Abstract
In the present paper, the micellization of an amphiphilic drug, promazine hydrochloride, and gemini surfactants (16-s-16) with s = 4-6 and the monomeric hexadecyltrimethylammonium bromide (CTAB) counterparts has been examined conductometrically in the pure and mixed states in aqueous solutions at different compositions and temperatures (298.15-308.15 K). Dicationic gemini surfactants provide much better environment for the micellization behavior than the corresponding monocationic counterpart CTAB. The critical micelle concentration (cmc) values are lower than the cmc for ideal mixing, cmc(id), suggesting attractive interactions between the two components in mixed micelles. The micellar mole fractions of surfactants, evaluated by different models, show greater contributions of surfactants in mixed micelles and increase with increasing concentrations of these surfactants. The negative values of beta suggest synergism in the mixtures, which is highly beneficial as it reduces the total amount of surfactants required in a particular application, leading to reductions of cost and environmental impact. Activity coefficients (f(1) and f(2)) are always less than unity showing nonideality in the systems. The data have been also used for evaluation of thermodynamic parameters.