Nanocomposite materials made of silicate platelets dispersed in a crosslinked polymer have been produced by photoinitiated polymerization of a multifunctional acrylic resin containing organophilic clay. Exfoliation of the silicate nanoparticles was demonstrated by X-ray diffraction spectroscopy and by transmission electron microscopy. Under intense illumination, the solvent-free hybrid formulation was transformed within seconds into a hard and tough material at ambient temperature. The UV-curing reaction was followed by infrared spectroscopy (mid-IR, near-IR and ATR) through the decrease upon UV exposure of the characteristic IR bands of the acrylate double bond. The organoclay was found to have no detrimental effect on the photopolymerization reaction. The performance of the UV-cured polymer, microcomposite (clay) and nanocomposite (organoclay) samples were compared with respect to their tensile strength, break elongation, hardness and moisture resistance. Nanocomposites were found to outperform microcomposites in most of these properties. They proved particularly resistant to accelerated weathering in the presence of adequate light- stabilizers. (C) 2004 Elsevier Ltd. All rights reserved.