A composite polymeric membrane to be used as electrolyte in polymer electrolyte membrane fuel cells has been prepared and characterized. The membrane is composed of an acidic polymer, sulfonated polyetheretherketone, and of basic filler, amino-diphenylsilandiol, a functionalized organically modified silane. Attenuated total reflectance (ATR)/fourier transform infrared spectroscopy (FTIR) demonstrated the occurrence of a specific interaction of the polymer ?SO3H groups with the basic function of the filler. Such interaction reflected in reduced swelling, enhanced thermal stability, and good proton conductivity values at intermediate temperatures (s approximate to 10(-2) S cm(-1) at 100 degrees C). (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012