Polyetheretherketone (PEEK)-based polymer electrolyte membrane (ssPEEK) was prepared by successive grafting of divinyl benzene (DVB) and ethyl styrenesulfonate (ETSS) onto PEEK film, followed by hydrolysis of the ETSS graft chains to form styrenesulfonate (SS) graft chains. In comparison with the commercial Nafion membrane, the obtained ssPEEK membrane possesses superior proton conductivity and mechanical property, comparable fuel cell performance at a lower temperature and higher relative humidity (80 degrees C, 100 RH%), and substantially better fuel cell performance at a higher temperature and lower relative humidity (95 degrees C, 40 RH%). Furthermore, the ssPEEK membrane maintains good performance in a fuel cell after operation at 95 degrees C and 40 RH% for more than 250 h, while the Nafion membrane deteriorated under such conditions. (C) 2008 Elsevier B.V. All rights reserved.