Transforming Anionic Reverse Micelles: The Potential of Hydrophobic Natural Deep Eutectic Solvents. How the mixture between camphor and menthol can be an excellent choice for reverse micelle preparation.

Introduction: Reverse micelles are nanostructures formed by dissolving surfactants in low-polarity organic solvents. A commonly used anionic surfactant is AOT (sodium dioctyl sulfosuccinate), which forms aggregates capable of encapsulating water in their core. The amount of water solubilized is expressed as W₀ = [H₂O]/[Surfactant]. In green chemistry, Natural Deep Eutectic Solvents (NADES), such as the 1:1 mixture of camphor and menthol (CM), offer a sustainable alternative as non-polar external phases. This study evaluated the formation of reverse micelles with AOT, water, and CM, using NMR techniques.
Results: The CM NADES dissolved AOT up to 0.5 M and allowed the incorporation of water, achieving a maximum W₀ of 5. DOSY NMR studies confirmed the presence of reverse micelles and the encapsulation of water. Micellar diameters ranged from 1.5 to 3.5 nm, increasing with water content. ¹H NMR chemical shift changes revealed hydrogen bonding interactions between water and the polar region of AOT, affecting the interfacial conformation and reducing NADES penetration into the polar core.
Conclusion: The study demonstrated the formation of reverse micelles and allowed for the evaluation of the interface formed by CM/AOT at different water contents. Thus, it is possible to generate reverse micelles using a hydrophobic NADES, easily prepared, as the non-polar external solvent, paving the way for a new era in biocompatible organized systems. This is particularly interesting for future applications in the food industry or medicine.