene fluoride-co-hexafluoro propylene) (PVDF-HFP). The formation of blend (miscibility of the two polymeric components) is confirmed by studying varieties of spectroscopic and thermodynamical techniques. The results obtained from these studies attribute the presence specific interactions and partial miscibility between the two polymers. The hydrophobicity of PVDF-HFP controls the amount of phosphoric acid (PA) loading and is found to be the responsible for lower water uptake of the blend membrane compared to pristine PBI. The blending significantly reduces the increase in thickness and swelling ratio of the membranes upon doping with PA. The presence of fluorine atoms of PVDF-HFP in the blend membranes helps to obtain significantly higher proton conductivity than the native PBI and enhance the oxidative stability substantially. PA doped blend membranes display superior mechanical stability compared to neat PA doped PBI. Hence the current blend membranes bear all the essential physical characteristics which are required for the PEM to be use in fuel cell.