Abstract
ABSTRACTThe 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 (276–350 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 the experimental tensions with quantitative agreement 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.
Highlights
IntroductionIn addition to the higher resolution (atomistic and united-atom) force fields mentioned earlier, CG models have been developed for n-alkanes [60,61,62,63] and for perfluoro-n-alkanes [64,65]; we are not, aware of an integrated CG model which can deal quantitatively with the subtleties of having the two chemical moieties fused on the PFAA molecule
Perfluoroalkylalkanes (PFAAs) are linear chain molecules formed from perfluorinated and hydrogenated alkyl segments chemically bonded together, with the general structure F(CF2)i(CH2)jH
We develop the statistical associating fluid theory (SAFT)-γ CG Mie force field for PFAA molecules, based on the Mie intermolecular potential to describe the interactions between the various chemical segments
Summary
In addition to the higher resolution (atomistic and united-atom) force fields mentioned earlier, CG models have been developed for n-alkanes [60,61,62,63] and for perfluoro-n-alkanes [64,65]; we are not, aware of an integrated CG model which can deal quantitatively with the subtleties of having the two chemical moieties fused on the PFAA molecule For this purpose, the SAFT-γ Mie force fields developed in our current study are assessed by comparing the simulated and experimental surface tension data of PFAAs which are not used to parameterize the model; the comparison serves as a validation of the molecular models. The results are interpreted by comparison with the corresponding properties for nalkanes, perfluoro-n-alkanes, and their mixtures, though the analysis is hampered by the lack and inconsistency of existing data
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
