Impact of ethanol and NaCl on the acid yellow dye mediated self-aggregation of sodium dodecyl sulfate: A combined investigation by conductivity and molecular dynamics simulation

Md Ariful Haque, Jahangirnagar University
Md Khalid Bin Islam, BICCB
Shamim Mahbub, University of Dhaka
Mohammad A. Halim, Kennesaw State University


Herein, we report the micellization behavior of the mixture of sodium dodecyl sulfate (SDS), and acid yellow (AY) dye in water, water + ethanol, and water + NaCl media. The degree of interaction between SDS and AY has been assessed quantitatively from the estimated values of critical micelle concentration (cmc). Three cmc values were observed for the AY + SDS systems at each temperature and solvents utilized, which exhibit a reversed U-shaped variation with respect to the change of temperature in aqueous/NaCl solution while increased monotonically in ethanolic medium almost in all cases. The extent of micellization was found to be disfavored in presence of AY dye. The micellization was also found to be disfavored up to 15% ethanol and favored in the addition of electrolyte species. The values of counterion binding were found to be temperature dependent. The Gibbs free energy (ΔGmo), which was found negative, reveal a spontaneous micellization of AY + SDS system. The other thermodynamic parameters, like enthalpy (ΔHmo) and entropy (ΔSmo) of micellization along with different transfer energies, were also assessed to have an insight on the mode of interaction of surfactant and dye assemblies. The molecular level interaction between SDS and AY has been unveiled by Molecular Dynamics (MD) simulation and exhibits good agreement with experimental results.