Volumetric, acoustic, and conductometric studies of ionic surfactants in aqueous ammonium acetate-ethylene glycol deep eutectic solvent

This study investigates the molecular interactions between cationic surfactants cetyltrimethylammonium bromide (CTAB) and dodecyltrimethylammonium bromide (DTAB) in aqueous deep eutectic solvent (DES) solution over the temperature range of 293.15–313.15 K. Key parameters, including density, sound velocity, and electrical conductivity, was experimentally measured to derive a range of volumetric, acoustic, and conductometric properties that provide insights into the molecular behavior of these solutions. Apparent molar volume (ф_v), indicative of solute–solvent interactions; isentropic compressibility (K_S), reflecting medium elasticity; and apparent molar compressibility (ф_K), which elucidates solute-induced compressibility changes, were determined from the experimental data. Additionally, specific acoustic impedance (Z), represents the medium's resistance to sound propagation; relative association (RA), indicative of solute–solvent interaction strength; intermolecular free length (L_f), corresponding to the average distance between molecules; and the sound velocity number (U), which relates to the structural compactness of the solution, were also calculated. Collectively, these parameters offer a comprehensive understanding of the molecular interactions, solvation dynamics, and structural organization in the surfactant systems in the presence of DESs, enhancing our knowledge of their behavior under varying conditions.