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14N Nuclear Quadrupole Resonance Dips in the Proton Relaxation Dispersion of Nematic and Smectic Liquid Crystals

  • D. J. Pusiol
  • R. Humpfer
  • F. Noack
Conference paper

Abstract

The 14N quadrupolar coupling constant K and the asymmetry parameter η of the nitrogen sites in some nematic and smectic liquid crystals (alkyloxy-azoxybenzenes, cyano-biphenyls, oxycyano-biphenyls) have been studied by means of the Larmor frequency dependence of the proton spin relaxation time T1, which reveals the presence and asymmetry of nitrogen bonds by small dips in the 1H relaxation dispersion profile. Both the steady temperature dependences of K and η within the mesophase ranges, as well as the strong discontinuities of these parameters at, phase transitions, can be interpreted by changes of the anisotropic molecular rotations. It is found that the temperature effects are significantly more pronounced for the biaxial smectic-C phase of the heptyloxy-azoxybenzene compound (HpAB) than for the uniaxial smectic-A phase of the Investigated biphenyls (8CB, 9CB, 90CB, 11CB), and also compared with the results obtained for these biphenyls and some azoxybenzenes (PAA, BAB, HAB, HpAB) in the nematic state.

References

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Copyright information

© Springer-Verlag Berlin Heidelberg 1990

Authors and Affiliations

  • D. J. Pusiol
    • 1
  • R. Humpfer
    • 2
  • F. Noack
    • 2
  1. 1.FAMAF, Universidad Nacional de CórdobaCórdobaArgentina
  2. 2.Physikalisches InstitutUniversität StuttgartStuttgartGermany

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