Surface Reactions on Thin Layers of Silane Coupling Agents

The reactivity of immobilized functional groups in thin layers of (3-aminopropy1)triethoxy~ilane (APS), (3-mercaptopropyl)trimethoxy~ilane, (3-bromopropyl)trimethoxysilane, and (8-bromoody1)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-a~ninopropy1)triethoxysilane on oxidized aluminum react with chlorodimethylsilane to give [(-0)3Si(CH2)3NH2+SiMe2HICland single layers of (3-mercaptopropy1)trimethoxysilane on oxidized aluminum react with phenylmercury hydroxide togive [(-0)fii(CHz)aSHgPh] , while no substitution reaction of (3-bromopropy1)trimethoxyailane and (8-bromoodyl)trimethoxyailaue monolayers occurred with cyanide. Films of APS were further utilized to immobilize pepsin. It is discuesed to which extent known reactions from solution can be transferred to interface reactions.