Apolar bimesogens and the incidence of the twist-bend nematic phase

Richard J. Mandle*, Edward J. Davis, Craig T. Archbold, Constantin C A Voll, Jessica L. Andrews, Stephen J. Cowling, John W. Goodby

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The nematic twist-bend phase (N<inf>TB</inf>) was, until recently, only observed for polar mesogenic dimers, trimers or bent-core compounds. In this article, we report a comprehensive study on novel apolar materials that also exhibit N<inf>TB</inf> phases. The N<inf>TB</inf> phase was observed for materials containing phenyl, cyclohexyl or bicyclooctyl rings in their rigid-core units. However, for materials with long (>C7) terminal chains or mesogenic core units comprising three ring units, the N<inf>TB</inf> phase was not observed and instead the materials exhibited smectic phases. One compound was found to exhibit a transition from the N<inf>TB</inf> phase to an anticlinic smectic C phase; this is the first example of this polymorphism. Incorporation of lateral substitution with respect to the central core unit led to reductions in transition temperatures; however, the N<inf>TB</inf> phase was still found to occur. Conversely, utilising branched terminal groups rendered the materials non-mesogenic. Overall, it appears that it is the gross molecular topology that drives the incidence of the N<inf>TB</inf> phase rather than simple dipolar considerations. Furthermore, dimers lacking any polar groups, which were prepared to test this hypothesis, were found to be non mesogenic, indicating that at the extremes of polarity these effects can dominate over topology.

Original languageEnglish
Pages (from-to)8158-8167
Number of pages10
JournalChemistry : A European Journal (Weinheim an der Bergstrasse, Germany)
Issue number22
Early online date20 Apr 2015
Publication statusPublished - 18 May 2015


  • Liquid crystals
  • Self-assembly
  • Structure-property relationships
  • Twist-bend nematic phase

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