(471c) Structure and Stability of Self-Assembled Aqueous AOT Aggregates in Molecular Dynamics Simulations

Surfactants are widely used as detergents, emulsifiers, and dispersants. Dioctyl sulfosuccinate (AOT) is one of the most commonly studied surfactants and has served as a model for many experimental and theoretical studies. Previously, we have reported molecular dynamics (MD) simulations of the formation of reverse micelles of AOT in organic solvents in the presence of metallic ions, showing close agreement between theoretical and experimental scattering curves. Expanding on previous findings, we report the self-assembly of AOT micelles and bilayers in aqueous solvents in MD simulations. Simulation time and length scales have been expanded to calculate additional theoretical structural characteristics in the presence of tens to hundreds of AOT molecules. Thus, morphological heterogeneity, polydispersity, and formation kinetics can be readily observed and quantified. Radius of gyration, relative shape anisotropy, prolateness, and size distributions of modeled aggregates have been calculated from MD trajectories at a range of temperatures and solute concentrations. Results match available experimental phase diagrams and provide additional molecular level detail about micelle and bilayer structuring. These simulations provide a tool to generate hypothetical physics-based micelle structures that can be used to rationalize scattering curves (e.g., DLS, SANS, SAXS) and other potentially ambiguous experimental observations. We foresee the application of developed models to the optimization of surfactant compatibility within aqueous solutions.