Imidazolium and benzimidazolium groups containing anion exchange membranes (AEMs) were synthesized by the functionalization of poly(styrene-co-vinylbenzyl chloride) with methylimidazole and methylbenzylimidazole, respectively. The essential properties for AEMs used in anion exchange membrane fuel cells (AEMFCs) including ion exchange capacity, water uptake, hydration number, and ionic conductivity were investigated. A comparative study of these two AEMs focusing on the alkaline stability was conducted in the present work. We have used TGA, FTIR, H-1 NMR, and C-13 NMR techniques to evaluate the susceptibility to alkaline degradation. Meanwhile, we have performed density functional theory (DFT) calculations to confirm the experimental results of the alkaline degradation study. It has been found that the benzimidazolium cations would be more easily attacked by OH- anions leading to ring-opening compared to the imidazolium cations. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.