Organic-inorganic hybrid materials, incorporating nanostructured silica networks within a poly(ethylene oxide) matrix (PEO), were produced via the sol-gel process from water solution mixtures of poly(ethylene oxide) and prehydrolyzed tetraethylorthosilicate (TEOS) in the presence of a trialkoxysilane compatibilization agent, gamma-glycidyloxypropyltrimethoxysilane (GOTMS). These mixtures were cast into films by evaporating the solvent and finally drying in an air-circulating oven at 60degreesC. By varying the composition of the alkoxysilane solution mixture and mixing conditions, different morphologies were obtained, ranging from semi-interpenetrating networks of PEO within highly cross-linked siloxane domains, to finely dispersed nanostructured systems exhibiting either co-continuous or particulate structure. The effects of pH, type of solvents, mixing temperatures and time, as well as the concentration of the compatibilization agent was found to be extremely important in controlling the morphology and properties of the final PEO-SiO2 hybrid films. (C) 2004 Wiley Periodicals, Inc.