The air-liquid interfacial behaviour of linear perfluoroalkylalkanes (PFAAs) is reported
through a combined experimental and computer simulation study. The surface
tensions of seven liquid PFAAs (perfluorobutylethane, F4H2; perfluorobutylpentane,
F4H5; perfluorobutylhexane, F4H6, perfluorobutyloctane, F4H8; perfluorohexylethane,
F6H2; perfluorohexylhexane, F6H6; and perfluorohexyloctane, F6H8) are experimentally
determined over a wide temperature range (276 to 350 K). The corresponding surface
thermodynamic properties and the critical temperatures of the studied compounds are
estimated from the temperature dependence of the surface tension. Experimental
density and vapour pressure data are employed to parameterize a generic
heteronuclear coarse-grained intermolecular potential of the SAFT- γ family for PFAAs.
The resulting force field is used in direct molecular dynamics simulations to predict
with quantitative agreement the experimental tensions and to explore the
conformations of the molecules in the interfacial region revealing a preferential
alignment of the PFAA molecules towards the interface and an enrichment of the
perfluoro-groups at the outer interface region.