The scaling of diffusion with molecular weight has seen division in the scientific community for some time. The original reptation theory by de Gennes predicts a scaling of diffusion with molecular weight to the -2.0. The issue becomes readily apparent by examining the difference between self-diffusion measurements, which are shown to scale with molecular weight to approximately the -2.4, and trace-diffusion measurements which have shown a -2.0. The common thought today is that self-diffusion scales differently from the original reptation prediction due to contour length fluctuation, however, this is problematic as the trace-diffusion data should behave with the same -2.4 scaling then. More recently it was proposed that constraint release was the actual mechanism behind this deviation, as supported by experiments done on entangled polymer melts. To try and resolve this debate, experiments using the pulse-gradient NMR technique were carried out on entangled 1,4 polybutadiene solutions.
|School:||The University of Akron|
|School Location:||United States -- Ohio|
|Source:||MAI 57/05M(E), Masters Abstracts International|
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