Sulfonated poly(phthalazinone ether ketone) (SPPEK) impregnated Solupor (R) microporous film (SPPEK-PE)and pure SPPEK membranes with two different ion-exchange capacities (IECs) were prepared and characterized for use in DMFC applications. Swelling, proton conductivity, diffusion and DMFC experiments were performed at various methanol concentrations to understand the effect of impregnation of an ion-conductive polymer membrane to the fuel cell performance. Impregnating SPPEK into PE decreases swelling degree and methanol permeability of the membranes, but at the same time the proton conductivity. Unlike perfluorinated membranes, SPPEK-PE shows an increase in its DMFC performance at high methanol concentration and that makes it more attractive for mobile DMFC applications where high methanol concentrations are needed to compete with Li-ion batteries. (c) 2008 Elsevier B.V. All rights reserved.