A design approach to obtaining highly polar liquid crystal dimers.

Zattarin, Amerigo; Cruickshank, Ewan; Pociecha, Damian; Storey, John M.D.; Gorecka, Ewa; Imrie, Corrie T.

Abstract

The synthesis and characterisation of 10 members of the [4[(E)-[4-[4-[ω-(4-cyanophenyl)phenoxy]alkyloxy]-3-nitrophenyl]methylideneamino]phenyl] 2,4-dimethoxybenzoates is reported in which the number of methylene units in the flexible spacer is increased from three to twelve. The mesogenic units are based on cyanobiphenyl and 3-nitrobenzylideneaniline benzoate and linked by the spacer such that their dipoles are parallel giving rise to a large longitudinal dipole moment. All 10 members of the series show a nematic phase, and the nematic-isotropic transition temperatures, TNI, and associated entropy changes show a strong dependence on the length and parity of the spacer. This behaviour is attributed to the average shapes of the molecules and their flexibility. The heptyl member was further characterised using dielectric spectroscopy revealing a high value of dielectric permittivity reflecting the large dipole moment of the molecules and possibly indicating local short-range ferroelectric order. The synthesis and characterisation of two members of the [4[(E)-[4-[4-[3-(ω-cyanophenyl)phenoxy]alkyloxy]-4-nitrophenyl]methylideneamino]phenyl] 2,4-dimethoxybenzoates are also described for which the difference in shape between odd and even members is reduced. Both dimers are exclusively nematogenic and the difference between TNI for the odd and even member is smaller reflecting the more similar molecular shapes. The potential for developing dimers that exhibit the ferroelectric nematic phase is discussed.

Citation

ZATTARIN, A., CRUICKSHANK, E., POCIECHA, D., STOREY, J.M.D., GORECKA, E. and IMRIE, C.T. 2024. A design approach to obtaining highly polar liquid crystal dimers. Liquid crystals [online], 51(6): a festschrift in honour of Professor Lech Longa, pages 1035-1046. Available from: https://doi.org/10.1080/02678292.2024.2374524

• Journal Article Type: Article
• Acceptance Date: Jun 19, 2024
• Online Publication Date: Jul 11, 2024
• Publication Date: Jun 30, 2024
• Deposit Date: Jul 19, 2024
• Publicly Available Date: Aug 1, 2024
• Journal: Liquid crystals
• Print ISSN: 0267-8292
• Electronic ISSN: 1366-5855
• Publisher: Taylor and Francis
• Peer Reviewed: Peer Reviewed
• Volume: 51
• Issue: 6
• Pages: 1035-1046
• DOI: https://doi.org/10.1080/02678292.2024.2374524
• Keywords: Liquid crystal dimers; Odd-even effect; Nematic; Ferroelectric nematic
• Public URL: https://rgu-repository.worktribe.com/output/2408695
• 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.