Drug-surfactant comicellization: Propranolol hydrochloride-surface active ionic liquid systems in aqueous medium

Mixed micellization behavior of an antidepressant amphiphilic drug propranolol hydrochloride (PPL) with each of two surface-active ionic liquids (SAILs), 1-decyl-3-methylimidazolium chloride (DMImCl) and 1-hexadecyl-3-methylimidazolium chloride (HDMImCl) in aqueous solutions has been studied using conductometric, and tensiometric techniques. The structures of PPL and SAILs have been optimized using Density Functional Theory (DFT) calculations and the possible coordination of PPL with the head group of the SAILs has also been studied. The critical micellar concentration (cmc) (for pure as well as mixed surfactants), micellar composition of the surfactants, interaction parameter (βR) along with the degree of counterion binding (α) have been ascertained in this study. In particular, the regular solution theory, put forward by Rubingh, was employed to obtain the SAIL-PPL interaction parameters (βR) in the micellar state from the cmc values of the corresponding SAILs and drug in their mixtures. Analyses of the results have also been made on the basis of the theories of Clint and Motomura to gain important insight into the nature of interactions prevailing among the components in the mixed micelle. Different interfacial and thermodynamic parameters for comicellization have also been derived and information as to the spontaneity of the comicellization process, thermal stability of the micellar aggregates, alteration of the surface activity of PPL in presence of the SAILs, geometrical shapes of the micellar aggregates etc. have been obtained.