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Soft Matter and Biological Physics
Eur. Phys. J. E 10, 201-207 (2003)
DOI: 10.1140/epje/i2002-10108-y

Flow birefringence, stress optical rule and rheology of four micellar solutions with the same low shear viscosity

J.P. Decruppe1 and A. Ponton2

1  Laboratoire de Physique des Liquides et Interfaces, Groupe Rhéophysique des Colloïdes, Université de Metz, 1 Bd. F. Arago, 57078 Metz, France
2  Laboratoire de Biorhéologie et d' Hydrodynamique Physico-Chimique, Université de Paris 7, 2, place Jussieu, 75251 Paris, Cedex 05, France

Decruppe@lpli.sciences.univ-metz.fr

(Received 18 November 2002 / Published online: 1 April 2003)

Abstract
The flow birefringence and the rheological properties of four viscoelastic solutions having nearly the same zero shear viscosity and subjected to shear flows are investigated in the linear and non-linear domains. The surfactant used for the samples is the cetyltrimethylammonium chloride in water at the concentration of 100 mmol/l with an organic salt, the sodium salicylate. The low shear viscosity curve versus the salt concentration is non-monotonic and has two maxima separated by a minimum forming four domains in which the salt concentration is chosen. For the two solutions belonging to the inner branch, i.e. between the two maxima, a simple Maxwellian behaviour is observed and shear banding occurs as confirmed by the flow birefringence pictures. Contrary to the results of P. Fisher (1996) where the unstable flow regime is restricted to the first decreasing part of the low shear viscosity curve of a cetylpyridinium chloride solution, we show that shear banding exits in a wider domain of the salt concentration.

PACS
82.70.Dd - Colloids.
83.85.Cg - Rheological measurements - rheometry.
78.20.Fm - Birefringence.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003