A telechelic organic-inorganic polymer (SiPPSU) where -SiPh(OH)2 groups are covalently linked to the polymeric chain of polyphenylsulfone (PPSU) was prepared and characterized. The polymer was sulfonated up to a degree of sulfortation (DS) equal to 2 (SiSPPSU), then used to prepare blends with sulfonated polyetheretherketone (SPEEK) having DS = 0.9 in 5 and 10 wt.% concentration. The synthesized polymers and the blends were characterized by ATR/FT-IR spectroscopy. Membranes were prepared with these materials and their proton conductivity was measured using electrochemical impedance spectroscopy (EIS). The formation of the blends substantially altered the physicochemical characteristics of SPEEK: the membrane prepared with the blend at the concentration of 5 wt.% exhibited high and stable conductivity values at 120 degrees C: both when dry (sigma = 6.1 x 10(-3) S/cm) and wet conditions (sigma = 6.4 X 10(-2) S/cm for a 50% water uptake), hence, being suitable for application as electrolyte in intermediate temperature polymer electrolyte membrane fuel cells (PEMFCs). (c) 2005 Elsevier B.V. All rights reserved.