Study on the structure and spreading properties of hard disk lubricants

Molecular dynamics simulations based on a coarse-grained, bead-spring model were adopted to investigate the structure and spreading properties of hard disk lubricants functional perfluoropolyether (PFPE) on amorphous carbon surfaces. The simulation results of structure properties show that there is a complex layered structure in functional PFPE films, characterized by a layering structure with a thickness around one atomic diameter in the surface layer and a bi-polymer structure with a thickness of (4-5) R_g(gyration radius) in the bulk layer. The simulation results of spreading properties show that the spreading exhibits terraced profiles, characterized by the formation of a precursor, a shoulder and a vertical step, which corresponds to the structure properties well. The spreading profiles with different endbeads were compared, which indicate that the endbead-substrate interaction and the endbead-endbead interaction, especially the latter, have a significant effect on the spreading behavior.