J. Phys. II France
Volume 4, Numéro 5, May 1994
Page(s) 873 - 879
DOI: 10.1051/jp2:1994171
J. Phys. II France 4 (1994) 873-879

The intermediate coherent scattering function of entangled polymer melts: a Monte Carlo test of des Cloizeaux' theory

J. Wittmer, W. Paul and K. Binder

Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, D-55099 Mainz, Germany

(Received 30 July 1993, accepted in final 31 January 1994)

Using the bond fluctuation model for flexible polymer chains in a dense melt the intermediate coherent scattering function for chains containing N = 200 monomers is calculated and interpreted in terms of a recent theory of des Cloizeaux. The theory yields an explicit description for the crossover from the Rouse model to the regime where reptation prevails, for the limit $N\rightarrow \infty$. While the Monte Carlo data are qualitatively compatible with this description, an accurate estimation of the tube diameter is prevented due to the onset of a diffusive decay of the scattering function, not included in the theory. For a full quantitative analysis of the Monte Carlo data (as well as of experiments on chains with not extremely large molecular weight) an extension of the theory for finite N would be required.

© Les Editions de Physique 1994