Regensburg 2010 – scientific programme
Parts | Days | Selection | Search | Downloads | Help
SYMR: Symposium Nuclear Magnetic Resonance: from Applications in Condensed-Matter Physics to New Frontiers
SYMR 6: Polymer Dynamics
SYMR 6.3: Talk
Wednesday, March 24, 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 t0.5 to t0.25) are only well developed beyond Z≥ 10 entanglements per chain. Similar power law regimes are present for bond time-autocorrelation functions (P1 ∝ t−0.5 and t−0.25). NMR experiments measure a correlation function proportional to the second Legendre polynomial P2 of the bond correlations, which is found to be proportional to the square of P1 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.