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 ( X 1 m ) from ideal micellar mole fraction ( X 1 ideal ), the values of interaction parameter ( β ) and activity coefficients ( f i ) (for both mixed micelles and mixed monolayer) explained the non‐ideal behavior (i.e., synergistic behavior) of binary mixtures. The excess free energy (∆ 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 ( Γ max ), minimum head group area at air/water interface ( A min ), free energy of micellization ( Δ G m o ), and standard Gibbs energy of adsorption (∆ G ads o ) were also evaluated for the systems. The standard entropy of adsorption (∆ S ads o ) was found higher than the standard entropy of micellization (∆ S m o ) at all mole fractions of AMT ( α 1 ).