Organic-inorganic hybrid materials incorporating phosphorus-containing dendrimers

Phosphorus-containing dendrimers of first, second, and third generation wit h various peripheral functional groups and bearing a hydrolyzable Si(OEt)(3 ) group at the core have been prepared. Two synthetic routes were used: eit her the Si(OEt)(3) group was introduced from the start by reaction of (EtO) (3)Si(CH2)(3)PPh2 with an azide according to the Staudinger reaction (A ser ies of dendrimers) or the Si(OEt)(3) group was grafted to the core in the l ast step by reaction of 3-aminopropyltriethoxysilane with a vinyl group at the core (B series of dendrimers). The silylated dendrimers were characteri zed by elemental analyses and H-1, C-13, P-31, and Si-29 NMR spectroscopies . The cohydrolysis and polycondensation of these macromolecules with a defi ned and varying number of equivalents of tetraethoxysilane (TEOS) was carri ed out via sol-gel protocol, giving rise to dendrimer-silica xerogels.: It was proven by P-31 NMR spectroscopy that the dendrimers were not damaged du ring the sol-gel process, and it was shown by Si-29 NMR spectroscopy that t he dendrimer was covalently linked to the silica matrix by one Si-C bond. T he texture of materials was determined by BET measurements. It was shown fr om elemental and thermogravimetric analysis that the percentage of incorpor ated organic part was notable but always inferior to the theoretical value.