How do closed-compact multi-lamellar droplets form under shear flow? A possible mechanism

L. Courbin; R. Pons; J. Rouch; P. Panizza

doi:doi:10.1209/epl/i2003-00229-y

DOI: 10.1209/epl/i2003-00229-y
Europhys. Lett., 61 (2) , pp. 275-281 (2003)

How do closed-compact multi-lamellar droplets form under shear flow? A possible mechanism

L. Courbin¹, R. Pons^{1, 2}, J. Rouch¹ and P. Panizza¹

¹ Centre de Physique Moléculaire Optique et Hertzienne, UMR 5798 Université Bordeaux I - 351 Cours de la Libération, 33400 Talence, France
² Departament de Tecnologia de Tensioactius, CID/CSIC Jordi Girona 18-26, 08034 Barcelona, Spain

ppanizza@cribx1.u-bordeaux.fr

(Received 5 August 2002; accepted in final form 28 October 2002)

Abstract
The formation of closed-compact multi-lamellar droplets obtained upon shearing both a lamellar phase $(L_{\alpha})$ and a two-phase-separated lamellar-sponge ( $L_{\alpha}$ - L₃) mixture is investigated as a function of the shear rate $\dot{\gamma}$ , using small-angle light scattering (SALS) and cross-polarized optical microscopy. In both systems the formation of droplets occurs homogeneously in the cell at a well-defined wave vector $q_{\ab{e}}\propto \dot{\gamma}^{1/3}$ via a strain-controlled process. These results suggest that the formation of droplets may be monitored in both systems by a buckling instability of the lamellae as predicted from a recent theory.

PACS
83.60.Rs - Shear rate-dependent structure (shear thinning and shear thickening).
82.70.-y - Disperse systems; complex fluids.
61.30.Eb - Experimental determinations of smectic, nematic, cholesteric, and other structures.

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