Berlin 2015 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 11: Nanoparticles and Composite Materials II (joint CPP/BP)

BP 11.3: Vortrag

Montag, 16. März 2015, 15:30–15:45, C 243

Disentanglement in polymer-star mixtures — •Hendrik Meyer — Institut Charles Sadron, CNRS UPR22, 67034 Strasbourg, France

We present a molecular dynamics simulation study of entangled melts mixed with particles of the order of the tube diameter. The choice of compact stars represents a model system of nanocomposites without polymer-particle adsorption. The particles remain well dispersed over the whole concentration range and the stars are sufficiently compact that the pure system is jammed. For this system, we observe a weak compression of the matrix chains with increasing volume fraction of stars. Short (unentangled) matrix chains get slowed down by adding particles to the system. When the matrix chains become significantly longer than the entanglement length, this trend is inversed and the matrix chains become faster because the particles dilute the entanglement network. The center-of mass (CM) dynamics exhibits regimes of anomalous diffusion in accordance with viscoelastic hydrodynamic interactions (VHI) [1]. At low and intermediate star-particles concentration, the particles themselves vary little in mobility, only at high concentration (above percolation), they become slowed down because of colloidal packing. As a result, the viscosity as a measure of the collective mobility drops when adding few particles to the melt because of disentanglement, and at high particle volume fraction the viscosity increases again because of colloidal caging. [1] J. Farago et al. PRL 107, 178301 (2011); PRE 85, 051807 (2012).