Thermodynamic Insights of the Molecular Interactions of Dopamine (Neurotransmitter) with Anionic Surfactant in Non-Aqueous Media

Abstract

This study was aimed at establishing the interactions prevailing in an anionic surfactant, sodium dodecyl sulfate, and dopamine hydrochloride in an alcoholic (ethanol) media by using volumetric, conductometric, and tensiometric techniques. Various methods were utilized to estimate the critical micelle concentration (cmc) values at different temperatures. The entire methods yielded the same cmc values. The corresponding thermodynamic parameters viz. the standard free energy of micellization ((Formula presented.)), enthalpy of micellization ((Formula presented.)), and entropy of micellization ((Formula presented.)) were predicted by applying the pseudo-phase separation model. The experimental density data at different temperatures (298.15 K, 303.15 K, 308.15 K, and 313.15 K) were utilized to estimate the apparent molar volumes ((Formula presented.)) at an infinite dilution, apparent molar volumes ((Formula presented.)) at the critical micelle concentration, and apparent molar volumes ((Formula presented.)) upon micellization. Various micellar and interfacial parameters, for example, the surface excess concentration ((Formula presented.)), standard Gibbs free energy of adsorption at the interface ((Formula presented.)), and the minimum surface area per molecule ((Formula presented.)), were appraised using the surface tension data. The results were used to interpret the intermolecular interactions prevailing in the mixed systems under the specified experimental conditions.