Solvent Effects on Molecular Packing and Tribological Properties of Octadecyltrichlorosilane Films on Silicon

Self-assembled monolayer films of octadecyltrichlorosilane were prepared on silicon substrates using hexadecane, toluene, chloroform, and dichloromethane to determine the effects of solvent on molecular packing and tribological properties. Topographical atomic force microscopy images were used to evaluate the film quality and determine surface roughness, and tribological measurements, including friction, adhesion, and elasticity, provided additional information on the local nanoscale packing of the films. Our results showed that solvent viscosity and polarity affected the tribological properties of the films, with films prepared using hexadecane exhibiting superior properties. Langmuir−Blodgett experiments indicated that intermolecular interactions were stronger between octadecyltrichlorosilane and hexadecane molecules than for any other solvent in this study. These results demonstrate that solvent properties are an important consideration in monolayer film preparation and optimization for friction controlled surfaces.