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Soft Matter and Biological Physics

Eur. Phys. J. E 1, 93-97

Viscosity at small scales in polymer melts

F. Brochard Wyart1 - P.G. de Gennes2

1 PSI, Institut Curie, 11 rue P. et M. Curie, 75231 Paris Cedex 05, France
2 Collège de France, 11 place M. Berthelot, 75231 Paris Cedex 05, France
pierre-gilles.degennes@espci.fr

Received 19 April 1999

Abstract
Flows around small colloidal particles of diameter b, or in thin films, capillaries, etc., cannot always be described in terms of the macroscopic polymer viscosity. We discuss these features for entangled polymer melts, where two distinct regimes can be found: (a) the thin regime where b is smaller than the coil radius R0, but larger than the diameter $d_{\rm t}$of the Edwards tube; (b) the ultrathin regime, where $b<d_{\rm t}$. We consider (i) non adsorbing particles, where slippage may occur between the melt and the solid surface; (ii) ``hairy'' particles, which carry some bound polymer chains. We obtain scaling predictions for mobilities of spheres, of needles, and of clusters of particles. We also discuss translational and rotational diffusion of needles.

PACS
05.60.Cd Classical transport - 82.70.Dd Colloids - 83.70.Hq Heterogeneous liquids: suspensions, dispersions, emulsions, pastes, slurries, foams, block copolymers, etc.

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