Crystallography and the liquid crystal phase: a new approach to structural studies on a thermo-tropic smectic Schiff base
In spite of the apparent contradiction between ‘liquid crystals’ (LC, materials exhibiting some degree of disorder) and ‘crystallography’ (a paradigmatic ordered kingdom), X-ray diffraction (XRD) studies make a substantial contribution to the field of LC. Focusing this review on smectic (Sm, lamella...
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| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_0889311X_v24_n1_p3_Piro |
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todo:paper_0889311X_v24_n1_p3_Piro2023-10-03T15:41:13Z Crystallography and the liquid crystal phase: a new approach to structural studies on a thermo-tropic smectic Schiff base Piro, O.E. Echeverría, G.A. Cukiernik, F.D. Liquid crystals powder X-ray diffraction vs. temperature Schiff base single-crystal X-ray diffraction smectic mesophases Crystallography Liquid crystals Liquids Single crystals X ray diffraction Liquid crystal phase Molecular organization Powder X ray diffraction Schiff-base Single crystal x-ray diffraction Smectic mesophases Topological changes Variable temperature X ray crystallography In spite of the apparent contradiction between ‘liquid crystals’ (LC, materials exhibiting some degree of disorder) and ‘crystallography’ (a paradigmatic ordered kingdom), X-ray diffraction (XRD) studies make a substantial contribution to the field of LC. Focusing this review on smectic (Sm, lamellar) LC, we first describe how extremely careful XRD studies performed on mono-domain samples in the LC phase helped to elucidate the molecular structure of ordered Sm phases. Then, we describe selected examples in which single-crystal (SC) XRD on the solid-state phase of the mesogens provided information about their supra-molecular organization in the Sm phase. Finally, we present a different approach to this problem in the case of a thermo-tropic Schiff base (SB) which undergoes crystal ↔ LC ↔ isotropic liquid phase transformations. By combined SC and variable-temperature powder XRD, we show that the SB LC is a hexatic smectic B phase that derives from the crystal phase by relatively small topological changes promoted by the set-in of thermal rotational disorder around the long SB molecular axis. © 2017 Informa UK Limited, trading as Taylor & Francis Group. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_0889311X_v24_n1_p3_Piro |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Liquid crystals powder X-ray diffraction vs. temperature Schiff base single-crystal X-ray diffraction smectic mesophases Crystallography Liquid crystals Liquids Single crystals X ray diffraction Liquid crystal phase Molecular organization Powder X ray diffraction Schiff-base Single crystal x-ray diffraction Smectic mesophases Topological changes Variable temperature X ray crystallography |
| spellingShingle |
Liquid crystals powder X-ray diffraction vs. temperature Schiff base single-crystal X-ray diffraction smectic mesophases Crystallography Liquid crystals Liquids Single crystals X ray diffraction Liquid crystal phase Molecular organization Powder X ray diffraction Schiff-base Single crystal x-ray diffraction Smectic mesophases Topological changes Variable temperature X ray crystallography Piro, O.E. Echeverría, G.A. Cukiernik, F.D. Crystallography and the liquid crystal phase: a new approach to structural studies on a thermo-tropic smectic Schiff base |
| topic_facet |
Liquid crystals powder X-ray diffraction vs. temperature Schiff base single-crystal X-ray diffraction smectic mesophases Crystallography Liquid crystals Liquids Single crystals X ray diffraction Liquid crystal phase Molecular organization Powder X ray diffraction Schiff-base Single crystal x-ray diffraction Smectic mesophases Topological changes Variable temperature X ray crystallography |
| description |
In spite of the apparent contradiction between ‘liquid crystals’ (LC, materials exhibiting some degree of disorder) and ‘crystallography’ (a paradigmatic ordered kingdom), X-ray diffraction (XRD) studies make a substantial contribution to the field of LC. Focusing this review on smectic (Sm, lamellar) LC, we first describe how extremely careful XRD studies performed on mono-domain samples in the LC phase helped to elucidate the molecular structure of ordered Sm phases. Then, we describe selected examples in which single-crystal (SC) XRD on the solid-state phase of the mesogens provided information about their supra-molecular organization in the Sm phase. Finally, we present a different approach to this problem in the case of a thermo-tropic Schiff base (SB) which undergoes crystal ↔ LC ↔ isotropic liquid phase transformations. By combined SC and variable-temperature powder XRD, we show that the SB LC is a hexatic smectic B phase that derives from the crystal phase by relatively small topological changes promoted by the set-in of thermal rotational disorder around the long SB molecular axis. © 2017 Informa UK Limited, trading as Taylor & Francis Group. |
| format |
JOUR |
| author |
Piro, O.E. Echeverría, G.A. Cukiernik, F.D. |
| author_facet |
Piro, O.E. Echeverría, G.A. Cukiernik, F.D. |
| author_sort |
Piro, O.E. |
| title |
Crystallography and the liquid crystal phase: a new approach to structural studies on a thermo-tropic smectic Schiff base |
| title_short |
Crystallography and the liquid crystal phase: a new approach to structural studies on a thermo-tropic smectic Schiff base |
| title_full |
Crystallography and the liquid crystal phase: a new approach to structural studies on a thermo-tropic smectic Schiff base |
| title_fullStr |
Crystallography and the liquid crystal phase: a new approach to structural studies on a thermo-tropic smectic Schiff base |
| title_full_unstemmed |
Crystallography and the liquid crystal phase: a new approach to structural studies on a thermo-tropic smectic Schiff base |
| title_sort |
crystallography and the liquid crystal phase: a new approach to structural studies on a thermo-tropic smectic schiff base |
| url |
http://hdl.handle.net/20.500.12110/paper_0889311X_v24_n1_p3_Piro |
| work_keys_str_mv |
AT pirooe crystallographyandtheliquidcrystalphaseanewapproachtostructuralstudiesonathermotropicsmecticschiffbase AT echeverriaga crystallographyandtheliquidcrystalphaseanewapproachtostructuralstudiesonathermotropicsmecticschiffbase AT cukiernikfd crystallographyandtheliquidcrystalphaseanewapproachtostructuralstudiesonathermotropicsmecticschiffbase |
| _version_ |
1807315078262816768 |