Abstract
This paper summarizes recent works in which the entanglement effect on diffusion and viscoelasticity was mainly studied on solutions of narrow-distribution polystyrene (PS) in dibutylphthalate (DBP) over a wide range of temperature T, concentration C and molecular weight M. The temperature dependence of the self diffusion coefficient Ds and the tracer diffusion coefficient Dtr was described by the WLF equation with values of the WLF coefficients same as found for the solution viscosity η. The effects of entanglements on the self diffusion behavior and the viscoelastic behavior were examined from data analysis in terms of the two parameters, the effective friction coefficient of a segment ζand the molecular weight between entanglements Me. The product Dsη/C was close to the theoretical prediction based on the free Rouse chain up to M/Me-1 and, for M/Me>10, showed universal behavior characterized by the linear proportionality to M/Me. The ratio of the two characteristic times for viscoelasticity and diffusion took approximately a constant value of 0.15±0.05 over the whole range of M/Me studied. Reduction of diffusion data on the basis of the two-parameter scheme was so successful that one master curve was obtained for each set of Ds and Dtr∞ data. The both master curves were proportional to (M/Me)-2.5 in the highly entangled region, being not in harmony with either the prediction of the reputation theory or the observation for PS melts. The tracer diffusion behavior in the unentangled concentrated solution was described by the partial-draining model.
