Dielectric properties of three‐ring fluorinated compounds

Abstract

Four three‐ring compounds, consisting of two cyclohexyl rings and one mono‐ or difluorinated phenyl ring, were studied using dielectric spectroscopy methods over a broad frequency range (1 kHz–3 GHz). They exhibit a nematic phase in a broad temperature interval, enriched by a smectic B phase in one case. The static and dynamic dielectric properties were analysed. It was established that the bridging CH₂CH₂ group placed between cyclohexyl and phenyl rings considerably changes the reference frame of the molecule, unlike the situation when it links two cyclohexyl rings. In the nematic and smectic B phases the motion around the short axis is a Debye process, whereas the rotation around the long axis is split into two processes: independent rotation of the whole molecule and its fluorophenyl part.

Keywords:

• nematic phase
• dielectric anisotropy
• relaxation time
• dipole moment
• three‐ring compound