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.
Proceedings of the National Academy of Sciences of the United States of America
Copyright 2011 National Academy of Sciences. Available on publisher's site at http://dx.doi.org/10.1073/pnas.1100087108.
Tortora, Luana; Lavrentovich, Oleg (2011). Chiral Symmetry Breaking by Spatial Confinement in Tactoidal Droplets of Lyotropic Chromonic Liquid Crystals. Proceedings of the National Academy of Sciences of the United States of America 108(13) 5163-5168. doi: 10.1073/pnas.1100087108. Retrieved from https://oaks.kent.edu/cpippubs/348