Dr. Paul H. Kasai, Technical Consultant, MORESCO Corporation, Japan

Title: Self-Protecting Disk Lubricant: D-MH₂

Abstract: PFPE’s (perfluoropolyethers) are lubricants of choice for disks in hard disk drives of the current generation. D-4OH, the most topically adopted has the following formula. HO-CH₂-CH (OH)-CH₂-O-CH₂-CF₂-CF₂-[O-CF₂-CF₂-CF₂]n-O-CF₂-CF₂-CH₂-O-CH₂-CH(OH)-CH₂-OH. Most unfortunately these lubricants are prone to degrade undergoing an intramolecular disproportionation reaction as depicted below.


The reaction is catalyzed by Lewis acid centers generated on the slider, the contacting side of the read/write head made mostly of aluminum oxide.

The thickness of the disk lubricant has been reduced to the level of a sub-monomolecular film. For a mono- or a sub-mono-molecular film of a PFPE terminated with a primary hydroxyl unit at both ends, each lubricant molecular chain is chemically bound to the carbon substrate at both ends, and if it has a hydrocarbon sector inserted at its center, the hydrocarbon sectors would assemble at the top of the mono-, or sub-mono-molecular film. Molecular orbital calculations revealed that the HOMO (the highest occupied molecular orbital) of PFPE embodying a hydrocarbon sector is completely localized within the hydrocarbon sector. They are thus poised most aptly to react as a Lewis base (an electron donor) to the Lewis acid centers on the slider, thus passivating the degradation process.