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'liquid crystals' in keywords Facet   section ZfN Section A  [X]
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1Author    K. H. Schweikert, F. NoackRequires cookie*
 Abstract    The frequency dependence of the longitudinal proton spin relaxation time Tx was measured by field-cycling and standard NMR techniques in the nematic, smectic and reentrant nematic mesophases of the reentrant liquid crystal 6OCB-8OCB. The results clearly demonstrate that, in contrast to conclusions reported in the literature, the underlying relaxation mechanisms are the same for the nematic and reentrant nematic order, but different in the nematic and smectic phase. In particular, at low frequencies the nematic and reentrant samples reveal a square-root dispersion profile (T, ~ v1 2) characteristic for nematic director fluctuations, whereas the smectic samples show a dissimilar and only very narrow dispersion step. It can be attributed to a linear relaxation time increase (Tx ~ v1) expected for smectic-type order fluctuations. The experimental data are described and discussed in terms of four molecular processes, namely nematic or smectic order fluctuations, self-diffusion, rotational motions, and a resonant proton nitrogen coupling. 
  Reference    Z. Naturforsch. 44a, 597 (1989); received April 19 1989 
  Published    1989 
  Keywords    Spin relaxation Field-cycling, Liquid crystals, Reentrant nematic 
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 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0597.pdf 
 Identifier    ZNA-1989-44a-0597 
 Volume    44