Eur. Phys. J. B 12, 269-276 (1999)
https://doi.org/10.1007/s100510051004

Structure and rheology of the defect-gel states of pure and particle-dispersed lyotropic lamellar phases

¹ Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560012, India
² Department of Chemical Engineering, Indian Institute of Science, Bangalore 560012, India
³ Unilever Research India, 64 Main Road, Whitefield, Bangalore 560 066, India

Corresponding author: ^a sriram@physics.iisc.ernet.in

Received: 19 April 1999
Revised: 20 May 1999
Published online: 15 November 1999

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.