Title

Chiral Symmetry Breaking by Spatial Confinement in Tactoidal Droplets of Lyotropic Chromonic Liquid Crystals

Publication Title

Proceedings of the National Academy of Sciences of the United States of America

Publication Date

3-29-2011

Document Type

Article

DOI

10.1073/pnas.1100087108

Keywords

nematic tactoids, light-scattering, phase-separation, parity-breaking, defects, model, condensation, transition, mesophases, molecules

Disciplines

Physics

Abstract

In many colloidal systems, an orientationally ordered nematic (N) phase emerges fromthe isotropic (I) melt in the form of spindle-like birefringent tactoids. In cases studied so far, the tactoids always reveal a mirror-symmetric nonchiral structure, sometimes even when the building units are chiral. We report on chiral symmetry breaking in the nematic tactoids formed in molecularly nonchiral polymer-crowded aqueous solutions of low-molecular weight disodium cromoglycate. The parity is broken by twisted packing of self-assembled molecular aggregates within the tactoids as manifested by the observed optical activity. Fluorescent confocal microscopy reveals that the chiral N tactoids are located at the boundaries of cells. We explain the chirality induction as a replacement of energetically costly splay packing of the aggregates within the curved bipolar tactoidal shape with twisted packing. The effect represents a simple pathway of macroscopic chirality induction in an organic system with no molecular chirality, as the only requirements are orientational order and curved shape of confinement.

Comments

Copyright 2011 National Academy of Sciences. Available on publisher's site at http://dx.doi.org/10.1073/pnas.1100087108.

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