17:15 Uhr im Seminarraum 1.27 Von-Danckelmann-Platz 4, 06120 Halle
Institut für Physik, Technische Universität Ilmenau
“Relaxation and diffusion in polymer melts and solutions: new experimental approaches to probe molecular dynamics in homopolymers and copolymers”
Abstract:
The time-dependence of the rms displacements of chain segments in polymer melts has been a cornerstone of experimental tests of various chain motion models. Rouse and Reptation dynamics (below and above the entanglement limits for chain lengths, respectively) are described by characteristic power-laws. Neutron spin echo and gradient NMR studies have tested and confirmed these power-laws, but have also found discrepancies in some cases. The wide time gap between these two techniques is partially covered by NMR relaxometry. Again, relaxometry finds power-law relationships between NMR relaxation times and Larmor frequency, but both the dependence on frequency and molecular weight were shown to deviate substantially from tube-reptation predictions.
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