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 leads to the reproducible formation of complete, well-ordered monolayers of octadecylsiloxane (ODS) on mica. The complementary information provided by atomic force microscopy (AFM), sum frequency spectroscopy (SFS), and contact angle measurements has been used to validate the protocol and to characterize the structure and coverage of the films. The essential prerequisites for reproducibility were found to be fresh octadecyltrichlorosilane (OTS), a clean reaction environment, controlled surface hydration, and hilgh-purity anhydrous solvents. During the reaction itself the well-recognized parameters of reaction temperature and the degree of bulk hydration required strict regulation. Reactions were performed at 19 degreesC and as expected, a mixed ODS growth regime was observed consisting of ordered islands and a disordered diffuse phase. The formation of complete, well-ordered monolayers was favored by low OTS concentrations and extended reaction times of up to 24 h.