Proton exchange membranes (PEMs) were prepared by pre-irradiation induced grafting of styrene (S) or styrene/divinylbenzene (S/DVB) into the radiation-crosslinked polytetrafluoroethylene (RX-PTFE) films and then sulfonated. The thicknesses of the obtained PEMs were lower than 20 mu m and the ion exchange capacity (IEC) values were around 2 meq g(-1). The surfaces of the PEMs and carbon electrodes were coated with Nafion (R) dispersion, and then membrane electrode assembles (MEAs) were prepared by hot-pressing them together. A MEA based on a Nation (R) 112 membrane was also prepared under same procedure for comparison. The performances of the MEAs in a single cell were tested under different cell temperatures and humidifications. Electrochemical impedance spectra (EIS) were measured with ac frequencies which ranged from 100 kHz to 1 Hz at a dc density of 0.5 A cm(-2). The obtained impedance curves in Nyquist representation were semicircular. (c) 2006 Elsevier B.V. All rights reserved.