Structure and rheology of the defect-gel states of pure and particle-dispersed lyotropic lamellar phases
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 firstname.lastname@example.org
Revised: 20 May 1999
Published online: 15 November 1999
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.
PACS: 47.50.+d – Non-Newtonian fluid flows / 61.30.Jf – Defects in liquid crystals / 83.70.Hq – Heterogeneous liquids: suspensions, dispersions, emulsions, pastes, slurries, foams, block copolymers, etc.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1999