Transition from antagonistic to synergistic interaction in mixed micellar system by increase in alkyl chain length of alkyl trimethylammonium bromide

Herein, the electrical conductivity technique used to measure the critical micelle concentration (cmc) for pure cationic surfactants (Dodecyl/cetyltrimethylammonium bromides) and phenothiazine drug (Promethazine hydrochloride), as well as their different mole fractions in 10−3 ​mol/kg 1-methyl-3-octylimidazolium chloride (C8mim.Cl) at different temperatures. By using the cmc values the regular solution theory used to evaluate the micellar mole fraction for DTAB/CTAB-PMT mixed systems. The clint's model used to calculate the ideal critical micelle concentration (cmc∗) that helps to evaluate the ideal micellar mole fraction for studied mixed systems, both explain the deviation from ideality. In addition, interaction parameter βm helps to confirm the nature of interaction (either antagonistic or synergistic) for the studied systems. The calculated parameters confirm a transition in the binding nature from antagonistic to synergistic with the increase in alkyl chain length of cationic surfactant i.e., component of the binary mixed system. The ease of micellization for the studied systems discussed by the standard Gibb's energy of micellization (ΔGm0), as well as the standard enthalpy and standard entropy of micellization were (ΔHm0) and (ΔSm0), respectively to discuss the stability of the studied systems.