Poly (aryl hexafluoro sulfone benzimidazole) and poly (aryl hexafluoro ethoxy benzimidazole), termed as PArF6SO2BI and PArF6OBI, are synthesized and characterized systematically. PArF6SO2BI membranes illustrate good chemical stability in terms of oxidative weight loss due to the electron-withdrawing sulfone functional group. PArF6OPBI membranes exhibit weak chemical stability after immersion in Fenton's solution. Many of the membranes show good conductivities. Higher conductivities of 3.26 x 10(-2) S cm(-1) at 160 degrees C with 286.8 wt% acid doped level for 3:1 (2.335 mmol of 4,4'-sulfonyldibenzoic acid and 7.005 mmol of 2, 2-bis(4-carboxyphenyl) hexafluoropropane) ratio of PArF6SO2BI and 7.31 x 10(-2) S cm(-2) with 356.9 wt% for 3:1 ratio of PArF6OBI are observed. PArF6SO2BI and PArF6OPBI membranes exhibit good conductivity, thermal and mechanical stabilities which are crucial requirements for high temperature fuel cells. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.