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

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

Abstract

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.

Citation

CRUICKSHANK, E., SALAMOŃCZYK, M., POCIECHA, D., STRACHAN, G.J., STOREY, J.M.D., WANG, C., FENG, J., ZHU, C., GORECKA, E. and IMRIE, C.T. 2019. Sulfur-linked cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase. Liquid crystals [online], 46(10), pages 1595-1609. Available from: https://doi.org/10.1080/02678292.2019.1641638

• Journal Article Type: Article
• Acceptance Date: Jun 25, 2019
• Online Publication Date: Aug 1, 2019
• Publication Date: Aug 9, 2019
• Deposit Date: Aug 17, 2023
• Publicly Available Date: Aug 25, 2023
• Journal: Liquid crystals
• Print ISSN: 0267-8292
• Electronic ISSN: 1366-5855
• Publisher: Taylor and Francis
• Peer Reviewed: Peer Reviewed
• Volume: 46
• Issue: 10
• Pages: 1595-1609
• DOI: https://doi.org/10.1080/02678292.2019.1641638
• Keywords: Twist-bend nematic phase; Liquid crystal dimers; Birefringence[; Sulfur linked; Cyanobiphenyl; Resonant X-ray scattering
• Public URL: https://rgu-repository.worktribe.com/output/2043784
• Additional Information: This article has been published with separate supporting information. This supporting information has been incorporated into a single file on this repository and can be found at the end of the file associated with this output.