Investigations on micellization and surface properties of sodium dodecyl sulfate in aqueous solutions of triflupromazine hydrochloride at different temperatures

Abstract

Micellization behavior of sodium dodecylsulfate (SDS) has been studied in the presence of phenothiazine drug triflupromazine hydrochloride (TFP) in the concentration range (0.01–0.50mM) in water as well as in aqueous solutions of ethanol (1–10%, v/v) using conductivity and surface tension measurements. Critical micelle concentration (CMC), degree of micelle dissociation (β), Gibbs free energy of micellization (ΔGomic), standard enthalpy (ΔHomic) and entropy (ΔSomic), maximum surface excess concentration (Γmax), minimum area per surfactant molecule (Amin), Gibbs free energy of adsorption (ΔGoads) and packing parameter (p) have been calculated from the above measurements. CMC values decrease with concentration of ethanol as well as of TFP in water. However in aqueous ethanol solutions, CMC values of SDS do not follow a regular decrease with TFP concentration. Surface parameters, Γmax and Amin indicate comparatively less availability of surfactant molecules at the air–water interface in the presence of additives. The p values suggest that the micellar shape remains the same in the studied concentration range of TFP as well as ethanol. 1H NMR spectroscopy has also been employed to acquire an idea about the nature of molecular interactions prevailing among the reacting species from the changes in chemical shift observed.