NONSPHERICAL MICELLES IN THE SODIUM DODECYL-SULFATE BRINE SYSTEM - A FLUORESCENCE QUENCHING AND NUCLEAR-MAGNETIC-RESONANCE STUDY

The size of elongated micelles in a system containing 2 wt.% sodium do decylsulfate (SDS), 3.5 wt.% NaCl and 94.5 wt.% water has been studied by means of two different nuclear magnetic resonance (NMR) methods an d time-resolved fluorescence quenching with special emphasis on a comp arison between the results from the three methods. The two NMR methods were the determination of self-diffusion coefficients by means of the pulsed-gradient spin-echo method and the determination of relaxation rates for specifically deuterium labelled SDS. In the analysis of the former data, the obstruction effect due to the finite micellar concent ration was taken into account. In the analysis of the relaxation data, the combined effect of lateral surfactant diffusion over the micellar surface and micellar rotational tumbling was taken into account in an exact manner for the case of prolates and in an approximate way for t he case of hemisphere-capped rods. The results obtained from the three methods were in reasonable agreement. If the micelles are modelled as prolates, the axial ratios obtained was ca. 6 while if they are descr ibed as hemisphere-capped rods, the axial ratio is ca. 5.