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Title: Multi-block thermotropic liquid crystals
Author: Lehmann, Petra
ISNI:       0000 0001 3607 8385
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2003
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These compounds are characterised by an increased number of incompatible units and different symmetries of their rigid segments and show a complex interplay between the mesogenic units and the siloxane moiety. Precursor molecules falling in one of the following classes are synthesised and investigated: (1) combination of the extended cycloaliphatic core of a steroidal unit and the rod-like core of a typical nematogen via a flexible spacer of varying length, (2) calamitic aromatic units linked by an organometallic complex, and (3) a calamitic aromatic unit linked to a perfluorinated chain of varying length. The mesomorphic and electro-optic properties of these materials are compared to those of their siloxinated analogues of different geometry. The estradiol-cyanobiphenyl bimesogenic materials show unusually strong flexoelectro-optic effects and respond on a submillisecond timesecond. This effect could be retained in some of the oligomeric cyclo-organosiloxanes based on these materials. In case of the organometallic siloxanes, the first ferrocene containing low molar mass organosiloxane liquid-crystalline materials were prepared, and ferroelectric properties could be demonstrated for the first time in these compounds. Novel organosiloxane dimers that contain both siloxane and perfluoroalkyl chains as an orthogonal set of incompatible groups were synthesised and investigated. It could be shown, that these compounds undergo microphase-segregation. Antiferroelectric phases are induced by odd-numbered siloxane spacers.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available