Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline Mesophases
Liquid crystalline dimers and dimesogens have attracted significant attention due to their tendency to exhibit twist-bend modulated nematic (N<sub>TB</sub>) phases. While the features that give rise to N<sub>TB</sub> phase formation are now somewhat understood, a comparable s...
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doaj-f8154efad34047378c83ce82a62a50c52021-01-21T00:05:45ZengMDPI AGMolecules1420-30492021-01-012653253210.3390/molecules26030532Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline MesophasesEmily E. Pocock0Richard J. Mandle1John W. Goodby2Department of Chemistry, University of York, Heslington, York YO10 5DD, UKDepartment of Chemistry, University of York, Heslington, York YO10 5DD, UKDepartment of Chemistry, University of York, Heslington, York YO10 5DD, UKLiquid crystalline dimers and dimesogens have attracted significant attention due to their tendency to exhibit twist-bend modulated nematic (N<sub>TB</sub>) phases. While the features that give rise to N<sub>TB</sub> phase formation are now somewhat understood, a comparable structure–property relationship governing the formation of layered (smectic) phases from the N<sub>TB</sub> phase is absent. In this present work, we find that by selecting mesogenic units with differing polarities and aspect ratios and selecting an appropriately bent central spacer we obtain a material that exhibits both N<sub>TB</sub> and intercalated smectic phases. The higher temperature smectic phase is assigned as SmC<sub>A</sub> based on its optical textures and X-ray scattering patterns. A detailed study of the lower temperature smectic ‘’X’’ phase by optical microscopy and SAXS/WAXS demonstrates this phase to be smectic, with an in-plane orthorhombic or monoclinic packing and long (>100 nm) out of plane correlation lengths. This phase, which has been observed in a handful of materials to date, is a soft-crystal phase with an anticlinic layer organisation. We suggest that mismatching the polarities, conjugation and aspect ratios of mesogenic units is a useful method for generating smectic forming dimesogens.https://www.mdpi.com/1420-3049/26/3/532liquid crystalnematicsX-ray scatteringNTB |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Emily E. Pocock Richard J. Mandle John W. Goodby |
spellingShingle |
Emily E. Pocock Richard J. Mandle John W. Goodby Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline Mesophases Molecules liquid crystal nematics X-ray scattering NTB |
author_facet |
Emily E. Pocock Richard J. Mandle John W. Goodby |
author_sort |
Emily E. Pocock |
title |
Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline Mesophases |
title_short |
Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline Mesophases |
title_full |
Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline Mesophases |
title_fullStr |
Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline Mesophases |
title_full_unstemmed |
Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline Mesophases |
title_sort |
experimental and computational study of a liquid crystalline dimesogen exhibiting nematic, twist-bend nematic, intercalated smectic, and soft crystalline mesophases |
publisher |
MDPI AG |
series |
Molecules |
issn |
1420-3049 |
publishDate |
2021-01-01 |
description |
Liquid crystalline dimers and dimesogens have attracted significant attention due to their tendency to exhibit twist-bend modulated nematic (N<sub>TB</sub>) phases. While the features that give rise to N<sub>TB</sub> phase formation are now somewhat understood, a comparable structure–property relationship governing the formation of layered (smectic) phases from the N<sub>TB</sub> phase is absent. In this present work, we find that by selecting mesogenic units with differing polarities and aspect ratios and selecting an appropriately bent central spacer we obtain a material that exhibits both N<sub>TB</sub> and intercalated smectic phases. The higher temperature smectic phase is assigned as SmC<sub>A</sub> based on its optical textures and X-ray scattering patterns. A detailed study of the lower temperature smectic ‘’X’’ phase by optical microscopy and SAXS/WAXS demonstrates this phase to be smectic, with an in-plane orthorhombic or monoclinic packing and long (>100 nm) out of plane correlation lengths. This phase, which has been observed in a handful of materials to date, is a soft-crystal phase with an anticlinic layer organisation. We suggest that mismatching the polarities, conjugation and aspect ratios of mesogenic units is a useful method for generating smectic forming dimesogens. |
topic |
liquid crystal nematics X-ray scattering NTB |
url |
https://www.mdpi.com/1420-3049/26/3/532 |
work_keys_str_mv |
AT emilyepocock experimentalandcomputationalstudyofaliquidcrystallinedimesogenexhibitingnematictwistbendnematicintercalatedsmecticandsoftcrystallinemesophases AT richardjmandle experimentalandcomputationalstudyofaliquidcrystallinedimesogenexhibitingnematictwistbendnematicintercalatedsmecticandsoftcrystallinemesophases AT johnwgoodby experimentalandcomputationalstudyofaliquidcrystallinedimesogenexhibitingnematictwistbendnematicintercalatedsmecticandsoftcrystallinemesophases |
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