Mechanisms of Intermolecular Interactions and Molecular Dynamics in Anionic and Nonionic Surfactant Microemulsions

Area of Science:

• Physical Chemistry
• Colloid and Surface Science
• Materials Science

Background:

• Microemulsions are thermodynamically stable, isotropic liquid mixtures of oil, water, and surfactant.
• Understanding molecular interactions is crucial for designing stable microemulsion systems.
• Surfactant structure and concentration significantly influence microemulsion properties.

Purpose of the Study:

• To investigate the molecular interactions and self-assembly behaviors in microemulsions.
• To compare the effects of nonionic (C12E5) and anionic (SDBS, SDS) surfactants on microemulsion stability.
• To elucidate the role of surfactant concentration on interaction energies and interfacial structure.

Main Methods:

• Quantum mechanical weak interaction analysis.
• Molecular dynamics simulations.
• Radial distribution function (RDF), molecular polar surface area (MPSA), and reduced density gradient (RDG) analyses.

Main Results:

• Surfactant concentration impacts interaction energies between microemulsion components.
• C12E5 demonstrated a lower interaction energy increase between water and pentanol at higher concentrations (1.79%) compared to SDBS (-65.03%) and SDS (-23.38%).
• Anionic surfactants induced greater energy fluctuations and structural changes at the interface.

Conclusions:

• C12E5 promotes a more stable microemulsion system.
• Anionic surfactants lead to less stable interfaces with pronounced energy fluctuations.
• The study provides a framework for analyzing weak interactions in microemulsions and surfactant behavior.