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Abstract
Broad band dielectric spectroscopy, DTA calorimetry and polarizing microscopy have been used to study smectic polymorphysim and molecular dynamics of a well known ferroelectric material DOBAMBC and of fluorinated substance 3-(3-Flunoryo-nonyl)-6[4-Heptyloxyphenyl]-Pyridine (in short FNHPh-P). Both materials exhibit rich polymorphism and highly ordered phases. The SmG* phase of FNHPhP is ferroelectric with distincly longer switching times than those observed for the SmC* phase. High frequency dielectric measurements of DOBAMBC have been performed in GHz range for the first time as far as we know. The high frequency relaxation which is connected with the reorientation of molecules around their long axes has been detected in ferroelectric SmC* phases and also in highly ordered phases of both substances. The spectrum of critical frequencies is presented for both materials; for DOBAMBC the literature data were used as far as tlie radio frequency range is concerned. The spectrum is tlisscused in terms of theoretical models.