Covalent binding of amino, carboxy, and nitro-substituted aminopropyltriethoxysilanes to oxidized silicon surfaces and their interaction with octadecanamine and octadecanoic acid studied by X-ray photoelectron spectroscopy and ellipsometry

Three silanized silicon substrates were prepared by treating cleaned oxidized silicon wafers with N-(3-triethoxysilylpropyl)octadecanamide (1), 9-[N-(triethoxysilylpropyl)amino]-9-oxononanoic acid methyl ester (2), and N-(3-triethoxysilylpropyl)-12-nitrododecanamide (4). The carbomethoxyl of 2 immobilized on silicon was hydrolysed to yield the corresponding ω-carboxylic surface (3) and the nitro group of the surface 4 reduced to afford the ω-amino surface (5). All five silanized surfaces were treated with octadecanoic acid and octadecanamine used as models for acidic and basic polymeric adhesives and the interactions were followed by ellipsometry and X-ray photoelectron spectroscopy. While the surfaces 1 and 2 reacted only by physisorption, the carboxylic surface 3 and the amino surface 5 showed a strong reaction with octadecanamine and octadecanoic acid, respectively. The nitro surface 4 exhibited a strong interaction with both probes, but by different pathways.