Micellar behavior of the aqueous solutions of dodecylethyldimethylammonium bromide. A characterization study in the presence and absence of hydroxypropyl-beta-cyclodextrin

Conductivity and static fluorescence measurements have been carried out to study the micellar behavior of the aqueous solutions of dodecylethyldimethylammonium bromide (D(12)EDMAB) in the absence and in the presence of hydroxypropyl-beta-cyclodextrin (HPBCD) at 25 degrees C. Several micellar parameters, as the aggregation number (n), the critical micelle concentration (cmc), and the dissociation degree of the micelle (beta) have been determined for the aqueous surfactant solution. In the presence of HPBCD, the D(12)EDMAB forms an inclusion complex with a 1:1 stoichiometry and a binding constant K=3200 M(-1). The effect of this complex in the micellar parameters, such as the cmc*, the beta, and the free [D(12)EDMAB] available to the micellization process have been analyzed. The ionic molar conductivities lambda(i)(o) of the D(12)EDMA(+) ion, both in the nonassociated and the associated forms, have been calculated as well. The results have been discussed and compared with those previously reported for other cyclodextrin/dodecyltrimethylammonium bromide/water systems.