The monolayer film thickness as a function of molecular weight for perfluoropolyethers based on the n-perfluorobutylene oxide monomer unit

Abstract

Abstract “C4-4OH” represents a new family of liquid, low molecular weight perfluoropolyether (PFPE) boundary lubricants based on the n-perfluorobutylene oxide monomer unit, -[(CF2)nO]- where n = 4, terminated by two hydroxyl groups (“Tetraol”) on each chain end. C4-4OH, PFPEs with n = 1.5–3 have been well-utilized as boundary lubricants in technological applications. Here the monolayer film thicknesses for C4-4OH as a function of molecular weight on rigid magnetic media are quantified using three metrological techniques including contact angle goniometry, film burnishing and ellipsometric imaging to corroborate the monolayer film thicknesses. The molecular weight dependence of the monolayer film thickness reveals that the adsorbed film structure of C4-4OH scales with its radius of gyration at the full monolayer film thickness.