Relationship between friction and molecular structure: Alkylsilane lubricant films under pressure

We demonstrate that energy losses during friction of alkylsilane self-assem bled monolayers with sharp atomic force microscope tips can be correlated t o molecular events occurring at specific threshold loads. Under these lends , discrete molecular tilts occur, which are dictated by the geometrical req uirements of the close packing of molecules. The barriers overcome during t hese tilt events give rise to discrete changes in the frictional forces. [S 0031-9007(99)05798-0].