PVT MEASUREMENTS ON 4'-N-HEXYL-BIPHENYL-4-CARBONITRILE (6CB) AND 4'-N-HEPTYL-BIPHENYL-4-CARBONITRILE (7CB) UP TO 300 MPA

P, V-m, T data were established for 4'-n-hexyl-biphenyl-4-carbonitrile (6CB) and 4'-n-heptyl-biphenyl-4-carbonitrile (7CB) between 300 and 3 70 K up to 300 MPa, and specific volumes were determined for the liqui d crystalline, isotropic, and also partly for the crystal phases. Volu me and enthalpy chang es at the phase transitions are also presented. In the case of 6CB, a new crystal phase has been detected, correspondi ng to a triple point at 338 K and 196 MPa. The p, V-m, T data enabled us to separate the entropy change into a volume-dependent part and con figurational part. From the molar volumes along the nematic-isotropic phase transition T-NI(p), the molecular field parameter gamma = delta lnT(NI)/delta lnV(NI) was determined.