Dielectric Studies of Monoester and Diester Nematogens

  • M. F. Bone
  • A. H. Price
  • M. G. Clark
  • D. G. McDonnell


The permittivities of several monoester nematogens have been studied in the nematic and isotropic phases at frequencies up to 18 GHz. The dielectric relaxations observed in the nematic phase are in agreement with theoretical predictions for a rigid nematogen. Values for the nematic order parameter and the angle between the “long axis” of the molecule and its electric dipole are estimated from the data, and the definition of the “long axis” in the molecular theory of nematics is discussed. Two distinct relaxation frequencies are observed in the isotropic phase of substituted phenyl benzoates, probably due to anisotropic rotational molecular diffusion indicative of residual nematic-like short-range order. This interpretation is supported by quantitative comparison with nematic phase data, and by data on a benzene solution and the non-nematic phenyl benzoate parent. Data on cyclohexane carboxylate esters reveals interesting similarities and contrasts with the benzoate esters. Recent developments in liquid crystal materials for two-frequency addressed devices are considered in the context of the data on monoesters together with studies of dielectric relaxation in monoester/diester mixtures.


Dielectric Relaxation Nematic Phase Isotropic Phase Rotational Diffusion Dielectric Anisotropy 
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Copyright information

© Plenum Press, New York 1984

Authors and Affiliations

  • M. F. Bone
    • 1
  • A. H. Price
    • 1
  • M. G. Clark
    • 2
  • D. G. McDonnell
    • 2
  1. 1.Edward Davies Chemical LaboratoriesUniversity College of WalesAberystwythUK
  2. 2.Royal Signals and Radar EstablishmentMalvern WorcestershireUK

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