File Download

There are no files associated with this item.

  Links for fulltext
     (May Require Subscription)
Supplementary

Article: Thermotropic liquid crystals based on extended 2,5-disubstituted-1,3,4- oxadiazoles: Structure-property relationships, variable-temperature powder X-ray diffraction, and small-angle X-ray scattering studies

TitleThermotropic liquid crystals based on extended 2,5-disubstituted-1,3,4- oxadiazoles: Structure-property relationships, variable-temperature powder X-ray diffraction, and small-angle X-ray scattering studies
Authors
KeywordsLiquid crystals
Materials science
Mesophases
Phase transitions
X-ray diffraction
Issue Date2006
PublisherWiley - V C H Verlag GmbH & Co. KGaA. The Journal's web site is located at http://www.wiley-vch.de/publish/en/journals/alphabeticIndex/2451
Citation
Chemistry - An Asian Journal, 2006, v. 1 n. 6, p. 814-825 How to Cite?
AbstractA class of extended 2,5-disubstituted-1,3,4-oxadiazoles R 1-C 6H 4-{OC 2N 2}-C 6H 4-R 2 (R 1 = R 2 = C 10H 21O 1a, P-C 10H 21O-C 6H 4-C≡C 3a, p-CH 3O-C 6H 4-C≡C 3b; R 1=C 10H 21O, R 2 = CH 3O 1b, (CH 3) 2N 1c; F 1d; R 1 = C 10H 21O-C 6H 4- C≡C, R 2 = C 10H 21O 2a, CH 3O 2b, (CH 3) 2N 2c, F 2d) were prepared, and their liquid-crystalline properties were examined. In CH 2Cl 2 solution, these compounds displayed a room-temperature emission with λ max at 340-471 nm and quantum yields of 0.73-0.97. Compounds 1d, 2a-2d, and 3 a exhibited various thermotropic mesophases (monotropic, enantiotropic nematic/smectic), which were examined by polarized-light optical microscopy and differential scanning calorimetry. Structure determination by a direct-space approach using simulated annealing or parallel tempering of the powder X-ray diffraction data revealed distinctive crystal-packing arrangements for mesogenic molecules 2b and 3 a, leading to different nematic mesophase behavior, with 2b being monotropic and 3 a enantiotropic in the narrow temperature range of 200-210°C. The structural transitions associated with these crystalline solids and their mesophases were studied by variable-temperature X-ray diffractometry. Nondestructive phase transitions (crystal-to-crystal, crystal-to-mesophase, mesophase-to-liquid) were observed in the diffracto-grams of 1b, 1d, 2b, 2d, and 3a measured at 25-200°C. Powder X-ray diffraction and small-angle X-ray scattering data revealed that the structure of the annealed solid residue 2b reverted to its original crystal/molecular packing when the isotropic liquid was cooled to room temperature. Structure-property relationships within these mesomorphic solids are discussed in the context of their molecular structures and intermolecular interactions. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.
Persistent Identifierhttp://hdl.handle.net/10722/68889
ISSN
2015 Impact Factor: 4.592
2015 SCImago Journal Rankings: 1.833
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorHan, Jen_HK
dc.contributor.authorChui, SSYen_HK
dc.contributor.authorChe, CMen_HK
dc.date.accessioned2010-09-06T06:08:39Z-
dc.date.available2010-09-06T06:08:39Z-
dc.date.issued2006en_HK
dc.identifier.citationChemistry - An Asian Journal, 2006, v. 1 n. 6, p. 814-825en_HK
dc.identifier.issn1861-4728en_HK
dc.identifier.urihttp://hdl.handle.net/10722/68889-
dc.description.abstractA class of extended 2,5-disubstituted-1,3,4-oxadiazoles R 1-C 6H 4-{OC 2N 2}-C 6H 4-R 2 (R 1 = R 2 = C 10H 21O 1a, P-C 10H 21O-C 6H 4-C≡C 3a, p-CH 3O-C 6H 4-C≡C 3b; R 1=C 10H 21O, R 2 = CH 3O 1b, (CH 3) 2N 1c; F 1d; R 1 = C 10H 21O-C 6H 4- C≡C, R 2 = C 10H 21O 2a, CH 3O 2b, (CH 3) 2N 2c, F 2d) were prepared, and their liquid-crystalline properties were examined. In CH 2Cl 2 solution, these compounds displayed a room-temperature emission with λ max at 340-471 nm and quantum yields of 0.73-0.97. Compounds 1d, 2a-2d, and 3 a exhibited various thermotropic mesophases (monotropic, enantiotropic nematic/smectic), which were examined by polarized-light optical microscopy and differential scanning calorimetry. Structure determination by a direct-space approach using simulated annealing or parallel tempering of the powder X-ray diffraction data revealed distinctive crystal-packing arrangements for mesogenic molecules 2b and 3 a, leading to different nematic mesophase behavior, with 2b being monotropic and 3 a enantiotropic in the narrow temperature range of 200-210°C. The structural transitions associated with these crystalline solids and their mesophases were studied by variable-temperature X-ray diffractometry. Nondestructive phase transitions (crystal-to-crystal, crystal-to-mesophase, mesophase-to-liquid) were observed in the diffracto-grams of 1b, 1d, 2b, 2d, and 3a measured at 25-200°C. Powder X-ray diffraction and small-angle X-ray scattering data revealed that the structure of the annealed solid residue 2b reverted to its original crystal/molecular packing when the isotropic liquid was cooled to room temperature. Structure-property relationships within these mesomorphic solids are discussed in the context of their molecular structures and intermolecular interactions. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.en_HK
dc.languageengen_HK
dc.publisherWiley - V C H Verlag GmbH & Co. KGaA. The Journal's web site is located at http://www.wiley-vch.de/publish/en/journals/alphabeticIndex/2451en_HK
dc.relation.ispartofChemistry - An Asian Journalen_HK
dc.subjectLiquid crystalsen_HK
dc.subjectMaterials scienceen_HK
dc.subjectMesophasesen_HK
dc.subjectPhase transitionsen_HK
dc.subjectX-ray diffractionen_HK
dc.titleThermotropic liquid crystals based on extended 2,5-disubstituted-1,3,4- oxadiazoles: Structure-property relationships, variable-temperature powder X-ray diffraction, and small-angle X-ray scattering studiesen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=1861-4728&volume=1&issue=6&spage=814&epage=825&date=2006&atitle=Thermotropic+liquid+crystals+based+on+extended+2,5-disubstituted-1,3,4-oxadiazoles:+Structure-property+relationships,+variable-temperature+powder+X-ray+diffraction,+and+small-angle+X-ray+scattering+studiesen_HK
dc.identifier.emailChui, SSY: chuissy@hkucc.hku.hken_HK
dc.identifier.emailChe, CM: cmche@hku.hken_HK
dc.identifier.authorityChui, SSY=rp00686en_HK
dc.identifier.authorityChe, CM=rp00670en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1002/asia.200600252en_HK
dc.identifier.pmid17441124-
dc.identifier.scopuseid_2-s2.0-33845930609en_HK
dc.identifier.hkuros137609en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-33845930609&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume1en_HK
dc.identifier.issue6en_HK
dc.identifier.spage814en_HK
dc.identifier.epage825en_HK
dc.identifier.isiWOS:000243223400005-
dc.publisher.placeGermanyen_HK
dc.identifier.scopusauthoridHan, J=26643236400en_HK
dc.identifier.scopusauthoridChui, SSY=8297453100en_HK
dc.identifier.scopusauthoridChe, CM=7102442791en_HK

Export via OAI-PMH Interface in XML Formats


OR


Export to Other Non-XML Formats