Proton conductors comprising phosphonic acid units are very promising due to their oxidative stability as well as high proton conductivity. In the present work, the membrane materials were produced by mixing of poly(vinylphosphonic acid) (PVPA) with sulfated nano-titania at various concentrations to get PVPATS(x) where x designates the molar ratio of the polymer repeating units to sulfate units (varied from 1 to 4). The structure of the nanocomposite polymer membrane is confirmed by FT-IR spectroscopy. The TGA results verify that the presence of sulfated nano-titania in the complex polymer electrolytes suppressed the formation of phosphonic acid anhydrides up to 200 degrees C. DSC results indicate that the T-g of the materials shifts to higher temperatures as sulfated nano-titania content increases. In the anhydrous state, the proton conductivity of PVPATS is found to be 0.03 (S cm(-1)) at 150 degrees C. Proton conductivity of these membranes are also measured and compared with previous studies. The results suggest that proton conduction is occurred between surface of the nano-titania particles with the aid of sulfonic acid and phosphonic acid units. (C) 2012 Elsevier B.V. All rights reserved.