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Coarse-grained modeling of the oil–water–surfactant interface through the local definition of the pressure tensor and interfacial tension

Abstract : Mesoscopic simulations are conducted to study the dodecane–water interface in the presence of an increasing quantity of sodium dodecyl sulfate. Dissipative Particle Dynamics and Molecular Dynamics using the MARTINI force field were used to model the dodecane–SDS–water system through a coarse-grained description. We have used a full description of the water and oil phases to study the structure of the interface. We have calculated the interfacial tension at the dodecane–water interface and established the accuracy of the calculation by checking the mechanical equilibrium and the stability of the interface. The local components of the pressure tensor are calculated along the interface by comparing both atomistic and molecular definitions. Both coarse-grained models give a good description of the system structure, with SDS molecules located at the interfaces. Increasing the number of SDS results in a drastic decrease in the interfacial tension and a saturation of the interface with SDS molecules. Higher SDS concentrations do not affect the interface structure, as it is saturated. The limiting value of the interfacial tension is very low and corresponds to the formation of a SDS film between the dodecane and water phases. Both coarse-grained potentials studied in this work are suitable for the study of surfactants in equilibrium with an oil–water interface. They provide a good description of the dodecane–SDS–water system and quantitative results for interfacial tension and interfacial concentrations. © 2017, Springer-Verlag Berlin Heidelberg.
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https://hal-univ-rennes1.archives-ouvertes.fr/hal-01508398
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Submitted on : Friday, April 14, 2017 - 9:44:27 AM
Last modification on : Monday, March 2, 2020 - 4:07:22 PM

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M. Ndao, F. Goujon, Aziz Ghoufi, P. Malfreyt. Coarse-grained modeling of the oil–water–surfactant interface through the local definition of the pressure tensor and interfacial tension. Theoretical Chemistry Accounts: Theory, Computation, and Modeling, Springer Verlag, 2017, 136 (1), pp.21. ⟨10.1007/s00214-016-2038-y⟩. ⟨hal-01508398⟩

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