Highly conductive aromatic ionomers with perfluorosulfonic acid side chains for elevated temperature fuel cells

A versatile and facile synthetic approach to a new class of ionomers with rigid aromatic backbone and pendant perfluorinated sulfonic acid groups is described. Characterization of the prepared polymers has been carefully carried out by ¹H and ¹⁹F NMR, elemental analysis, intrinsic viscosity, TGA and DSC. It is shown that the perfluorosulfonic acids greatly enhance the proton conductivity of ionomers under high temperature and low humidity conditions. The aromatic ionomers exhibit comparable proton conductivity to Nafion over a wide humidity range at elevated temperatures, while maintaining other outstanding properties of aromatic polymers, e.g. low gas permeability, excellent thermal and chemical stability and good mechanical properties. It is also demonstrated that the maximum power density and current density of the aromatic ionomers are 30% and 43% higher, respectively, than those of Nafion in initial fuel cell tests at 120 °C.