The relationships between interfacial friction and the conformational order of organic thin films

This report describes studies of the relationships between the structures of organic monolayers and their molecular-scale frictional properties. Several distinct self-assembled monolayers (SAMs) were formed by the adsorption of a series of spiroalkanedithiols and a single structurally related normal alkanethiol. Measurements of hexadecane wettability, infrared vibrational spectroscopy, and X-ray photoelectron spectroscopy revealed that the films possessed a wide range of interfacial structures and conformational orders. Atomic force microscopy was used to measure the frictional properties of the well-characterized SAMs on the molecular scale. Comparison of the frictional data with structural information derived from complementary analytical techniques revealed a high correlation between the conformational order of the films and the observed frictional response.