Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Optical measurements of orientational order in uniaxial and biaxial nematic liquid crystals
AU - Gleeson, H. F.
AU - Southern, C. D.
AU - Brimicombe, P. D.
AU - Goodby, J. W.
AU - Gortz, V.
PY - 2010
Y1 - 2010
N2 - 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.
AB - 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.
KW - orientational order parameters
KW - polarised Raman spectroscopy
KW - biaxial order
KW - X-RAY-DIFFRACTION
KW - RAMAN-SPECTROSCOPY
KW - PHASE-TRANSITIONS
KW - PARAMETERS
KW - SCATTERING
KW - POLYMERS
KW - BEHAVIOR
U2 - 10.1080/02678292.2010.488818
DO - 10.1080/02678292.2010.488818
M3 - Journal article
VL - 37
SP - 949
EP - 959
JO - Liquid Crystals
JF - Liquid Crystals
SN - 0267-8292
IS - 6-7
M1 - 923874813
ER -