Studies on diffusion behavior of dyes in aqueous polymer solution - Part 2: Diffusion coefficients of dyes in aqueous ionic polymer solutions

The diffusion coefficients of dyes in aqueous ionic polymer solutions, D, and those in water, Do, were measured at 25 degrees C with the diaphragm cell method. The dyes examined were p-nitroaniline(p-NA) and Orange II (ORII). The polymers used were sodium carboxymethyl cellulose (CMC) and sodium polystyrene sulfonate (PSS). The D/D-0 value in every system decreased with increasing polymer concentration. The decreases were greater in OR-II systems than p-NA systems. The interaction between dye and polymer was estimated by a dialysis method. The number of water molecules which act as an obstacle of dye diffusion, in the neighborhood of polymer molecules, was calculated on the basis of Wang's obstruction theory. And, the D/D-0 values obtained in this study were compared with those calculated by modified Wang's, Colton's, and Geankoplis's theoretical equations. On these examinations, the decrease in D/D-0 values was explained by the binding of dye to polymers in p-NA systems, the electrostatic repulsion of polymers against dye in OR-II systems, and the obstruction for the diffusion of dye by polymer molecules and the water molecules in the neighborhood of polymer molecules in both systems.