An ionically conductive polymer has the chemical structure 1 as shown herein. Examples of the polymer include 4,4′-(4-(1H-benzo[d]imidazol-2-yl)butane-2,2-diyl)diphenol, sulfonated poly(aryl ether sulfone) containing benzimidazole backbone, sulfonated poly(aryl ether sulfone) containing carboxylic acid backbone, and sulfonated poly(aryl ether sulfone) containing benzimidazole backbone from carboxylic acid containing sulfonated poly(aryl ether sulfone). The polymer has intrinsic ion conducting properties so that it is effectively conductive even under low water conditions. In one embodiment, the polymer has an ionic conductivity of at least 1×10−5 S/cm at a temperature of 120° C. when the polymer is substantially anhydrous.