DIELECTRIC STUDIES OF LIQUID-CRYSTALS UNDER HIGH-PRESSURE .4. STATIS PERMITTIVITY AND LOW-FREQUENCY RELAXATION PROCESS IN 4-N-HEXYL-4'-CYANOBIPHENYL (6CB)

Dielectric studies of 4-n-hexyl-4'-cyanobiphenyl (6CB) were performed in the pressure range 0.1-150 M Pa, the frequency range 1 kHz-13 MHz a nd the temperature range 290-327 K. The temperature and pressure depen dencies of the static permittivity epsilon0 parallel-to and the relaxa tion time tau(parallel-to) are analysed and compared with analogous da ta obtained recently for 5CB and 6CHBT (parts I-III of this series). I t was shown that in the nematic phases of both 4-n-alkyl-4'-cyanobiphe nyls the dipole-dipole correlations are broken by relatively low press ure.