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The Determination of Moments of the Orientational Distribution Function in Liquid Crystals by the Depolarization of Fluorescence of Probe Molecules

  • L. Lawrence Chapoy
  • Donald B. DuPré
  • Edward T. Samulski

Abstract

The approach to the mathematical formulation of the distribution function that describes long range orientational ordering of molecules in liquid crystals is necessarily an approximation. Some workers propose model forms with one or more adjustable parameters used to fit data of some experimental property sensitive to an average over this unattainable function. These attempts are open to criticism of the reasonableness and uniqueness of the chosen form of the approximation. An alternative procedure, which is mathematically rigorous and unambiguous, is to write the function as a truncated series expansion whose coefficients are experimentally determinable moments of the real distribution. This method is usually limited by the availability of only the second moment. Raman (1–4), electron spin resonance (5), and fluorescent emission spectroscopy (1,2) are capable of supplying both the second and fourth moments, hence extending the expansion and making it a more fiithful representation of the real distribution. The fluorescence technique, however, has inherent complications in that there is usually a significant delay (1–10 nsec) between the absorption and emission process and emitted radiation may emanate polarized along a different axis in the excited molecule.

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References

  1. 1.
    D. I. Bower, J. Poly. Sci. Poly. Phys. Ed. 10 2135 (1972).Google Scholar
  2. 2.
    D. I. Bower, Structure and Properties of Oriented Polymers, I. M. Ward, Ed., Applied Science Publ. Ltd. London 1975. Chapter 5.Google Scholar
  3. 3.
    E. B. Priestley and P. S. Pershan, Mol. Cryst. Liq. Cryst. 23 369 (1973).CrossRefGoogle Scholar
  4. 4.
    S. Jen, N. A. Clark, P. S. Pershan and E. B. Priestley, Phys. Rev. Lett. 31 1552 (1973).CrossRefGoogle Scholar
  5. 5.
    G. R. Luckhurst and R. Poupko, Chem. Phys. Letters 29 191 (1974).CrossRefGoogle Scholar
  6. 6.
    L. L. Chapoy and D. B. DuPré, to be published.Google Scholar
  7. 7.
    A. C. Albrecht, J. Mol. Spectry. 6 84 (1961).CrossRefGoogle Scholar
  8. 8.
    J. R. Lombardi, J. W. Raymonda, and A. C. Albrecht, J. Chem. Phys. 40 1148 (1964).CrossRefGoogle Scholar
  9. 9.
    C. R. Desper and I. Kimura, J. Chem. Phys. 38. 4225 (1967).Google Scholar
  10. 10.
    S. Nomura, H. Kawai, I. Kimura, and M. Kagiyama, J. Poly. Sci. A-2 8 383 (1970).Google Scholar
  11. 11.
    E. B. Priestley, P. J. Wojtowicz, and P. Sheng, Eds., Introduction to Liquid Crystals, Plenum Press, New York, 1975 pp. 72.Google Scholar
  12. 12.
    A. Saupe, Z. Naturforsch. 19a 161 (1964); Angew. Chem. Int. Ed. 61 947 (1974).Google Scholar
  13. 13.
    Y. Nishijma, J. Poly. Sci. PtC. 37 353 (1970).Google Scholar
  14. 14.
    G. Weber, “Polarization of the Fluorescence of Solutions”, chapter 8 in Fluorescence and Phosphorescence Analysis, Interscience Publ. New York 1966.Google Scholar
  15. 15.
    K. A. Valiew and L. D. Eskin, Optics and Spectroscopy 12 429 (1962). (English Transl.).Google Scholar
  16. 17.
    F. Perrin, J. Phys. 1 390 (1926).Google Scholar
  17. 18.
    G. Baur, A. Stieb, and G. Meier, Mol. Cryst. Liq. Cryst. 22 261 (1973).CrossRefGoogle Scholar
  18. 19.
    G. R. Luckhurst and R. N. Yeats, Mol. Cryst. Liq. Cryst. Letters, 34, 57 (1976).CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1978

Authors and Affiliations

  • L. Lawrence Chapoy
    • 1
  • Donald B. DuPré
    • 2
  • Edward T. Samulski
    • 3
  1. 1.Instituttet for KemiindustriThe Technical University of DenmarkLyngbyDenmark
  2. 2.Department of ChemistryUniversity of LouisvilleLouisvilleUSA
  3. 3.Department of Chemistry and Institute of Materials ScienceUniversity of ConnecticutStorrsUSA

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