ZERO-SHEAR VISCOSITY PROPERTIES OF SOLUTIONS OF FLEXIBLE POLYMERS IN LIGHT OF RENORMALIZATION-GROUP THEORIES

The zero-shear viscosity behavior, in the dilute and semidilute regime s, in solutions of polystyrene under good and theta solvent conditions , is analyzed in the framework of a recent theoretical model due to Sh iwa. At good solvent conditions, this model, which takes into account the gradual screening of both hydrodynamic and excluded-volume interac tions as well as entanglement constraints, is consistent with the larg e amount of experimental data collected from the literature. In the co urse of this study the behavior of the radius of gyration as a functio n of an experimentally accessible reduced concentration variable is te sted against experimental results. A reasonably good agreement is foun d. In the analysis of the universal viscosity properties, it is argued for the use of the reduced dynamic scaling variable c[eta] in lieu of the static counterpart c/c. At the theta state the viscosity feature s are observed to be more complex.