Thermodynamic measurements on selected liquid crystals at normal and elevated pressures

Densities have been determined for two 5-n-alkyl-2-(4-isothiocyanatophenyl) -1,3-dioxanes (6DBT, 10DBT), 4-n-tetradecyl-4'-cyanobiphenyl (14CB), 4-n-oc tyl-4'-thiocyanatobiphenyl (8BT) and two laterally aryl-branched mesogens 4 -cyanobenzyl 5-(4-n-octyloxybenzoyloxy)-2-undecyloxybenzoate (4CNOUB), 3-cy anobenzyl 2,5-bis(4-n-octyloxybenzoyloxy)benzoate (3CNBOB). The densities h ave been measured in the isotropic, nematic (only 3CNBOB) and smectic phase s with a vibrating tube densimeter. The densities decrease with increasing alkyl chain length within a homologous series. Furthermore the enthalpy cha nges accompanying the phase transitions have been determined by DSC.