Self-assembly of anionic surfactant and its effect on oil–water interface: Implications for enhanced oil recovery

Abstract

Surfactant micellization is a self-assembly process governed by complex interplay of solvent-mediated interactions. However, quantitative modeling of micelle formation and its effect on oil–water interface are not yet completely understood. In this work, dissipative particle dynamics simulations were used to investigate the self-assembly behavior of anionic surfactants of alcohol alkoxy sulfate (AAS) and its structural influence on the interfacial properties of oil–water at the mesoscopic scale. Our results indicate that with the increase of surfactant concentration, the morphology of surfactant aggregates varied from spherical micelles to rod-shaped micelles, and finally formed worm-like micelles. The larger the number of propylene oxide (PO) groups, the easier the formation of large micelles and the more tightness of formed micelles. On the oil–water interface, the interfacial tension of solutions decreased with increasing surfactant concentration below the critical micelle concentration, whereas a positive correlation was found for the tightness of surfactant arrangement. When surfactants formed micelles, the overall coverage area of AAS decreased and a lower root mean square end distance of individual PO group directly affected interfacial properties of AAS. The obtained results could provide a solid theoretical basis for the rational design of efficient surfactants in oil recovery and soft matter applications.