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

We describe an infrared technique for studying reactions on silica sur faces in CCl4 that provides access to the spectral region below 1300 c m(-1). The region below 1300 cm(-1) is important in the study of the a dsorption of self-assembled monolayers of alkylchlorosilanes because i t 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 o f adsorbed species and on the nature of the bonding with the surface o f the silica. The potential of this technique is demonstrated using th e reaction of octadecyltrichlorosilane (OTS) with water on a fumed sil ica. It is confirmed that OTS does not adsorb on silica in CCl4 and hy drolyses when surface water is present. Evidence is also presented whi ch shows that the type of adsorbed species varies with the amount of s urface water initially present on the