Modulating effect of ionic liquid 1-butyl-2,3-dimethylimidazolium chloride on micellization behaviour of cationic surfactant dodecyltrimethylammonium bromide in aqueous media

The micellization behaviour of cationic surfactant dodecyltrimethylammonium bromide (DTAB) has been studied upon addition of 1-butyl-2,3-dimethylimidazolium chloride, [bdmim][Cl], a trisubstituted imidazolium based ionic liquid (IL) in aqueous media. The critical micelle concentration (cmc) and degree of dissociation (α) for the micelles were determined from conductance measurements for a temperature range of 298.15–318.15 K at different wt% of IL in the medium. The thermodynamic parameters (ΔGm°, ΔHm° and ΔSm°) of micellization were evaluated by applying the charged pseudo-phase separation model for the micellar systems. Further fluorescence probe analysis has been utilized to obtain cmc value as a complementary to conductivity in order to validate the cmc values obtained from conductivity measurements. A continuous decrease in cmc was observed with addition of 10.0 wt% of IL but further addition of IL causes an increase in cmc of the surfactant solution. The aggregation number, Nagg and size of aggregates in aqueous DTAB solutions at different wt% of IL were determined by fluorescence quenching of pyrene and dynamic light scattering (DLS) studies, respectively. 1H NMR measurements of post-micellar solution at lower wt% of IL have been done to understand the different inter-molecular interactions of surfactant molecules with [bdmim][Cl].