2013-12-11
10:45 at HCI J 574

Dynamics and topological constraints in ring-linear polymer melts from atomistic-level simulations

Vlasis Mavrantzas

Polymer Physics, Department of Materials, ETH Zurich

We will present results for the conformational and dynamic properties of ring polymer melts and of ring-linear polymer blends obtained from molecular simulations. The simulations have been executed with a very accurate atomistic model for polyethylene oxide (PEO) and refer to PEO melts with molecular weight (MW) both below and below the corresponding entanglement MW of pure linear PEO (5,000 g/mol). Initially, we will review quickly the Rouse theory for rings. And then, we will present the simulation predictions for: 1) The scaling of the radius-of-gyration of rings with their MW 2) The relaxation of normal modes and the diffusivity of the ring centers-of-mass; also how these properties are altered when the ring is contaminated by linear chains 3) The nature of topological interactions (ring threading by linear molecules) in ring-linear blends and how these affect the dynamics of the ring molecules. At the very end of the talk, we will briefly report some very recent data from non-equilibrium MD (NEMD) simulations for the shear rheology of PEO ring melts. In all cases, the simulation predictions will be compared with the Rouse theory, very recent experimental data, and other simulation results in the literature obtained with a coarse-grained (bead-spring chain) model.