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

Organic-inorganic hybrid materials were prepared by a convenient two-step c uring procedure based on sol-gel condensation and subsequent photopolymeriz ation. Novel bismethacrylate-based hybrid monomers with pendant, condensabl e alkoxysilane groups were prepared by Michael addition and possessed numbe r-average molecular weights between 580 and 1600 g/mol. The formation of in organic networks by sol- gel condensation of the alkoxysilane groups in the presence of aqueous methacrylic acid was monitored with rheological measur ements. The condensation conversion was monitored with solid-state Si-29 cr oss-polarization/magic-angle spinning NMR spectroscopy. Subsequent photopol ymerization led to organic-inorganic hybrid networks and low volume shrinka ge, ranging from 4.2 to 8.3%, depending on the molecular weight of the hybr id monomer applied. Highly filled composite materials with glass filler fra ctions greater than 75% showed attractive mechanical properties with Young' s moduli of 2700-6200 MPa. (C) 2001 John Wiley & Sons. Inc.