DIRECT OBSERVATION OF THE SURFACE BONDS BETWEEN SELF-ASSEMBLED MONOLAYERS OF OCTADECYLTRICHLOROSILANE AND SILICA SURFACES - A LOW-FREQUENCY IR STUDY AT THE SOLID-LIQUID INTERFACE

We describe an infrared technique for studying reactions on silica surfaces in CCl4 that provides access to the spectral region below 1300 cm(-1). The region below 1300 cm(-1) is important in the study of the adsorption of self-assembled monolayers of alkylchlorosilanes because it contains the characteristic bands due to Si-O-Si, Si-O, Si-C and Si-Cl modes. It is these bands that provide direct evidence of the type of adsorbed species and on the nature of the bonding with the surface of the silica. The potential of this technique is demonstrated using the reaction of octadecyltrichlorosilane (OTS) with water on a fumed silica. It is confirmed that OTS does not adsorb on silica in CCl4 and hydrolyses when surface water is present. Evidence is also presented which shows that the type of adsorbed species varies with the amount of surface water initially present on the