A new type of mono-sheet bipolar membrane was produced from a porous polyethylene (PE) substrate using simultaneous irradiation grafting polymerization of acrylic acid (AA) on one side and chloromethylstyrene (CMS) on the other side. PE film with absorbent filter paper absorbing AA on one side and paper absorbing CMS on the other side was irradiated in the cobalt-60 gamma ray irradiation field, followed by quaternization with trimethylamine aqueous solution. AA and CMS were grafted on the substrate membrane simultaneously. The performance of the final membrane is significantly affected by the irradiation time. For short irradiation time, the prepared membrane behaves as a bipolar membrane; whereas for long irradiation time, the final membrane behaves as a charge mosaic membrane. Therefore, by controlling the conditions, a bipolar membrane with good current rectification can be prepared, across which the voltage drop is similar to2.0 V at the current density 800 A/m(2) in 1.0 M NaOH. This preparation method is simple and can be applied both in laboratory and in industry. (C) 2003 Wiley Periodicals, Inc.