A protocol for the reproducible silanization of mica validated by sum frequency spectroscopy and atomic force microscopy

A reaction protocol has been developed which when rigorously adhered to lea ds to the reproducible formation of complete, well-ordered monolayers of oc tadecylsiloxane (ODS) on mica. The complementary information provided by at omic force microscopy (AFM), sum frequency spectroscopy (SFS), and contact angle measurements has been used to validate the protocol and to characteri ze the structure and coverage of the films. The essential prerequisites for reproducibility were found to be fresh octadecyltrichlorosilane (OTS), a c lean reaction environment, controlled surface hydration, and hilgh-purity a nhydrous solvents. During the reaction itself the well-recognized parameter s of reaction temperature and the degree of bulk hydration required strict regulation. Reactions were performed at 19 degreesC and as expected, a mixe d ODS growth regime was observed consisting of ordered islands and a disord ered diffuse phase. The formation of complete, well-ordered monolayers was favored by low OTS concentrations and extended reaction times of up to 24 h .