Frictional properties of thin chain alcohol films

We used the surface forces apparatus (SFA) to measure the viscosity and friction of confined films of octanol and undecanol as a function of film thickness. In contrast to structurally similar alkanes, the alcohols retain their bulk-like lubrication properties down to a thickness of only one (bi)layer. Only the self-assembled monolayers of alcohol molecules that form spontaneously on each mica surface display solid-like stick-slip motion upon shearing. During stick-slip motion, microscopic creep is found to precede macroscopic slip events at high loads. Apart from this creep process, we find a well-defined critical shear stress during stick-slip motion, which decreases weakly with increasing sliding speed.