Europhys. Lett., 47 (6), pp. 729-735 (1999)
Concentration dependence of the low-shear viscosity of polyelectrolyte micro-networks: Froni hard spheres to soft microgels
R. BORREGA1, M. CLOITRE1, I. BETREMIEUX2, B. ERNST2 and L. LEIBLER1
1 Unité Mixte de Recherche CNRS-Elf Atochem
95 rue Danton, 92303 Levallois-Perret, France
2 Elf Atochem, Cerdato - 27470 Serquigny, France
(received 2 December 1998; accepted in final form 12 July 1999)
PACS. 83.7OHq - Heterogeneous liquids: suspensions, dispersions, emulsions, pastes, slurries, foams, block copolymers, etc.
PACS. 61.25Hq - Macromolecular and polymer solutions; polymer melts; swelling. PACS. 82.7ODd -Colloids.
Abstract. - 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.