Sodium bis(2-ethylhexyl)sulfosuccinate self-aggregation in vacuo: molecular dynamics simulation

Area of Science:

• Physical Chemistry
• Supramolecular Chemistry
• Computational Chemistry

Background:

• Reverse micelles are self-assembled aggregates with a polar core and nonpolar shell.
• Understanding their structure and dynamics is crucial for applications in catalysis, drug delivery, and nanotechnology.
• Bis(2-ethylhexyl)sulfosuccinate (AOT) is a common surfactant used in forming reverse micelles.

Purpose of the Study:

• To investigate the aggregation behavior and structural properties of bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles using molecular dynamics simulations.
• To analyze the influence of counter-ion type (Na+, Li+, K+, Cs+) on the aggregate structure.
• To explore the dynamical properties and stability of these reverse micelle systems.

Main Methods:

• Molecular dynamics (MD) simulations were performed for systems of AOT anions and various cations (Na+, Li+, K+, Cs+) in vacuo and in CCl4 solution.
• Simulations covered systems with varying numbers of AOT anions (n) up to n=20.
• Statistical analyses included gyration radius, atomic pair correlation functions, atomic B-factor, and moment of inertia tensor calculations.

Main Results:

• Reverse micelle-like aggregates were consistently observed, featuring a compact, solid-like core of cations and polar heads.
• The overall aggregate structure was characterized as an elongated and relatively flat ellipsoid.
• The study elucidated structural and dynamical properties, providing insights into the stability of these aggregates.

Conclusions:

• AOT anions and cations self-assemble into stable reverse micelle-like structures with distinct core-shell characteristics.
• The simulations provide a detailed molecular-level understanding of AOT reverse micelle formation and properties.
• These findings contribute to the fundamental knowledge of surfactant aggregation and micellar systems.