Fuel cells are considered as one of the promising clean energy technologies in the context of present and future energy challenges. Proton exchange membranes (PEMs) are one of the key components of fuel cells act primarily as solid electrolyte. In this regard, Dupont’s Nafion®, sulfonated tetrafluoroethylene based copolymers are the most commonly used materials because of their excellent oxidative and chemical stability along with high proton conductivity. However, deterioration in the conductivity and the mechanical strength at temperature above 80 oC, and high preparation cost of Nafion® urge the necessity to develop alternative proton conducting polymers. In the serch of development of new PEM materials a series of fluorinated sulfonated poly(arylene ether sulfone)s copolymers (HPPQSH-XX)and its grafted form HPPQSH-XX PS were synthesized by developing a novel methodology to get high proton conductivity along with desirable set of other PEM properties. The random copolymers HPPQSH-XX with different statistical distribution of –SO3H moiety showed very small ionic clusters (5–10 nm) whereas the grafted copolymers showed larger ionic domains (60–100 nm) on their TEM images. All ionomer membranes showed good mechanical properties, high oxidative and dimensional stability with low water uptake and swelling ratios. In this series the HPPQSH-30 PS copolymer with highest ion exchange capacities exhibited maximum proton conductivity of 125 mS/cm at 80 °C and 142 mS/cm at 90 °C, which was very close to the conductivity of Nafion® 117 membrane.
