Diffusion of XXXX micelles in agarose gels.

@entity1219 @entity2827 @entity3208 @entity214
The gradient diffusion of ionic @entity3208 micelles in agarose gel was investigated at moderate concentrations above the CMC. Of particular interest were the effects of micelle, gel, and @entity2827 concentration on the micelle diffusivity. Holographic interferometry was used to measure the gradient diffusion coefficient at three @entity2827 concentrations (0, 0.03, 0.10 M), three gel concentrations (0, 1, 2 wt%), and several surfactant concentrations. Time-resolved fluorescence quenching was used to measure aggregation numbers both in solution and gel. The micelle diffusivity increased linearly with surfactant concentration at the two larger @entity2827 concentrations and all gel concentrations. In general, the strength of this effect increased with decreasing @entity2827 concentration and increased with gel concentration. This behavior is evidence of decreasing micelle-micelle electrostatic interactions with increasing @entity2827 concentrations, and increasing excluded volume effects and hydrodynamic screening with increasing gel concentration, respectively. The only exception was at 0.1M @entity2827 and 2 wt% agarose, which showed a slight reduction in the slope compared to 1 wt% agarose. It was found that the concentration effect is quite strong for charged solutes: at a @entity1219 concentration of 0.03 M in a 2% agarose gel, in a solution with 3% @entity214 micelles by volume, the micelle diffusion coefficient is doubled relative to its value in the same gel at infinite dilution. The extrapolated, infinite-dilution diffusion coefficients and the rate at which the micelle diffusivity increased with surfactant concentration were compared with predictions of previously published theories in which the micelles are treated as charged, colloidal spheres and the gel as a Brinkman medium. The experimental data and theoretical predictions were in good agreement.
