The Composition of Mixed Micelles Formed by Dodecyl Trimethyl Ammonium Bromide and Benzethonium Chloride in Water

JOSÉ LUIS RODRÍGUEZ; ROSANNA M. MINARDI; ERICA P. SCHULZ; OLGA PIERONI; PABLO C. SCHULZ

JOURNAL OF SURFACTANTS AND DETERGENTS

SPRINGER HEIDELBERG

Año: 2012 vol. 2 p. 147 - 155

1097-3958

   The composition of the mixed micelles formed by hyamine (Hy) and dodecyltrimethylammonium bromide (DTAB) in water were experimentally determined by a combination of surfactant ion-selective electrodes and UV-vis spectroscopy measurements. Results were compared with the computed compositions from three theories on mixed micelles available in literature (Regular Solution, Motomura’ and  Georgiev’s). Also the basis of Junquera and Aicart method and the determination of the micelle aggregation number (N) by pyrene fluorescence quenching,  i.e., the constancy of N and the mixed micelle composition when the total concentration is changed, were not supported by our experimental results. Experimental micelle compositions were statistically equal to those computed by Regular Solution Theory. The mixed micelle composition and the amount of non-micellised surfactant molecules change  with concentration above the critical micelle concentration, and then do not  support the assumptions used in the Junquera and Aicart procedure and in the determination of the micelle aggregation number (N) by pyrene fluorescence quenching. The reason why the latter procedure gives N values similar to those obtained from other techniques is discussed.