Linear and branched perfluoropolyether coatings on diamond-like carbon films: covalent linkage and physical deposition
The progresses in the magnetic media technologybrought to the application of liquid lubricant films ondiamond-like carbon (DLC) coatings. Hard surfaces aretypically lubricated with fluorinated or perfluorinated organiccompounds, such as perfluoropolyethers (PFPE) (1). Manyattempts have been done to obtain a stable layer of PFPElubricant on the DLC surface by dip-coating or by vapourdeposition so as to minimize any friction and wear (2, 3).Diamond-like carbons are formed by an amorphous mixtureof sp3 and sp2 hybridized carbon atoms with hydrogen atomsincorporated in the structure (a-C:H DLC). We have establisheda specific methodology for the straight-forward introductionof perfluorinated groups with carbon-carbon bond formationon a variety of unsaturated materials (4-8). Indeed, by usingthis methodology, perfluorinated radicals can directly bondto the sp2 sites of the DLC structure avoiding any spacer, thatusually decreases both thermal and chemical stabilities of theresulting fluorinated layers (9, 10).