ReaxFF molecular dynamics study of mechanochemical degradation of PFPE lubricants on DLC in heat-assisted magnetic recording†

Abstract

Understanding the degradation mechanisms of perfluoropolyether (PFPE) lubricants is critical for the reliability of Heat-Assisted Magnetic Recording (HAMR) systems. In this study, we conducted ReaxFF reactive molecular dynamics simulations to investigate the role of diamond-like carbon (DLC) surfaces in PFPE degradation under confined shear and at elevated temperature. The results show that confined shear plays a more dominant role than temperature, with the decomposition rate constant increasing with shear velocity. PFPE degradation primarily initiates through C–OH bond rupture at end groups, typically after the OH group bonds to the DLC surfaces. Bonded PFPE molecules adopt bridge and loop conformations, both contributing comparably to degradation with increasing shear velocity, with bridges being slightly more sensitive to shear. Our analysis suggests that bridge dissociation is facilitated by shear-induced end-to-end stretching, while loop dissociation is driven by entanglement of conformationally flexible main chains. These insights provide guidance regarding further development of reliable HAMR systems.