Condensation of free volume in structures of nematic and hexatic liquid crystals

Richard Mandle, Nina Stock, Stephen James Cowling, Rachel Roberta Parker, Sam J. Hart, Adrian C. Whitwood, John William Goodby

Research output: Contribution to journalArticlepeer-review


Eight novel liquid crystalline materials were prepared containing highly branched terminal chains, either 2,4,4-trimethylpentyl or 3,5,5-trimethylhexyl. All materials exhibit nematic mesophases, with additional smectic (Sm) C, hexatic B and SmI phases for certain homologues. Analysis by small- and wide-angle X-ray scattering reveals continual build-up of the correlation length within the nematic
phases, where we also observe splitting of the small angle peak into four lobes, indicating pretransitional Sm fluctuations. Connoscopy confirms the nematic phase to be uniaxial and optically positive. We observe that in the solid state, the molecules exist as staggered antiparallel pairs as a consequence of the sterically demanding bulky terminal group, and this would also appear to manifest in
the hexatic B phase, where the layer spacing was found to be greater than the molecular length. If true, this is an example of pair formation driven by sterics rather than dipole–dipole interactions and suggests that reentrant systems driven purely by steric frustration may be found.
Original languageEnglish
Pages (from-to)114-123
Number of pages10
Issue number1
Early online date24 May 2018
Publication statusPublished - 2019

Bibliographical note

© 2018 The Author(s).


  • Liquid crystals
  • SAXS
  • hexatic phases
  • smectic phases

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