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Lyotropic phase behavior of triethylammoniodecyloxycyanobiphenyl bromide and the influence of added thermotropic mesogens

Lyotropic phase behavior of triethylammoniodecyloxycyanobiphenyl bromide and the influence of added thermotropic mesogens
Lyotropic phase behavior of triethylammoniodecyloxycyanobiphenyl bromide and the influence of added thermotropic mesogens
The lyotropic mesophases formed by the "amphitropic" surfactant triethylammoniodecyloxycyanobiphenyl bromide in water have been studied using optical microscopy, X-ray diffraction, and NMR. Only a lamellar mesophase occurs, but this has a wide temperature and composition range. There is a marked decrease in the estimated bilayer thickness (decrease in alkyl chain "ordering", increase of micelle surface curvature) with an increase of temperature, particularly at the lower surfactant concentrations. This is likely to arise from the occurrence of a defect-full lamellar phase with water-filled holes rather than a conventional structure with continuous bilayers. The influence on the liquid crystals of added thermotropic mesogens (pentylcyanobiphenyl and heptyloxycyanobiphenyl) has been compared with that of a conventional alkane, hexane. The mesogenic additives stabilize the (defective) lamellar phase, while hexane destabilizes it. The phase behavior and the NMR and the X-ray data all suggest that in the mesophase there are significant anisotropic attractive interactions between the oxycyanobiphenyl moieties, which are increased when the mesogenic additives are present. Some pointers for future directions in the search for true amphitropic mesophases are given.
pentadecafluorooctanoate water-system, amphitropic liquid-crystals, chain nonionic surfactant, angle neutron-scattering, aqueous mixtures, molecular design, lamellar phases, mesh phase, x-ray, mesophases
0743-7463
8712-8718
Attard, G. S.
15b1b53e-25e4-4c5b-bc58-3601527f90d9
Fuller, S.
fc6af72b-1db5-4b6b-85d4-12ed80448889
Howell, O.
8c37a6ac-c82a-4c26-8334-f0706cca0cda
Tiddy, G. J. T.
abd12043-d0ed-45d9-ae3b-bc071e237598
Attard, G. S.
15b1b53e-25e4-4c5b-bc58-3601527f90d9
Fuller, S.
fc6af72b-1db5-4b6b-85d4-12ed80448889
Howell, O.
8c37a6ac-c82a-4c26-8334-f0706cca0cda
Tiddy, G. J. T.
abd12043-d0ed-45d9-ae3b-bc071e237598

Attard, G. S., Fuller, S., Howell, O. and Tiddy, G. J. T. (2000) Lyotropic phase behavior of triethylammoniodecyloxycyanobiphenyl bromide and the influence of added thermotropic mesogens. Langmuir, 16 (23), 8712-8718. (doi:10.1021/la000296m).

Record type: Article

Abstract

The lyotropic mesophases formed by the "amphitropic" surfactant triethylammoniodecyloxycyanobiphenyl bromide in water have been studied using optical microscopy, X-ray diffraction, and NMR. Only a lamellar mesophase occurs, but this has a wide temperature and composition range. There is a marked decrease in the estimated bilayer thickness (decrease in alkyl chain "ordering", increase of micelle surface curvature) with an increase of temperature, particularly at the lower surfactant concentrations. This is likely to arise from the occurrence of a defect-full lamellar phase with water-filled holes rather than a conventional structure with continuous bilayers. The influence on the liquid crystals of added thermotropic mesogens (pentylcyanobiphenyl and heptyloxycyanobiphenyl) has been compared with that of a conventional alkane, hexane. The mesogenic additives stabilize the (defective) lamellar phase, while hexane destabilizes it. The phase behavior and the NMR and the X-ray data all suggest that in the mesophase there are significant anisotropic attractive interactions between the oxycyanobiphenyl moieties, which are increased when the mesogenic additives are present. Some pointers for future directions in the search for true amphitropic mesophases are given.

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More information

Published date: 14 November 2000
Keywords: pentadecafluorooctanoate water-system, amphitropic liquid-crystals, chain nonionic surfactant, angle neutron-scattering, aqueous mixtures, molecular design, lamellar phases, mesh phase, x-ray, mesophases

Identifiers

Local EPrints ID: 18979
URI: http://eprints.soton.ac.uk/id/eprint/18979
ISSN: 0743-7463
PURE UUID: 95b89d06-4657-48d0-8353-0dccb5b03170

Catalogue record

Date deposited: 18 Jan 2006
Last modified: 15 Jul 2019 19:28

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