Aqueous reverse micelles have been utilized as proxies for atmospheric aerosols. We simulated such reverse micelles composed of surfactant dioctyl sodium sulfosuccinate (AOT), water represented by TIP3P model and isooctane solvent. These simulations involved swapping the Na+ counter cation to the negatively charged sulfonate head-group of the surfactant with K+. The reverse micelles were created using Packmol, and constant pressure-temperature simulations were conducted using GROMACS molecular dynamics package. These fully atomistic simulations were carried out using the CHARMM 36 force field. The reverse micelle was prepared initially to be spherical and left unconstrained during the simulation. Thus, the dynamics of the aggregate were captured and analyzed during the simulation. The simulated reverse micelles had w0 values of 5, 10, 15, and 20. The w0 number is the ratio of water to surfactant molecules. We experimented with two drastically different compositions of reverse micelles while keeping the same ratio of water to surfactant. Our analysis of pair density functions clearly demonstrate the various water layers present in the simulation. Our analysis of population fractions of the cations (Na+ & K+) indicates remarkable similarity in the ionic distribution despite the substantial differences in system size. Our results highlight the stability of the reverse micelle while sampling multiple shapes as measured by the eccentricity of the aggregate.

Molecular dynamics simulations of AOT reverse micelles with various counter cations

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.