Proton conducting inorganic–organic hybrid polymer electrolytes were developed in the last decade based on sulfonated, methacryl and epoxy functionalized alkoxysilanes for thin film cells [Electrochim. Acta 45 (2000) 137]. To improve the electrochemical stability of the materials for applications like polymer electrolyte membranes for direct methanol fuel cells, the less stable methacryl and epoxy alkoxysilanes of the former test system [Electrochim. Acta 45 (2000) 137] were replaced by styrene derivative functionalized alkoxysilanes. These alkoxysilanes were synthesized with a new modified Grignard reaction. The sol–gel materials were prepared in a two-step reaction: first, an alkoxysilane containing a sulfonated group and an alkoxysilane containing at least a nitrogen heterocycle, an amine group or a sulfonamide group were separately hydrolyzed and co-condensed each with one half of the amount of a styrene derivative functionalized alkoxysilane. Then, these two co-condensates were mixed. After evaporation of the solvent, the resin was cast in Teflon® moulds or applied on a substrate as a film and finally organically cross-linked via UV and/or thermal curing. The influence of the sample composition on the conductivity and the mechanical properties was studied. Conductivities of 3×10⁻³ S cm⁻¹ at room temperature were obtained for membranes free of water, whose precursor composition consists of 60% sulfonated alkoxysilane, finally mixed with 2 mol imidazole per mol ---SO₃H. If the imidazole is exchanged by water (max. 15 mass% absorption within membrane), the membranes show conductivities up to 8×10⁻³ S cm⁻¹ at room temperature. A thermal stability of the inorganic–organic matrix of up to 180 °C (<5% weight loss) was measured by thermo-gravimetric (TG) analysis.