The preparation and characterization of hybrid organic-inorganic films based on poly(dimethylsiloxane), PDMS, crosslinked with nanoclusters obtained from pentaerythrithol triacrylate (PETA) and 2-aminoethyl-3-aminopropyltrimethoxysilane (AS), are reported. The introduction of silica nanoclusters, obtained from tetraethoxysilane as an additional crosslinker, improved the mechanical stability of the films and also produced a noticeable decrease in the solvent sorption and in the distance between the nodes of the polymeric networks. The performance of these films as membranes for gas separation processes was similar to those reported for commercial PDMS, although they presented polar organic PETA/AS crosslinker nuclei. (C) 2004 Wiley Periodicals, Inc.