LAUSR

Abstract Mixed micelle formation between surface active ionic liquid (1-dodecyl-3-methylimidazolium bromide, IL) and two amphiphilic drugs consisting of imipramine hydrochloride (IMP) and amitriptyline hydrochloride (AMT) were investigated in different mole fractions at 298 K using electrical conductivity measurements. The experimental results of mixed antidepressant drugs (IMP and AMT) with ionic liquid in aqueous solution indicated that CMC values decreased with the addition ionic liquid in mixture. Also, the CMC values in AMT/IL system are comparatively lower than those found in IMP/IL system, which indicates that the formation of mixed micelle is more favorable in presence of AMT. The different theoretical models (Clint, Rubingh, Motomura and Rodenas) were used to evaluate the micellar mole fractions ( X i ), interaction parameter ( β m ) and activity coefficients of components (f1 and f2) in the mixed micelle. In both studied systems, the values of interaction parameter suggest the synergistic effects in mixed state. Activity coefficients are less than unity which means non-ideal mixing. Also, the excess free energy of micellization ( Δ G ex ) values have been estimated using activity coefficients at different compositions. This parameter not only confirm that mixed micellization is spontaneous in nature but also is extra stable than individual micelle.