In this paper, a new preparation route for a series of bipolar membranes is proposed. The bipolar membranes are initiated directly from same base polymer poly(2.6-dimethyl-1,4-phenylene oxide) (PPO), in which the anion exchange layer is prepared by bromination with bromine and then quaternary amination instead of chloromethylation with chloromethyl methyl ether and then quaternary amination and the cation exchange layer prepared by conventional sulfonation. The fundamental characteristics of bipolar membranes, current-voltage curves, are fully discussed based on the properties of anion exchange layers which can be controlled by bromination position and content as well as the amination time. The results show that the prepared bipolar membranes can exhibit lower voltage drop over 100 mA/cm(2) and possess excellent industrial application potentials if the bromination process and amination process of anion exchange layers are properly controlled. (C) 2004 Elsevier B.V. All rights reserved.