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

Abstract

This study investigates the molecular interactions between cationic surfactants cetyltrimethylammonium bro- mide (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 elec- trical 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 (фv), indicative of solute–solvent interactions; isentropic compressibility (KS), reflecting medium elasticity; and apparent molar compressibility (фK), 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 (Lf), 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 organi- zation in the surfactant systems in the presence of DESs, enhancing our knowledge of their behavior under varying conditions.