Simulations Of Interfacial Behaviors For Surfactants Hybrid

Molecular dynamics method can provide an intuitive physical image on molecular level, which is important for understanding the interfacial tension reducing mechanism and predicting the performance of a certain surfactant. In this paper, it's used to study the interfacial properties of water, water-surfactant system and oil-water-surfactant system. Comparisons of the effects of different water models and different temperatures on the simulation results have been made from the perspectives of interface thickness, interfacial tension, and density distribution in both phases. Similar trends are observed within different water models:the body density of gas phase increases, while it decreases in bulk liquid; the interface thickness increases; the interfacial tension gradually weakens; results of SPCE model is closer to experimental values in terms of interface thickness and interfacial tension. The simulation method above is also applied to explore the vapor-liquid and oil-water interfacial properties of an anionic surfactant sodium dodecyl sulfate (SDS) and a non-ionic surfactants lauryl alcohol ethoxylates (C12E2). It comes out that the results differ slightly though it takes less time with United Atomic force field than All Atom force field. The interface thickness increases and the interfacial tension decreases in water-surfactant system with increasing temperature, and C12E2 shows better performance than SDS.In oil-water-surfactant system, the effect of temperature on the interface activity of surfactants is more complicated. C12E2 has higher temperature resistance, as a result, it precedes SDS in reducing interfacial tension. Besides, its ability to reduce interfacial tension at different temperatures follows:?343K>?313K>?353K>?328K.The profile of interfacial tension is consistent with that of interface thickness.Molecular dynamics simulation takes longer and covers smaller scale, while mesoscopic simulation can overcome these disadvantages. In this paper, mesoscopic simulation method with appropriate model and key parameters is used to analyze the impact of oil-water ratio on interfacial properties. The results show that with the increase of oil-water ratio, three different forms appear, namely:r<0.5, oil in water (o/w) microemulsion; 0.5<r<2.0, clear oil-water interface; r>2.0, oil-in-water microemulsion (w/o).