Proton exchange membranes were prepared by y-ray radiation-induced grafting onto ETFE films, crosslinking with styrene/divinylbenzene (DVB) mixtures and a subsequent sullonation. Effects of the DVB content on the membrane properties such as ion exchange capacity (lEC), proton conductivity, and methanol permeability were investigated. Membrane-electrode assemblies (MEA) containing the prepared membranes were fabricated for direct methanol fuel cells (DMFC), and the MEA performance was examined in operation with various concentrations of methanol. Durability of the MEAs was investigated using a 3 M methanol solution for 1000 h, and the polarization curves and impedance spectra were measured. Physicochemical properties of catalysts and membrane before and after the long-term operation were analyzed by TOM, XRD, lEC, and proton conductivity. Performance and durability of the selected membranes were also confirmed in the operation of a 6-cell stack with 3 M methanol solution. (C) 2014 Elsevier B.V. All rights reserved,