PVT MEASUREMENTS ON 4-N-PENTYL-4'-CYANO-BIPHENYL (5CB) AND TRANS-4-(4'-OCTYL-CYCLOHEXYL)-BENZONITRILE (8PCH) UP TO 300 MPA

Specific volumes are presented for 4-n-pentyl-4'-cyanobiphenyl (5CB) a nd trans-4-(4'-octyl-cyclo-hexyl)-benzonitrile (8PCH) for temperatures between 300 and 370 K up to 300 MPa. The p,V-m,T data were determined for the liquid crystalline and isotropic phases, and partly also for the solid phase adjacent to the melting curve. Stable and metastable c rystal phases can be distinguished. The density and melting temperatur e of the metastable form are lower than for the stable one. Volume and enthalpy changes accompanying the phase transitions are reported as w ell. The p, V-m, T data allow to calculate the entropy change for a hy pothetical transition at constant volume. The molar volumes along the nematic-isotropic phase transition T-NI(p) allow to determine the mole cular field parameter gamma = partial derivative ln T-NI/partial deriv ative ln V-NI.