Modulating the aggregation behavior of aqueous sodium dodecylsulphate (SDS) with addition of trisubstituted imidazolium based ionic liquid 1-butyl-2,3-dimethylimidazolium tetrafluoroborate [bdmim][BF4]

The aggregation behavior of an anionic surfactant sodium dodecylsulphate (SDS) in aqueous system in the presence of 1-butyl-2,3-dimethylimidazolium tetrafluoroborate [bdmim][BF4], a trisubstituted ionic liquid (IL) has been studied. Critical micelle concentrations (cmcs) were determined from conductance measurements at a temperature range of 298.15–318.15 K and using fluorescence probe at different wt% of IL. Results obtained from these methods are in good agreement with each other. An increase in cmc was observed for all the studied systems with increase in temperature as well as with increase in wt% of IL. Further the degree of dissociation, α and thermodynamic parameters viz. free energy of micellization, Δ G m o and entropy of micellization, Δ S m o has been evaluated. The aggregation number, Nagg of aqueous SDS micelles in the absence and presence of different wt% of [bdmim][BF4] is determined by fluorescence quenching of pyrene. 1H NMR measurements of post-micellar solutions have also been done to understand the different inter-molecular interactions of surfactant molecules in [bdmim][BF4].