Dresden 2003 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 6: Computational Soft Matter Physics
CPP 6.1: Hauptvortrag
Dienstag, 25. März 2003, 09:30–10:00, ZEU/160
Polymer Melts and Networks: The Entanglement Concept Revisited — •Kurt Kremer1, Ralf Everaers1, Carsten Swaneborg1, Satish Sukumaran1 und Gary S. Grest2 — 1Max-Planck-Institut für Polymerphysik, Ackermannweg 10, 55128 Mainz — 2Sandia National Laboraties, Albuquqerque NM 87185-1415, USA
Polymer melts and networks display unique (visco-)elastic and relaxational properties. Though there is a huge quantitative variation depending on chemical species and e. g. temperature, the general or properties are universal.
The presentation will review the role of the fact, that long chain molecules (flexible threads) exhibit special dynamic and elastic properties due to the fact that the threads cannot cut through each other. It will be shown, that for networks of long chain molecules, the elasticity as well as the swelling in solvent crucially depends on the conservation of links between network loops. By comparing analytic theoretical approaches, computer simulations as well as experiments, the effect of conserved topology of linked threads will systematically be isolated and demonstrated. Concepts like the Gaussian linking numbers between pairs of closed paths and other standard approaches from knot theory are not sufficient to understand the systems, because "many chains" effects are needed to stabilize the complex topological structure of a polymer melt or network. While for melts, these effects are transient in time, networks are stabilized and behave as very soft solids. Recently similar effects for semiflexible polymers have been studies as well.