Anomalies in the twist elastic behaviour of mixtures of calamitic and bent-core liquid crystals

S. Srigengan, H. Liu, M. A. Osipov, R. Mandle, S. J. Cowling, H. F. Gleeson

Research output: Contribution to journalArticle

Abstract

The splay, twist and bend elastic constants (K11, K22 and K33) have been measured as a function of temperature in bent-core/calamitic mixtures based on three different calamitic materials (5CB, 8CB and ZLI1132) and two bent-core dopants. The behaviour of the splay and bend constants are as expected; a reduction in K33 of ~20%, in line with predictions from mixing rules and other observations. Interestingly, no change is seen in the splay constant, K11 of the calamitic hosts. Surprisingly though, the twist elastic constant exhibits a reduction of 30–40% in all mixtures across the nematic range, an effect not previously reported and much larger than mixing rules can explain. The elastic behaviour is universal in our mixtures. We explain part of the reduction in the twist deformation by considering the influence of the chiral conformer fluctuations of the bent-core molecules on the twist elastic constants of the mixtures. However, the dramatic reduction can only be fully explained by also including contributions from chiral conformer fluctuations of the calamitic host, a form of chiral amplification.

Original languageEnglish
Pages (from-to)895-907
Number of pages13
JournalLiquid Crystals
Volume47
Issue number6
Early online date21 Nov 2019
DOIs
Publication statusPublished - 2 May 2020

Keywords

  • bent-core liquid crystals
  • calamitic liquid crystals
  • chirality
  • elastic properties
  • liquid crystal mixtures
  • polarity

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