UV radiation-induced photografting of styrene into poly (tetrafluoroethylene-co-ethylene) (ETFE) films for the preparation of fuel cell membranes was carried out. The proton conductivity in the thickness direction of membranes prepared by the vapor- and liquid-phase photografting can reach as high as 0.065 and 0.087 S/cm, respectively. The higher conductivity in the liquid-phase grafting is close to the homogeneity of graft chain distribution in the membrane. (c) 2006 The Electrochemical Society.