Chia-Cheng Lin

29 Si NMR, Sec and Ftir Studies of The Hydrolysis and Condensation of Si(OC 2 H 5 ) 4 and Si 2 O(OC 2 H 5 ) 6

The hydrolysis and initial condensation reactions of Si(OC 2 H 5 ) 4 and low order polyethoxysiloxanes have been studied with high resolution 29 Si NMR and size exclusion chromatography/FTIR spectroscopy. The effects of various parameters such as H 2 O/TEOS mole ratio, catalyst, pH, solvent, temperature and aging have been observed in the different nature of the reaction products. The products include partially hydrolyzed and unhydrolyzed Si(OC 2 H 5 ) 4 , Si 2 O(CH 2 H 5 ) 6 , and Si 3 O 2 (OC 2 H 5 ) 8 . The rate of formation and concentration of each product obtained under different conditions provides information about the reactivity of various silanol-containing species and the factors that affect the overall reaction scheme.

NMR Characterization of Precursors to Chemically Derived Ceramics

High resolution 29 Si NMR spectroscopy has been used to study the hydrolysis and condensation reactions of TEOS and related silicon alkoxides under a range of conditions selected to model initial steps in the formation of ceramic precursors. Kinetic results have led to a detailed description of the role of various reaction parameters and to differences in reactivity of various polyethoxysiloxanes. Reactivity studies have provided insight into the processes that form multicomponent alkoxide/oxide materials. Titanium alkoxides in particular can act as catalysts for silanol condensation in addition to forming Si-O-Ti linkages, and the former role may predominate in certain systems.