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

Abstract Diluted solutions of linear polystyrene (PS) in toluene and dioxane were studied by the light‐scattering method. The solutes were mixtures of high‐M̄ w and low M̄ w PS. The dissolved PS mixtures were regarded as polymer solutions containing microgels, the high‐M̄ w PS being looked upon as the microgel counterpart. The calculation method as proposed by Strazielle 1 and Burchard 2 was used to evaluate the microgel percentage and particle size, whereby the method could be verified against mixtures with well‐known weight composition and \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {\left( {r_g ^2 } \right)} ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $\end{document} . The \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {\left( {r_g ^2 } \right)} ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $\end{document} values evaluated for the mixtures from the experimental data were compared with those estimated from the molecular weights of the components, their weight concentrations, and their \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {\left( {r_g ^2 } \right)} ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $\end{document} values. The method 1,2 was found to be useful for evaluating the microgel content in a sample, but not for \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {\left( {r_g ^2 } \right)} ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $\end{document} values as calculated by Guinier's procedure nor those calculated by Zimm's procedure; the former were low and the latter were even incongruous. A comparative analysis of the theoretical function P −1 (θ)‐versus‐sin 2 (θ/2) and experimental ( Kc / R (θ)) c =0 ‐versus‐sin 2 (θ/2) curves allowed to discuss the effect of the course of these curves at samll angles from 0° to 30° on M̄ w and \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {\left( {r_g ^2 } \right)} ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} $\end{document} as determined for the high and low molecular weight polystyrene mixtures in toluene as solvent.