Interactions of short chain phenylalkanoic acids within ionic surfactant micelles in aqueous media

The solubilization and interactions of phenylalkanoic acids induced by the cationic surfactant, cetyltrimethylammonium bromide (CTAB) and the anionic surfactant sodium dodecyl sulfate (SDS) was investigated spectropho-tometrically at 25.0 degree C. The UV spectra of the additives (acids) were measured with and without surfactant above and below the critical micelle concentration (cmc) of the surfactant. The presence of an alkyl chain in phenylalkanoic acids was responsible for hydrophobic interactions resulting in a shift of the spectra towards longer wavelengths (red shift). The value of partition coefficient (K sub(x)) between the bulk water and surfactant micelles and, in turn, the standard free energy change of solubilization ( Delta G super( Theta ) sub(p) were also estimated by measuring the differential absorbance ( Delta A) of the additives in micellar solutions.