Linear and branched perfluoropolyether coatings on diamond-like carbon films: covalent linkage and physical deposition

ABSTRACT: The progresses in the magnetic media technology brought to the application of liquid lubricant films on diamond-like carbon (DLC) coatings. Hard surfaces are typically lubricated with fluorinated or perfluorinated organic compounds, such as perfluoropolyethers (PFPE) (1). Many attempts have been done to obtain a stable layer of PFPE lubricant on the DLC surface by dip-coating or by vapour deposition so as to minimize any friction and wear (2, 3). Diamond-like carbons are formed by an amorphous mixture of sp3 and sp2 hybridized carbon atoms with hydrogen atoms incorporated in the structure (a-C:H DLC). We have established a specific methodology for the straight-forward introduction of perfluorinated groups with carbon-carbon bond formation on a variety of unsaturated materials (4-8). Indeed, by using this methodology, perfluorinated radicals can directly bond to the sp2 sites of the DLC structure avoiding any spacer, that usually decreases both thermal and chemical stabilities of the resulting fluorinated layers (9, 10).