Abstract
AbstractThis review article scrutinizes and reanalyzes the extensively available literature data on the tracer and self chain diffusion coefficients Dtr and Ds along with the corresponding zero‐shear viscosity η0 to show that Ds ∝ M−ν starts with ν > 2.0 and converges to the asymptotic scaling exhibited by Dtr ∝ M−2.0 as the molecular weight M increases beyond M/Me = 10–20, in contrast to the onset of the asymptotic scaling M3 for η0 taking place typically for M/Me ≫ 10–20. A coherent analysis of these observations leads to the suggestion that the observed crossover in Ds is due to the constraint release effect, which diminishes around M/Me = 10–20 and is negligible in measurements of Dtr when the matrix molecular weight P is much greater than M. The contour length fluctuation (CLF) effect, which is believed to cause the molecular weight scaling of η0 to deviate significantly from its limiting behavior of M3, has little direct influence on the chain diffusion. The absence of the CLF effect on Ds leads to a much stronger than linear dependence of the product η0Ds on M, which has been observed previously. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1589–1604, 2003
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