Multinuclear 1D- and 2D-NMR study of the hydrolysis and condensation of bis-1,2-(triethoxysilyl)ethane

This paper focuses on the study of the effect of aging on the composition of the solutions used for deposition of silane films onto metals. Such films are used for corrosion protection and adhesion applications. The silane films interact with metallic surfaces by reactions between the OH groups of both materials with elimination of water. Therefore, prior to the immersion of the metal into the silane solution, the silane has to be hydrolysed in order to generate a maximum of silanol (SiOH) groups, while minimizing condensation leading to siloxane (SiOSi) groups. One of the main factors influencing the amounts of silanol and siloxane groups produced is the solution aging. This paper demonstrates by NMR spectroscopy that in the case of a bridged silane, namely bis-1,2-(triethoxysilyl)ethane, a stable plateau offering a good compromise between hydrolysis and condensation in the solution is obtained between 24 h and a few days of aging.