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

Research output: Contribution to Journal/MagazineJournal articlepeer-review

  • C. D. Southern
  • P. D. Brimicombe
  • S. D. Siemianowski
  • S. Jaradat
  • N. Roberts
  • V. Gortz
  • J. W. Goodby
  • H. F. Gleeson
Article number56001
<mark>Journal publication date</mark>06/2008
Issue number5
Number of pages6
Publication StatusPublished
<mark>Original language</mark>English


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 degrees 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 [P(400)]) and biaxial ([P(220)], [P(420)] and [P(440)]) order parameters, are deduced. We show unequivocally the presence of a uniaxial to biaxial nematic phase transition approximately 30 degrees 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 [P(220)], [P(420)] and [P(440)], respectively. Copyright (c) EPLA, 2008.