Hisae Yoshizawa

Recent advances in molecular level understanding of adhesion, friction and lubrication

Abstract In order to investigate the mechanism of boundary friction, adhesion and friction experiments were carried out with a variety of surfactant-monolayer-coated surfaces using the surface forces apparatus. The friction forces were measured as a function of monolayer coverage and phase state, load, temperature, shear rate and relative humidity. We report on two important findings. (i) Stick-slip motion can occur not only between a “static” and a “kinetic” state but also between a static or kinetic state and some “superkinetic” state that exhibits ultralow friction. (ii) The friction coefficient is not directly correlated with adhesion but rather with the adhesion hysteresis, which is a measure of the energy dissipated during an irreversible adhesion ( e.g. loading-unloading) cycle. We also conclude that chain interdigitation is the most important molecular mechanism that gives rise to “boundary” friction and adhesion hysteresis of monolayer-coated surfaces.