Organic–inorganic hybrid networks by the sol–gel process and subsequent photopolymerization

Organic–inorganic hybrid materials were prepared by a convenient two-step curing procedure based on sol–gel condensation and subsequent photopolymerization. Novel bismethacrylate-based hybrid monomers with pendant, condensable alkoxysilane groups were prepared by Michael addition and possessed number-average molecular weights between 580 and 1600 g/mol. The formation of inorganic networks by sol–gel condensation of the alkoxysilane groups in the presence of aqueous methacrylic acid was monitored with rheological measurements. The condensation conversion was monitored with solid-state 29Si cross-polarization/magic-angle spinning NMR spectroscopy. Subsequent photopolymerization led to organic–inorganic hybrid networks and low volume shrinkage, ranging from 4.2 to 8.3%, depending on the molecular weight of the hybrid monomer applied. Highly filled composite materials with glass filler fractions greater than 75% showed attractive mechanical properties with Young's moduli of 2700–6200 MPa. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4274–4282, 2001