| | 1 | Author
| Stanislaw Urban, Albert Wiirflinger3 | Requires 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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| default:Reihe_A/56/ZNA-2001-56a-0489.pdf | | | | Identifier
| ZNA-2001-56a-0489 | | | | Volume
| 56 | |
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