Study On The Composition, Structures And Properties Of Organic Modified Silica Gel Matrix

Research on doping a photoactive organic phase into an inorganic matrix has been intensified in recent years. The barrier of using these materials is their porosity, proved to be brittle and have optical losses. An alternative approach to overcome this problem is to incorporate organic molecules into the inorganic matrix, not only the structures but also the properties of materials being improved. The research background and recent progress of organic-inorganic hybrid materials and organic modified silicates(ORMOSILs), together with the problems existing in theoretical research on organic modified silica xerogels, are reviewed in this paper. Methyl, dimethyl, vinyl and γ -glycidoxypropyl modified silica xerogels were prepared by sol-gel technique. The xerogels were characterized to obtain its composition, structures and properties (optical, thermal and mechanical properties). Infrared spectrum and pore size distribution of different organic group and different content methyl modified silica xerogels were studied. The chemical composition and the bonding states of the xerogels were investigated by X-ray photoelectron spectroscopy. All xerogels were tested by UV-Vis, DSC and Nanoindenter. The results show that organic groups were successfully bonded to silica network as network modifiers or network formers. The average pore sizes of silica xerogels are dramatically decreased after organically modifying, resulting in denser structures and up to 90% transparency through the visible region. An increase in the hardness and Young's modulus is thus achieved. A new fitting method which is called theoretical ratio method was proposed to fit Si2p peaks, proved to be better than conventional method in this experiment. There is a shift to low binding energy in binding energy of each element of SiO2 xerogels after modified. Except its neighbor atoms, the bonding states of the element are affected by other atoms' inductive and conjugative effects. The structural models of silica and modified silica xerogels are built, which indicates the nature of organic modification.