A fully sulfonated poly(aryl ether ketone) bearing pendent sulfoalkyl groups in the side chain (SNPAEK-100) is synthesized and used as the matrix membrane. Two series of composite membranes are obtained by introducing epoxy resins (TMBP) and two different curing agents with or without sulfonic acid groups (DDS and BDSA). All the membranes are investigated in detail as polymer electrolyte membranes. As expected, the water uptake, the methanol permeability, and the proton conductivity of the crosslinked membranes decrease with increasing epoxy resin content. Compared with STD-x membranes (0.101 S cm(-1)-0.233 S cm(-1)), the STB-x (0.171 S cm(-1)-0.266 S cm(-1)) membrane series reduce the loss of proton conductivity because of the sulfonated curing agent, BDSA. Other properties of the composite membranes, such as the mechanical properties and the thermal properties are also investigated. All the results indicate that the composite membranes based on SNPAEK-100 and BDSA are promising membrane candidates for direct methanol fuel cells. (C) 2012 Elsevier B.V. All rights reserved.