Dissipative particle dynamics simulation and experimental analysis of effects of Gemini surfactants with different spacer lengths on stability of emulsion systems

Abstract

Understanding the effects of the structure of surfactants on the interfacial properties and dynamic processes of emulsions is critical for the rational design and selection of surfactants for the formation of stable emulsions. In this study, a series of Gemini cationic surfactants with different spacer lengths and an anionic surfactant were examined. The effects of single surfactants, as well as mixed surfactant systems, on the interfacial properties of oil/water systems were systematically investigated using dissipative particle dynamics simulations. The Gemini surfactants were modeled as “π-shaped” coarse-grained molecules with different spacer lengths to examine variations in their properties, including the radial distribution function, interfacial tension, and interfacial thickness. We found that Gemini surfactants with shorter spacers exhibit better surface activity. Longer spacers result in the binding of more oil molecules to the chain, which reduces the surface activity. The effect of mixed surfactant systems on the reduction of interfacial tension is significant. Emulsion systems constructed from anionic surfactants and Gemini cationic surfactants with shorter spacers exhibited a lower sedimentation index after aging. Emulsion models were able to capture the dynamic process of emulsion breaking at the microscopic level and were used to analyze the effects of surfactants on emulsion stabilization. Based on the analysis of the effect of surfactants on the oil-water interface, this work further analyzes the effect of surfactants on the stability of emulsions. In addition, an ingenious emulsion system is established, which provides a basis for the rational design and selection of high-efficiency surfactants to prepare stable emulsion systems.