Permittivity of liquid crystals of the alkylcyanobiphenyl group in a decimeter wavelength range

The high-frequency dielectric spectra of liquid crystals of the alkylcyanobiphenyl group with various length of the mobile alkyl chain C_nH_2n+1 (n=5–8) are experimentally studied. It is established that a resonance feature is observed in the frequency range of 300 MHz for all the crystals on the high-frequency branch of the orientational part of dielectric spectra. It is shown that the position of the dielectric resonance is virtually independent of the temperature and the degree of crystal dilution by benzene, but its intensity essentially depends on both factors. The nature of the dielectric resonance found is probably caused by the intramolecular motion of methylene fragments, which are strongly bound with a rigid core of molecules.