The strong synergistic interaction between surface active ionic liquid and anionic surfactant in the mixed micelle using the spectrophotometric method

Abstract

The strong synergistic interaction between surface active ionic liquid (1-dodecyl-3-methylimidazolium bromide or IL) and anionic surfactant (N-lauryl sarcosine sodium or NLS) has been studied in the mixed micelle at 25 °C. The critical micelle concentration (CMC) values of the studied mixture at various compositions are much less than that of pure surfactants (due to the strong electrostatic attraction between components). In this work, the keto-enol tautomerism of benzoylacetone (1-phenyl-1, 3-butadione) as probe were used to determine the CMC (pure and mixture) in aqueous solution by spectrophotometric method. The data obtained from experimental measurements were used to specify the mole fractions of components in the mixed micelle (X1m and X2m) and interaction parameter (βm) by Regular Solution Theory (RST). The results obtained show that the mixed micelle will tend to produce a 1:1 ratio of surfactant molecules (NLS and IL) with the oppositely charged head groups in aqueous mixtures(X1m≈X2m) even when the bulk mixing ratio is far from equimolar. The interaction parameter (βm) is high negative values at all compositions showing strong attractive interactions between components. Finally, the azeotrope micellization point was determined using Kamrath model for this system (IL-NLS) and compared with the results of Rubingh approach.