The surface of sulfonated poly(arylene ether ketone) bearing carboxyl groups (SPAEK-C) was modified by alternating deposition of oppositely charged polypyrrole (PPY) and phosphotungstic acid (PWA) via the layer-by-layer (LBL) method in order to prevent the crossover of methanol in the direct methanol fuel cell (DMFC). FT-IR confirms that PPY and PWA are assembled in the multilayers successfully. The morphology of the membranes studied in detail by SEM shows the presence and stability of thin PPY/PWA layers coated on SPAEK-C membranes. Methanol permeability was determined and was shown to be effectively reduced. The selectivity of SPAEK-C-(PPY/PWA)(n) is 1 order more than Nafion (R) 117, which is attractive in DMFCs. Thermal stability, water uptake, water swelling and proton conductivity of the SPAEK-C and SPAEK-C-(PPY/PWA)(n) membranes were also investigated. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.