Commercial polyetheretherketone (Victrex PEEK) was sulfortated up to 90% degree of sulfonation (DS), then reacted with SiCl4 to obtain a hybrid polymer. The product was characterized by Si-29 NMR and ATR/FrlR spectroscopies demonstrating the formation of covalent bonds between the organic and inorganic components. No dispersed inorganic silicon was present in the product as evidenced by the lack of any resonance at delta < - 100 ppm. Despite the high DS the physicochemical properties of the hybrid were suitable for the preparation of membranes exhibiting high and stable conductivity values (10(-2) S/cm), hence suitable for application as ion exchange membrane. (C) 2004 Elsevier Ltd. All rights reserved.