Structural characterization of the organic/inorganic networks in the hybrid material (TMOS–TMSM–MMA)

Using a sol–gel process, we had previously investigated the reaction mechanisms (hydrolysis and condensation of alkoxysilan monomers, polymerization of methacrylate groups) allowing to give a specific hybrid material (tetramethylorthosilicate (TMOS)–3(trimethoxysilyl)propyl methacrylate (TMSM)–methylmethacrylate (MMA)). The superimposition and the competition of the chemical reactions lead to a system where reactions are generally not fully completed. The formed networks in each of the TMOS, TMSM and (TMOS–TMSM) gels have been identified. Condensation of TMOS shows that the SiOSi bonds join together in order to form a three-dimensional (3D) network made of porisities, which have the fundamental characteristics of fused quartz networks. On the other hand, condensation of TMSM gives several species having different structures. Incorporating TMSM in an inorganic network modifies its periodicity degree. The chains are formed to bring, between them, various SiO 2 blocks having TMOS as origin. FTIR absorption and Raman scattering have also shown that the inorganic network was mainly 3D. Interpretation of small angle X-ray scattering (SAXS) data has shown that the inorganic part of the material, i.e. the SiOSi bonds (from either TMOS or TMSM) join together in order to form a 3D network made of porisities having a diameter of about 1.2 nm. Inside these microporisities, organic groups are formed. They are bond by means of methacrylate groups polymerization. Free MMA oligomers may also exist inside the porosities. A microscopic representation of a hybrid material (TMOS–TMSM–MMA) is proposed. The intimate structure of a porisity is detailed and the description of a fully detailed microstructure of hybrid material (TMOS–TMSM–MMA) is proposed.