Evidence of wormlike micellar behavior in chromonic liquid crystals: rheological, X-ray, and dielectric studies.
We report rheological, X-ray, and dielectric investigations on a chromonic liquid-crystalline system formed by aqueous solutions of a food coloring agent, Sunset Yellow, in the absence and upon addition of salt. The salt-concentration dependence of the steady-state viscosity at low shear rates has a non-monotonic variation and is qualitatively similar to the behavior seen in wormlike micellar systems, a surprising result since chromonic systems are expected to be non-micellar in character. More interestingly, for a particular low concentration of the salt (20 mM), the viscosity increases by 3 orders of magnitude in comparison with that of the pure chromonic material. The dynamic (oscillatory) rheological data bring out features which can be described in terms of a microstructure formation. X-ray and dielectric studies show that certain characters of the aggregates formed by the Sunset Yellow molecules are not altered by the addition of salt.
Centre for Liquid Crystal Research, Jalahalli, Bangalore 560013, India. skpras@gmail.com
S Krishna
SK
Prasad
Geetha G
GG
Nair
Gurumurthy
G
Hegde
V
V
Jayalakshmi