Dielectric characterization of B-3 and B-4 phases

Dielectric measurements on two samples formed from banana-shaped molecules with terminal alkyl or alkyloxy groups were carried out in a frequency rang e between 10(-3) Hz and 10 MHz. Both samples exhibit B-2 and B-3 phases; on e of them has a B-4 state as well. As usual, two ranges of relaxation were detected in the B-2 phase, the fast reorientation about the long axes of th e molecules and a slow collective process. Only one dielectrically active l ow frequency process could be separated in the B-3 and B-4 phases; this is probably related to the dynamics of superstructures. The high frequency lim it of the dielectric constants gives a hint that neither phase is a classic al solid. A quite strong increase in the conductivity at the transition int o the B-3 phase is critically discussed.