Effects of molecular structure on the conformation and dynamics of perfluoropolyether nanofilms

With the increase of areal density of magnetic recording, several new perfluoropolyether (PFPE) lubricants, including A20H, DDPA-S, and Ztetraol multidentate, have been recently reported to enhance the performance and reliability of hard disk drive with ultra-low head-media spacing. At the molecular level, the static conformation and detailed dynamic structure of these PFPE films are still not well-determined. In this paper, molecular dynamics simulations with bead-spring models were employed to investigate the conformation and dynamics of new types of PFPE films. The detailed static structures were revealed by functional end bead density profiles and visualization. The distribution of anisotropic radius of gyration was examined to investigate the conformations of PFPE monolayers. And the self-diffusion coefficient quantifying the mobility of films was compared for these PFPE monolayers. It was found that the molecular structure played a critical role in the conformation and dynamics of PFPE thin films.