Molecular Simulation of Surfactants in Span Series at the Decane/water Interface

Abstract

This paper aims to determine the electric field intensity in the emulsion dehydration from the microscopic perspective. For this purpose, molecular dynamics (MD) simulation and density functional theory (DFT) were adopted to model the surface feature, hydrophilic groups, and hydrophobic groups of three types of Span surfactants, namely, Span 20, Span 60, and Span 80. Considering the stability of the microemulsion and application of electric fields, the structural changes and the nature of the surfactants were discussed in details under the external electric field. The results show that the simulated interfacial tension agrees well with the experimental data, an evidence to the rationality and reliability of the simulation system; the surfactant hydrophilic groups could form medium-strong hydrogen bonds with water; the deformation of surfactant space structure enhanced the role of hydrogen bonding under the electric field, thus reducing the emulsion stability. The research findings shed new light on the molecular simulation of Span surfactants.