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1

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

100%

Czub J., Urban S., Dąbrowski R., Gestblom B.

Acta Physica Polonica A

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2005

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vol. 107

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issue 6

947-958

EN

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: ε_ǁ, 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 τ_ǁ 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.

2

Dielectric and X-ray Studies of Eleventh and Twelfth Members of Two Isothiocyanato Mesogenic Compounds

100%

Jasiurkowska M., Budziak A., Czub J., Urban S.

Acta Physica Polonica A

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2006

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vol. 110

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issue 6

795-805

EN

Results of the dielectric and X-ray studies of the long-alkyl-chain members (n=11, 12) of two homologous series: nBT (4-n-alkyl-4'-isothiocyanato-biphenyl) and nCHBT (4-trans-4'-n-alkyl-cyclohexyl-isothiocyanato-benzene) in their liquid crystalline phases are presented. These compounds exhibit different polymorphisms: the nematic phase for $n$CHBTs and the smectic E and smectic A phases for nBTs. The dielectric measurements were performed in a wide frequency range of 1 kHz-3 GHz. The layer thickness in the smectic E and smectic A phases and the orthorhombic unit cell parameters of the smectic E phase were determined using the small angle X-ray diffraction method. In the smectic E phase the layer-thickness-to-molecular-length ratios are found to be close to 1. The corresponding ratios observed for the smectic A phase of $n$BTs are considerably higher (≈1.24), which indicates that an alternating head-to-tail arrangement of molecules in the layers is favored. The rotational dynamics of molecules in the smectic E phases is discussed in relation to their packing in a unit cell.

3

Molecular Dynamics of n-p-(Ethoxybenzylidene) P'-Propylaniline in Nematic and Solid Phases as Studied by Dielectric Relaxation Spectroscopy

100%

Bąk A., Massalska-Arodź M., Urban S.

Acta Physica Polonica A

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2000

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vol. 97

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issue 2

323-330

EN

The complex dielectric permittivity ε*(ν,T) = ε'(ν,T) - iε''(ν,T) of n-p-(ethoxybenzylidene) p'-propylaniline has been measured in the frequency range from 1 Hz to 13 MHz and temperature range from 360 K to 180 K on heating and on cooling the sample. Dielectric relaxations have been found in nematic and solid phases. A detailed analysis of the observed processes has been performed and the parameters describing molecular dynamics have been evaluated. The comparison of results with those obtained for the other Schiff bases is discussed.

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3 Acta Physica Polonica A

1 2006

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1 2000

3 Urban S.

2 Czub J.

1 Budziak A.

1 Bąk A.

1 Dąbrowski R.

1 Gestblom B.

1 Jasiurkowska M.

1 Massalska-Arodź M.

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

Dielectric and X-ray Studies of Eleventh and Twelfth Members of Two Isothiocyanato Mesogenic Compounds

Molecular Dynamics of n-p-(Ethoxybenzylidene) P'-Propylaniline in Nematic and Solid Phases as Studied by Dielectric Relaxation Spectroscopy