FT‐IR Study of the Hydrolysis and Polymerization of Tetraethyl Orthosilicate and Polydimethyl Siloxane in the Presence of Tetrabutyl Orthotitanate

Abstract

In this work, we have used FT‐IR spectroscopy to study the hydrolysis and polymerization reactions of tetraethyl orthosilicate (TEOS) and polydimethyl‐siloxane (PDMS) in the presence of tetrabutyl orthotitanate (TBOT). These reactions are used for obtaining SiO2–PDMS–TiO2 organically modified silicates (Ormosils). In order to obtain semi‐quantitative information about such reactions, a deconvolution procedure of the FT‐IR spectra has been done by use of a computer program. Hydrolysis reactions have been characterized by Me–O–C (Me = Si, Ti) bonds, and polymerization reactions by Me–O–Me bonds. Instantaneous hydrolysis of TEOS has been observed, together with condensation reactions between Si–OH groups, which give crosslinked and linear Si–O–Si structures. The TBOT is also hydrolyzed, but the high acid concentration inhibits condensation reactions between Ti–OH groups. The PDMS also condenses mainly with Si–OH groups and probably with Ti–OH, finally forming Me–O–PDMS bonds. The formation of Si–O–Si crosslinked structures and also Me–O–PDMS structures continues until the end of reaction. The gelling time is dependent on TBOT concentration in the reaction medium and, therefore, polycondensation reactions are dependent on TBOT concentration.