SURFACE-REACTIONS ON THIN-LAYERS OF SILANE COUPLING AGENTS

The reactivity of immobilized functional groups in thin layers of (3-aminopropyl)triethoxysilane (APS), (3-mercaptopropyl)trimethoxysilane, (3-bromopropyl)trimethoxysilane, and (8-bromooctyl)trimethoxysilane on oxidized aluminum substrates was studied with reflection-adsorption infrared spectroscopy (RAIR), optical ellipsometry and contact-angle measurements. Mass changes on the surface associated with the surface-confined reactions were measured with the quartz crystal microbalance (QCM). Single layers of (3-aminopropyl)triethoxysilane on oxidized aluminum react with chlorodimethylsilane to give [(-O)3Si(CH2)3NH2+SiMe2H]Cl- and single layers of (3-mercaptopropyl)trimethoxysilane on oxidized aluminum react with phenylmercuryhydroxide to give [(-O)3Si(CH2)3SHgPh], while no substitution reaction of (3-bromopropyl)trimethoxysilane and (8-bromooctyl)trimethoxysilane monolayers occurred with cyanide. Films of APS were further utilized to immobilize pepsin. It is discussed to which extent known reactions from solution can be -transferred to interface reactions.