Light-scattering studies on solutions of high and low molecular weight polystyrene mixtures used as models of microgel-containing solutions

Abstract

SynopsisDiluted solutions of linear polystyrene (PS) in tolueneand dioxan5were studied by the lightscattering method. The solutes were mixtures of high-M, and low-M, PS. The dissolved PS mixtures were regarded as polymer solutions containing microgels, the high-& PS being looked upon as the microgel counterpart. The calculation method as proposed by Strazielle' and Burchard' was used to evaluate the microgel percentage and particle sizeEhereby the method could be verified against mixtures with well-known weight composition and (rg2)lI2. The (rg2)l12 values evaluated for the mixtures from the experimental data were compared with thosGtimated from the molecular weights of the components, their weight concentrations, and their (rg2)lI2 values. Tkmethod1V2 was found to be useful for evaluating the microgel content in a sample, but not for (rg2)l12 values as calculated by Guinier's procedure nor those calculated by Zimm's procedure; the former were low and the latter were even incongruous. A comparative analysis of the theoretical function P1(8)-versus-sin2 (8/2) and experimental (Kc/R(e)),,o-versus-sin' (8/2) curvEdlowed to discuss the effect of the course of these curves at small angles from Oo to 30° on a, and (rg2)lI2 as determined for the high and low molecular weight polystyrene mixtures in toluene as solvent.