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Ribbon phase in a phase-separated lyotropic lamellar-sponge mixture under shear flow.
G Cristobal1, J Rouch, P Panizza
1Centre de Physique Moléculaire Optique et Hertzienne, Université Bordeaux I, 351 Cours de la Libération, 33400 Talence, France.
Summary
Shear flow transforms lyotropic lamellar and sponge phases into aligned ribbons. At high rates, these ribbons break into droplets, causing shear thickening in surfactant systems.
Area of Science:
- Materials Science
- Soft Matter Physics
- Rheology
Background:
- Lyotropic liquid crystals exhibit complex phase behavior.
- Understanding phase transitions under flow is crucial for material applications.
Purpose of the Study:
- Investigate the impact of shear flow on phase-separated lyotropic lamellar (Lα) and sponge (L3) systems.
- Characterize the structural evolution and rheological response under varying shear rates.
Main Methods:
- Utilized optical microscopy to observe structural changes.
- Employed small-angle light and X-ray scattering for structural analysis.
- Applied rheological measurements to determine flow behavior.
Main Results:
- Observed the formation of multilamellar ribbon-like structures aligned with the flow direction.
- Identified an instability at high shear rates leading to ribbon breakup.
- Documented the formation of monodisperse droplets post-breakup.
Conclusions:
- Shear flow induces a transition to an ordered, ribbon-like state in the Lα/L3 system.
- High shear rates trigger a morphological transition to droplets, resulting in shear thickening.
- The study reveals a novel shear-induced phase transition and rheological behavior in complex fluid mixtures.