Mixed micellization between amphiphilic drug promethazine hydrochloride and cationic surfactant (conventional as well as gemini)

The micellization behavior of an amphiphilic drug (promethazine hydrochloride (PMT)) in the presence of cationic surfactants (conventional as well as gemini) has been investigated conductometrically at different concentrations and temperatures. The micellar mole fractions of the surfactant (X-1(Rub), X-1(M), X-1(Rod), and X-1(Id)), calculated by different proposed models, show greater contribution of surfactant in mixed micelle and increases with the increase in concentration of the surfactant. Although alpha(1) (mole fraction of surfactant) is higher for DTAB than that of 12-4-12, the contribution of 12-4-12 is almost equal to that of DTAB. The interaction parameter (beta) is negative at all temperatures and at all compositions indicating attractive interactions. Activity coefficients (f(1) and f(2)) are always less than unity suggesting nonideality in the systems. Thermodynamic parameters suggest dehydration of the hydrophobic part of the drug at or above a certain temperature. (C) 2012 Elsevier B.V. All rights reserved.