Self-assembled organic-inorganic membranes that are achieved via sol-gel polymerizations of silicon alkoxides around sulfonated outer blocks of polystyrene-[soft block]-polystyrene block copolymers during film formation are described. The nanoscopic morphologies, molecular structure of very hydrophilic silicate nanophases, and methods of studying the structure and transport of water through these membranes are discussed. These hydrocarbon-based hybrids are contrasted with the earlier successful efforts to generate Nafion((R))/silicate nanocomposite membranes produced in similar fashion, but using pre-formed films. (C) 2004 Elsevier Ltd. All rights reserved.