The structure of γ-aminopropyltriethoxysilane films on iron mirrors

• Published in: Journal of colloid and interface science Vol. 73; no. 2; pp. 416 - 424
• Main Authors: Boerio, F.J, Armogan, L, Cheng, S.Y
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.01.1980
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/0021-9797(80)90087-9

The structure of γ-aminopropyltriethoxysilane (γ-APS) films deposited on mechanically polished iron mirrors from aqueous solutions has been investigated using reflection-absorption infrared spectroscopy. Films formed at the natural pH of 1% aqueous solutions of γ-APS (∼10.5) were about 120 Å in thickness and were composed of highly hydrolyzed oligomers characterized by infrared bands near 1550 and 1480 cm −1. These bands were assigned to NH 2 deformation modes in amino groups that were very strongly hydrogen bonded with silanol groups to form cyclic structures. Films formed at pH = 12 were characterized by infrared bands near 1580 and 1488 cm −1 that were assigned to deformation modes of NH + 3 groups obtained by essentially complete proton transfer from silanol groups to amino groups. In all cases the as-formed films were stable in a dry environment but exposure to atmospheric humidity disrupted the strong hydrogen bonding, enabling the oligomers to condense to form polysiloxanes.