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Soft Matter and Biological Physics


Eur. Phys. J. E 6, 245-253 (2001)

Universal properties of lamellar systems under weak shear

C. Meyer, S. Asnacios and M. Kléman

Laboratoire de Minéralogie-Cristallographie de Paris (UMR7590), T16 case 115, 4 place Jussieu, F-75252 Paris cédex 05, France

maurice.kleman@mines.org

(Received 18 April 2001 and Received in final form 25 October 2001)

Abstract
We have observed that different lamellar phases (thermotropic, lyotropic of surfactants or blockcopolymers) share the same rheological properties $\dot\gamma = A(T)\sigma ^m$, m = $1.67\pm0.1$, independently of their chemical nature, in a range of shear rates $\dot\gamma$, shear stresses $\sigma$, and temperatures T, where the flow is stationary. It is argued that the key phenomenon is the appearance of screw dislocations whose glide under an applied shear counterbalances plastically the applied vorticity, and stabilizes the layers, whose slip past each other is thus made more feasible. The theory, which makes use in other respects of the high-temperature creep model in solids, reproduces correctly the power law behavior and the values of A(T).

PACS
61.30.Cz - Molecular and microscopic models and theories of liquid crystal structure.
83.85.Cg - Rheological measurements - rheometry.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001