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

WALTER NAVARRINI1, MAURIZIO SANSOTERA1*, FRANCESCO VENTURINI1, CLAUDIA L. BIANCHI2, ANTONIO GUARDA3, GIUSEPPE RESNATI1
*Corresponding author
1. Politecnico di Milano, Dipartimento di Chimica, Materiali e Ingegneria Chimica, via Mancinelli 7, Milano, I-20131, Italy
2. Università degli Studi di Milano, Dipartimento di Chimica Fisica ed Elettrochimica, via Golgi 19, Milano, I-20133, Italy
3. C.R.S. Solvay-Solexis, viale Lombardia 20, Bollate (MI), I-20021, Italy

Abstract

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).