Association of anions to cationic micelles

The relative association degrees of different anions to micelles of hexadecyltrimethylammonium bromide (CTA) were measured by spectrophotometrically determining the amounts of p-toluenesulfonate (TOS) or benzenesulfonate (BS) anions desorbed from the micelles by addition of increasing amounts of NaNO3, NaBr, NaCl, NaOH, NaF, NaOAc, Na2SO4, Na2HPO4, Na2CO3, and Na2B4O7. A simple ion-exchange model was used for interpreting the results in a quantitative way and values for the ion-exchange constants were calculated. These values are discussed in terms of the hard and soft acid-base principle. © 1980 American Chemical Society