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Zhang, Rui-Bin, Grunwald, Marco A., Zeng, Xiang-Bing, Laschat, Sabine, Cammidge, Andrew N. 
ORCID: https://orcid.org/0000-0001-7912-4310 and Ungar, Goran
(2024)
Orientational transitions of discotic columnar liquid crystals in cylindrical pores.
Soft Matter, 20 (31).
pp. 6193-6203.
ISSN 1744-683X
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Abstract
Confined in a cylindrical pore with homeotropic anchoring condition, the hexagonal columnar phase of discotic liquid crystals can form a "log-pile" configuration, in which the columns are perpendicular to the long axis of the pore. However, the {100} planes of the hexagonal lattice can orient either parallel (termed (100)& Vert; orientation) or perpendicular ((100)perpendicular to) to pore axis. Here we experimentally show that the (100)& Vert; orientation is found in narrower cylindrical pores, and the (100)& Vert;-(100)perpendicular to transition can be controlled by engineering the structure of the molecules. The (100)& Vert; orientation is destroyed in asymmetric discotics hepta(heptenyloxy)triphenylene (SATO7); replacing the oxygen linkage in hexa(hexyloxy)triphenylene (HATO6) by sulphur (HATS6) improves the (100)& Vert; orientation in small pores; adding a perfluorooctyl end to each alkyl chain of HATO6 (HATO6F8) moves the (100)& Vert;-(100)perpendicular to transition to larger pores. We have provided a semi-quantitative explanation of the experimental observations, and discussed them in the context of previous findings on related materials in a wider pore size range from 60 nm to 100 mu m. This allows us to produce a comprehensive picture of confined columnar liquid crystals whose applications critically depend on our ability to align them. Configurations of soft columns confined in a hard cylindrical pore tuned by pore size, column flexibility and surface anchoring.
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| Additional Information: | Acknowledgements: We thank Professor Richard Bushby of Leeds University for kindly providing a sample of HATO6, as well as Shanghai Institute of Microsystem and Information Technology for providing the DRIE membranes. For support with experiments at Diamond Light Source we thank Dr Olga Shebanova and Prof. Nick Terill (I22) and Dr Gareth Nisbet and Prof. Steve Collins (I16). We are grateful to Dr Patrick Baker for his support with the in-house X-ray experiments. The work was financially supported by EPSRC (EP/P002250/1, EP/T003294/1), by NSFC (92356306, 22250710137), by the Deutsche Forschungsgemeinschaft (LA 907/21-1), the Bundesministerium für Bildung und Forschung (shared instrumentation grant 01 RI05177), the Carl-Schneider-Stiftung Aalen (shared instrumentation grant). We would like to thank Jonathan Wischnat and Eric Wimmer for skillful experimental assistance. |
| Faculty \ School: | Faculty of Science > School of Chemistry, Pharmacy and Pharmacology |
| UEA Research Groups: | Faculty of Science > Research Groups > Centre for Photonics and Quantum Science Faculty of Science > Research Groups > Chemistry of Materials and Catalysis Faculty of Science > Research Groups > Chemistry of Light and Energy |
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| Depositing User: | LivePure Connector |
| Date Deposited: | 28 Aug 2024 10:30 |
| Last Modified: | 01 Nov 2024 00:52 |
| URI: | https://ueaeprints.uea.ac.uk/id/eprint/96371 |
| DOI: | 10.1039/d4sm00621f |
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