Copolymerization of Alkoxysilanes: An Interesting Route to Core-Shell Silica-Silicone Nanoparticles

Copolymerization of silicon alkoxides in alcoholic basic medium using trialkyl- or triarylchlorosilanes as terminator was investigated. Tetraethoxysilane (TEOS), phenyltriethoxysilane (PTEOS) and vinyltriethoxysilane (VTEOS) were used as monomers and triphenylchlorosilane (TPCS) and trimethylchlorosilane (TMCS) as terminator. The copolymerization of TEOS with PTEOS and VTEOS produces core-shell silica-silicone nanospherical hybrids containing large amounts of functional groups in the structure of their external layer. The structure is the result of the fast hopolymerization of TEOS in a first stage of the reaction, forming the core, followed by copolymerization of TEOS and the alkyl- or vinyl-trialkoxysilane comonomer in its last stage. The structure was confirmed by Raman and FTIR spectroscopy, wide angle X-ray scattering (WAXS) and thermogravimetry. The control of particle size is effectively made by the termination reaction and particles with average diameter between 20 and 100 nm were obtained. Introduction of other chemical functions on the surface of these nanoparticles can be carried out by common reactions with the functional surface groups. As an example, sulfonation of particles containing phenyl groups on the surface by direct sulfuric acid and chlorosulfonic acid was investigated and the results discussed.