Thermotropic biaxial nematic order parameters and phase transitions deduced by Raman scattering

C. D. Southern; P. D. Brimicombe; S. D. Siemianowski; S. Jaradat; N. Roberts; V. Görtz; J. W. Goodby; H. F. Gleeson

doi:10.1209/0295-5075/82/56001

Thermotropic biaxial nematic order parameters and phase transitions deduced by Raman scattering

C. D. Southern, P. D. Brimicombe, S. D. Siemianowski, S. Jaradat, N. Roberts, V. Görtz, J. W. Goodby, H. F. Gleeson

Research output: Contribution to journal › Article › peer-review

Abstract

Raman Scattering was used to investigate biaxiality in the nematic phase formed by the bent-core material, C5-Ph-ODBP-Ph-OC12. Linearly polarised light was normally incident on a homogeneously aligned sample, and the depolarisation ratio was measured over a 360°rotation of the incident polarisation for the Raman-active phenyl stretching mode. By modeling the bent-core structure and fitting to the depolarisation data, both the uniaxial (〈P 200〉 and 〈P400〉) and biaxial (〈P 220〉, 〈P420〉 and 〈P 440〉) order parameters, are deduced. We show unequivocally the presence of a uniaxial to biaxial nematic phase transition approximately 30°C above the underlying smectic phase. Further, we report the temperature evolution of the biaxial and uniaxial order parameters, which increase in magnitude continuously with reducing temperature, reaching values of 0.1, -0.15 and -0.18 for 〈P220〉, 〈P420〉 and 〈P440〉, respectively. Copyright © EPLA, 2008.

Original language	English
Article number	56001
Journal	EPL
Volume	82
Issue number	5
DOIs	https://doi.org/10.1209/0295-5075/82/56001
Publication status	Published - 1 Jun 2008

Keywords

LIQUID-CRYSTALS
ORIENTATIONAL ORDER
MOLECULES
SYMMETRY
MESOGENS

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10.1209/0295-5075/82/56001

Communicating Physics through the Royal Society
Mao, S. (Participant), Rattenbury, N. (Participant), Maffei, B. (Participant), Dickinson, C. (Participant), Gleeson, M. (Participant), Dierking, I. (Participant), Dickinson, M. (Participant), Novoselov, K. (Participant), Geim, A. (Participant), Flavell, W. (Participant), Binks, D. (Participant), Spencer, T. (Participant), Fuller, M. (Participant), Avison, A. (Participant), Duerdoth, I. (Participant), Wengler, T. (Participant), Oh, A. (Participant), Soldner-Rembold, S. (Participant), Schwanenberger, C. (Participant) & Petridis, K. (Participant)
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Cite this

@article{04bf13aafde34fa186c34e1be0354ddc,

title = "Thermotropic biaxial nematic order parameters and phase transitions deduced by Raman scattering",

abstract = "Raman Scattering was used to investigate biaxiality in the nematic phase formed by the bent-core material, C5-Ph-ODBP-Ph-OC12. Linearly polarised light was normally incident on a homogeneously aligned sample, and the depolarisation ratio was measured over a 360°rotation of the incident polarisation for the Raman-active phenyl stretching mode. By modeling the bent-core structure and fitting to the depolarisation data, both the uniaxial (〈P 200〉 and 〈P400〉) and biaxial (〈P 220〉, 〈P420〉 and 〈P 440〉) order parameters, are deduced. We show unequivocally the presence of a uniaxial to biaxial nematic phase transition approximately 30°C above the underlying smectic phase. Further, we report the temperature evolution of the biaxial and uniaxial order parameters, which increase in magnitude continuously with reducing temperature, reaching values of 0.1, -0.15 and -0.18 for 〈P220〉, 〈P420〉 and 〈P440〉, respectively. Copyright {\textcopyright} EPLA, 2008.",

keywords = "LIQUID-CRYSTALS, ORIENTATIONAL ORDER, MOLECULES, SYMMETRY, MESOGENS",

author = "Southern, {C. D.} and Brimicombe, {P. D.} and Siemianowski, {S. D.} and S. Jaradat and N. Roberts and V. G{\"o}rtz and Goodby, {J. W.} and Gleeson, {H. F.}",

note = "Southern, C. D. Brimicombe, P. D. Siemianowski, S. D. Jaradat, S. Roberts, N. Gortz, V. Goodby, J. W. Gleeson, H. F. 30 EDP SCIENCES S A LES ULIS CEDEX A 307EP",

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AU - Southern, C. D.

AU - Brimicombe, P. D.

AU - Siemianowski, S. D.

AU - Jaradat, S.

AU - Roberts, N.

AU - Görtz, V.

AU - Goodby, J. W.

AU - Gleeson, H. F.

N1 - Southern, C. D. Brimicombe, P. D. Siemianowski, S. D. Jaradat, S. Roberts, N. Gortz, V. Goodby, J. W. Gleeson, H. F. 30 EDP SCIENCES S A LES ULIS CEDEX A 307EP

PY - 2008/6/1

Y1 - 2008/6/1

N2 - Raman Scattering was used to investigate biaxiality in the nematic phase formed by the bent-core material, C5-Ph-ODBP-Ph-OC12. Linearly polarised light was normally incident on a homogeneously aligned sample, and the depolarisation ratio was measured over a 360°rotation of the incident polarisation for the Raman-active phenyl stretching mode. By modeling the bent-core structure and fitting to the depolarisation data, both the uniaxial (〈P 200〉 and 〈P400〉) and biaxial (〈P 220〉, 〈P420〉 and 〈P 440〉) order parameters, are deduced. We show unequivocally the presence of a uniaxial to biaxial nematic phase transition approximately 30°C above the underlying smectic phase. Further, we report the temperature evolution of the biaxial and uniaxial order parameters, which increase in magnitude continuously with reducing temperature, reaching values of 0.1, -0.15 and -0.18 for 〈P220〉, 〈P420〉 and 〈P440〉, respectively. Copyright © EPLA, 2008.

AB - Raman Scattering was used to investigate biaxiality in the nematic phase formed by the bent-core material, C5-Ph-ODBP-Ph-OC12. Linearly polarised light was normally incident on a homogeneously aligned sample, and the depolarisation ratio was measured over a 360°rotation of the incident polarisation for the Raman-active phenyl stretching mode. By modeling the bent-core structure and fitting to the depolarisation data, both the uniaxial (〈P 200〉 and 〈P400〉) and biaxial (〈P 220〉, 〈P420〉 and 〈P 440〉) order parameters, are deduced. We show unequivocally the presence of a uniaxial to biaxial nematic phase transition approximately 30°C above the underlying smectic phase. Further, we report the temperature evolution of the biaxial and uniaxial order parameters, which increase in magnitude continuously with reducing temperature, reaching values of 0.1, -0.15 and -0.18 for 〈P220〉, 〈P420〉 and 〈P440〉, respectively. Copyright © EPLA, 2008.

KW - LIQUID-CRYSTALS

KW - ORIENTATIONAL ORDER

KW - MOLECULES

KW - SYMMETRY

KW - MESOGENS

U2 - 10.1209/0295-5075/82/56001

DO - 10.1209/0295-5075/82/56001

M3 - Article

SN - 0295-5075

VL - 82

JO - EPL

JF - EPL

IS - 5

M1 - 56001

ER -

Thermotropic biaxial nematic order parameters and phase transitions deduced by Raman scattering

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Keywords

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