MICROVISCOSITY AND MICELLAR PHASE-DIAGRAMS DETERMINED WITH FLUORESCENCE PROBES

The dependence of microviscosity on salt and surfactant concentrations was determined in micellar solutions of alkyltrimethylammonium bromides by using two fluorescent probes, auramine and 1,3-dipyrenylpropane (P3P). The microviscosity increased with the growth of the micelles, it changed at the sphere to rodlike micelles transition point, and it became constant above the overlap threshold point of rod micelles, that is, the overlapping of micelles did not influence the microviscosity. The transition points of the micellar solutions (the critical micelle concentrations, the sphere-rod transition point, and the micelle overlapping point) determined by the present method were in good agreement with those in the literature. Phase diagrams of the micellar solutions were determined from the above data.