Synthesis, Characterization And Mesomorphic Properties Of Symmetric And Non-Symmetric Isoflavone Oligomers
| dc.contributor.author | Chan, Tze Nee | |
| dc.date.accessioned | 2019-06-18T02:38:48Z | |
| dc.date.available | 2019-06-18T02:38:48Z | |
| dc.date.issued | 2012-05 | |
| dc.description.abstract | Four new series of symmetric and non-symmetric isoflavone-based liquid crystal oligomers have been synthesized and characterized. These oligomers comprised of three series of non-symmetric dimers, namely 7-[{4-[4'-((S)-2''-methylbutyloxy)carbonylphenyl]phenoxy}alkyloxy]-3-(4'-decyloxyphenyl)-4H-1-benzopyran-4-ones (BP-n-I), 7-[{4-[4'-((S)-2''-methylbutyloxy)carbonyl phenyl]phenoxy}decyloxy]-3-(4'-substitutedphenyl)-4H-1-benzopyran-4-ones (BPI-R) and 7-[{4-[(4'-methoxyphenyl)diazenyl]phenoxy}alkyloxy]-3-(4'-methoxy phenyl)-4H-1-benzopyran-4-ones (AB-n-I), and a series of symmetric trimers: 1,3-bis{[3-(4'-decyloxyphenyl)-4H-1-benzopyran-4-one-7-oxy]alkyloxy}benzenes (BI-n-B). All oligomeric mesogens differ from one another in term of mesogenic moieties and spacer length. The molecular structures of these oligomers were elucidated via CHN, FT-IR, 1H-NMR, 13C-NMR, 1H-1H COSY, 1H-13C HMQC and 1H-13C HMBC spectroscopy prior to the investigation of their liquid crystalline properties using POM, DSC and XRD. Mono- and/or polymorphism were observed in all oligomers. They exhibited a rich variety of phases including mono- and enantiotropic chiral nematic (N*), monolayer and intercalated smectic A (SmA and SmAc, respectively), synclinic (SmCsyn) and anticlinic smectic C (SmCanti) phases. Furthermore, pronounced odd-even effect in phase transition temperatures (Tm and Tc) upon varying the spacer length was observed for BP-n-I, AB-n-I and short homologues of BI-n-B (n = 3-7). One special feature worth mentioning was the de Vries type behaviour exhibited by the shortest homologue of BP-n-I. Apart from this, a crossover of geometry from intercalated rod-shaped for short homologues to bent-shaped for long homologues in BI-n-B had resulted in the observation of an unusual mesomorphic behaviour wherein short and long trimers exhibited SmA and/or metastable SmC phase(s) while homologues with intermediate spacer length were purely nematogenic with broad temperature range. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/8312 | |
| dc.language.iso | en | en_US |
| dc.publisher | Universiti Sains Malaysia | en_US |
| dc.subject | Mesomorphic properties of symmetric and | en_US |
| dc.subject | non-symmetric isoflavone oligomers | en_US |
| dc.title | Synthesis, Characterization And Mesomorphic Properties Of Symmetric And Non-Symmetric Isoflavone Oligomers | en_US |
| dc.type | Thesis | en_US |