Reversible shear-induced crystallization above equilibrium freezing temperature in a lyotropic surfactant system

Rathee, Vikram and Krishnaswamy, Rema and Pal, Antara and Raghunathan, VA and Imperor-Clerc, Marianne and Pansu, Brigitte and Sood, AK (2013) Reversible shear-induced crystallization above equilibrium freezing temperature in a lyotropic surfactant system. In: Proceedings of the National Academy of Sciences of the United States, 110 (37). pp. 14849-14854.

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Abstract

We demonstrate a unique shear-induced crystallization phenomenon above the equilibrium freezing temperature (T-K(o)) in weakly swollen isotropic (L-i) and lamellar (L-alpha) mesophases with bilayers formed in a cationic-anionic mixed surfactant system. Synchrotron rheological X-ray diffraction study reveals the crystallization transition to be reversible under shear (i.e., on stopping the shear, the nonequilibrium crystalline phase L-c melts back to the equilibrium mesophase). This is different from the shear-driven crystallization below T-K(o), which is irreversible. Rheological optical observations show that the growth of the crystalline phase occurs through a preordering of the L-i phase to an L-alpha phase induced by shear flow, before the nucleation of the Lc phase. Shear diagram of the L-i phase constructed in the parameter space of shear rate ((gamma)) over dot vs. temperature exhibits L-i -> L-c and L-i -> L-alpha transitions above the equilibrium crystallization temperature (T-K(o)), in addition to the irreversible shear-driven nucleation of L-c in the L-i phase below T-K(o). In addition to revealing a unique class of nonequilibrium phase transition, the present study urges a unique approach toward understanding shear-induced phenomena in concentrated mesophases of mixed amphiphilic systems.

Item Type:	Journal Article
Publication:	Proceedings of the National Academy of Sciences of the United States
Publisher:	National Academy of Sciences
Additional Information:	Copyright of this article belongs to National Academy of Sciences.
Keywords:	Shear-Induced Phase Separation; Strongly Binding Counterions; Coagels
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	25 Oct 2013 05:31
Last Modified:	25 Oct 2013 05:31
URI:	http://eprints.iisc.ac.in/id/eprint/47538

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