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Title: Synthesis and study of 2,7-disubstituted fluorenes in the search for mesogenic behaviour
Author: Davidson, Ian Robert
Awarding Body: University of London
Current Institution: Royal Holloway, University of London
Date of Award: 1984
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A variety of 2,7-disubstituted fluorenes were prepared in order to investigate their mesogenic behaviour and evaluate their usefulness as possible components of mixtures in liquid crystal display devices. A series of 2-alkyl-7-cyanofluorenes were synthesised, some of which gave monotropic nematic phases. A ternary eutectic mixture of 2-alkyl-7-cyanofluorenes was prepared and the birefringence, viscosity and transition temperatures of the material were determined. Other measurements obtained for this material include the dielectric anisotropy, electro-optic threshold voltages and order parameter which were compared with those of an analogous mixture of 4,41-disubstituted biphenyls. 2-Pentyl-7-pentyloxyfluorene was also synthesised, but this compound displayed no mesogenic properties. Enantiotropic 2,7-disubstituted fluorene mesogens were synthesised by linking a phenyl ring to the fluorene core of the structure. The linkages used were -CH2CH2-" -COCH2- and ester moieties, and the transition temperatures along with some birefringence and viscosity data were determined for the mesogens. Attempted syntheses of 2,7-disubstituted fluorenone derivatives and 3,9-disubstituted-5,7-dihydrodibenz[c,e]oxepin are also described, but no mesogenic compounds were obtained. In addition, syntheses of hydrogenated fluorene derivatives were attempted with only partial success, again yielding non-mesogenic compounds. General aspects of liquid crystals are reviewed with special reference to nematogens useful in liquid displays.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Physical Chemistry