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Dielectric and Conductivity Anisotropy in Liquid Crystalline Phases of Strongly Polar Thioesters

100%

Mikułko A., Fraś M., Marzec M., Wróbel S., Ossowska-Chruściel M., Chruściel J.

Acta Physica Polonica A

2008

vol. 113

issue 4

1155-1160

The main objective of this paper is to study dielectric properties of two compounds of acronyms 5OSCl and 6OSCl having strongly polar bond (C-Cl) at para position. Dielectric measurements were done in the frequency range from 40 Hz to 15 MHz. The dielectric spectra were measured for two principal alignments. For homeotropic alignment, the reorientation of molecule around the short molecular axis was observed. Both substances studied exhibit large positive dielectric anisotropy and the anisotropy of conductivity was obtained in smectic A as well as nematic phase.

Dielectric and Electrooptic Investigations of B Phases οf Banana-Shaped Thioesters

84%

Wierzejska-Adamowicz M., Ossowska-Chruściel D., Chruściel J., Douali R., Legrand C., Marzec M., Mikułko A., Sikorska A., Wróbel S.

Acta Physica Polonica A

2010

vol. 117

issue 4

557-561

Electrooptic and dielectric measurements were done for B phases of two banana-shaped homologues 1,3-phenylene bis{4-[(4-nonylo-xy-benzoyl)sulfanyl]benzoate (9OSOR) and 1,3-phenylene bis{4-[(4-dodecylo-xy-benzoyl)sulfanyl]benzoate (12OSOR). Polarizing microscopy allowed to identify B_{1} phase for 9OSOR and B_{2} phase for 12OSOR on the basis of texture observation. Spontaneous polarization measurements were performed using reversal current method. The current response to applied triangular voltage shows that B_{1} phase is a ferroelectric and B_{2} phase - antiferroelectric one for which two well separated peaks were observed. Polarization for phase B_{1} of 9OSOR is rather small and its temperature dependence is unusual for ferroelectric liquid crystals - it increases with temperature. Spontaneous polarization for B_{2} phase of 12OSOR compound is of about 600 nC/cm^{2}. Dielectric spectra measured with bias field for B_{2} phase of 12OSOR show two well separated relaxation processes. In the low frequency range the relaxation process is connected with fluctuations of ferroelectric domains. The relaxation process in the high frequency range appearing also without bias field is connected with molecular reorientation. The dielectric spectra measured for B_{1} phase of 9OSOR with and without bias voltage showed only one dielectric relaxation process connected with molecular reorientation around the short axis.

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2 Acta Physica Polonica A

1 2010

1 2008

2 Chruściel J.

2 Marzec M.

2 Mikułko A.

2 Wróbel S.

1 Douali R.

1 Fraś M.

1 Legrand C.

1 Ossowska-Chruściel D.

1 Ossowska-Chruściel M.

1 Sikorska A.

1 Wierzejska-Adamowicz M.

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Dielectric and Conductivity Anisotropy in Liquid Crystalline Phases of Strongly Polar Thioesters

Dielectric and Electrooptic Investigations of B Phases οf Banana-Shaped Thioesters