Thermal analysis and X-ray studies of chiral ferroelectric liquid crystalline materials and their binary mixtures |
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Authors: | Dusanka Ž Obadović Anikó Vajda Maya Garić A Bubnov Vera Hamplová M Kašpar Katalin Fodor-Csorba |
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Institution: | (1) Department of Physics, Faculty of Sciences, University of Novi Sad, Trg D. Obradovića 4, Novi Sad, Serbia and Montenegro;(2) Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, 1525 Budapest, P.O. Box 49, Hungary;(3) Department of Physics, Faculty of Sciences, University of Novi Sad, Trg D. Obradovića 4, Novi Sad, Serbia and Montenegro;(4) Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Prague, Czech Republic;(5) Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Prague, Czech Republic;(6) Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Prague, Czech Republic;(7) Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, 1525 Budapest, P.O. Box 49, Hungary |
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Abstract: | Summary Thermal properties of a homologous series of ferroelectric liquid crystals S-(-)-4-(2-n-alkoxy-propionyloxy)]biphenyl-4'-n-alkoxy-(3,5-dimethyl)]benzoate have been investigated by polarizing optical microscopy and differential scanning calorimetry.
The mesophases were identified and confirmed by X-ray too. Three binary mixtures were prepared from the individual homologues.
In one of the mixtures (Mix1), the ferroelectric SmC* phase has broadened and became enantiotropic. This mesophase remained
monotropic in the other two mixtures (Mix2, Mix3). The chiral nematic N* phase did not appear in Mix1, but remained monotropic
for the other two mixtures. Two molecular parameters, the layer spacing and the average intermolecular distance have been
calculated from the X-ray results for the homologues and their mixtures. An intercalated tail-to-tail packing of molecules
was found both in the single compounds and their mixtures resulting in the layer spacing about half of the molecular length
of the single compounds. |
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Keywords: | X-ray diffraction phase transition DSC ferroelectric liquid crystal intermolecular distance layer spacing |
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