Structure and Tribological Properties of Ultrathin Alkylsilane Films Chemisorbed to Solid Surfaces

Abstract

The tribological properties of monomolecular layers of alkylsilanes were investigated. The monolayers were obtained by a self-assembly process of alkylchlorosilanes with different chain lengths and varying number of functional groups at the silane moiety. These ultrathin films were characterized using ellipsometry, Fourier transform infrared spectroscopy, and quartz microbalance measurements. Ordered, dense films oriented almost normal to the surface were obtained with monofunctional silanes with chains up to 18 CH2 units, while films with longer chains or di- and trifunctional head groups exhibited disorder and poor orientation. The frictional behavior of the organic films attached to both pin and disk surfaces was studied in sliding experiments. The removal of organic films was followed in situ during sliding experiments with scanning microellipsometry. It was found that the lifetime of the coated surfaces increased strongly with increasing chain length of the alkyl substituent. © 1993, American Chemical Society. All rights reserved.