Nano- and microscale friction behaviors of functionalized self-assembled monolayers

Abstract

The nano- and microscale friction behaviors of self-assembled monolayers (SAMs) of pi-functional n-alkanethiol surfactants were investigated in order to provide fundamental information regarding the effect of molecular structure of boundary lubricant on its lubrication performance. The SAMs with different terminal group and hydrocarbon chain length were prepared on gold substrates and atomic force microscopy tips by chemical adsorption and characterized by contact angle and X-ray photoeletron spectroscopy (XPS) measurements. The nano- and microscale friction coefficients of the SAMs were measured by a lateral force microscopy (LFM) and an oscillating friction and wear tester, respectively. As results, it is found that both the nano- and microscale friction behaviors were significantly affected by the terminal functionality and the hydrocarbon chain length of the SAMs. In addition, the nano- and microscale friction behaviors showed similar trends of the molecular structure effects.