Preparation of tetraethoxysilane for the production of monodisperse spherical silica particles. Part 2. Impurities and their influence on the size of the forming globules

Monodisperse spherical silica particles, as a basis for creating supramolecular 3D matrices, are currently of increasing interest due to the prospects for their wide application in the synthesis of new nanocomposite materials. At the same time, one of main problems of their large-scale synthesis is associated with the unstable behavior of tetraethoxysilane (TEOS) during hydrolysis, which leads both to the deviation of the particles from a given size and their shape from a spherical one. In this paper, on the basis of the study of tetraethoxysilane from various manufacturers, we continued to work on determining factors that can influence the process of hydrolysis of tetraethoxysilane and, as a result, the monodispersity and size of the formed particles, and also other factors. To solve this task, all TEOS samples were studied by various physicochemical methods of analysis, including Fourier IR and Raman spectroscopy, gas chromatography-mass spectrometry. As a result of the studies, we showed that the presence of di- and trisiloxanes in the system did not significantly affect the size of the formed silica particles, while significantly accelerating the rate of formation of silica spheres. Moreover, the presence of methoxyl groups in the initial silane, and an insignificant content of ethanol in the system did not affect the size stability of the formed particles. At the same time, the replacement of part of the ethoxy groups in the initial TEOS by methyl or ethyl groups, as they are not capable of participating in the hydrolysis reaction, largely contribute to the deviation of sizes of the formed silica particles from each other. The results obtained on the effect of impurities on the size of the formed silica globules are important, among other things, for understanding the processes of formation of natural supramolecular structures of silica.