Fourier Transform Near-Infrared Attenuated Total Reflectance Spectroscopy of Silane Coupling Agents on Glass IRE

Abstract

Attenuated total reflectance (ATR) has been shown to be highly sensitive for surface analysis. The major advantage of ATR is that the region of the specimen is restricted to a thin layer adjacent to the internal reflectance element (IRE). In an investigation of the surface reactions and interfacial effect of silane coupling agents on the surface of glass, a glass IRE was used in the near-infrared region (7000–4000 cm−1). This technique is useful for analyzing the near-surface of the glass IRE. By a comparison between each measured ATR spectrum and the transmission spectrum of the same glass IRE, it is possible to determine the mechanism of reaction of the silane coupling agent on the glass substrate. The process of dehydration was also investigated by calibration, with the use of the intensity of the band due to Si-OH groups. A condensation reaction occurs between molecules of the silane coupling agent in the bulk film. However, a small fraction of the agent reacts with the Si-OH groups of the glass at a lower rate. In this study, we show the transmission and ATR spectra of silane coupling agent reacted on a glass plate used for the IRE in the ATR method. With the use of the ATR method, the state of the dehydration condensation reaction, which involves hydrolyzing Si-OH at the surface, can be observed. Furthermore, the process of dehydration condensation reaction on the substrate of glass can also be compared with the bulk reactions measured by transmission.