Tracer diffusion coefficient, D*, and the Newtonian zero shear-rate viscosity, η0, were measured for a high molecular weight random copolymer (SAN) of styrene and acrylonitrile. As predicted by the reptation model, D*was in agreement with the molecular-weight scaling of Mw−2(Mw is the weight average molecular weight of the chain being probed) and was independent of matrix molecular weight. η0 showed a molecular-weight scaling of MW3.4. While the temperature dependence of these two relaxation processes could be well explained by the free-volume model up to 252 °C, they showed a discrepancy in activation enthalpy, Ea, of about 20%, with a larger value for diffusion.
Enthalpy Diffusion Coefficient Styrene High Molecular Weight Relaxation Process
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