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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 8: POSTER: Polymer Physics

CPP 8.34: Poster

Monday, March 26, 2007, 16:00–18:00, Poster B

Development of Entanglements in a Polymer Melt — •Thomas Vettorel, Thomas A. Vilgis, and Kurt Kremer — Max-Planck-Institut fuer Polymerforschung, 55128 Mainz, Germany

Recent work by Rastogi et al. has shown that it is possible to prepare a polymer melt in an initially disentangled state. This system then relaxes to the normal, entangled melt state but gives rise to a long-lived metastable ”new melt” in which different parts of the chains exhibit different mobilities due to an unusual distribution of entanglements. This yields a material whose particular mechanical properties could be of interest for many purposes.

We study the mechanisms leading to the relaxation to the entangled state by means of computer simulations, using a normal bead-spring model, with and without explicit bending rigidity. A fully disentangled polymeric system is created as a collection of chains collapsed in a globular state, packed together at the melt density. We then monitor the relaxation of this strongly out-of-equilibrium system, looking more particularly at the evolution of the entanglements: The entanglement length N_e is measured using the Primitive Path Analysis.

The first results show that in the case of relatively short chains (up to N ≈ 20 N_e), the relaxation of the entanglement length is very fast, suggesting that the situation is better described by a scenario like de Gennes’ explosion upon melting, even if a slowing down is observed in the diffusion of chains’ centers of mass before equilibrium is reached, indicating a confinement effect.