The acoustic and dielectric relaxations have been studied for liquid crystal phases with different types of symmetry.
The temperature dependences of ultrasonic velocity and absorption factor have been obtained in the frequency
interval 0.3 – 47 MHz and those of the dielectric constant in the interval 1 kHz – 2 MHz. The temperature dependence
of the rotational viscosity coefficient in the nematic phase has been obtained. The polarization relaxation time
has been calculated on the basis of a classical Debye model. It has been found that acoustic and dielectric relaxations
in the nematic phase can be described by similar molecular mechanisms. These mechanisms have been shown to be
essentially different in smectic phases.
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