Liquid Structuring and Dynamics in Hydrophobic Deep Eutectic Mixtures of MEN/THY and 1-Decanol

This work considers the liquid structuring and dynamic behavior of the hydrophobic deep eutectic solvent composed of menthol and thymol (MEN/THY, 1:1 molar ratio) when mixed with 1-decanol over the entire composition range. The system, although ternary in nature, is treated as a binary mixture between the preformed eutectic solvent and 1-decanol in order to isolate the mixing process and elucidate the underlying molecular interactions governing the transition from DES-rich to alcohol-rich domains. A comprehensive experimental study was conducted including measurements of density, viscosity, refractive index, thermal conductivity, and pH, complemented by Raman spectroscopy to probe microscopic organization and intermolecular forces. Thermophysical data were analyzed through polynomial and excess property correlations to assess the evolution of volume, cohesive energy, and free volume upon mixing. Molecular dynamics simulations were further employed to rationalize the macroscopic observations, providing atomistic insights into hydrogen-bond topology, dispersion interactions, and dynamic rearrangements within the liquid. The combined experimental–computational framework establishes a coherent molecular interpretation of hydrophobic DES–alcohol mixtures, advancing the understanding of how associative and dispersive forces determine liquid structuring, dynamics, and potential solvent design strategies.