Self-assembly of octadecyltrichlorosilane monolayers on mica

Abstract

A method is described to deposit a securely attached, self-assembled monolayer of octadecyltrichlorosilane (OTS) on the surface of freshly cleaved muscovite mica. Comparison of the infrared methylene spectra with those of closely packed Langmuir-Blodgett films implies that the surface coverage of the OTS films was a fraction 0.8–0.9 that of films formed by Langmuir-Blodgett (LB) methods. However, LB monolayers are less securely attached to the substrate. The contact angle of water on these self-assembled monolayers remained over 100° for over 24 h and it suffered no noticeable degradation after prolonged reflux in cyclohexane. The method to form an OTS monolayer on mica involves three steps; first, ion exchange of the native K⁺ ions of cleaved mica for H⁺ ions; second, control of the quantity of resulting water on the mica surface; third, adsorption and surface polymerization of octadecyltrichlorosilane (OTS) by self-assembly from dilute cyclohexane solution.