Dielectric Properties of Liquid Crystalline Isothiocyanato-tolane Derivatives with Fluorine Atom at Various Lateral Positions

J. Czuba, S. Urbana, R. Dąbrowskib and B. Gestblomc aInstitute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland bInstitute of Chemistry, Military University of Technology, Kaliskiego 2, 00-908 Warsaw, Poland cInstitute of Physics, Uppsala University, Uppsala, Sweden

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Received: 12 01 2005;

Dielectric studies were performed for several isothiocyanato-tolane compounds having the F atom attached to the benzene rings at different lateral positions and the alkoxy or alkyl chain at the p-position. They form the nematic phase in broad temperature intervals. The static as well as dynamic properties of the compounds in the nematic and isotropic phases were studied. Tensor permittivity components: εǁ, ε⊥, Δε, as functions of temperature were measured. The complex dielectric permittivity, ε*(f)=ε'(f)-iε''(f), was measured in the frequency range of 1 kHz - 3 GHz from which the relaxation times τǁ and τ⊥ were calculated. The order parameter S(T) was determined from the dielectric data. It was found that the close vicinity of the F atom and the alkoxy group results in blocking of the internal rotation of the wing around the O-phenyl bond.

DOI: 10.12693/APhysPolA.107.947 PACS numbers:64.70.Md, 77.22.Gm, 77.84.Nh