Polybenzimidazoles containing bulky substituents and ether linkages for high-temperature proton exchange membrane fuel cell applications

Novel solution-processable polybenzimidazoles P1-P3 were prepared from three new teteraamines and 4,4'-oxybis(benzoic acid) in Eaton's reagent at 145 degrees C. These tetraamines were 4,4',5,5'-tetra-aminodiphenyldiphenyl ether containing bromide, phenyl and trifluoromethyl-substituted phenyl substituents at 2 and 2' positions, respectively. P1-P3 exhibited good thermal stability, oxidative stability and mechanical properties. Phosphoric acid-doped P1-P3 membranes also exhibited high proton conductivity in the range of 5.30 x 10(-2) -8.80 x 10(-2) S cm(-1). They also demonstrated high performance on single cell test, with open circuit voltages of 0.84-0.98 V and peak power density of 478-636 mW cm(-2) at 160 degrees C with acid uptakes of 199-241%. Especially, the fuel cell based on P3 with an open circuit voltage of 0.95 V and peak power density of 636 mW cm(-2) exhibited better performance than the one based on m-PBI. These membranes provided new options as proton exchange membranes for high-temperature PEMFC applications. (C) 2016 Elsevier B.V. All rights reserved.