Unwinding of a cholesteric liquid crystal and bidirectional surface anchoring

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Abstract

We examine the influence of bidirectional anchoring on the unwinding of a planar cholesteric liquid crystal induced by the application of a magnetic field. We consider a liquid crystal layer confined between two plates with the helical axis perpendicular to the substrates. We fixed the director twist on one boundary and allow for bidirectional anchoring on the other by introducing a high-order surface potential. By minimizing the total free energy for the system, we investigate the untwisting of the cholesteric helix as the liquid crystal attempts to align with the magnetic field. The transitions between metastable states occur as a series of pitchjumps as the helix expels quarter or half-turn twists, depending on the relative sizes of the strength of the surface potential and the bidirectional anchoring. We show that secondary easy axis directions can play a significant role in the unwinding of the cholesteric in its transition towards a nematic, especially when the surface anchoring strength is large.
Original languageEnglish
Article numbern/a
Pages (from-to)19-28
Number of pages10
JournalJournal of Engineering Mathematics
Volume87
Issue number1
Early online date1 Oct 2013
DOIs
Publication statusPublished - 2013

Keywords

  • cholesteric liquid crystal
  • helix unwinding
  • weak anchoring

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