Influence of Thermodynamic Quality of a Solvent upon Non‐Newtonian Viscosity of Poly(methyl Methacrylate) Solutions

Unlike the monotonous decrease of both the reduced and intrinsic viscosity with the increase in shearing stress with polystyrene, polyisobutylene, and other polymers in thermodynamically good and poor solvents, the dependence of the viscosity on the shearing stress, with poly(methyl methacrylate) solutions in the vicinity of θ‐temperature, shows an anomalous course. Reduced viscosity at first decreases with the increase in shearing stress; at 50 to 150 dynes/cm. 2 it reaches a minimum but thereafter rises. The effect disappears with infinite dilution. The increase of reduced viscosity with the increase in shearing stress is in connection with a great increase of the Huggins constant, which means a high molecular interaction. Since this behavior at θ temperature does not occur with other polymers, it seems to depend on the specific structure of poly(methyl methacrylate).