Synthesis and characterization of poly(m-tolyloxy-co-4-pyridinoxy phosphazene)s and their application as proton exchange membranes

A novel set of polyphosphazenes are synthesized to produce three polymers with varying side group ratios for proton exchange membranes. The designed heterosubstituted polymers here are the rare examples of polyphosphazenes of this kind to serve as proton exchange membranes with optimized structural stability and high temperature ionic conductivity. High quality polyphosphazenes with narrow polydispersity and rather low Tg values were prepared. These poly(m-tolyloxy-co-4-pyridinoxy phosphazene)s are sulfonated under a range of conditions and characterized in order to investigate the synergetic effect of the heteroatom on the proton conductivity of the proton exchange membranes. The effect of sulfonation temperature and time on the fuel cell relevant properties is also investigated. Hydrolytically stable proton exchange membranes with high thermal and chemical stabilities are achieved. Additionally, resultant membranes exhibit proton conductivity, IEC and water uptake values comparable with commercial Nafion® membranes