A study of organotitanium coupling agents for adhesion promotion and of chemical reactions on alumina surfaces by inelastic electron tunnelling spectroscopy

Chemical reactions taking place on an alumina surface have been investigated by incorporating this surface within an Al-AlOx~Pb tunnelling junction and scanning the inelastic electron tunnelling spectrum. This approach has been employed to study reactions involved in substrate-coating situations, of particular relevance to adhesive bonding. It has been shown that the glass-fibre circuit board (PCB) substrates used in this study may be reused after suitable cleaning. A "dry atmosphere" bag has been incorporated into the procedure to facilitate the doping and subsequent study of air- sensitive materials. Three organotitanium compounds; titanium acetyl-acetonate (TAA), triethanolamine titanate (TEAT) and octylene glycol titanate (OGT), which are used commercially as primers or adhesion promoters for surface coatings have been investigated. Mechanisms of their solution hydrolysis and of their interaction with the alumina surface are proposed. The interaction of these primed alumina surfaces with simulated organic coating bases has also been studied. Hence a mechanism for the interaction of a coating promoter with both a metal oxide surface and with the surface coating itself has been evaluated. In addition, since atmospheric surface contamination will undoubtedly affect any subsequent process, the surface reactions of simple gaseous molecules on alumina have been investigated. These have incidentally thrown light onto the mineralogical theory of the origin of life. The first experimental support for Bernal and Cairns-Smith's mineralogical theory for the origin of life has been established by demonstrating that an alumina surface incorporated in a tunnel junction has the catalytic ability to synthesize amino acids from ammonia, water and carbon dioxide, and sugars from wet carbon monoxide or formaldehyde. These reactants were likely components of the earth's prebiotic atmosphere. The role of such an inorganic template in the surface catalyzed theory of the origin of life is considered