Micellar properties of a phenothiazine drug in presence of additives

In this study micellar properties of a phenothiazine drug, promazine hydrochloride, at different concentrations of NaCl and cationic surfactants (conventional as well as gemini surfactants) are presented. The parameters studied are cmc (critical micelle concentration), X (1) (mole fraction of surfactant in micelles), f (1), f (2) (activity coefficients) and Delta G (ex) (excess free energy). Cl- ions (from NaCl) get adsorbed on the micellar head groups and, by decreasing the repulsion among them, lower the cmc. Surfactants form mixed micelles with the drug and the values of X (1), X (1) (id) (mole fraction of the surfactant in micelles in ideal state), interaction parameter beta, f (1) and f (2) all suggest non-ideal but synergistic nature. The Delta G (ex) values are negative indicating that the mixed state is more stable than the pure micelle state.