Abstract
Dielectric spectra for the SmA and SmC phases of a room temperature ferroelectric liquid crystalline mixture FELIX-008 have been studied in the frequency range from a few Hz to 13 MHz. It has been found that in the vicinity of the SmA-SmC transition there is a pronounced soft mode dielectric spectrum, the dielectric parameters of which obey a Curie-Weiss law given by the mean-field theory. In the SmC phase a distinguished Debye-type dielectric spectrum of the Goldstone mode has been detected, and upon increasing the bias field to 35 V it is suppressed and a new non-Debye-type dielectric spectrum-originating most probably from the so-called domain mode-shows up. Spontaneous polarization and tilt angle measurements show that the transition SmA-SmC is of the second order type. The dielectric and electro optic studies make it possible to compute the rotational viscosity, which is of great importance for practical applications. It turns out that the energy barrier for rotational viscosity (19.6 kJ/mol) is comparable with the energy barriers found for the reorientational motion of molecules around the long axes in many liquid crystalline phases. This allows one to suggest that in the SmC phases there is a strong coupling between the molecular precession around the cone and the reorientation around the long molecular axis.
Original language | English |
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Pages (from-to) | 211-222 |
Number of pages | 12 |
Journal | Ferroelectrics |
Volume | 166 |
Issue number | 1 |
DOIs | |
State | Published - 1 Apr 1995 |
Keywords
- Ferroelectric mixture
- Goldstone mode
- rotational viscosity
- soft mode
- spontaneous polarization
- tilt angle