Polymer chain dimensions in mixed‐solvent media

Abstract

Abstract The equilibrium between a linear polymer molecule and a binary solvent mixture in which it is immersed has been treated. An equation has been derived relating the resulting molecular expansion to the thermodynamic parameters for the ternary system and to the solvent composition. Intrinsic viscosity measurements are reported for polystyrene fractions in three mixed‐solvent systems: methyl ethyl ketone‐methanol, carbon tetrachloride‐cyclohexane, and benzene‐cyclohexane. Intrinsic viscosities measured for polystyrene fractions in critical consolute mixtures agree with those found in single poor solvents at the analogous Theta points. Intrinsic viscosities have been measured over ranges of mixed‐solvent composition for the second and third solvent mixtures mentioned. Poor agreement with theory is observed for the former, but the more extensive measurements in benzene‐cyclohexane mixtures agree very well with theoretically calculated intrinsic viscosities.