A Novel Interpretation of Polymer Viscosity in Mixed Solvents

A novel interpretation of the viscosity of a polymer in mixed solvents in the dilute concentration regime is presented. The ternary system polymer/solvent 1/solvent 2 was considered as a quasi-binary system and the presence of the polymer acts as a perturbation on the mixed solvents where the interaction between unlike molecules was quantified by the Grunberg-Nissan constant, d'. Thus, a pseudo-Grunberg-Nissan constant, d(p)', was introduced to quantify the interaction between the unlike molecules of the mixed solvents in the presence of the polymer. The effect of the polymer addition on the interaction between unlike molecules was quantified by introducing the deviation of the Grunberg-Nissan constant, delta d(0)' = d(p') - d', concept which is connected to both the intrinsic polymer viscosity and the Huggins constant in pure and mixed solvents. This novel interpretation of the viscosity data was used to study the effect of polystyrene dissolution on the interaction between benzene and ethyl acetate at 20 degrees C.