Abstract
The simple and reliable conductivity measurement method has been inaugurated to disclose the mixed micellization behavior of two ionic surfactants (tetradecyltrimethylammonium bromide (TTAB) plus sodium dodecyl sulfate (SDS)) in H2O/NH2-CO-NH2 (urea) medium at several temperatures and compositions. The experimentally evaluated critical micelle concentration (cmc) are different those from their corresponding ideal critical micelle concentration (cmcid) which signifies the mutual interaction (attractive/repulsive) amongst the current constituents. The higher cmc values of distinct surfactant and mixed system in occurrence of NH2-CO-NH2 compare to water medium which also further increase through raising the amount of urea. In urea medium, the extent of degree of dissociation (g) is lower at superior composition of TTAB which implying better packing of surfactants aggregates. The magnificence of micellar mole fractions of TTAB depending of various proposed models & their ideal X1id values were executed and the executed outcomes suggesting the strong contributions of TTAB in the SDS-TTAB mixed micellization. Activity coefficients of TTAB & SDS, f1 &f2 < 1 indicate the attractive interaction amid SDS and TTAB. The negative values of ΔG0m & ΔH0m suggest the spontaneity of micellization & exothermic micellization process respectively. The executed ΔS0m values were positive in all cases studied herein.
•Interactions amongst surfactant mixtures in aqueous/urea medium were studied.•In presence of urea higher in cmc values were obtained as compared to aqueous medium.•Activity coefficients of TTAB and SDS are below 1 also indicating the attractive interaction amid constituents.•The negative values of enthalpy connote the micellization is exothermic process.•Excess free energy (ΔGex) illustrates the stability of the attained mixed micelles.