# Regensburg 2010 – wissenschaftliches Programm

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# SYMR: Symposium Nuclear Magnetic Resonance: from Applications in Condensed-Matter Physics to New Frontiers

## SYMR 6: Polymer Dynamics

### SYMR 6.3: Vortrag

### Mittwoch, 24. März 2010, 10:30–10:45, H48

**Bond-correlation functions determined in MD simulations of entangled polymer melts** — •Hendrik Meyer — Institut Charles Sadron, CNRS UPR22, 67034 Strasbourg, France

The polymer dynamics of entangled bead-spring chains is analysed based on large scale molecular dynamics simulations.
As found in previous studies, the predicted power law regimes of mean-square displacements attributed to Rouse-motion in the tube (cross-over from *t*^{0.5} to *t*^{0.25}) are only well developed beyond *Z*≥ 10 entanglements per chain.
Similar power law regimes are present for bond time-autocorrelation functions (*P*_{1} ∝ *t*^{−0.5} and *t*^{−0.25}).
NMR experiments measure a correlation function proportional to the second Legendre polynomial *P*_{2} of the bond correlations, which is found to be proportional to the square of *P*_{1} only for flexible chains, whereas a slower time decrease is found for chains with a small angular potential.
Clear evidence is found that the terminal relaxation time increases stronger than predicted by reptation theory for *Z*>5.
We critically compare this finding with theories of contour length fluctuations, often invoked as the main explanation of this slowing down.