Hybrid organic-inorganic nanocomposites containing PEO segments linked to a methacrylate network were prepared through a dual-curing process, which involved photopolymerization and condensation of alkoxysilane groups. A system based on an alpha,omega-dimethacrylate PEO oligomer (BEMA 1400) added with methacryloyl-oxypropyl-trimethoxysilane (MEMO) and tetraethoxysilane (TEOS) was used. The surface properties of the obtained films were investigated through XPS analyses and contact angle measurements. A selective enrichment of the MEMO additive towards the outermost layers of the films was evidenced either in the presence or in the absence of TEOS. SEM analyses were performed on the cross section of the films coated on PET substrates, determining the film composition at different depth by EDS analysis. The Si content was found constant, moving from the PET surface towards the air-surface of the films. The barrier properties, with respect to oxygen, of the hybrid films coated on a PET substrate were measured. A decrease of the permeability and of the oxygen transmission rate using hybrid coatings was observed. (c) 2006 Wiley Periodicals, Inc.