A change in stripes for cholesteric shells via anchoring in moderation

  • Date: Jun 30, 2017
  • Time: 10:15 AM - 11:15 AM (Local Time Germany)
  • Speaker: Lisa Tran
  • Department of Physics and Astronomy, University of Pennsylvania
  • Location: Max-Planck-Institut für Dynamik und Selbstorganisation (MPIDS)
  • Room: SR 0.77
  • Host: DCF
  • Contact: corinna.maass@ds.mpg.de
Chirality, ubiquitous in complex biological systems, can be controlled and quantified in synthetic materials such as cholesteric liquid crystal (CLC) systems. I will present our studies on spherical shells of CLC under weak anchoring conditions. We induce anchoring transitions at the inner and outer boundaries using two independent methods: by changing the surfactant concentration or by raising the temperature close to the clearing point. The shell confinement leads to new states and associated surface structures: a state where large stripes on the shell can be filled with smaller, perpendicular sub-stripes, and a focal conic domain (FCD) state, where thin stripes wrap into at least two, topologically required, double spirals. Focusing on the latter state, we use a Landau-de Gennes model of the CLC to simulate its detailed configurations as a function of anchoring strength. By abruptly changing the topological constraints on the shell, we are able to study the interconversion between director defects and pitch defects, a phenomenon usually restricted by the complexity of the cholesteric phase. I will also present preliminary work that demonstrates how these structures can serve as self-assembly blueprints of surface-active nano-materials. This work extends the knowledge of cholesteric patterns, structures that not only have potential for use in self-assembly but are pervasive in biological systems.
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