Surface analytical study of the interaction between γ-amino propyl triethoxysilane and E-glass surface

Abstract

Angle-resolved X-ray photoelectron spectroscopy (XPS) has been used to study the interaction of hydrolysed γ-aminopropyltriethoxysilane (HAPS) with a flat E-glass slide surface. Formation of a HAPS coating with a thickness of about 6 nm, which consists of three components of differing molecular structure on the glass surface, was confirmed. The results provided further evidence for the incorporation of aluminium ions from the glass substrate into the HAPS coating. At the outer surface, a warm-water-soluble oligomer exists in which the amino group of the HAPS molecule is in the form of a free -NH₂. Beneath, there is a three-dimensional graded network whose ends, after extraction with warm water, are involved in an internally hydrogen-bonded structure between the amino and silanol groups, probably in a cyclised conformation. Adjacent to the glass surface, a molecular layer of HAPS remained after extraction with hot water, which was chemically bound to the glass surface through siloxane and/or aluminoxane bonds. The results tend to favour the former with Al(OH)₃ copolymerized into the siloxanol deposit.