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1995 (1)
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1Author    I. D. Ierking1, F. G. Ießelm Ann1, P. Zugenm, H. R2, H. Z. Aschke2, W. Kuczynski3Requires cookie*
 Title    The Origin of the Helical Twist Inversion in Single Component Cholesteric Liquid Crystals  
 Abstract    The cholesteric twist inversion by temperature variation o f a single com ponent thermotropic liquid crystalline system was experimentally investigated and is explained by the partial twisting power model, evaluating the temperature dependent pitch o f five different configurations of a benzoic acid biphenyl ester with two chiral centers. The temperature dependence o f the twisting power and the cholesteric pitch for several stereoisomeric com pounds can in first approximation be predicted by the partial twisting powers of the individual chiral centers determined from the partially racemic configurations. 
  Reference    Z. Naturforsch. 49a, 1081—1086 (1994); received August 12 1994 
  Published    1994 
  Keywords    Liquid crystal, Chirality, Cholesteric mesophase, Twist inversion 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-1081.pdf 
 Identifier    ZNA-1994-49a-1081 
 Volume    49 
2Author    Ingo Dierking, Frank Gießelmann, Peter ZugenmaierRequires cookie*
 Title     
 Abstract    n O p tic a l M e th o d f o r th e D e te r m in a tio n o f th e C h o le s te r ic P itc h in L iq u id C r y s ta ls Preparation of a cholesteric liquid crystalline phase in planar orienting liquid crystal cells exhibits discontinuous colour changes with temperature when viewed between crossed polarizers. The trans­ mission spectra of such a system can be described by a modified de Vries equation, with the bire­ fringence dispersion included in a simplified single-band model. With a suitable choice of the cell gap as compared to the cholesteric pitch, the procedure can be used as a new method to determine the temperature dependence of the cholesteric pitch. 
  Reference    Z. Naturforsch. 50a, 589—594 (1995); received December 17 1994 
  Published    1995 
  Keywords    Liquid crystal, cholesteric mesophase, pitch determination, birefringence dispersion, twist inversion 
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 TEI-XML for    default:Reihe_A/50/ZNA-1995-50a-0589.pdf 
 Identifier    ZNA-1995-50a-0589 
 Volume    50