Nano-Mechanics of Perfluoropolyether Films: Compression Versus Tension

As the head-disk spacing decreases, the contact mechanics between the head and disk becomes one of the critical issues for the head-disk tribology integration. In this paper, molecular dynamics (MD) is employed to simulate the nano-mechanics (i.e., "compression" and "tension") of confined molecularly thin perfluoropolyether (PFPE) films to examine the contact tribology fundamentals. For the "compression" process, functional PFPE demonstrates slightly higher clearance than nonfunctional PFPE; while during the "tension" process, an apparent fluid bridge was observed for functional PFPE. The normal stress profiles were calculated for both "compression" and "tension" processes, where the hysteresis phenomenon indicates the irreversible nature of functional PFPE nano-mechanics. N-modes Maxwell model was then further introduced to analyze the nano-mechanics relaxation process, suggesting that a second relaxation mode in the two-mode Maxwell model was induced by functional endgroups.