Impact of sodium polystyrene sulfonate on micellization behaviour of cetyltrimethylammonium bromide in the presence of methyl red in ethanol–water mixture: A conductometric investigation

Abstract

The triple interaction between dyes, surfactants, and polyelectrolytes is entirely novel and of great research interest due to their potential applications in various fields. In this work, we explored the impact of sodium polystyrene sulfonate (NaPSS) on the micellization behavior of cetyltrimethylammonium bromide (CTAB) in the presence of methyl red (MR) varying ethanol volume fraction (0, 0.1, 0.2, and 0.3) and temperatures (298.15, 308.15, and 318.15 K) by conductometric approach. From conductivity plots, we determined critical aggregation concentration (CAC), apparent critical micelle concentration (CMC*), and degree of counter ion dissociation (α) for the CTAB-NaPSS and MR-CTAB-NaPSS systems, and the CMC*, CAC, and α values in the presence of the dye for the MR-NaPSS-CTAB system decrease as compared to the NaPSS-CTAB. The CAC, CMC*, and α values obtained, however, increase with increasing temperature and the volume fraction of ethanol. Therefore, the order of CMC* and CAC determined from conductivity data for ethanol–water is (CMC*)0.3>(CMC*)0.2>(CMC*)0.1>(CMC*)water, (CAC)0.3>(CAC)0.2>(CAC)0.1>(CAC)water, and with temperature: (CAC)318.15>(CAC)308.15> (CAC)298.15 and (CMC*)318.15>(CMC*)308.15>(CMC*)298.15. Further, we also determined thermodynamic parameters like the standard free energy change of micellization (ΔGm0), the standard free energy change of binding (ΔGb0), the standard enthalpy change of micellization (ΔHm0), the standard entropy change of micellization (ΔSm)0, the standard free energy change of bound micelles (ΔGmb0), and the standard free energy change of tail transfer (ΔGtrans0) to assess the feasibility of the micellization process. The more positive values of ΔSm0 and more negative values of ΔGm0, ΔGb0, ΔHm0, and ΔGmb0 for the MR-NaPSS-CTAB system, the corresponding values for the NaPSS-CTAB system show that the process of micellization with MR in the ethanol–water mixture is thermodynamically easier, feasible, spontaneous, and stable. Changes in the ΔGm0 with different solvent and solvophobic parameters provide us with valuable insights into the solution's thermodynamic stability, solvent structure, fluidity, micellization and aggregation tendencies, solvent polarity, and the degree of NaPSS-CTAB interaction in aqueous ethanol solutions with and without MR. The findings of this study significantly broaden our knowledge of the intricate relationships between molecules and the implications of these relationships in a variety of scientific, industrial, ecological, medicinal, and technological fields.