The aqueous Triton X-100 - Dodecyltrimethylammonium bromide micellar mixed system. Experimental results and thermodynamic analysis

Abstract

The micellization process of the aqueous mixed system Triton X-100 (TX100)-Dodecyltrimethylammonium Bromide (DTAB) was studied with a battery of procedures: surface tension, static and dynamic light scattering and ion-selective electrodes. Results were also analysed with two thermodynamic procedures. The system shows some changes in its behaviour with changing the mole fraction of DTAB, $\alpha_{DTAB}$, in the whole surfactant mixture. For $ \alpha_{DTAB} < 0.40$ micelles are predominantly TX100 with scarce solubilized DTA+ ions, and TX100 acts as a nearly ideal solvent. In the range $0.50 < \alpha_{DTAB} < 0.75$ it seems that none of the components acts as a solvent, and above $\alpha_{DTAB} > 0.75$ there are abrupt changes in the size and electrophoretic mobility of micelles. These phenomena have been interpreted in the light of the thermodynamic results and some TX100-ionic surfactant mixtures of literature.