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On the twist-bend nematic phase formed directly from the isotropic phase

On the twist-bend nematic phase formed directly from the isotropic phase
On the twist-bend nematic phase formed directly from the isotropic phase
The intriguing twist-bend nematic (NTB) phase is formed, primarily, by liquid crystal dimers having odd spacers. Typically, the phase is preceded by a nematic (N) phase via a weak first-order transition. Our aim is to obtain dimers where the NTB phase is formed directly from the isotropic (I) phase via a strong first-order phase transition. The analogy between such behaviour and that of the smectic A (SmA)–N–I sequence suggests that this new dimer will require a short spacer. This expectation is consistent with the prediction of a molecular field theory, since the decrease in the spacer length results in an increase in the molecular curvature. A vector of odd dimers based on benzoyloxybenzylidene mesogenic groups with terminal ethoxy groups has been synthesised with spacers composed of odd numbers of methylene groups. Spacers having 5, 7, 9 and 11 methylene groups are found to possess the conventional phase sequence NTB–N–I; surprisingly, for the propane spacer, the NTB phase is formed directly from the I phase. The properties of these dimers have been studied with care to ensure that the identification of the NTB phase is reliable.
1366-5855
2-12
Dawood, Alya A.
1a010c9a-0293-468e-b235-a0f8b490fae3
Grossel, Martin C.
403bf3ff-6364-44e9-ab46-52d84c6f0d56
Luckhurst, Geoffrey R.
7807d1c6-54a1-414f-9abe-22de4d9c30f7
Richardson, Robert M.
7f9c8a3d-62cc-4760-9687-afb083d6b68b
Timimi, Bakir A.
845f8bba-a04b-4e8d-adfe-51b13e9f29ca
Wells, Neil
86312185-007b-495b-86da-4e2e5b9b8025
Yousif, Yousif Z.
1790104f-75a6-458a-8f03-e888cac0c004
Dawood, Alya A.
1a010c9a-0293-468e-b235-a0f8b490fae3
Grossel, Martin C.
403bf3ff-6364-44e9-ab46-52d84c6f0d56
Luckhurst, Geoffrey R.
7807d1c6-54a1-414f-9abe-22de4d9c30f7
Richardson, Robert M.
7f9c8a3d-62cc-4760-9687-afb083d6b68b
Timimi, Bakir A.
845f8bba-a04b-4e8d-adfe-51b13e9f29ca
Wells, Neil
86312185-007b-495b-86da-4e2e5b9b8025
Yousif, Yousif Z.
1790104f-75a6-458a-8f03-e888cac0c004

Dawood, Alya A., Grossel, Martin C., Luckhurst, Geoffrey R., Richardson, Robert M., Timimi, Bakir A., Wells, Neil and Yousif, Yousif Z. (2016) On the twist-bend nematic phase formed directly from the isotropic phase. Liquid Crystals, 43 (1), 2-12. (doi:10.1080/02678292.2015.1114158).

Record type: Article

Abstract

The intriguing twist-bend nematic (NTB) phase is formed, primarily, by liquid crystal dimers having odd spacers. Typically, the phase is preceded by a nematic (N) phase via a weak first-order transition. Our aim is to obtain dimers where the NTB phase is formed directly from the isotropic (I) phase via a strong first-order phase transition. The analogy between such behaviour and that of the smectic A (SmA)–N–I sequence suggests that this new dimer will require a short spacer. This expectation is consistent with the prediction of a molecular field theory, since the decrease in the spacer length results in an increase in the molecular curvature. A vector of odd dimers based on benzoyloxybenzylidene mesogenic groups with terminal ethoxy groups has been synthesised with spacers composed of odd numbers of methylene groups. Spacers having 5, 7, 9 and 11 methylene groups are found to possess the conventional phase sequence NTB–N–I; surprisingly, for the propane spacer, the NTB phase is formed directly from the I phase. The properties of these dimers have been studied with care to ensure that the identification of the NTB phase is reliable.

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More information

Accepted/In Press date: 26 October 2015
Published date: 8 January 2016

Identifiers

Local EPrints ID: 391405
URI: http://eprints.soton.ac.uk/id/eprint/391405
ISSN: 1366-5855
PURE UUID: 9fad5175-769d-49f5-93a3-c1632adaeb2c
ORCID for Martin C. Grossel: ORCID iD orcid.org/0000-0001-7469-6854
ORCID for Neil Wells: ORCID iD orcid.org/0000-0002-4607-5791

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Date deposited: 12 Apr 2016 10:51
Last modified: 15 Mar 2024 02:58

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Contributors

Author: Alya A. Dawood
Author: Geoffrey R. Luckhurst
Author: Robert M. Richardson
Author: Bakir A. Timimi
Author: Neil Wells ORCID iD
Author: Yousif Z. Yousif

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