Conformation of Ultrathin PFPE Lubricants With Different Structure on Magnetic Disks—Direct Observation and MD Simulation

Abstract

Three types of PFPE lubricants (Z-tetraol, TA-30, and D-4OH) with different molecular structures were coated on magnetic disks and the conformations of these films were studied by atomic force microscopy using a fluoride-coated probe. The molecular conformations of these lubricant films were found to be different from each other. The Z-tetraol film showed the highest molecular height and lowest coverage among these lubricants. The TA-30 film showed a double-layer structure and the highest coverage among the lubricant films. The D-4OH film showed a monolayer structure and higher coverage than the Z-tetraol film. These observed were in agreement with the results of molecular dynamics simulations. In these simulations, the TA-30 film showed the highest coverage and lowest molecular height among the three lubricant films because the TA-30 molecules did not form a random coil shape and were adsorbed rigidly on the disk surface. The Z-tetraol molecules were adsorbed and formed a random coil shape. The D-4OH molecules were also adsorbed and formed a spiral shape.