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ORAL PRESENTATION
Session: 2 Multiscale modeling and molecular simulations
(scheduled: Monday, 08:50 )
Primitive Path Identification and Entanglement Statistics in Polymer Melts: Results from a Direct Topological Analysis on Atomistically Detailed Polyethylene Models
K. Foteinopoulou1,2, N.Ch. Karayiannis1,2, V.G. Mavrantzas1,2, M. Kröger3
1 Department of Chemical Engineering, University of Patras, GR 26504, Greece
2 FORTH-ICE/HT, Patras GR 26504, Greece
3 ETH Zurich, Polymer Physics, Wolfgang-Pauli-Str. 10, CH-8093 Zurich, Switzerland
A large number of well equilibrated atomistic configurations of linear, strictly monodisperse polyethylene (PE) melts of molecular length ranging from C78 to C1000, obtained with the Double Bridging Monte Carlo algorithm, have been subjected to a detailed topological analysis with the Z code [Kröger, Comp. Phys. Comm., 2005]. The code constructs primitive paths that connect the two ends of a polymer chain (which in all cases are considered as fixed in space) geometrically under the constraint of no chain crossability, such that the multiple disconnected (coarse-grained) path has minimum contour length. When applied to a given, dense polymer configuration in 3-d space, it allows us to obtain the primitive path (PP) and the related number and positions of entanglements (kinks) for all chains in the simulation box, and extract information about the topological structure (the primitive path network) hidden in bulk PE. Results will be presented for the distribution and mean values of the number of entanglements per chain, the entanglement length, the tube diameter, the Kuhn step length and the contour length [1]. In particular, our analysis demonstrates that with increasing chain length, the entanglement molecular length reaches a plateau value characteristic of entangled polymeric behavior, which for the PE systems analyzed here comes out to be about 60 carbon atoms. We further validate recent predictions [Schieber, J. Chem. Phys., 2003] about the shape of the distribution of number of strands in a chain at equilibrium. At the same time we show, that the number of entanglements obtained by assuming random walk statistics [Everaers et al., Science, 2004] deviates significantly from these predictions which we regard as a clear sign of evidence that the direct counting of entanglements and related quantities, as proposed here, offers advantages for a quantitative analysis of the statistical nature of entanglements in polymeric systems. © IWNET 2006
[1] K. Foteinopoulou, N.Ch. Karayiannis, V.G. Mavrantzas, M. Kröger, Macromolecules 39, 4207 (2006) »
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and Kleanthi for IWNET 2006