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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 8: POSTERS Dynamics and Diffusion

CPP 8.15: Poster

Montag, 25. Februar 2008, 16:45–19:00, Poster A

viscosity and structural alteration of a coarse-grained model of polystyrene under steady shear low studied by reverse nonequilibrium molecular dynamics — •paola carbone, xiaoyu chen, and florian müller-plathe — Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Petersenstrasse20 D-64287 Darmstadt, Germany

The reverse nonequilibrium molecular dynamics (RNEMD) method is implemented to predict the viscosity of a coarse-grained model of short-chain polystyrene. The coarse-grained model has been derived to reproduce the structure of polystyrene. It is therefore not a generic model, but polymer-specific. The zero-shear viscosity from simulation result is linearly dependent on the molecular weight for short-chain systems, in agreement with experiments and the theoretical prediction of the Rouse model. The shear-thinning behaviour for all studied systems follows a power law. The exponent of the power law depends on the chain length and it increases with the molecular weight. The zero-shear viscosity is also compared with experimental data, where the pronounced difference found is originated mainly by the inherent dynamic properties of the coarse-grained model used. The structural changes under shear are quantitatively investigated, indicating that the process of chain alignment, in combination with chain stretching, leads to a macroscopic anisotropy of the material.

References

1.X. Chen, P. Carbone, W. Cavalcanti, G. Milano, F. Müller-Plathe, Macromolecules, 2007, 40, 8087-8095