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Structure and Rheology of the Defect-gel States of Pure and Particle-dispersed Lyotropic Lamellar Phases

Geetha Basappa·Suneel·V. Kumaran·Prabhu R. Nott·Sriram Ramaswamy·V. M. Naik·Deeleep Rout
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Abstract

We present important new results from light-microscopy and rheometry on a moderately concentrated lyotropic smectic, with and without particulate additives. Shear-treatment aligns the phase rapidly, except for a striking network of oily-streak defects, which anneals out much more slowly. If spherical particles several microns in diameter are dispersed in the lamellar medium, part of the defect network persists under shear-treatment, its nodes anchored on the particles. The sample as prepared has substantial storage and loss moduli, both of which decrease steadily under shear-treatment. Adding particles enhances the moduli and retards their decay under shear. The data for the frequency-dependent storage modulus after various durations of shear-treatment can be scaled to collapse onto a single curve. The elasticity and dissipation in these samples thus arises mainly from the defect network, not directly from the smectic elasticity and hydrodynamics.

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Geetha Basappa, Suneel, V. Kumaran, Prabhu R. Nott, Sriram Ramaswamy, V. M. Naik, Deeleep Rout. 1999-07-14. Structure and Rheology of the Defect-gel States of Pure and Particle-dispersed Lyotropic Lamellar Phases. https://doi.org/10.1007/s100510051004

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