Effect of Gemini surfactant structure on water/oil interfacial properties: A dissipative particle dynamics study

Understanding the structural effects of Gemini surfactants on interfacial properties is pivotal towards the rational design of efficient Gemini surfactants. Herein, a series of alkylbenzene sulfonate Gemini surfactants have been constructed, and their influences on the interfacial properties of dodecane/water systems are systematically explored by using dissipative particle dynamics simulation. The Gemini surfactants are modeled as ‘π-shaped’ coarse-grained molecules, and their spacer lengths and hydrophobic chain lengths are varied for examining the properties including radial distribution functions, interfacial tension and thickness, and self-assembly morphologies. We find that when increasing the hydrophobic chain length, the critical micelle concentration decreases, and the oil molecules tend to penetrate into the space between two hydrophobic chains, causing nano-mixing phenomenon. This phenomenon is further enhanced when increasing the spacer length, and consequently, the oil–water interface gradually becomes curved and blurred due to the enhanced surfactant efficiency, and the system evolves from the lamellar interface state to micelle state. This work provides a theoretical basis for rational designing efficient Gemini surfactants.