Orientational transitions of discotic columnar liquid crystals in cylindrical pores.
Soft Matter
; 20(31): 6193-6203, 2024 Aug 07.
Article
em En
| MEDLINE
| ID: mdl-39045629
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)â orientation) or perpendicular ((100)â¥) to pore axis. Here we experimentally show that the (100)â orientation is found in narrower cylindrical pores, and the (100)â-(100)⥠transition can be controlled by engineering the structure of the molecules. The (100)â 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)â orientation in small pores; adding a perfluorooctyl end to each alkyl chain of HATO6 (HATO6F8) moves the (100)â-(100)⥠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 µm. This allows us to produce a comprehensive picture of confined columnar liquid crystals whose applications critically depend on our ability to align them.
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MEDLINE
Idioma:
En
Ano de publicação:
2024
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Article