Europhys. Lett, 47 (6), pp. 729-735 (1999)
Concentration dependence of the low-shear viscosity of polyelectrolyte micro-networks: From hard spheres to soft microgels
R. Borrega 1, M. Cloitre 1, I. Betremieux 2, B. Ernst 2 and L. Leibler 1
1Unité Mixte de Recherche CNRS-Elf Atochem
95 rue Danton, 92303 Levallois-Perret, France
2Elf Atochem, Cerdato - 27470 Serquigny, France
(received 2 December 1998; accepted in final form 12 July 1999)
PACS. 83.70Hq - Heterogeneous liquids: suspensions, dispersions, emulsions, pastes, slurries,
foams, block copolymers, etc.
PACS. 61.25Hq - Macromolecular and polymer solutions; polymer melts; swelling.
PACS. 82.70Dd - Colloids.
The low-shear viscosity of polyelectrolyte microgels is studied as a function of concentration, crosslink density and ionic strength. The variation of the viscosity with volume fraction is very similar to that found in hard-sphere colloidal suspensions. In salt-free dispersions, osmotic effects are responsible for the de-swelling of microgels at high polymer concentration. This "softening'' effect modifies the viscosity near the overlap concentration.
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