Self-assembly and viscosity changes of binary surfactant solutions: A molecular dynamics study

• Published in: Journal of colloid and interface science Vol. 585; pp. 250 - 257
• Main Authors: Zhou, Jun, Ranjith, P.G.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.03.2021
• Subjects: CAPB/SDS mixture; Molecular dynamics; Morphology transition; Surfactant micelle; Viscosity; Viscosity; Molecular dynamics; CAPB/SDS mixture; Surfactant micelle; Morphology transition
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2020.11.022

[Display omitted] •New Martini force field can better model the self-aggregation of single/binary surfactant system.•Synergistic effects in morphology transitions of SDS/CAPB have been successfully reproduced through MD simulations.•Martini 3b force field fails to simulate the viscosity changes of binary surfactant system induced by the evolution of micellar morphologies. Hypothesis: Structure and self-assembly of surfactants in the solution shows a fundamental influence on its viscosity. Through molecular simulations using Martini force field, synergistic effects in aggregation as well as the viscosity changes of a binary ionic surfactant system can be modelled. Simulations: Coarse-grained molecular dynamics simulations are performed to model the SDS/CAPB binary surfactant solution, and both equilibrium and non-equilibrium methods are used to calculate the viscosity of the equilibrated micellar systems. Findings: Our simulation results indicate that the new version of the Martini force field can provide more reasonable self-assembly of surfactant, both single and binary system. Synergistic effects in micelle formation for SDS/CAPB have been successfully reproduced, that is, the formation of cylindrical micelles or even wormlike micelles at a lower concentration when compared with the pure system. Meanwhile, both equilibrium and non-equilibrium methods provide quantitatively comparable viscosity for each system. For pure micellar system, the viscosity linearly increases with the total concentration. Nevertheless, our simulation fails to capture the viscosity enhancement of the solution in corresponding with the formation of rodlike or wormlike micelles, and a full parameter optimization of force field is still necessary.