A careful examination of Fig nbsp reveals that the cmc

In this present study, both IL [bdmim][Br] and surfactant TTAB carry positive charge on their head groups which restricts the interactions between these two species. Here rather counter-ion of the IL interacts with the head group of surfactant monomers. These electrostatic interactions between [Br]− IPI-504 of IL and [TTA]+ cation of TTAB leads to lowering in head group repulsions among monomers. As explained above, this favors the micellization to occur at a lower concentration than cmc, thus decreases the cmc of aqueous TTAB solution or it can be said that enhances its surface activity. The cmc of TTAB decreases to 1.0 mmol kg− 1 at 0.5 wt.% of IL this is about three times less than the pure surfactant value which is 3.8 mmol kg− 1. This is interestingly closer to the cmc value of higher homologue of TTAB i.e., cetyltrimethylammonium bromide, CTAB which has cmc value 0.98 mmol kg− 1[34]. This behavior of IL [bdmim][Br] is similar to that observed in case of electrolytes such as sodium chloride and sodium bromide when added to cationic surfactants, decreases the cmc [35] and [36]. Although with the increase in temperature cmc value increases as shown in Table 1. This is due to the thermal agitation in the solution caused by the high temperature which disrupts the water structure. It increases the solubilization of surfactant molecules and prevents the surfactant monomers to come closer and delays the micellization process. The cation of some IL molecules near micellar surface has an interaction with [Br]− ions present in the Stern layer of micelles. Here contrasting results have been obtained if compared to our previous systems, where aggregation behavior of anionic surfactant SDS has been modified using ILs, [bdmim][Cl] and [bdmim][BF4] [30] and [31]. There ILs led to an increase in the cmc of surfactant SDS. It was due to the stronger solvophobic interaction between alkyl chains of IL cation [bdmim]+ and surfactant anion [DS]−, which stabilized SDS monomers in the aqueous media and delayed the aggregation process. Due to the presence of opposite charges on the interacting species, [DS]− and [bdmim]+ ions of SDS and IL respectively, these did not repel each other rather allow each other in their vicinity. The large size of [bdmim]+ ion prevented SDS monomers to come closer for micellization. Here for the wt.% of IL ? 0.5, conductance measurements become unreliable rendering it impossible to draw any meaningful conclusion. Above this wt.%, conductance due to IL itself increases appreciably so the change in conductance due to surfactant micellization becomes insignificant.