Sulfonated poly(arylene ether sulfone)/modified phosphotungstic acid containing amine group membranes was fabricated in order to evaluate the effect of introduced functional groups for use as polymer electrolyte membrane fuel cells. In order to resolve the inherent solubility problem of phosphotungstic acid particles, the sol-gel method was used to prepare the modified phosphotungstic acid particles, which have an insoluble property in solar solvents such as water. The sulfonated poly(arylene ether sulfone)/phosphotungstic acid composite membrane was prepared via solution casting and evaporation of the solvent. The mechanical and thermal property performances of the membranes prepared for use in fuel cells were investigated using their water uptake, water retention, and proton conductivity properties. The mechanical and thermal properties of the composite membranes were improved with the introduction of functional sites such as amine and silanol groups in the modified phosphotungstic acid. The proton conductivity of the nano-composite membranes at 100% relative humidity was increased due to the creation of a proton-conducting path through the amine-sulfonic acid group networks between the modified nanoparticles and the polymer. The functional group in the polymer matrix was also presumed to provide molecular water absorption ability, which resulted in an increase in the proton conductivity. These composite membranes can be used as a proton conductivity membrane for fuel cell applications. (C) 2013 Elsevier B.V. All rights reserved.