Slider wear is investigated as a function of D-4OH lubricant film thickness and molecular weight. Slider wear increases with decreasing lubricant film thickness and with increasing molecular weight when compared at the same film thickness in the submonolayer film thickness regime. The two sets of observations are readily interpreted on the basis of the monolayer fraction which corrects the film thickness for the molecular weight-dependent surface coverage.

The interfacial properties of perfluoropolyether (PFPE) films having the [(CF 2 ) n O] main chain with n = 1.5, 3 and 4, were systematically compared on carbon surfaces. The monolayer thickness decreases with increasing n, indicating that stiffer chains (larger n) lie flatter on the surface. The surface energy-derived disjoining pressure also increased with increasing n. Spin-stand tribological experiments indicated that clearance (slider-disk spacing) increased and PFPE lubricant pick-up decreased with increasing disjoining pressure and main chain stiffness. Slider wear rate increased with decreasing PFPE coverage and increasing main chain stiffness. Structure-property correlations are developed and discussed.

Star PFPE (perfluoropolyether) polymers based on an aromatic benzene core and a non-aromatic cyclotriphosphazene (CTP) core are investigated as boundary lubricant films on rigid magnetic media. The effect of the benzene and CTP cores on head-disk spacing are measured by the changes in the acoustic emission signal as a function of head-disk spacing at similar lubricant film thicknesses. The earlier head-disk contact observed with the CTP core is attributed in part to its larger size perpendicular to the plane of the disk surface. The adhesion of the benzene and CTP cores to the underlying carbon film is investigated by ab initio quantum chemistry. The nonaromatic nature of the CTP ring and the lack of steric accessibility to the CTP core nitrogen atoms prevent good adhesive interactions with the underlying carbon film. Conversely, the π-electrons of aromatic benzene create a quadrupole moment in the direction perpendicular to the plane of the benzene that can interact with the underlying carbon surface and hence provide weak adhesion. Electron-withdrawing and-donating substituents on the benzene ring can be used to exert a "push-pull" effect on the π-electrons to alter the strength of the intermolecular interactions to specific functional groups of the underlying carbon surface. These effects are visualized by mapping the electrostatic potential of the benzene core as a function of electron-withdrawing and-donating substituents and computing model dimer optimized geometries and intermolecular interaction energies. Finally, the thermal stability of the star PFPE polymers are quantified by measuring the evaporation rate of thin films (11 Å) as a function of time at the HDD temperature (~ 60°C). Thermogravimetric analyses (TGA) of the neat polymers also provide direction for improvement of the synthetic lubricants.

The tribological properties of some novel single component perfluoropolyether (PFPE) boundary lubricants with chemically integrated mixture end groups are investigated. Chemically integrated mixture end groups composed of hydroxyl- and anisole-terminated PFPE boundary lubricant films on the –(CF2CF2CF2O)– main chain are reported. These PFPE-based boundary lubricants explore a new method by which single component PFPE lubricants with mixture end groups might be used to tailor boundary film properties instead of using physical mixtures of two or more PFPEs with different end groups. Lubricant transfer to the low-flying read/write head, head wear, and siloxane adsorption as a function of PFPE film thickness and of type are compared. Normalization of the data to the monolayer fraction instead of film thickness allows direct comparison between anisole- and hydroxyl-terminated PFPEs. Lubricant transfer to the head and head wear are independent of the functional end groups. Siloxane adsorption decreases with increasing anisole substitution of the hydroxyl groups. One-component PFPEs with mixed end groups provide a methodology by which boundary film properties could be adjusted.