HYBRID ORGANIC-INORGANIC POLYDIMETHYLSILOXANE-VANADIUM-OXO MATERIALS CROSS-LINKED AT THE MOLECULAR-LEVEL

New hybrid materials made of dimethylsiloxane oligomers (linear and cy clic species) crosslinked at the molecular level by O=V(O-)(3) units w ith a very high degree of homogeneity and dispersion, even for a V:Si molar ratio of 10%, have been synthesized and characterized mainly by Si-29 and V-51 MAS NMR, DSC and DMA. The structure of these hybrids is very different from those proposed for other dimethylsiloxane-transit ion metal oxide systems. These dimethylsiloxane-vanadate copolymers ex hibit higher glass transition temperatures than is usual for PDMS, as well as a very sharp variation of the loss factor tan delta. These hyb rid materials exhibit, at low temperature, a strong phosphorescence us ually associated with a ligand-to-metal charge transfer process.