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

Research output: Contribution to journalArticlepeer-review

  • Authors:
  • C. D. Southern
  • P. D. Brimicombe
  • S. D. Siemianowski
  • S. Jaradat
  • N. Roberts
  • And 3 others
  • External authors:
  • V. Görtz
  • J. W. Goodby
  • H. F. Gleeson

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.

Bibliographical metadata

Original languageEnglish
Article number56001
JournalEPL
Volume82
Issue number5
DOIs
Publication statusPublished - 1 Jun 2008

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