Self-association and mixed micellization of an amphiphilic antidepressant drug, 5-[3-(Dimethylamino)propyl]-10,11-dihydro-5H-dibenz[b,f]azepine hydrochloride and a nonionic surfactant, poly(ethylene glycol) t-octylphenyl ether: Evaluation of thermodynamics

In the continuation of our earlier work [1], the self-association, surface properties and mixed micellization of an amphiphilic tricyclic antidepressant drug, 5-[3-(Dimethylamino)propyl]-10,11-dihydro-5H-dibenz[b,f]azepine hydrochloride (imipramine hydrochloride, IMP) and a non-ionic surfactant, poly(ethylene glycol) t-octylphenyl ether (Triton X-100) has been studied. In aqueous media, the surface and micellar properties (the critical micelle concentration (CMC), maximum surface excess concentration at the air/water interface (Γ_max) and the minimum area per surfactant molecule at the air/water interface (A_min) parameters, etc.) of IMP drug and Triton X-100 (independent as well as mixed) solutions are evaluated. The CMC as well as A_min increase and the Γ_max decreases with increasing concentration (mole fraction) of the IMP. We also report the thermodynamics of IMP in absence and presence of surfactant. The Gibbs energies (viz., at air/water interface (G_min^(s)), the standard Gibbs energy change of micellization (ΔG_mic⁰), the standard Gibbs energy change of adsorption (ΔG_ads⁰), the excess free energy change of micellization (ΔG_ex^m) were evaluated. The aggregation number (N_agg) of IMP and Triton X-100 pure as well as their mixed systems has been studied.