NMR and Theoretical Investigation of Cation Binding with Sol-Gel Silicates

摘要

Previous reports suggest that the choice of base catalyst affects both thekinetics and structural evolution of SiO2 gelation from tetraethoxysilane (TEOS). Furthermore, these effects have been attributed to the interaction of the alkaline cations with charged silicate fragments. In this study, NMR analysis of alkali-metal nuclei and of 29Si directly shows that during the condensation of silicon alkoxides in basic alcohol solutions, cations form ion-pair complexes with negatively charged silicate groups. It is determined that the ion pair is formed most favorably with potassium. In seeking a predictive model of complex stability, we found it most successful to use a bond orbital electronegativity equalization model developed by Bergman and Hinze.... SiO 2, Sol/gel, NMR, Electronegativity equalization, Cation.