Molecular Dynamics Calculation of Interfacial Tension in a Two-Phase Liquid Hydrocarbon–Water–Surfactant System: From Rarefied to Superdense Surfactant Monolayer.

A method is proposed for calculating low interfacial tension (IFT) based on molecular dynamics simulation of systems with superdense packing of surfactant molecules at the water–liquid hydrocarbon interface. The interfacial tension was calculated by the molecular dynamics method using the all-atom and coarse-grained models in water–alkane (decane, dodecane) two-phase systems in the presence of various individual surfactants. The following ionic and nonionic surfactants were considered: sodium dodecyl sulfate (SDS), cetyltrimethylammonium chloride (CTAC), sodium dodecylbenzenesulfonate (SDBS), sodium decet-6 sulfate C₁₀E₆SO₄Na, hexaethylene glycol monodecyl ether (C₁₀E₆), triethylene glycol monononadecyl ether (C₁₉E₃), and octapropoxypentaethylene glycol monododecyl ether (C₁₂P₈E₅). It was shown that the interfacial tension decreases to zero when surfactant adsorption increases to the limiting values. [ABSTRACT FROM AUTHOR]