Mixed Micellization and Interfacial Properties of Ionic Liquid-Type Imidazolium Gemini Surfactant with Amphiphilic Drug Amitriptyline Hydrochloride and its Thermodynamics

The thermodynamics of mixed micellization of amitriptyline hydrochloride (AMT) with ionic liquid-type imidazolium gemini surfactant ([C-10-4-C(10)im] Br-2), was investigated at different mole fractions and temperatures by surface tension measurements. The deviation of the critical micelle concentration (CMC) from the ideal critical micelle concentration (CMC*), micellar mole fraction () from ideal micellar mole fraction (), the values of interaction parameter () and activity coefficients () (for both mixed micelles and mixed monolayer) explained the non-ideal behavior (i.e., synergistic behavior) of binary mixtures. The excess free energy (a dagger G (ex)) for the AMT-[C-10-4-C(10)im] Br-2 binary mixtures explained the mixed micelles stability in comparison to micelles of [C-10-4-C(10)im] Br-2 and pure AMT. Interfacial parameters, i.e., Gibbs surface excess (), minimum head group area at air/water interface (), free energy of micellization (), and standard Gibbs energy of adsorption (a dagger G (ads) (o) ) were also evaluated for the systems. The standard entropy of adsorption (a dagger S (ads) (o) ) was found higher than the standard entropy of micellization (a dagger S (m) (o) ) at all mole fractions of AMT (alpha (1)).