Novel physically crosslinked polymer membranes were prepared by simply blending densely sulfonated poly(fluorenyl ether sulfone) with imidazolium-functionalized poly(ether sulfone). The blend showed well-defined ionic channels originating from the densely sulfonated structure and was physically crosslinked by ionic interactions. These two factors combined to enhance the physical stability and chemical stability of the prepared membranes while offering a conductivity over 0.24 S/cm at 80 degrees C for various amounts of crosslinker in the blend. The influence of this crosslinker amount on the chemophysical properties of the blend membranes was studied in a systematic way. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.