Authors Lang, M.
Title Relation between Cross-Link Fluctuations and Elasticity in Entangled Polymer Networks
Date 13.03.2017
Abstract Computer simulation data on junction fluctuations in end-linked model networks are analyzed using the framework of the constraint junction model and the slip tube model for entangled networks. It is argued that cross-linking freezes in conformational fluctuations of chains and cross-links, which creates a small preload of entangled strands. This can be modeled using a “confinement degree of polymerization” Nc(N) with a weak dependence on the degree of polymerization N. The confined motion of network junctions with f active connections to the network is well described by using the exact solution of the constrained junction model with a constraining term that is given by the superposition of f/2 entanglement tubes with confinement Nc(N). It is shown that the modulus of end-linked model networks is the sum of a phantom and an entanglement contribution, whereby the entanglement contribution shows the same correction Nc(N) as both the cross-link fluctuations and the time average bond orientations. The results for the cross-link fluctuations allow to compute instantaneous or time average segment orientations and, thus, are necessary to understand birefringence experiments or double quantum nuclear magnetic resonance data of entangled networks.
Journal Macromolecules 50 (2017) 2547-2555

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