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2001 (1)
1Author    Stanislaw Urban, Albert Wiirflinger3Requires cookie*
 Title    DTA and Dielectric Studies under Pressure of a Smectogen Substance with a Strong Perpendicular Dipole Moment  
 Abstract    The phase diagram of a substance with two CN groups attached to the benzene ring at lateral posi­ tions (CNCN) has been obtained with differential thermal analysis (DTA). The pressure range of the smectic A phase is limited, resulting in a triple point (Cr, SA, L) at 135 MPa and 371 K. However, the SA-phase exists also above the triple point as a metastable phase. The transverse relaxation times rx were obtained from the dielectric spectra measured for several isotherms as a function of pressure with­ in the SA-phase of CNCN. The activation volume, A#Vj_ = RT (d In = (52 ± 3) cm3/mol is larg­ er than A Vj|, recently derived from the pressure dependence of the longitudinal relaxation times for other substances in the SA-phase. It is concluded that due to steric hindrances made by the cyano groups the molecular rotations around the long axes become strongly slowed down by pressure and the smec­ tic phase disappears 
  Reference    Z. Naturforsch. 56a, 489—4 (2001); received April 23 2001 
  Published    2001 
  Keywords    Liquid Crystals, Smectic A, DTA, Phase Diagram, Dielectric Relaxation, High Pressure 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0489.pdf 
 Identifier    ZNA-2001-56a-0489 
 Volume    56