Effect of hydrophilic ionic liquid on aggregation behavior of aqueous solutions of sodium dodecylsulfate (SDS)

• Physicochemical characterization of the association between [C5mim][BF4] and SDS is carried out using conductivity and spectroscopic studies.
• Micellization process gets delayed in presence of IL.
• NMR studies are made to interpret the solubilization site of IL to the micellar system.

This paper delineates the change in aggregation behavior of aqueous sodium dodecylsulfate (SDS), an anionic surfactant upon addition of “hydrophilic” ionic liquid (IL) 3-methy-1-pentylimidazolium tetrafluoroborate in an increase in critical micelle concentration (cmc). The results demonstrate the presence of electrostatic and hydrophobic interactions between the ions of IL and the head group of the surfactant. From the cmc   values and their temperature dependence, the thermodynamic parameters, viz. free energy of micellization (ΔGm0) and entropy of micellization (ΔSm0) were evaluated to permit speculation of the interactions existing in the studied aqueous surfactant-IL systems. Further, 1H NMR chemical shift measurements in micelle solutions containing IL have also been carried out. The results obtained are compared with the conclusions drawn from the conductance and fluorescence measurements.