题 目：The tube axis and entanglements in polymer melts

 

报告人： Prof. Alexei Likhtman

Department of Mathematics

Universityof Reading

 

Abstract
 

Although the tube theory is very popular and successful, the tube concept remains evasive and ill defined. In the first part of the talk, I will go carefully over main definitions and assumptions of the tube theory, and also review alternative models, such as slip-springs simulation.

In the second part of the talk I'll describe a simple computer algorithm to construct the tube axis as a centre line of the cloud of chain configurations at different moments of time. We test this algorithm on trajectories generated from simulations of concatenated well entangled ring polymers, thus avoiding all disentanglement processes. We find that entanglements are clearly manifested through the curvature of tube axis, and we can successfully identify binary and ternary entanglements in molecular dynamics simulations. Several quantitative characteristics of entanglements are reported and discussed. The third part of this talk will discuss a definition of entanglements as persistent contacts between the mean paths of polymer chains. This definition will be tested in molecular dynamics simulation of linear melts. We trace the dynamics of individual entanglements and study their lifetime, distribution along the chain and the way they are created or destroyed.