Coarse-Grained Molecular Dynamics Simulations of the Breakage and Recombination Behaviors of Surfactant Micelles

Surfactant molecules can form micellar network structures that can be applied for turbulent drag reduction through their breakage and recombination behaviors. One of the mechanisms of turbulent drag reduction by surfactants is the “viscoelastic theory” as proposed by DeGennes. However, evaluating the rupture and coalescence properties of network micelles is challenging. Here, we study the breakage and recombination behaviors of an individual rodlike micelle using Martini coarse-grained force field molecular dynamics simulations. The flexibility of an individual micelle can be measured by its breakage energy. Micelle recombination behaviors can be attributed to three mechanisms: the coalescence energy, zeta potential, or hydrophobic driving effect of the surfactant micelles. Thus, an excellent micelle that is beneficial for turbulent drag reduction is difficult to rupture but easy to recombine. The breakage behavior should be considered prior to the recombination behavior, because the breakage energy of an individual micelle is approximately 1–2 magnitudes greater than its coalescence energy under various conditions. Organic counterion salts, such as salicylate sodium, favor micelle recombination because of their electrostatic screen effect and uneven distribution on the surfactant micelle surface. Furthermore, this work brings a novel approach to understanding the breakage and recombination behaviors of surfactant micelles, providing an essential and scientific guidance to the effective use of surfactants in turbulent drag reduction. It also provides direct evidence to support the viscoelastic theory.