Dynamical properties of the slithering-snake algorithm: A numerical test of the activated-reptation hypothesisL. Mattioni1, J.P. Wittmer1, J. Baschnagel2, J.-L. Barrat1 and E. Luijten3, 4
1 Département de Physique des Matériaux, Université Claude Bernard and CNRS, 69622 Villeurbanne Cedex, France
2 Institut Charles Sadron, 6 rue Boussingault, 67083 Strasbourg, France
3 Institut für Physik, Johannes-Gutenberg-Universität Mainz, 55099 Mainz, Germany
4 Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green St., Urbana, IL 61801, USA
(Received 18 December 2002 and Received in final form 22 March 2003 / Published online: 12 May 2003)
Correlations in the motion of reptating polymers in a melt are investigated by means of Monte Carlo simulations of the three-dimensional slithering-snake version of the bond-fluctuation model. Surprisingly, the slithering-snake dynamics becomes inconsistent with classical reptation predictions at high chain overlap (created either by chain length N or by the volume fraction of occupied lattice sites), where the relaxation times increase much faster than expected. This is due to the anomalous curvilinear diffusion in a finite time window whose upper bound is set by the density of chain ends . Density fluctuations created by passing chain ends allow a reference polymer to break out of the local cage of immobile obstacles created by neighboring chains. The dynamics of dense solutions of "snakes" at is identical to that of a benchmark system where all chains but one are frozen. We demonstrate that the subdiffusive dynamical regime is caused by the slow creeping of a chain out of its correlation hole. Our results are in good qualitative agreement with the activated-reptation scheme proposed recently by Semenov and Rubinstein (Eur. Phys. J. B, 1 (1998) 87). Additionally, we briefly comment on the relevance of local relaxation pathways within a slithering-snake scheme. Our preliminary results suggest that a judicious choice of the ratio of local to slithering-snake moves is crucial to equilibrate a melt of long chains efficiently.
61.25.Hq - Macromolecular and polymer solutions; polymer melts; swelling.
83.10.Kn - Reptation and tube theories.
83.80.Sg - Polymer melts.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003