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Micellar and intermolecular interaction study of cetyltrimethyl ammonium bromide (CTAB) and Tween-20 mixed aqueous solutions

Journal of Analytical & Pharmaceutical Research
Sisay Merera,1 Ashok Kumar,2 O.P. Yadav3


From surface tension measurements critical micelle concentration (CMC) of aqueous binary mixtures of a cationic surfactant, cetyltrimethylammonium bromide (CTAB) and a nonionic surfactant polyoxyethylene (20) sorbitan monolaurate (Tween-20) have been determined at different mole fractions. Using the CMC value as an input, composition of mixed micelles and the interaction parameter, β, were determined by Rubingh’s theory. Activity coefficient of each surfactant in mixed micelle was less than unity. The observed negative value of the interaction parameter (β) and decrease of Gibb’s free energy indicated synergism in lowering the CMC of the mixed surfactant system and more stability of the mixed micellar system. The observed synergistic effect of mixed surfactant system in lowering as well stabilizing the CMC may be useful in pharmaceuticals for designing efficient targeted drug delivery system, improving mineral floatation process, more efficient petroleum recovery in the tertiary process, and managing effectively the problem of coastal oil spill. 


pharmaceuticals, CMC, interaction parameter, surfactant, synergistic