Macroscopic Tribological Testing of Alkanethiol Self-assembled Monolayers (SAMs): Pin-on-disk Tribometry with Elastomeric Sliding Contacts

We demonstrate that the frictional properties of alkanethiol self-assembled monolayers (SAMs) with various surface-chemical and structural features can be investigated on a macroscopic scale by employing an elastomer as the sliding partner in pin-on-disk tribometry. The mild contact conditions at the elastomeric tribological interface allow the SAM films to remain virtually intact despite the tribological stress. Sliding contact between SAMs and elastomers over the speed range available from an ordinary tribometer in a liquid environment induced a broad range of lubrication mechanisms, ranging from boundary to fluid-film lubrication regimes. Thus, the impact of both the chemical and structural characteristics of SAMs on the formation of fluid films and interfacial friction forces could be probed in the absence of wear processes. Given the large SAM “toolbox” that is readily available for the modification of surface-chemical characteristics, this approach provides an opportunity to investigate the influence of surface chemistry on the frictional properties of elastomeric tribological contacts.