Dielectric characterization of B3 and B4 phases

Dielectric measurements on two samples formed from banana-shaped molecules with terminal alkyl or alkyloxy groups were carried out in a frequency range between 10-3 Hz and 10 MHz. Both samples exhibit B2 and B3 phases; one of them has a B4 state as well. As usual, two ranges of relaxation were detected in the B2 phase, the fast reorientation about the long axes of the molecules and a slow collective process. Only one dielectrically active low frequency process could be separated in the B3 and B4 phases; this is probably related to the dynamics of superstructures. The high frequency limit of the dielectric constants gives a hint that neither phase is a classical solid. A quite strong increase in the conductivity at the transition into the B3 phase is critically discussed.