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The interaction between octaethylene glycol mono-n-dodecyl ether (C12Eg) and ethylhydroxyethyl cellulose (EHEC) in aqueous solution has been studied by measuring the C&g self-diffusion coefficient in the presence of EHEC at 25 OC. Micelle diffusion is influenced by the polymer in two ways, i.e. obstruction due to the polymer network and association of micelles to the polymer chains. It is demonstrated that, from studies using polymers of different polarity, a separation between obstruction and association effects can be achieved. It is found that the interaction between a relatively hydrophobic EHEC and the surfactant is dominated by a strong attraction leading to a formation of polymer-surfactant complexes. This observation is consistent with phase diagram findings. Taking into account the obstruction from both micelles and polymer chains, the binding isotherm of C&g to the hydrophobic EHEC is calculated by using a two-site model.

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The diffusion processes underlying the observed transport properties of the polar solvent in some reverse aggregated, L2 phase microemulsions has been studied. Three different surfactant-oil-polar solvent systems with the surfactants sodium bis(2-ethylhexyl) sulfosuccinate (AOT), didodecyldimethylammonium bromide (DDAB), and tetraethylene glycol dodecyl ether (C12E4), respectively, were investigated. The polar solvent was dilute aqueous solutions of either N-methylformamide or tetramethylammonium chloride. These additives used have essentially no influence on the phase behavior compared to pure water. Following the approach of a previous publication (J. Phys. Chem. 1988,92,6675) we have measured the self-diffusion coefficients of the two polar species in the microemulsions, the ratio being sensitive to the nature of the diffusion process. In the AOT system a dominating aggregate diffusion process was found at lower temperatures indicating closed isolated reversed micellar aggregates. With increasing temperature, structural changes cause a crossover to a dominating molecular diffusion in a medium similar to the neat aqueous solution. This implies a crossover to a bicontinuous network at higher temperatures. In contrast, we found no region of dominating aggregate diffusion process in the DDAB and C12E4 systems. A dominating or almost dominating molecular diffusion process was detected even when the absolute diffusion coefficients of the polar solvent species were low.