IR studies of adhesion promoters. Part 3.—Adsorption and coupling of bifunctional silanes on silica at the solid/liquid interface

Abstract

IR spectra are reported of silica immersed at 293 K in carbon tetrachloride solutions of the silane coupling agents 1-aminopropyltrimethoxysilane and 3-glycidoxypropyltrimethoxypropane and the bonding reagents epoxypropane and 1-aminopropane. Negligible chemisorption or chemical reaction occurred. Dominant surface–adsorbate interactions involved competition between different functional groups in solute molecules for the formation of hydrogen bonds with isolated silanol groups on the silica surface. The coupling agents under-went changes in orientation in the adsorbed state with increasing surface coverage. These changes could also be induced by co-adsorbates. Adjacent interacting silanol groups on silica were less likely than isolated silanol groups to act as adsorption sites.