The molecular weight distributions of well‐characterized polystyrenes were determined from their stress relaxation modulus as a function of time G(t). Linear viscoelastic measurements were made in the ‘‘terminal zone’’. The weight fraction of chains as a function of molecular weight was determined by assuming that the shorter (relaxed) chains, which are the first to disentangle from the transient network of entanglements, act as diluent for the longer (unrelaxed) chains. Nearly monodisperse samples were found to have false bimodal distributions although the breadth of these distributions was clearly distinguishable from the samples with broader molecular weight distributions. The distributions determined for a broader distribution sample or ones with truly bimodal distributions were closer to the shapes determined by size exclusion chromatography. The unexpected results for the narrow distribution samples were attributed to the oversimplified dilution assumption stated above.
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August 1990
Research Article|
August 01 1990
Determining the molecular weight distribution from the stress relaxation properties of a melt
W. J. McGrory;
W. J. McGrory
E. I. du Pont de Nemours & Company, Inc. Experimental Station, Polymer Products Department, P. O. Box 80356, Wilmington, Delaware 19880‐0356
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W. H. Tuminello
W. H. Tuminello
E. I. du Pont de Nemours & Company, Inc. Experimental Station, Polymer Products Department, P. O. Box 80356, Wilmington, Delaware 19880‐0356
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J. Rheol. 34, 867–890 (1990)
Article history
Received:
December 06 1989
Accepted:
April 03 1990
Citation
W. J. McGrory, W. H. Tuminello; Determining the molecular weight distribution from the stress relaxation properties of a melt. J. Rheol. 1 August 1990; 34 (6): 867–890. https://doi.org/10.1122/1.550104
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