The structure of γ-aminopropyltriethoxysilane on glass surfaces

The structure of γ-aminopropyltriethoxysilane (APS) has been studied in aqueous solution and as a solid using Fourier transform infrared spectroscopy. The monomeric aminosilane forms an internal cyclic chelate structure when hydrolyzed. Two vibrational bands have been found near 1575 and 1600 cm−1 in condensed aminopropylsiloxane polymer. The band at 1575 cm−1 is assigned to the NH2 deformation mode of the acceptor amine groups involved in strong hydrogen bonding and the band at 1600 cm−1 is assigned to the NH2 groups. Heat treatment causes the formation of nonring chain-structured aminosilanes. In the study of the structure of APS coupling agent on high-surface-area silica gel (Cab-O-Sil) and E-glass fibers, it was found that the aminosilane adsorbed on silica as essentially a monolayer and the amino group chemically interacted with the glass surface. The adsorbed APS on E-glass fiber exists as a multilayer, and formed a predominately cyclic ring structure in the coupling agent interphase.