Temperature and solvent effects on the intrinsic viscosities of a star-shaped polystyrene

The excluded-volume effect on the solution behaviour of a star-shaped polystyrene has been studied by measuring intrinsic viscosities over the temperature range 25–55°C. Two good solvents (benzene, dioxane) were selected together with two poor solvents (cyclohexane, 71.4% dioxane-28.6% methanol). The viscosity-temperature coefficients and apparent activation energies were compared. Other parameters investigated were: α (the expansion factor), θ (the theta or Flory temperature), ψ 1 (the entropy parameter of the solvent) and κ 1 (the enthalpy parameter of the solvent). Since measurements were carried out in dilute solutions, the Kirkwood approximation was assumed, namely that polymers behave hydrodynamically like spheres. The classical method developed by Flory and Fox was used for analysis. The theory of Flory and Fox modified by Benoit and coworkers is discussed.