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Optical measurements of orientational order in uniaxial and biaxial nematic liquid crystals

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  • H. F. Gleeson
  • C. D. Southern
  • P. D. Brimicombe
  • J. W. Goodby
  • V. Gortz
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Article number923874813
<mark>Journal publication date</mark>2010
<mark>Journal</mark>Liquid Crystals
Issue number6-7
Volume37
Number of pages11
Pages (from-to)949-959
Publication StatusPublished
<mark>Original language</mark>English

Abstract

The use of optical methods to study the orientational order in nematic liquid crystals is both convenient and powerful. Some of the earliest approaches made use of measurements of the refractive index anisotropy, following the methodology of Halle [1] to measure the order parameter, [image omitted]. This method is reviewed briefly and some typical areas of application are presented. Raman spectroscopy is a second approach discussed in this paper. Although technically a more complex methodology, Raman spectroscopy has the significant advantage that in addition to being able to measure [image omitted] it is also possible to determine [image omitted]. A review of current approaches is presented. Very recently, it has been shown that polarised Raman spectroscopy can be employed to determine biaxial order parameters in liquid crystals. The methodology is described, and data are presented for such measurements on a series of bent-core nematic materials that could exhibit the elusive biaxial nematic phase.