Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: POSTERS Driven Soft Matter

CPP 20.27: Poster

Mittwoch, 27. Februar 2008, 16:00–18:30, Poster A

Energy elastic effects in flowing polymeric liquids, and the concept of nonequilibrium temperature — •Markus Hütter, Clarisse Luap, and Hans Christian Öttinger — ETH Zürich, Department of Materials, Polymer Physics, CH-8093 Zürich, Switzerland

Entropy elasticity of rubbers serves as a starting point for most of the current models to describe the flow of polymeric liquids with an internal conformation tensor, while consideration of energetic effects is scarce. Such exclusive subscription to entropy elasticity can be considered a little surprising, in particular in view of microscopic modeling where potential forces between (united) atoms play a dominant role. In this regard, it is interesting to discuss the possible ramifications of energy elasticity on the flow behavior of polymeric liquids. After discussing previous approaches in literature for capturing energy elastic effects, we develop a thermodynami- cally consistent model in terms of the momentum density, the local entropy density, the mass density, and the conformation tensor as dynamic variables. The choice of the local entropy as a variable in contrast to temperature or total entropy is of primary importance, as will be explained in due detail. Specifically, we avoid working with a temperature concept that is ill-defined in flow. In order to render the conclusions of the model more specific, a microscopically motivated toy model with energetic effects is introduced, for which both the coarse-grained energy and entropy are calculated in a generalized canonical ensemble.