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Multi-block thermotropic liquid crystals

Multi-block thermotropic liquid crystals
Multi-block thermotropic liquid crystals

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.

University of Southampton
Lehmann, Petra
46ea0f85-0f09-42a1-ba70-0ffea79e18a6
Lehmann, Petra
46ea0f85-0f09-42a1-ba70-0ffea79e18a6

Lehmann, Petra (2003) Multi-block thermotropic liquid crystals. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

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.

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Published date: 2003

Identifiers

Local EPrints ID: 465795
URI: http://eprints.soton.ac.uk/id/eprint/465795
PURE UUID: 993344a5-7024-4609-a13d-6ef9430d8a57

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Date deposited: 05 Jul 2022 03:07
Last modified: 16 Mar 2024 20:22

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Author: Petra Lehmann

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