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

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 - 2010/6

Y1 - 2010/6

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

UR - http://www.scopus.com/inward/record.url?scp=77954255413&partnerID=8YFLogxK

U2 - 10.1080/02678292.2010.488818

DO - 10.1080/02678292.2010.488818

M3 - Article

SN - 0267-8292

VL - 37

SP - 949

EP - 959

JO - LIQUID CRYSTALS

JF - LIQUID CRYSTALS

IS - 6-7

ER -