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Właściwości sprężyste ciekłych kryształów

Raszewski Zbigniew, Kłosowicz Stanisław, Zieliński Jerzy, Mazur Rafał

Biuletyn Wojskowej Akademii Technicznej

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2023

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Vol. 72, nr 3

15--42

PL

W artykule omówiono właściwości sprężyste ciekłych kryształów, koncentrując się na fazie nematycznej. Przedstawiono zarys rozwoju teorii opisujących te właściwości. sformułowano model ciekłego kryształu jako ośrodka ciągłego. szczegółowo omówiono krzywiznową teorię sprężystości nematycznych ciekłych kryształów opartą na podejściu Zochera - Oseena - Franka. w tym ujęciu opisano podstawowe deformacje sprężyste nematyków oraz charakteryzujące je parametry materiałowe.

EN

The paper presents elastic properties of liquid crystals, especially their nematic phase. An outline of a development of theories describing these properties is given. The model describing liquid crystal as continuous medium is formulated. The curvature theory of elasticity of nematic liquid crystals based on Zocher - Oseen - Frank’s approach is discussed in details. in this way, essential elastic properties of nematics as well their relative material parameters are described.

2

Investigation of transmission properties of a tapered optical fibre with gold nanoparticles liquid crystal composite cladding

Moś Joanna E., Stasiewicz Karol A., Jaroszewicz Leszek R.

Opto-Electronics Review

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2022

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Vol. 30, No. 4

art. no. e143936

EN

The article presents a study of a hybrid structure based on the combination of a tapered optical fibre and gold nanoparticles dispersed in a liquid crystal material. Sensitivity to changes of the refractive index of the environment in which the structure is located, as well as the possibility of changing the refractive index of liquid crystals by external factors, such as temperature and electric field, were investigated. Electro- and thermally-induced changes of the refractive index of a liquid crystal through the rotation of a molecule director, which cause changes in the light propagated in a tapered optical fibre, were described. The most important issue in the article is to determine the influence of doping a liquid crystal with gold nanoparticles the concentration of which varies between 0.1 and 0.3 wt.%. The paper presents transmission measurements in a wide optical range depending on voltage, temperature, and frequency changes. Additionally, time courses of the obtained signal were measured. The study shows that the appropriate selection of nanoparticle concentration has a huge impact on the optical wave propagation. The experimental results show that the optical changes obtained for the investigated hybrid structure prefer it for use as an electrooptical switcher, filter, or sensor.

3

Teorie średniego pola molekularnego dla stanu ciekłokrystalicznego

Raszewski Zbigniew, Zieliński Jerzy, Kłosowicz Stanisław

Biuletyn Wojskowej Akademii Technicznej

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2022

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Vol. 71, nr 1

83--113

PL

W artykule omówiono teorie średniego pola molekularnego opracowane dla nematycznych ciekłych kryształów, a także podkreślono ich zalety i ograniczenia. Przedstawiono rolę parametru uporządkowania w opisie fazy ciekłokrystalicznej. Zaznaczono rolę molekularnych momentów dipolowych.

EN

Theories of a mean molecular field developed for nematic liquid crystals are discussed. Their advantages and disadvantages are highlighted. The role of the order parameter in the description of a liquid crystalline phase is shown. The role of molecular dipole moments is underlined.

4

Stan mezomorficzny i rodzaje mezofaz

Kłosowicz Stanisław, Zieliński Jerzy, Raszewski Zbigniew

Biuletyn Wojskowej Akademii Technicznej

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2022

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Vol. 71, nr 1

115--135

PL

W artykule omówiono podstawowe rodzaje faz ciekłokrystalicznych, biorąc pod uwagę sposób ich otrzymywania oraz uporządkowanie nadmolekularne wewnątrz fazy. Przedyskutowano charakterystyczne cechy budowy molekularnej substancji mogących występować w fazie ciekłokrystalicznej oraz ich wpływ na właściwości ciekłokrystaliczne. Podano przykłady wpływu oddziaływań międzymolekularnych na sytuację fazową ciekłego kryształu.

EN

The paper presents basic types of liquid-crystalline phases obtained in different ways and supermolecular arrangement in those phases. characteristic features of molecular structure of mesogens are discussed, moreover their influence on liquid-crystalline properties are described too. Examples of the effect of intermolecular interactions on the phase situation of a liquid crystal are given.

5

Induction of the Orthogonal Smectic A Phase in Mixtures of Nematic Tolanes with Positive and Negative Dielectric Anisotropy

Zieja Paulina, Klucznik Barbara, Tykarska Marzena

Biuletyn Wojskowej Akademii Technicznej

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2022

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Vol. 71, nr 3

15--29

EN

Induction of the orthogonal smectic a phase occurs in mixtures of nematic compounds with positive and negative dielectric anisotropy. The aim of this work is to determine influence of a molecular structure of compounds on the induction strength of this phase. cyclohexyl tolanes with the terminal group -OCF₃, differing with a lateral substitution of a rigid core with fluorine atoms, were mixed with tolanes with two fluorine atoms in a lateral position and different lengths of a terminal alkoxy chain. Based on phase diagrams, obtained with the use of a polarising optical microscope, the influence of a structure of both types of compounds on the induction of the SmA phase is presented. Both, an increase in a number of fluorine atoms in a rigid core and a decrease in an alkoxy chain length cause a decrease in the strength of the SmA phase induction in the investigated systems.

PL

W mieszaninach związków ciekłokrystalicznych o dodatniej i ujemnej anizotropii dielektrycznej zaobserwowano indukcję fazy smektycznej A. celem pracy jest określenie wpływu struktury związków na temperaturowo-stężeniowy zakres występowania tej fazy. Cykloheksylotolany z terminalną grupą - OCF₃ różniące się lateralnym podstawieniem rdzenia atomami fluoru badano w układach z tolanami podstawionymi lateralnie dwoma atomami fluoru i różniącymi się długością terminalnego łańcucha alkoksylowego. na podstawie wykresów równowagi fazowej skonstruowanych z użyciem mikroskopu polaryzacyjnego określono wpływ obu grup związków na indukcję fazy smektycznej A. Zarówno zwiększenie liczby lateralnych atomów fluoru, jak i skrócenie łańcucha alkoksylowego powoduje zmniejszenie się indukcji fazy smektycznej A w badanych układach.

6

Historia badań ciekłych kryształów

Raszewski Zbigniew, Zieliński Jerzy, Kłosowicz Stanisław

Biuletyn Wojskowej Akademii Technicznej

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2022

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Vol. 71, nr 1

65--81

PL

Przedstawiono rys historyczny badań nad ciekłymi kryształami z uwzględnieniem zastosowań tych substancji. szczególną uwagę poświęcono badaniom prowadzonym w polskich ośrodkach naukowych od lat trzydziestych ubiegłego wieku do dziś.

EN

A historical view of studies on liquid crystals is presented. application of those materials are also taken into account. special attention is paid to the studies conducted at Polish scientific centres since the thirties of the last century till now.

7

Simulation of the light propagation in structured matrices with liquid crystal for optical sensor active medium designing

Wójcik Waldemar

Przegląd Elektrotechniczny

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2020

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R. 96, nr 10

98--101

EN

In our paper, the simulation of the ray propagation through the solid-state matrix-liquid crystal structure is described. The rays propagate at a considerable angle to the investigated structure surface. And as a result, it leads to a sharp decreasing of the efficiency coefficient of the structure and, as a consequence, a decreasing of the signal-to-noise ratio. By adjustment of the refraction coefficient and the cholesteric liquid crystal pitch can be possible to change the reflection coefficient, the bandwidth selectively reflection, thereby affecting the parameters of the primary convectors of optical sensors.

PL

W pracy opisano symulację rozchodzenia się promieni przez strukturę matryca półprzewodnikową – ciekły kryształ. Promienie te rozprzestrzeniają się pod znacznym kątem do powierzchni badanej struktury. W rezultacie prowadzi to do gwałtownego spadku współczynnika sprawności struktury, a w konsekwencji do zmniejszenia stosunku sygnału do szumu. Współczynnik załamania światła i skok cholesterycznego ciekłego kryształu, może zmieniać współczynnik odbicia, szerokość pasma selektywnie odbitego, wpływając tym samym na parametry pierwotnego przetwarzania czujników optycznych.

8

Analiza termo-optyczna (TOA) jako narzędzie badań zjawisk topnienia

Galewski Zbigniew, Korbecka Izabela, Osiecka-Drewniak Natalia

Wiadomości Chemiczne

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2019

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[Z] 73, 3-4

202--220

EN

In the work, after preliminary discussion of the complexity of the phenomenon of melting chemical compounds, two basic research methods are presented: calorimetric methods and thermooptical method. The physical basis of the five main calorimetry techniques is now detailed (adiabatic calorimetry, differential thermal analysis – DTA, differential scanning calorimetry with heat compensation – DSC heat compensated, differential scanning calorimetry with heat flow – DSC heat flux and differential scanning calorimetry with temperature modulation – MDSC) and thermo-optical techniques used in phase transitions investigations. The advantages and disadvantages of these methods are shown in numerous examples and the accuracy attainable by the individual measuring techniques is compared.

9

Polarization properties of nematic liquid crystal cell with tapered optical fiber

Marć Paweł, Stasiewicz K., Korec J., Jaroszewicz L. R., Kula P.

Opto-Electronics Review

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2019

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Vol. 27, No. 4

321--328

EN

In the paper, an extended analysis of the polarization properties of a liquid crystal cell with a biconically tapered single-mode telecommunication optical fiber was presented. These properties are a result of a sample geometry and used LC materials. They were analyzed by using two theoretical models based on the matrix decomposition methods, i.e., polar and singular-value one. By measuring Mueller matrices, information about losses, depolarization, dichroism and birefringence was obtained. In the experiment two types of tested samples filled with well-known 6CHBT and E7 liquid crystals were prepared and all optical parameters were shown as the voltage dependence. The tested samples have dichroic properties and for both models calculated PDL is similar and it increases from 2.6 to 6.6 dB for E7 and from 0.4 to 2.7 dB for 6CHBT with voltage changes within the range of 40 – 190 V. Optical losses simultaneously decrease from 30 dB to 27 dB and from 36 dB to 28 dB, respectively. The birefringence properties cannot be directly comparable due to differences between both applied models but voltage fluctuations of these parameters are not significant. These results confirm expected dichroic properties of designed device and complete knowledge about its working principles. Moreover, presented analysis validates usefulness of the singular-value decomposition model applied to dichroic optical fiber elements.

10

On the ordering of n-cyanobiphenyl mesogene molecules on graphene - a computer simulation study

Gwizdała Wojciech, Raczyńska Violetta, Raczyński Przemysław, Górny Krzysztof, Dendzik Zbigniew

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2018

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Vol. 22. No 2

105--111

EN

We studied ultrathin layers of n-cyanobiphenyl (n=5,6,7,8) mesogene molecules forming thin films on a graphene plane using molecular dynamics simulations in a wide temperature range (220–420K). Each modeled ensemble was heated to the maximum temperature and then cooled (reverse procedure). We calculated the second rank order parameter as a measure of the molecular order of mesogene molecules and we discuss the distribution of angles between them and the global sample director.

11

Parameters of LC molecules’ movement measured by dielectric spectroscopy in wide temperature range

Chausov D. N., Kurilov A. D., Belyaev V. V., Kumar S.

Opto-Electronics Review

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2018

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Vol. 26, No. 1

44--49

EN

Dielectric properties of a nematic liquid crystal (NLC) mixture ZhK-1282 were investigated in the frequency range of 10²–10⁶Hz and a temperature range of -20 to 80°C. On the basis of the Debye’s relaxation polarization model dielectric spectra of temperature dependence of the orientational relaxation time τ and the dielectric strength δe were numerically approximated at the parallel orientation of a molecular director relative to alternating electric field. Influence of ester components in the mixture plays crucial role in relaxation processes at low temperature and external field frequency. The activation energy of the relaxation process of a rotation of molecules around their short axis was measured in a temperature interval of -20 to +15°C in which the dispersion of a longitudinal component of the dielectric constant takes place. The energy of potential barrier for polar molecules rotation in the mesophase was calculated. The value of the transition entropy from the nematic to isotropic phase was obtained from this calculation. The values of the coefficient of molecular friction and rotational diffusion were obtained by different methods. The experimental data obtained are in a satisfactory agreement with the existing theoretical models.

12

Locally-induced permanent birefringence by polymer-stabilization of liquid crystal in cells and photonic crystal fibers

Chychłowski M. S., Ertman S., Rutkowska K., Strzeżysz O., Dąbrowski R., Woliński T. R.

Opto-Electronics Review

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2018

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Vol. 26, No. 3

242--246

EN

The aim of this work was to induce permanent birefringence both in typical liquid crystal cells and photonic crystal fibers (PCFs) by photo-polymerization. For this purpose three different liquid crystalline materials, namely E7, 5CB, and 6CHBT were combined with a mixture of RM257 monomer and a UV sensitive initiator with the percentage weight less than 10%. Due to the photo-polymerization process it was possible to achieve polymer-stabilized liquid crystal orientation inside LC cells and micro-sizedcylindrical glass tubes. In particular, periodic change in spatial molecular orientation was achieved by selective photo-polymerization. Successful results obtained in these simple geometries allowed for the experimental procedure to be repeated in PCFs leading to locally-induced permanent birefringence in PCFs.

13

Determination of the temperature dependence of the helical pitch in 1.m.7(HH) liquid crystalline compounds

Zieja P., Tykarska M., Strójwąs K.

Biuletyn Wojskowej Akademii Technicznej

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2018

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Vol. 67, nr 2

51--62

EN

Homologous series 1.m.7(HH) of liquid crystalline compounds, varying in the chiral chain length m (m=4-9), were studied. These compounds are characterized by a long helical pitch in an antiferroelectric phase, which is higher than the measuring range of the available instruments. The temperature dependence of the helical pitch of these compounds was determined by the extrapolation of the results obtained for the mixtures of 1.m.7(HH) compounds with 1.4.7(HF) compound of a known helical pitch value. The helical pitch measurements were made by spectrophotometry and phase transition temperatures were measured by polarizing thermomicroscopy. Extrapolation of the results let established that the investigated liquid crystals are characterized by the helical pitch increasing and then decreasing upon heating, which is accompanied by the helical twist sense inversion from the right-handed structure to the left-handed one.

PL

Przedmiotem badań był szereg homologiczny związków ciekłokrystalicznych 1.m.7(HH) różniących się długością łańcucha chiralnego m (m = 4-9). Związki te charakteryzują się długim skokiem helisy w fazie antyferroelektrycznej, większym niż zakres pomiarowy dostępnej aparatury. Zależność skoku helisy od temperatury wyznaczono, ekstrapolując wyniki pomiarów skoku helisy otrzymane dla mieszanin związków 1.m.7(HH) ze związkiem 1.4.7(HF) o znanym skoku. Pomiary skoku helisy wykonano metodą spektrofotometryczną, natomiast temperatury przemian fazowych zmierzono za pomocą polaryzacyjnego mikroskopu optycznego. Ekstrapolacja wyników pozwoliła ustalić, że badane ciekłe kryształy charakteryzują się skokiem helisy zwiększającym się, a następnie zmniejszającym ze wzrostem temperatury, czemu towarzyszy inwersja skrętności helisy z prawoskrętnej na lewoskrętną.

14

Examination of refractive indices and propagation losses in PSLC mixtures with various monomer concentration

Pachacz A., Rutkowska K.

Aparatura Badawcza i Dydaktyczna

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2018

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T. 23, nr 3

128--137

EN

In this research study on liquid crystalline materials mixed with other compounds, specifically with monomers, is presented. Research covers measurements of the refractive indices and the attenuation constant of the polymer stabilized liquid crystals (PSLCs). The latter are specific type of mixture, containing liquid crystal together with less than 10% weight concentration of the monomer and UV-sensitive activator. In this sense, the variety of available liquid crystals and monomers, gives a huge number of different mixtures that can be potentially obtained [1]. Each combination of particular compounds and their weight ratios, results in different physical properties of the mixture, so knowledge about, how each of these factors influences the final product, is fundamental. PSLCs, thanks to their tunable properties, provide wide range of potential applications in integrated optics as e.g. varifocal lenses, sensors, waveguiding layers, etc., but first their optical parameters have to be examined in detail [2, 3].

PL

W niniejszym artykule przedstawiono badania nad ciekłymi kryształami połączonymi z innymi materiałami, w szczególności z monomerami. Badania obejmują pomiary współczynników załamania oraz współczynnika tłumienia w ciekłych kryształach stabilizowanych polimerem (ang. PSLC). PSLC to rodzaj mieszaniny, w której skład, oprócz ciekłego kryształu, wchodzi mniej niż 10% wagowego stężenia monomeru oraz śladowe ilości aktywatora optycznego. Biorąc pod uwagę różnorodność związków ciekłokrystalicznych i monomerów, można uzyskać ogromną liczbę mieszanin o różnych właściwościach fizycznych [1]. Znajomość tychże właściwości jest kluczowa w kontekście praktycznego zastosowania mieszanin PSLC. Mieszaniny tego typu, dzięki możliwości uzyskania związku o konkretnych właściwościach fizycznych i chemicznych, można zastosować w optyce zintegrowanej, np. do zmiennoogniskowych soczewek, czujników, jako warstwy falowodowe itp., jednak zanim to nastąpi, należy szczegółowo zbadać i wyznaczyć ich parametry optyczne [2, 3].

15

Mix-substituted phthalocyanines of a “push–pull”-type and their metal complexes as prospective nanostructured materials for optoelectronics

Usol'tseva N. V., Smirnova A. I., Kazak A. V., Giricheva N. I., Galanin N. E., Shaposhnikov G. P., Bodnarchuk V. V., Yablonskii S. V.

Opto-Electronics Review

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2017

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Vol. 25, No. 2

127--136

EN

To study the influence of structural features of phthalocyanine (Pc) derivatives on their physico-chemical properties in bulk and thin films, 23 new phthalocyanines with different quantity and ratio of donor (alkyloxy-groups, in fragment “A”) and acceptor (Cl-, in fragment “B”) substituents in one molecule of the A3B, ABAB and AABB types with varied length of alkyloxy-substituents and their metal complexes were designed and synthesized. A comparative analysis of spectral, mesomorphic and photoelectric properties of these mix-substituted phthalocyanines of a “push–pull” type was performed. It was shown that non-peripheral substitution by alkyloxy-fragments in hetero-substituted Pcs (similar to homo-substituted Pc) leads to red-shifting of the Q-band into near-IR region. The intensity of photoluminescence, position of peaks and their splitting are strongly connected with chemical structure of Pcs and the type of solvent. In contrast to non-mesogenic octyloxy-Pc (A4) having alkyloxy-substituents in non-peripheral positions, 22 of 23 synthesized compounds possess columnar mesomorphism. The change of donor–acceptor ratio can influence the type of mesophase. A new approach to the creation of materials for optoelectronics is proposed and implemented, which includes design of compounds possessing vitrification from mesophase with maintenance of a columnar order, absorption in the near IR-region of the spectrum and good performance electrophysical characteristics simultaneously.

16

Minimal Energy Dissipation Rate and Director Orientation Relative to External Dissipative Fields such as Temperature and Velocity Gradients in Nematic and Cholestric Liquid Crystals

Sarman S., Wang Y-L., Laaksonen A.

Computational Methods in Science and Technology

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2017

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Vol. 23, No. 3

239--250

EN

The purpose of this review article is to summarize observations accumulated over the years on director alignment phenomena in nematic and cholesteric liquid crystals by molecular dynamics simulation of molecular model systems and by experiment on real systems. The main focus is on the alignment angle between the director and external dissipative fields such as velocity gradients in various flow geometries and temperature gradients doing irreversible work on the system. A general observation is that the director attains an orientation relative to the field where the energy dissipation rate is minimal in the steady state. In the case of planar elongational flow, it can be proven by using symmetry arguments that the energy dissipation rate must be either maximal or minimal and simulations have shown that is minimal. In planar Couette flow both simulations and experiments imply that the energy dissipation rate is minimal in the steady state. Finally, in the case of heat conduction, symmetry arguments imply that the energy dissipation rate must be either minimal or maximal and simulations and experiments indicate that it is minimal. All these observations can be explained by applying a recently proven theorem according to which the energy dissipation rate is minimal in the steady state in the linear regime at low fields.

17

Wpływ struktury molekularnej na strukturę helikoidalną i na charakter widm NMR chiralnych estrów ciekłokrystalicznych

Drzewicz A., Tykarska M., Szala M., Żurowska M.

Biuletyn Wojskowej Akademii Technicznej

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2017

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Vol. 66, nr 2

25--35

PL

Przedmiotem badań były trójpierścieniowe chiralne związki ciekłokrystaliczne tworzące fazę antyferroelektryczną, różniące się budową łańcucha alkilowego oraz podstawieniem pierścienia benzenowego atomami fluoru. Wykonano pomiary skoku helisy metodą opartą na zjawisku selektywnego odbicia światła oraz zarejestrowano widma 1H i 13C NMR w temperaturze 25°C. Zaobserwowano wpływ budowy molekularnej na przesunięcie chemiczne sygnałów pochodzących od centrum chiralnego.

EN

Three-ring chiral liquid crystalline compounds, forming antiferroelectric phase, differing in the structure of alkyl chain and in the substitution of benzene ring by fluorine atoms were studied. The measurements of helical pitch, based on the selective light reflection phenomenon, were performed as well as 1H and 13C NMR spectra at room temperature were registered. The influence of molecular structure as well as the type of helicoidal structure on the chemical shift of signals coming from chiral center was observed.

18

Wpływ długości łącznika alkilowego oraz podstawienia atomami fluoru na charakter widm w podczerwieni chiralnych estrów ciekłokrystalicznych

Drzewicz A., Tykarska M., Żurowska M.

Biuletyn Wojskowej Akademii Technicznej

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2017

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Vol. 66, nr 3

63--74

PL

Dla szeregu trójpierścieniowych estrów ciekłokrystalicznych różniących się budową łańcucha alkilowego, podstawieniem pierścienia benzenowego atomami fluoru, a także typem struktury helikoidalnej w chiralnej fazie smektycznej CA o właściwościach antyferroelektrycznych zarejestrowano widma w podczerwieni. Zaobserwowano wpływ budowy molekularnej na przesunięcie pasm pochodzących od grupy karbonylowej w sztywnym rdzeniu.

EN

The infrared spectra were registered for series of three-ring liquid crystalline esters, differing in the structure of alkyl chain, in the substitution of benzene ring by fluorine atoms and in the type of helicoidal structure in the chiral smectic CA phase with antiferroelectric properties. The influence of molecular structure on the shift of signals coming from carbonyl group, located in the rigid core, was observed.

19

Light propagation mechanism switching in a liquid crystal infiltrated microstructured polymer optical fibre

Rutkowska K. A., Milenko K., Chojnowska O., Dąbrowski R., Woliński T. R.

Opto-Electronics Review

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2015

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Vol. 23, No. 4

252-258

EN

In this work studies on propagation properties of a microstructured polymer optical fibre infiltrated with a nematic liquid crystal are presented. Specifically, the influence of an infiltration method on the LC molecular alignment inside fibre air-channels and, thus, on light guidance is discussed. Switching between propagation mechanisms, namely the transition from modified total internal reflection (mTIR) to the photonic bandgap effect obtained by varying external temperature is also demonstrated.

20

Positron annihilation in liquid crystals

Dryzek E., Juszyńska-Gałązka E.

Nukleonika

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2015

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Vol. 60, No. 4, part 1

703--708

EN

Positron annihilation studies of liquid crystals are reviewed with particular reference to thermotropic liquid crystals with rod-like molecules. The studies of compounds exhibiting smectic A or smectic E phases indicate that local arrangement of dipole molecules play an important role because high electron density at the end group of molecules can influence substantially formation and annihilation of positronium. The obtained ortho-positronium lifetimes in these phases can be explained by antiparallel pairing of molecules in case of the smectic A phase or a structure with a nanosegregation of alkyl chains and others parts of molecules into sublayers and liquid-like state of alkyl chains in case of the smectic E phase.