Theoretical interpretation of anomalous diffusion coefficient of micellar solutions measured by light scattering
Wang, C. C.
Master of Science
A sodium di-2-ethyl hexylsulfosuccinate (AOTj/H2O/ decane (in the weight ratio of 3:5:95) system is believed to be a solution of micelles consisting of AOT coated water droplets dispersed in decane. A recent experiment of light scattering from such a system showed a diffusion coefficient strongly dependent on the scattering wave vector q. We examine several mechanisms which are known to cause q-dependence in diffusion coefficient. These include intermicelle interactions and mode-mode couplings. If the micelles are rigid, theories can not reproduce the data. In order to be consistent with data, the micelles should be deformate and stressless. That means the relative motion between parts of a micelle is hydrodynamic. The theory is tested by comparing the correlation length § determined from the scattering intensity with the § independently determined from the diffusion coefficient. We also found the "bare" diffusion constant to be negative.