Nanocomposite polyelectrolyte membranes based on phosphoric acid (H3PO4) doped polybenzimidazoles (PBIs) with various loading weights of organically modified montmorillonite (OMMT) were prepared and characterized for direct methanol fuel cell (DMFC) applications. X-ray diffraction analysis revealed the exfoliated structure of OMMT nanolayers in the polymeric matrices. An H3PO4 PBI/OMMT membrane composed of 500 mol % doped acid and 3.0 wt % OMMT showed a membrane selectivity of approximately 109,761 in comparison with 40,500 for Nafion 117 and also a higher power density (186 mW/cm(2)) than Nafion 117 (108 mW/cm(2)) for a single-cell DMFC at a 5M methanol feed. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 1227-1233, 2010