LAUSR

Abstract In this study, the interaction in binary mixtures comprising an amphiphilic drug (propranolol hydrochloride, PPL) and ionic surfactants (N-lauryl sarcosine sodium, NLS and 1-dodecyl-3-methylimidazolium bromide, SAIL) was investigated in micellar phase using conductometric technique in aqueous solution at 298.15 K. SAIL is a cationic surface-active ionic liquid with a specific critical micelle concentration(CMC). To identify the influence of polar head groups in interaction between components, the surfactants with the same alkyl chain length (C12) but with oppositely charged head groups were selected (NLS: anionic and SAIL: cationic). The deviation of experimental critical micelle concentration (CMCexp) from the corresponding ideal values of CMC (CMCid), the micellar compositions (X1 and X2), the mutual interaction parameter (βm), activity coefficients of the components in the mixed micelle (f1 and f2) and thermodynamic parameters have been calculated using different proposed theoretical models like Clint, Rubingh, and Motomura. The interaction parameter (βm) is negative values at all compositions for two systems (with two levels of values), showing attractive interactions between components. In comparison between the NLS/PPL and SAIL/PPL systems, the NLS/PPL system shows stronger micelle formation capability, smaller CMC values and stronger synergistic effect. The determined values of the micellar mole fraction of surfactant (X1) obtained from theoretical models signify the considerable contribution of surfactant in surfactant(1)/PPL(2) mixed micellization. Further, conductometry measurements indicate that the extent of counterion binding (α) of mixed micelles for SAIL/PPL system are higher than those found for NLS /PPL system.