We compare hybrid organic-inorganic polymers, based on sulfonated polyaryl-ether-ketones (S-PEEK) and different sulfonated and silylated molecules and macromolecules. The synthesis of the membranes and their water uptake and electrical conductivity at 25 degrees C are reported. A decent linear relation between the electrical conductivity and water uptake coefficient is obtained. Other correlations with the chemical composition of the membranes (especially, SO3, Si and OH content) are discussed and directions for future work are outlined. (c) 2008 Elsevier B.V. All rights reserved.