Dielectric relaxation behaviour of liquid crystals with opposite orientation of -COO ester group in molecular core

• Autorzy: Rutkowska, J. , Perkowski, P. , Piecek, W. , Raszewski, Z. , Kędzierski, J.
• Konferencja: Thw 17th Conference on Liquid Crystals : Chemistry Physics and Applications ; (17 ; 09.2007 ; Augustów, Poland)
• Języki publikacji: EN

Abstrakty

EN

Dielectric measurements were performed for two smectogens, being structurally analogous with the opposite space orientation of the -COO ester group in the molecular core, using a HP4192A impedance analyser. Gold coated electrode cells of different thicknesses were used. Temperature dependences of the relaxation frequency f_R and the inverse of the dielectric strength Δ ε '⊥⁻¹ obtained by fitting experimental values of perpendicular components, i.e., the real ε '⊥ and the imaginary ε "⊥ parts of the complex dielectric permittivity to the Cole-Cole equation as well as the investigation of modification of relaxation processes under bias were determined for the SmC*, SmA*, and N* phases of studied compounds. One can conclude, on the basis of the above results, that dielectric relaxation processes observed by us in the studied compounds are similar to those of the soft and Goldstone mode typically observed by others in the SmC*, SmA*, and N* phases. It is concluded from a comparison of their properties with other related compounds that the link between the biphenyl moiety and –COO ester group is closely related to the stability of smectic phases.

Słowa kluczowe

EN

ferroelectrics liquid crystals; dielectric relaxation; Goldstone mode; soft mode

• Czasopismo: Opto-Electronics Review
• Rocznik: 2008
• Tom: Vol. 16, No. 3
• Strony: 262-266
• Opis fizyczny: Bibliogr. 8 poz., wykr.

Twórcy

autor

Rutkowska, J.

autor

Perkowski, P.

autor

Piecek, W.

autor

Raszewski, Z.

autor

Kędzierski, J.

• Institute of Applied Physics, Military University of Technology, 2 Kaliskiego Str., 00-908 Warsaw, Poland,

Bibliografia

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• 4. F. Gouda, K. Skarp, and S.T. Lagerwall, “Dielectric studies of the soft mode and Goldstone mode in ferroelectric liquid crystals”, Ferroelectrics 113, 165-206 (1991).
• 5. S. Hiller, A.M. Biradar, S. Wróbel, and W. Hasse, “Dielectric behaviour at the smectic C*-chiral nematic phase transition of a ferroelectric liquid crystal”, Phys. Rev. E53, 641-649 (1996).
• 6. J. Hmine, C. Legrand, N. Isaert, and H.T. Nguyen, “Dielectric evidence of an electroclinic effect in the cholesteric phase near an N*-SmA-SmC* multicritical point”, Liq. Cryst. 30, 227-234 (2003)
• 7. J. Hemine, C. Legrand, A. Daoudi, N. Isaert, and H.T. Nguyen, “Influence of the proximity of an N*-SmA-SmC* multicritical point on the electronic effect in the cholesteric phase”, Liq. Cryst. 34, 241-249 (2007).
• 8. S. Kurogoshi and K. Hori, “The effects of the bulkiness of terminal chains on the stability os smectics deduced from the crystal structures of isomeric chiral bihpenyl esters”, Liq. Cryst. 23, 127-136 (1997).