Sulfur-linked cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase

Ewan Cruickshank, Mirosław Salamończyk, Damian Pociecha, Grant J. Strachan, John M.D. Storey, Cheng Wang, Jun Feng, Chenhui Zhu, Ewa Gorecka, Corrie T. Imrie* (Corresponding Author)

*Corresponding author for this work

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The synthesis and characterisation of two series of cyanobiphenyl-based liquid crystal dimers containing sulfur links between the spacer and mesogenic units, the 4ʹ-[1,ω-alkanediylbis(thio)]bis-[1,1ʹ-biphenyl]-4-carbonitriles (CBSnSCB), and 4ʹ-({ω-[(4ʹ-cyano[1,1ʹ-biphenyl]-4-yl)oxy]alkyl}thio)[1,1ʹ-biphenyl]-4-carbonitriles (CBSnOCB) are described. The odd members of both series show twist-bend nematic and nematic phases, whereas the even members exhibit only the nematic phase. An analogous cyanoterphenyl-based dimer, 34-{6-[(4ʹ-cyano[1,1ʹ-biphenyl]-4-yl)thio]-hexyl}[11,21:24,31-terphenyl]-14-carbonitrile (CT6SCB), is also reported and shows enantiotropic NTB and N phases. The transitional properties of these dimers are discussed in terms of molecular curvature, flexibility and biaxiality. The same molecular factors also influence the birefringence of nematic phases. Resonant X-ray scattering studies of the twist-bend nematic phase at both the carbon and sulfur absorption edges were performed, which allowed for the determination of critical behaviour of the helical pitch at the transition to the nematic phase, the behaviour was found to be independent of molecular structure. It was also observed that despite the different molecular bending angle and flexibility, in all compounds the helical pitch length far from the N-NTB transition corresponds to 4 longitudinal molecular distances.

Original languageEnglish
Pages (from-to)1595-1609
Number of pages15
JournalLiquid Crystals
Issue number10
Early online date1 Aug 2019
Publication statusPublished - 9 Aug 2019


  • birefringence
  • cyanobiphenyl
  • liquid crystal dimers
  • resonant X-ray scattering
  • sulfur linked
  • Twist-bend nematic phase


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