Chitosan is modified by phthaloylation using an excess of phthalic anhydride at 130 degrees C and blended with the sulfonated polyethersulfone (SPES) to produce composite blend membranes. In particular the introduction of the phthaloyl group into the chitosan matrix increases its solubility in organic solvent, film formability, flexibility, low methanol permeability and with suitable ion conductivity. SPES and N-phthaloyl chitosan (NPHCs) blend membranes with various compositions were prepared and detailed investigation on water uptake, proton conductivity and methanol permeability has been conducted for its suitability in fuel cell environments. Methanol permeability studies envisaged that NPHCs blend membranes are impervious to methanol. The thermograms display the good thermal stabilities of blend membranes than Nafion-117. Relatively high selectivity parameter values of these membranes indicated their greater advantages over Nafion-117 membrane for targeting on fuel cell applications, especially in direct methanol fuel cell (DMFC) environments. (C) 2015 Elsevier Ltd. All rights reserved.