Effect of Cosolvents DMSO and Glycerol on the Self-Assembly Behavior of SDBS and CPC: An Experimental and Theoretical Approach

The study of the effect of cosolvents on the micellization of ionic surfactants is relevant in different industrial applications. In this article, we studied the effects of binary aqueous mixtures of DMSO and glycerol on the micellization and thermodynamic behavior of sodium dodecyl benzenesulfonate (SDBS) and cetylpyridinium chloride (CPC) in the range of (293.15-308.15) K. The electrical conductivity method was employed to determine the parameters of micellization such as the critical micellar concentration (CMC) and degree of counterion dissociation (α). The temperature dependence of CMC values was used to calculate other thermodynamic parameters of micellization such as the standard free energy of micellization (ΔG_m ⁰), the standard enthalpy of micellization (ΔH_m ⁰), and the standard entropy of micellization (ΔS_m ⁰). Result analysis showed that the CMCs of both surfactants (SDBS and CPC) were directly proportional to the cosolvent concentration. The standard free energy of micellization (ΔG_m ⁰) was negative in all cases, and it increased with increases in the cosolvent concentration, thereby reducing the driving force for micellization. Quantum chemical calculations and molecular dynamic (MD) simulations were essential to understanding the phenomena and provide a well-supported molecular picture of the micellization process. In this work, a combined experimental and molecular modeling study on the effect of cosolvents such as DMSO and glycerol on the self-assembly behavior of SDBS and CPC was performed. It was found that the supramolecular assembly is inhibited by the presence of glycerol and DMSO because hydrophobic regions in the solvent media increased with increasing concentration of the nonaqueous solvents, imparting cosolvency and promoting the decrease in amphiphilic assembly.