Abstract

Zero-shear viscosity η0 and steady-state compliance Je of poly(α-methylstyrenes) in benzyl n-butyl phthalate (_??_=46°C) and polystyrene in dioctyl phthalate (_??_=22°C) were measured at temperatures lower than the _??_ points. Moreover, stress developments after onset of steady shear flow were measured and the strength of entanglement was estimated on the basis of network rupture model.The concentration and the molecular weight dependences of η0 at temperatures lower than the _??_ points are almost the same as those at the _??_ temperatures, but the magnitude of η0 increases with decreasing temperature. This suggests that the strength of entanglement increases with decreasing solvent power.On the other hand, Je values at the temperatures lower than the _??_ points are almost the same as those in good and _??_ solvents. This result indicates that the entangled structure of polymer solution effective to Je is almost independent of solvent power. Therefore, it is concluded that the gel-like behavior of polymer solution at temperatures lower than the _??_ points is caused by the long relaxation times due to the high viscosity.

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