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Room Temperature Ferroelectric Mixture of Chiral and Achiral Thioesters

100%
Czerwiec J., Ossowska-Chruściel M., Chruściel J., Wróbel S.
Acta Physica Polonica A
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2010
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vol. 117
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issue 4
549-552
EN
Dielectric properties of the mixture of two thioester compounds: 4-8-alkoxy-benzoate-thio-carboxyl S-4-pentyl-phenyl (8OS5), (s)-4-(1-methyl-heptyloxy)biphenyl-4-thio-carboksyl 4-9-alkil-phenyl (MHOBS9) are presented. The chiral compound exhibits nematic (N*) and ferroelectric smectic C* phase (SmC*). The achiral compound shows N, SmA and monotropic SmC and SmB phases. the mixture of both compounds of 0.5 molar fraction shows SmC* in the wider temperature range than pure MHOBS9. The mixture was studied using frequency domain dielectric spectroscopy. Dielectric measurements for the SmC* phase of the mixture revealed Goldstone mode at higher frequencies and Maxwell-Wagner relaxation at low frequencies.
2
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Equimolecular Mixture of Calamitic and Bent-Core Thiobenzoates

100%
Chruściel J., Wantusiak B., Ossowska-Chruściel M.
Acta Physica Polonica A
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2012
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vol. 122
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issue 2
375-377
EN
This article reports on the new results on phase transitions, mesomorphic and electro-optical properties of new equimolecular mixture of calamitic and bent-core thiobenzoates. Two following liquid crystals were the components of the binary mixture: (S)-(+)-4-(1-methylheptyloxy)biphenyl 4'-octylthiobenzoate (MHOBS8) having rode-like, calamitic-chiral molecules possessing among others ferroelectric smectic C (SmC*) and bis [4-(4'-octylphenylthiocarbonyl)phenyl] isophtalates from a homologous series of banana-shaped thioesters, referred to as IFOS8, where n = 8 denoted the number of carbon atoms in terminal alkyl chains in both mesogens, synthesized by us. The IFOS8 compound has two enantiotropic phases: B2 with antiferroelectric order and B6. The mesomorphic properties were investigated by means of three complementary methods: differential scanning calorimetry, polarized light optical microscopy, and transmitted light intensity. Electro-optical measurements were also carried out.
3
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Polymorphism and Initial Structure Modelling of a New Mesogen 9OSBch

100%
Kosyl M., Zając W., Ossowska-Chruściel M., Chruściel J.
Acta Physica Polonica A
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2013
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vol. 124
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issue 6
959-963
EN
We report the properties of a novel mesogen with high temperature cholesteric mesophase, which belongs to an unexplored as yet series of cholesteric esters. This compound is cholesteryl 4-(4-nonyloxybenzoylthio) benzoate (C_9H_{19}OC_6H_4COSC_6H_4COOch, where ch = cholesteryl), hereafter named 9OSBch. The chemical structure and purity of 9OSBch was established by ^1H NMR, ^{13}C NMR and FT-IR spectroscopy, and its mesomorphism was characterised by differential scanning calorimetry, polarizing optical microscopy, and transmitted light intensity. Differential scanning calorimetry measurements showed that substance is stable up to 270C and partially decomposes above this temperature. Observation under polarizing optical microscope revealed oily streak texture of cholesteric phase (Ch). The chemical structure of an isolated molecule was optimized by the density functional theory method. Energetically most favourable configuration is that of hockey stick geometry. At the same time this is the conformation best suited for the formation of highly ordered condensed phases.
4
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Dielectric and Conductivity Anisotropy in Liquid Crystalline Phases of Strongly Polar Thioesters

76%
Mikułko A., Fraś M., Marzec M., Wróbel S., Ossowska-Chruściel M., Chruściel J.
Acta Physica Polonica A
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2008
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vol. 113
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issue 4
1155-1160
EN
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.
5
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Dielectric and Electrooptic Investigations of B Phases οf Banana-Shaped Thioesters

64%
Wierzejska-Adamowicz M., Ossowska-Chruściel D., Chruściel J., Douali R., Legrand C., Marzec M., Mikułko A., Sikorska A., Wróbel S.
Acta Physica Polonica A
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2010
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vol. 117
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issue 4
557-561
EN
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.
6
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Polymorphism of Chiral Thioester Studied by Dielectric Spectroscopy

52%
Wawrzyniak A., Chruściel J., Douali R., Dubois F., Leblond J., Legrand C., Ossowska-Chruściel D., Marzec M., Ropa P., Czerwiec J., Wróbel S.
Acta Physica Polonica A
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2013
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vol. 124
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issue 6
933-936
EN
(S)-(+)-4'-[(4-(1-methylheptyloxycarbonylphenyl) thiocarbonylphenyl]-decyloxybenzoate (in short 10.OPOSMH) was studied by complementary methods. The substance shows rich polymorphism. In addition to ferroelectric and antiferroelectric smectic C* phases it possesses three ferrielectric sub-phases. Phase transitions between the phases were revealed by differential scanning calorimetry and static dielectric permittivity measurements. The aim of this paper was to study phase transitions and differences in dielectric spectra shown by different phases. Collective and molecular dynamics of all phases shown by 10.OPOSMH will be discussed in terms of theoretical models. Dielectric spectra of antiferroelectric phase show two characteristic dielectric relaxation modes: one connected with the molecular process (reorientation around the short axis) and the other originating from fluctuations of antiferroelectric order parameters.
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