Research and development efforts have been focussed over the last five years towards the preparation of new, but potentially commercially viable low-cost copolymers for use as proton exchange membrane for fuel cell and other membrane applications. Our primary efforts centered on the direct synthesis of disulfonated copolymers via step-polycondensation methods. These novel series of disulfonated copolymers include optionally fluorinated poly(arylene ethers), poly(thioethers), polyimides, polybenzimidazoles, and polybenzoxazoles, as well as multi-block copolymer systems. The first generation of alternative proton exchange membranes (PEMs) has focused on wholly aromatic, disulfonated poly(arylene ether sulfone) random copolymers. Detailed herein are the development and current state of these disulfonated poly(arylene ether sulfone) copolymers and their fuel cell performance in both hydrogen-air PEMFCs and direct methanol fuel cells (DMFC).