Physicochemical Study of Surfactants Using Molecular Simulation

Surfactant in aqueous solution forms various association structures, such as solids, liquid crystals, and micelles, depending on its concentration and temperature. Since association structures have effects on physicochemical properties including fluidity, advanced techniques for revealing the association mechanism are required for application of surfactants in various product formulations. However, the behavior of surfactant molecules in water contributing to that association has not been clarified.
In an industry-university collaboration between Kao Corporation and Nagoya University, the detailed structure of an association structure, the lamellar phase composed of surfactant bilayers, was investigated using molecular dynamics (MD) simulation. In this study, the dynamic behavior of sodium linear alkylbenzene sulfonate in each phase was investigated [Langmuir, 2019, 35(27), 9011-9019; Langmuir, 2019, 35(33), 10877-10884]. Furthermore, the rotational motion of the linear alkyl group was measured in 3 lamellar phases; hydrated crystal, tilted gel, and liquid crystal.
We will continue such studies in order to understand the surfactant physicochemical properties as a function of molecular dynamic behavior.