Adsorption and association in binary mixtures of cationic surfactants

The adsorption and solution properties of cationic surfactants dodecylammon ium chloride, tetradecylammonium chloride, and hexadecylammonium chloride, as well as hexadecyltrimtehylammonium bromide in pure and mixed states, wer e studied by surface tension and conductance measurements. The surfactants mixed non-ideally in both mixed monolayer and in the mixed micelles. The re gular solution theory was used for evaluating the non-ideal interactions be tween molecules in adsorbed and micellar states. Similar values of the mixe d monolayer and mixed micelle molecular interaction parameters in a mixture imply the molecules at the interface and in the mixed micelle have similar interactions. No synergism in surface tension effectiveness was observed. The adsorbed film at the air/water interface and mixed micelles were richer in more surface-active component.