Study of Micellar Behavior of a Tween 80 Surfactant in Aqueous Media Containing Diphenhydramine Hydrochloride


The surface properties of mixtures of a nonionic surfactant Tween 80 (Tw 80)and a cationic drug, diphenhydramine HCl (DPH) have been investigated. This wasdone by calculating the surface excess concentration (Γmax), minimum moleculararea (Amin), surface pressure at the CMC (ᴨcmc), Gibbs Free Energy of adsorption(ΔG°ads), Gibbs free energy of micellization (ΔG°m), the standard enthalpy ofmicellization (ΔH°m), and the standard entropy of micellization (ΔS°m). Thecalculation was performed using the surface tension in the temperature range of 293-323 K with the variation of surfactant concentration to determine the critical micelleconcentration (cmc) of the system studied. The variation of cmc values of drugconcentration (DPH) with temperature was used to calculate the parameters above.The results indicate that the cmc values of Tw 80 increased when the (DPH) wasadded and when the temperature increased at the whole temperature studied. Theresults obtained for interfacial properties show that Γmax decreases with the additionof DPH and decreases with DPH concentration increase from 10-5 to 10-4M anddecreases with temperature increases. The results of thermodynamic propertiesindicate that the micellization and adsorption at the interface are spontaneous andthe ΔGads are ore negative than ΔGm at all temperatures.