| | 1 | Author
| M. Sandmann, F. Hamann, A. Würflinger | Requires cookie* | | | Title
| PVT and DTA Measurements on trans-4-w-Hexyl- (4'-CyanophenyI)-Cyclohexane (6PCH) up to 300 MPa  | | | | Abstract
| The phase diagram of trans-4-n-hexyl-(4'-cyanophenyl)-cyclohexane, (6PCH) has been estab-lished by high-pressure differential thermal analysis. Specific volumes are presented for temper-atures between 300 and 370 K up to 300 MPa. The p,V m ,T data have been determined for the nematic, isotropic, and (partly, in the neighbourhood to the melting curve) solid phases. Volume and enthalpy changes along the phase transitions have also been calculated. As previously, the p,Vm,T data were used to calculate the volume entropy for the nematic-isotropic transition. The molar volumes along the clearing line T NI (p) enabled us to calculate the molecular field parameter 7 = ain T NI /3ln V NI , being 4.1. | | | |
Reference
| Z. Naturforsch. 54a, 281—286 (1999); received March 13 1999 | | | |
Published
| 1999 | | | |
Keywords
| 6PCH, High Pressure, pVT, Phase Transitions, Thermodynamics | | | |
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| default:Reihe_A/54/ZNA-1999-54a-0281.pdf | | | | Identifier
| ZNA-1999-54a-0281 | | | | Volume
| 54 | |
| 2 | Author
| Phineus Markwick, Stanislaw Urban, Albert Würflinger | Requires cookie* | | | Title
| High Pressure Dielectric Studies of 8CB in the Isotropic, Nematic, and Smectic A Phases | | | | Abstract
| The static and complex permittivity of 4-n-octyl-4'-cyanobiphenyl (8CB) has been measured for the isotropic, nematic and smectic A phases as functions of temperature and pressure. The ranges of 297 -361 K, 0.1 -220 MPa, and 0.1 -13 MHz, were covered. Only the parallel component of the complex permittivity, £*(/) = e'(f) — ie"(f), was measured. The relaxation times T||(p, T) as well as ris(p, T) were analysed at constant temperature, pressure and volumes yielding the activation volume, A ¥ V(T), activation enthalpy A^H(p), and activation energy lyU(V), respectively. All activation parameters calculated for the smectic A phase of 8CB are smaller than those obtained for the nematic phase. The activation energy constitutes approximately half of the activation enthalpy value in all three phases studied. The pressure study allowed to calculate the pressure dependence of the retardation factor g\\(p, T), from which the nematic potential q(p,T) can be derived. Using the relationships between g\\ and q/RT proposed by Kalmykov and Coffey, the order parameter (Piip, T)) was calculated as a function of pressure. | | | |
Reference
| Z. Naturforsch. 54a, 275—280 (1999); received March 13 1999 | | | |
Published
| 1999 | | | |
Keywords
| Liquid Crystals, 8CB, High Pressure, Dielectric, Thermodynamics, Order Parameter | | | |
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| default:Reihe_A/54/ZNA-1999-54a-0275.pdf | | | | Identifier
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| 54 | |
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