At the borderline between "classic" and B phases

Dielectric results of three bent shaped compounds are presented. An increase of the static dielectric constant in the isotropic phase by approaching the I-B2 transition is seen in the first sample. The second sample shows the polymorphism I-SmA-SmC-B2. Down to the SmC phase only the reorientation about the long molecular axis without a step in the relaxation time is observed. In the B2 phase an additional low frequency relaxation is detected resulting from the antiferroelectric structure. The interesting feature is the increase of the dielectric increment (Delta) 2 of the high frequency mechanism with decreasing temperature: Starting from about 2.5 in the SmA phase (Delta) 2 increases continuously and reaches at the transition into the B2 phase values of about 40. This result points to the step by step increase of the ferroelectric short range order within the SmA and specially the SmC phases. The last sample confirms this result for the polymorphism I-SmA-CPA, with one exception the low frequency process is missing.