Dorota Dardas

Dorota Dardas
Institute of Molecular Physics, Polish Academy of Sciences · Department of Physics of Liquid Crystals

Dr. Eng.

About

31
Publications
2,625
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223
Citations
Citations since 2016
11 Research Items
140 Citations
20162017201820192020202120220510152025
20162017201820192020202120220510152025
20162017201820192020202120220510152025
20162017201820192020202120220510152025
Additional affiliations
May 2006 - present
Institute of Molecular Physics, Polish Academy of Sciences
Position
  • Professor (Assistant)

Publications

Publications (31)
Article
Full-text available
We studied the electrooptical effects in ferroelectric liquid crystals at both the fundamental and the second harmonic frequency. The linear effects caused mainly by the changes in optic axis position give rise to the changes in the intensity of light passing the sample placed between crossed polarizers. The electric field causes also changes in th...
Article
Full-text available
The electrooptical effects occurring in antiferroelectric liquid crystals were investigated. The optical response was calculated, assuming that the external electric field coupled linearly to the residual spontaneous polarization (appearing due to the presence of helical structure) and quadraticaly to the dielectric anisotropy. The calculation show...
Article
Full-text available
Weak external electric field E causes two effects in chiral smectic liquid crystals: linear change of the optic axis direction and modification of the shape of the indicatrix. The relative changes in the light intensity consist of two components. The first component represents the modulation with the fundamental frequency f and the second one, with...
Article
Full-text available
An electro-optic method for determining the twist elastic coupling between smectic layers in antiferroelectric liquid crystals with a helical superstructure has been introduced. This method is based on a calibration procedure which enables a modulation of light intensity under an alternating applied electric field to relate to a respective modulati...
Article
Full-text available
Electrooptic phenomena caused by weak electric fields, much lower than those needed for the helix unwinding, in helical smectic liquid crystals were studied in thin planar samples. The investigations were performed in chiral liquid crystal 4-(1-methyl-heptyloxycarbonyl) phenyl 4′-(3-butanoyloxy propyl-1-oxy) biphenyl-4-carboxylate which exhibits an...
Article
A new scheme is investigated for evaluating the temperature dependence and dispersion relation of the Kerr constant (K) of an optically isotropic medium in isotropic and blue phases (BPs) liquid crystals. The scheme employs the measurement of the component of the transmitted light intensity of double modulated frequency using the modified in-plane-...
Article
Full-text available
Modification of the physical properties of the (S)-MHPOBC antiferroelectric liquid crystal (AFLC) by doping with low concentrations of gold nanoparticles is presented for the first time. We used several complementary experimental methods to determine the effect of Au nanoparticles on AFLC in the metal–organic composites. It was found that the dopan...
Article
A new approach to investigate subtle liquid crystal transitions and some of their light wavelength dependent physical properties is developed and demonstrated. In this method color texture changes obtained from a polarizing optical microscope are processed, and their color features are exploited. The significance of color features in image processi...
Article
Full-text available
The aim of this paper is to show, by systematic studies, the influence of γ-Fe2O3 nanoparticles on the physical parameters of the liquid crystalline matrix, exhibiting a ferroelectric phase in a wide temperature range. The detailed research was carried out by using diffraction (PXRD), microscopic (OM, SEM, FCPM, POM), thermal (DSC), optical (TLI),...
Article
In this paper, for the first time the influence of the BaTiO3 particles on the antiferroelectric liquid crystalline phase was shown. Low concentrations and two different sizes of BaTiO3 particles (nano– and sub-microparticles) were used. It was found that admixture of the ferroelectric particles causes a decrease in the concentration of free ions i...
Article
Physical properties of the partially fluorinated compound 3F5FPhF, with hockey stick-like molecules, were studied by complementary methods. Apart from the already reported paraelectric SmA*, ferroelectric SmC* and antiferroelectric SmC*A phases, the presence of the smectic C*α subphase in the phase sequence was proved by differential scanning calor...
Article
Full-text available
This work deals with determination of the viscoelasticity coefficient in chiral smectic liquid crystals possessing the helical structure and is the continuation of the work, in which the elasticity coefficient was presented [Phase Transitions 89 (2016) 368]. The measurements have been performed using optical detection in the small deformation limit...
Article
Full-text available
The chiral smectic phases of two liquid crystals (LCs) were investigated, one of them is a high tilted, long pitch, near ortoconic LC mixture and the second exhibits broad temperature of the phase. For both materials second-harmonic electro-optic (EO) spectra were studied. The particular LC phases were characterised by a specific temperature depend...
Article
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This study describes the properties of a binary liquid crystalline mixture composed of commercially available materials, Ce-3 (4-(n-hexyloxy phenyl)-1-(2-fuethyl butyl) biphenyl-4-carboxylate) and Ce-8 (4-(2-methylbutyl) phenyl-4-n-octylbiphenyl-4-carboxylate), in a weight ratio of 50:50. Both compounds show polymesomorphism and ferroelectric prope...
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In this manuscript, we report synthesis and physico-chemical characterization of 4-[[4-(butoxy)phenyl]diazenyl]phenyl alkanoates homologous series. For the first time, nineteen derivatives are described here. The enantiotropic nematic phase is typically observed among all members of this series. However, in the case of 4-[[4-(butoxy)phenyl]diazenyl...
Article
In this work, the physical properties of newly synthesized liquid crystalline compound exhibiting two liquid crystalline phases (ferroelectric and antiferroelectric) were studied. Based on the results of differential scanning calorimetry, polarizing microscopy, and photoelastic modulator methods, the temperature dependences of spontaneous polarizat...
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In this paper, we report on how flexoelectric and piezoelectric polarization components can be determined by a method based on simultaneous studies of dielectric and electrooptic properties of the chiral smectic liquid crystal in the regime of weak electric fields. As a rule, the measurements of spontaneous polarization are performed using switchin...
Article
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Theoretical and experimental studies of the director distribution of a chiral nematic liquid crystal placed in a wedge-shaped cell with weak surface anchoring were performed. We measured local value of pitch as function of position inside each Grandjean-Cano zone by registering selective reflection spectra from narrow stripes cut from each Cano zon...
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Characterization of structure and properties of the bicomponent mixture of partially fluorinated chiral three ring ester with an chiral alkyl compound by applied different methods such as the differential scanning calorimetry, the electro-optic and the dielectric spectroscopy, and the helical pitch measurement is presented. In particular, we invest...
Article
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We present the results of the study of three fluorinated mesogens with three aromatic rings and different length of alkyl chain. The investigated substances might be of interest for using in technical devices. Calorimetric, dielectric and electro-optical properties were examined. Special attention was paid to the dependence of the first and second...
Article
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The knowledge of the material parameters related to the microscopic structure of liquid crystals is one of the main problems in the construction of the liquid crystal devices. In the case of ferroelectric liquid crystals, the viscoelastic properties are very important as they determine the switching speed and the threshold voltage in displays. Ther...
Article
The long-range orientational order of some fluoro-substituted liquid crystals with different molecular structure was determined on the basis of the optical birefringence measurements. The high values of the second-rank order parameter in the whole mesophase range for the liquid crystals studied were found. The liquid crystals with the negative diel...
Article
Full-text available
Dynamic properties of surface stabilized ferroelectric liquid crystals driven by an alternating external electric field and confined inside measuring cells by air are studied. Using the electro-optic response method, it has been possible to register response spectra of small parts of liquid crystals near surfaces of their contact with air. This has...
Article
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A method is described for determination of bulk values of a twist elastic coefficient for smectic c-director in chiral smectic liquid crystals with a helical structure. The method was applied to 4-methylbutyloxy phenyl-4-octyloxy-benzoate (C8) in the chiral smectic C* phase. The measurements were performed using optical detection in a small deforma...
Article
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In this paper we present a series of novel compounds, bis(4-(4-alkylphenyl)azophenyl) 2-nitroisophtalates, which exhibit nematic and banana-type liquid-crystalline phases. The alkyl chain length varies from 1 to 18 carbons. The first ten members of this series exhibit nematic phase. The last eleven compounds exhibit banana-type liquid crystalline p...
Article
Full-text available
The method of determination of the bulk values of the rotational viscosity coefficient of the smectic c-director in chiral smectic liquid crystals with a helical structure is described. The measurements were performed using optical detection in the small deformation limit. In contrast to the usual methods, the initial deformation of the helix (caus...
Article
Full-text available
An analysis of consistency of dielectric and optical response methods is carried out for surface stabilized ferroelectric liquid crystals (SSFLC) with chevron geometry. The consistency is found both theoretically and experimentally for weak external electric fields of intermediate frequencies, for which the response of SSFLC is dominated by collect...
Article
Full-text available
The synthesis and physical properties of a liquid-crystalline material exhibiting the ferrielectric C n *-phase in a broad temperature range are described. The contradictory literature data on this substance are critically reviewed. Dielectric, optical, electrooptic, calorimetric and miscibility studies allowed us to verify the existing data and to...

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