A high degree of sulfonation is required to obtain high proton conductivity in proton exchange membranes. However, it inevitably undergoes increasing swelling ratio and poor mechanical properties. To overcome this problem, 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 and was physically crosslinked by ionic interactions. These two factors combined to enhance the physical stability and chemical stability. The influence of this crosslinker amount on the chemophysical properties of the blend membranes will be discussed.