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The liquid crystal properties of symmetric and non-symmetric dimers based on the azobenzene mesogenic group

The liquid crystal properties of symmetric and non-symmetric dimers based on the azobenzene mesogenic group
The liquid crystal properties of symmetric and non-symmetric dimers based on the azobenzene mesogenic group
A novel system of symmetric and non-symmetric dimers containing azobenzene groups has been synthesized and studied in an attempt to understand further the molecular origins of the intercalated smectic phases. For the non-symmetric dimers, the lack of symmetry was derived solely from the differences in length of the two terminal alkyl chains. Both the spacer and terminal chain lengths were varied. The spacer length was found to exert a profound influence on the clearing temperatures of these materials and a large odd-even effect was observed for the series. The smectic A phase stability was observed to increase with the terminal chain length, yet decrease with increasing spacer length. X-ray diffraction has revealed the structure of the smectic A phase of both the symmetric and non-symmetric azobenzene dimers to be of the monolayer type and not intercalated. The existence of the intercalated phase has previously been explained in terms of either a charge-transfer interaction, or by an electrostatic quadrupolar interaction. However, it has been thought that it may also be the result of an excluded volume or space filling constraint. For the non-symmetric liquid crystal dimers described here, a charge-transfer interaction should be minimal, as should the stabilization from the quadrupolar interaction between the two mesogens. However, it appears that some sort of specific interaction is required to stabilize the intercalated structure.
smectic-a-phase, model
1366-5855
775-787
Blatch, A. E.
503998a7-46e9-4e68-9a69-508db1af5272
Luckhurst, G. R.
923cc3f5-cc34-4c4c-8508-1fe3b83aac16
Blatch, A. E.
503998a7-46e9-4e68-9a69-508db1af5272
Luckhurst, G. R.
923cc3f5-cc34-4c4c-8508-1fe3b83aac16

Blatch, A. E. and Luckhurst, G. R. (2000) The liquid crystal properties of symmetric and non-symmetric dimers based on the azobenzene mesogenic group. Liquid Crystals, 27 (6), 775-787. (doi:10.1080/026782900202264).

Record type: Article

Abstract

A novel system of symmetric and non-symmetric dimers containing azobenzene groups has been synthesized and studied in an attempt to understand further the molecular origins of the intercalated smectic phases. For the non-symmetric dimers, the lack of symmetry was derived solely from the differences in length of the two terminal alkyl chains. Both the spacer and terminal chain lengths were varied. The spacer length was found to exert a profound influence on the clearing temperatures of these materials and a large odd-even effect was observed for the series. The smectic A phase stability was observed to increase with the terminal chain length, yet decrease with increasing spacer length. X-ray diffraction has revealed the structure of the smectic A phase of both the symmetric and non-symmetric azobenzene dimers to be of the monolayer type and not intercalated. The existence of the intercalated phase has previously been explained in terms of either a charge-transfer interaction, or by an electrostatic quadrupolar interaction. However, it has been thought that it may also be the result of an excluded volume or space filling constraint. For the non-symmetric liquid crystal dimers described here, a charge-transfer interaction should be minimal, as should the stabilization from the quadrupolar interaction between the two mesogens. However, it appears that some sort of specific interaction is required to stabilize the intercalated structure.

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More information

Published date: 1 June 2000
Keywords: smectic-a-phase, model

Identifiers

Local EPrints ID: 18983
URI: http://eprints.soton.ac.uk/id/eprint/18983
ISSN: 1366-5855
PURE UUID: 72693cbd-136b-4bed-8515-39af3175d5b5

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Date deposited: 18 Jan 2006
Last modified: 15 Mar 2024 06:09

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Contributors

Author: A. E. Blatch
Author: G. R. Luckhurst

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