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Guest-host mixtures using novel host-mimicking fluorescent dyes in ferroelectric and flexoelectric liquid crystal hosts

Guest-host mixtures using novel host-mimicking fluorescent dyes in ferroelectric and flexoelectric liquid crystal hosts
Guest-host mixtures using novel host-mimicking fluorescent dyes in ferroelectric and flexoelectric liquid crystal hosts

A perylene moiety was chemically attached to a siloxane core in the same way that the liquid crystal moiety is in the host material.  This similarity in molecular shape allowed miscibility of the dye in the host at concentrations as high as 50% (by mole).  Up to concentrations of 15-20% (molar) the dye does not drastically affect the electro-optic properties of the host and still shows a high tilt angle and fast response time.  The addition of such high concentrations of a fluorescent dye also showed the formation of stable excited state dimers, known as excimers, which cause a shift in the emitted fluorescent wavelength.

 A novel cyanobiphenyl chiral nematic host material was created with a rigid core that imposed a bent-core or ‘banana’ shape on the molecule.  With the addition of a small amount of chiral dopant these materials showed a 27-degree wide chiral nematic phase, with an optic axis switching angle of ˜38% for an applied field of the order of ± 2V/μm when aligned in the ‘uniform-lying helix’ texture, in accordance with the flexoelectroptic effect.

For use with this flexoelectric host, a fluorescent dye was synthesised that mimicked its molecular shape and again included a perylene moiety as the fluorophore.  The use of this dye also showed a high degree of miscibility and similarly showed that the addition of dye concentrations up to 20% would not drastically affect the electro-optic properties.  These also showed excimer formation, giving a potential for concentration-driven colour tunability.

The results taken with these materials are presented, and discussed including comments on their practical potential and ideas for future work in this field.

University of Southampton
de Hondt, Piers
6ebe37d9-13b3-4968-816c-8049f18c50ed
de Hondt, Piers
6ebe37d9-13b3-4968-816c-8049f18c50ed

de Hondt, Piers (2004) Guest-host mixtures using novel host-mimicking fluorescent dyes in ferroelectric and flexoelectric liquid crystal hosts. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

A perylene moiety was chemically attached to a siloxane core in the same way that the liquid crystal moiety is in the host material.  This similarity in molecular shape allowed miscibility of the dye in the host at concentrations as high as 50% (by mole).  Up to concentrations of 15-20% (molar) the dye does not drastically affect the electro-optic properties of the host and still shows a high tilt angle and fast response time.  The addition of such high concentrations of a fluorescent dye also showed the formation of stable excited state dimers, known as excimers, which cause a shift in the emitted fluorescent wavelength.

 A novel cyanobiphenyl chiral nematic host material was created with a rigid core that imposed a bent-core or ‘banana’ shape on the molecule.  With the addition of a small amount of chiral dopant these materials showed a 27-degree wide chiral nematic phase, with an optic axis switching angle of ˜38% for an applied field of the order of ± 2V/μm when aligned in the ‘uniform-lying helix’ texture, in accordance with the flexoelectroptic effect.

For use with this flexoelectric host, a fluorescent dye was synthesised that mimicked its molecular shape and again included a perylene moiety as the fluorophore.  The use of this dye also showed a high degree of miscibility and similarly showed that the addition of dye concentrations up to 20% would not drastically affect the electro-optic properties.  These also showed excimer formation, giving a potential for concentration-driven colour tunability.

The results taken with these materials are presented, and discussed including comments on their practical potential and ideas for future work in this field.

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Published date: 2004

Identifiers

Local EPrints ID: 465473
URI: http://eprints.soton.ac.uk/id/eprint/465473
PURE UUID: 1f55781d-0247-404b-bd49-1c7fe6091f02

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Date deposited: 05 Jul 2022 01:18
Last modified: 16 Mar 2024 20:12

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Author: Piers de Hondt

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