The zero-shear viscosity data of poly(a-methylstyrene) solutions in good, poor, and 0 solvents covering wide ranges of polymer concentration and molecular weight were accumulated and analyzed on the basis of the scaling concept of de Gennes, in comparison with the other theories. The theory was found to be useful for understanding the viscosity behavior in the semidilute region. However, the theory is not applicable if the polymer concentration is higher than ≃0.2 g/mL. The crossover point from the dilute to the semidilute region varies with solvent power.
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