Etude du comportement d'une série de polystyrènes linéaires dans des mélanges de solvants

The preferential solvation of anionically polymerised polystyrene by different solvent/non solvent mixtures (CCl₄/CH₃OH, C₆H₆/CH₃OH, dioxane/CH₃OH, C₆H₆/Heptane) was studied by light scattering. The parameter λ′ of preferential solvation depends on molecular weight M according to where λ′_∞ is the preferential solvation at infinite molecular weight and A a quantity characteristic for the composition of the mixed solvent. A increases with decreasing thermodynamic goodness of the solvent mixture. The above equation can be derived semi-empirically by assuming that the solvent composition near the chain depends on the density of chain segments. This hypothesis furthermore explains the observed anomalous behavior of the intrinsic viscosity/molecular weight relationship below molecular weights of about 160,000 in solvent/non solvent mixtures.