29Si, 17O Liquid NMR and 29Si CP-MAS NMR Characterization of Siloxane-Oxide Materials, [(CH3)2SiO/TiO2, (CH3)2SiO/ZrO2]

ABSTRACTSol-gel derived siloxane oxide materials are an entirely new family of hybrid systems at the frontier between silicones and glasses or ceramics, with a large variety of potential applications. Better control of the chemistry involved in their preparation should lead to an improvement in their properties, and this requires an investigation of the whole process, from the solution to the final materials. Nuclear Magnetic Resonance is a very suitable technique for this purpose, and this paper will give some illustrations on model systems (CH3)2SiO/TiO2, (CH3)2SiO/ZrO2, prepared from dimethyldiethoxysilane and titanium or zirconium alkoxides. It will be focused mainly on the use of 170 solution NMR which clearly shows the formation of Si-O-Ti or Si-O-Zr bonds, but also their disappearance during the aging process. 29Si MAS-NMR spectra of dried gels confirm that the difunctional units are mainly in polydimethylsiloxane chains, and that the system is phase separated. However, the use of cross-polarization techniques involving lK and 29Si nuclei will allow the detection of small number of units in a more constrained environment, certainly close to oxide-based particles.