Strong acid homogenous cation exchange membranes were obtained by simultaneously introducing sulfonic and bromine groups into poly(2,6-dimethyl-1,4-phenylene oxide) (PPO). The ion-exchange capacity (IEC), water content, transport number, diffusion coefficient, contact angle, and tensile strength of the obtained membranes were studied. The results show that the membrane intrinsic properties are largely dependent on the Substitution of bromine: the TEC and water content decrease with bromine content, while the area resistance and permselectivity of the membranes increase with this trend. Therefore, by properly balancing them, a series of homogenous cation exchange membranes having good electrical properties and physical stability can be obtained to comply with different industrial electromembrane processes, Such as diffusion dialysis, electrodialysis, electrodeionization, etc. (c) 2006 Wiley Periodicals,