Small Angle X-Ray Studies of Liquid Crystal Phase Transitions II. Surface, Impurity and Electric Field Effects

  • C. C. Gravatt
  • G. W. Brady
Conference paper


Phase transitions in nematic and cholesteric liquid forming materials have been investigated by small angle X-ray scattering. Measurements were performed on p-azoxyanisole in the isotropic and nematic liquid regions and on cholesteryl bromide in the isotropic and cholesteric liquid regions. For p-azoxyanisole premonitory phenomena have been observed in the isotropic liquid at temperatures considerably above the isotropic-nematic transition. These phenomena, which are indicative of ordering in the isotropic liquid, are strongly dependent upon sample purity, and are not evident in the purest materials. D.C. electric fields have also been found to induce ordering in the isotropic liquid. It was not possible to observe any similar ordering effects, or to detect the isotropic-cholesteric transition, in cholesteryl bromide by small angle X-ray scattering.

We have previously reported on results of a small angle X-ray study of the isotropic-nematic phase transition in p-azoxyanisole.(1) Before going into a discussion of the present experiments it is well to summarize our earlier findings and indicate some of the questions that required further investigation.


Liquid Crystal Pure Material Liquid Region Impurity Effect Electric Field Effect 
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  1. 1.
    C. C. Gravatt and G. W. Brady, Molecular Crystals and Liquid Crystals, 7, 355 (1969).CrossRefGoogle Scholar
  2. 2.
    J. G. Chistyakov, Soviet Physics Uspetki, 2, 551 (1967).CrossRefGoogle Scholar
  3. 3.
    J. Frenkel, Kinetic Theory of Liquids, Dover Publications (New York, 1956 ).Google Scholar
  4. 4.
    C. C. Gravatt and G. W. Brady, J. Appl. Cryst., in press.Google Scholar
  5. 5.
    C. C. Gravatt, G. W. Brady and J. L. Lundberg, Rev. Sci. Inst., 32, 1701 (1968).CrossRefGoogle Scholar
  6. 6.
    G. W. Gray, Molecular Structure and the Properties of Liquid Crystals, (Academic Press, New York, 1962 ), Chapter IV.Google Scholar

Copyright information

© Plenum Press, New York 1970

Authors and Affiliations

  • C. C. Gravatt
    • 1
  • G. W. Brady
    • 1
  1. 1.Bell Telephone Laboratories, Inc.Murray HillUSA

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