SAFT-γ force field for the simulation of molecular fluids: 8. Hetero-segmented coarse-grained models of perfluoroalkylalkanes assessed with new vapour–liquid interfacial tension data

Abstract

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, F 4 H 2 ; perfluorobutylpentane, F 4 H 5 ; perfluorobutylhexane, F 4 H 6 , perfluorobutyloctane, F 4 H 8 ; perfluorohexylethane, F 6 H 2 ; perfluorohexylhexane, F 6 H 6 ; and perfluorohexyloctane, F 6 H 8 ) 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.

Spontaneous self-assembly and structure of perfluoroalkylalkane surfactant hemimicelles by molecular dynamics simulations

“…In recent years we have accomplished a systematic experimental, computational, and theoretical study on the thermophysical properties of liquid PFAA, either pure or mixed with alkanes, perfluoroalkanes, and water. We have reported a number of properties of pure liquid PFAA [liquid density (45,46), vapor pressure (43), viscosity (47), and surface tension (48)] and their mixtures [partial molar volume at infinite dilution (49,50), solubility of water, and interfacial tension (44)] as a function of temperature, pressure, and relative length of the hydrogenated and fluorinated segments. These results were crucial for developing, parameterizing, and testing molecular models and force fields to be used in computer simulations and molecularbased theoretical calculations.…”

Predicting the pressure dependence of the viscosity of 2,2,4-trimethylhexane using the SAFT coarse-grained force field

“…The crux of the methodology is that the equation of state parameters can be directly employed in molecular simulations, thanks to the one-to-one correspondence between the theory and the underlying models. SAFT force fields have been successful in describing thermophysical [5] interfacial [6,7], confined fluid [8] and transport properties [9,10] of a wide range of fluids and mixtures [11,12] including polymers [13].…”

Molecular Dynamics Simulation of the Superspreading of Surfactant-Laden Droplets. A Review

“…The SAFT CG force-field has been used for the study of water-surfactant systems [19,66,67,[101][102][103] and particularly in the context of superspreading (Figure 4) [5,19,20,26,72]. This CG model is derived from the SAFT-γ molecular-based equation of state (EoS), which can describe analytically experimental data [104,105].…”