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Krzysztof Czupryński

Bio: Krzysztof Czupryński is an academic researcher from Military University of Technology in Warsaw. The author has contributed to research in topics: Liquid crystal & Phase (matter). The author has an hindex of 22, co-authored 118 publications receiving 1458 citations. Previous affiliations of Krzysztof Czupryński include Military Technical Academy & Vanderbilt University.


Papers
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TL;DR: The synthesis and properties of a few dozen highly evolved analogues of (S)-MHPOBC are reported in this paper, as evidenced by polarized optical microscopy and differential scanning calorimetry, respectively.
Abstract: The synthesis and properties of a few dozen highly evolved analogues of (S)-MHPOBC are reported The liquid crystal phases, and phase transition temperatures and enthalpies, as evidenced by polarized optical microscopy and differential scanning calorimetry, respectively, are given The helical pitch in pure compounds and some mixtures is estimated using the selective reflection method All of the compounds show antiferroelectric phases, and some key structure–property relationships for the new materials are reported Specifically, it is found that the length of the oligomethylene segment of a novel partially fluorinated alkoxy ether tail incorporated into the structures strongly influences the stability of the antiferroelectric phase and the observed phase sequences, as well as the values of the helical pitch and its temperature dependence The formulation of a family of broad temperature range eutectic mixtures possessing the highly desirable orthoconic antiferroelectric phases with long helical pitch is described

92 citations

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TL;DR: Despite significant differences between N, Sm-A, and Sm-E phases the same pretransitional behavior of epsilon and NDE in the isotropic phase, described by critical exponents gamma = 1 and alpha = 0.5, was found.
Abstract: Results of studies of static dielectric permittivity (epsilon) and nonlinear dielectric effect (NDE) in the isotropic phase of 4-n-4'-isothiocyanatobiphenyl (nBT) homologous series from n = 2 to n = 10 exhibiting the isotropic-smectic E (I-SmE) transition, are presented. They are compared with results of similar studies in 4-cyano-4-n-alkylbiphenyls (nCB) from n = 4 to n = 12. In this homologous series isotropic-nematic (I-N) and isotropic-smectic-A (I-Sm-A) transitions take place. Despite significant differences between N, Sm-A, and Sm-E phases the same pretransitional behavior of epsilon and NDE in the isotropic phase, described by critical exponents gamma = 1 and alpha = 0.5, was found. It has been shown that when the length of the alkyl chain of a compound increases the discontinuity of the transition drops in nBT and rises in nCB. The influence of pressure on the discontinuity is also discussed.

62 citations

Journal ArticleDOI
TL;DR: In this paper, two structurally similar homologous series of chiral esters with partially fluorinated alkoxyalkoxy terminal chains are described and their synthetic routes and mesomorphic properties, such as phase transitions temperatures and enthalpies, are characterized by polarizing optical microscope and differential scanning calorimetry.
Abstract: Two structurally similar homologous series of chiral esters with partially fluorinated alkoxyalkoxy terminal chains are described. Their synthetic routes and mesomorphic properties, such as phase transitions temperatures and enthalpies, are characterized by polarizing optical microscope and differential scanning calorimetry.

58 citations

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TL;DR: Two 4-alkoxyphenyl 12-pentylcarborane-1-carboxylate nematic liquid crystals have been synthesized in this article, which exhibit ideal mixing of nematic phases in their binary mixtures with analogous bicyclo[2.2] octane derivatives and with the polar nematogen 4-(4-isothiocyanatophenyl)-1-(trans-hexyl)cyclohexane.
Abstract: Two 4-alkoxyphenyl 12-pentylcarborane-1-carboxylate nematic liquid crystals have been synthesized. The materials are found to exhibit ideal mixing of nematic phases in their binary mixtures with analogous bicyclo[2.2.2]octane derivatives and with the polar nematogen 4-(4-isothiocyanatophenyl)-1-(trans-hexyl)cyclohexane. The smectic phases for the bicyclo[2.2.2]octanes are destabilized by addition of the carborane derivative. For carborane compound 5BC5 the extrapolated dielectric anisotropy and measured optical anisotropy are 1.3 and 0.057 respectively at 20°C. The refractive indices have been correlated with the calculated electronic polarizabilities and the low birefringence measured for 5BC5 can, at least in part, be attributed to the carborane cylindrical symmetry.

53 citations

Journal ArticleDOI
TL;DR: In this article, the effect of chain length on various physical properties of the CHBT series is discussed and the temperature dependence of density, refractive indices, apparent molecular length and intermolecular distance of 11CHBT, together with the static dielectric permittivities, e∥, e┴, e iso of 11 CHBT and 12 CHBT, are reported.
Abstract: The temperature dependence of density, refractive indices, apparent molecular length and intermolecular distance of 11CHBT, are reported, together with the static dielectric permittivities, e∥, e┴, e iso of 11CHBT and 12CHBT; the effect of chain length on various physical properties of the CHBT series is also discussed. All the temperatures T m, T NI and T NCr show an odd-even (OE) effect, but transition enthalpies ΔH m and ΔH c show no such behaviour. T m, T NI and T NCr and ΔH m are found to increase with chain length, while ΔH c shows a maxima at n = 6. At the common reduced temperature T* = 0.98 TNI, the density of the compounds are found to decrease with increasing chain length while the polarizability parameters αe, αo and α increase. However, the volume expansion coefficient, polarizability anisotropy and normalized polarizability anisotropy show a distinct OE effect. Similarly, n e decreases smoothly with chain length but n o and Δn show an OE effect like e┴ and Δe. The ratio ln ⟨P 2⟩ /ln ⟨ P 4⟩ r...

51 citations


Cited by
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Journal ArticleDOI
Michael Hird1
TL;DR: This critical review begins with a brief, but essential, introduction to the special nature of liquid crystal materials, their peculiar properties, and their commercial applications, followed by an introductory insight into the remarkable nature of the fluoro substituent, and its fascinating influence on the properties of organic compounds.
Abstract: This critical review begins with a brief, but essential, introduction to the special nature of liquid crystal materials, their peculiar properties, and their commercial applications, followed by an introductory insight into the remarkable nature of the fluoro substituent, and its fascinating influence on the properties of organic compounds. However, the main focus of the review is to discuss the enormous amount of exciting research on fluorinated liquid crystals that has been reported. The small size of the fluoro substituent enables its incorporation into all types of liquid crystal, including calamitic, discotic, banana, lyotropic, and polymers, without ruining the liquid crystalline nature of the material. However the fluoro substituent is larger than hydrogen, and hence causes a significant steric effect, which combined with the high polarity, confers many fascinating, and often remarkable, modifications to melting point, mesophase morphology and transition temperatures, and the many other very important physical properties, such as dielectric anisotropy, optical anisotropy, and visco-elastic properties. There are many different positions within a liquid crystal structure where a fluoro substituent can be located, including (i) a terminal position, (ii) within a terminal chain, as a semi-fluorinated or as a perfluorinated chain, or as one fluoro substituent at a chiral centre, (iii) as part of a linking group, and (iv) a lateral position in the core section. Such variety enables the interesting and advantageous tailoring of properties, both for the fundamental purposes of establishing structure–property relationships, and for materials targeted towards commercially-successful liquid crystal display applications.

657 citations

Journal ArticleDOI
TL;DR: In this paper, a review of the mechanisms underlying the relaxation properties of glass-forming liquids and polymers is provided, with an emphasis in the insight provided into the mechanism underlying the glass relaxation properties.
Abstract: An intriguing problem in condensed matter physics is understanding the glass transition, in particular the dynamics in the equilibrium liquid close to vitrification Recent advances have been made by using hydrostatic pressure as an experimental variable These results are reviewed, with an emphasis in the insight provided into the mechanisms underlying the relaxation properties of glass-forming liquids and polymers

638 citations

Journal ArticleDOI
TL;DR: An overview of the current state of research in the field of biaxial nematic liquid crystalline materials is given in this paper, where the major theoretical concepts are outlined, including the classification to different symmetries, the importance of cooperativity and cluster formation for the development of BN order and the conditions for the establishment of field induced and spontaneous BN in nematic phases.
Abstract: An overview over the current state of research in the field of biaxial nematic liquid crystalline materials is given. After a short introduction, providing some general aspects and summarizing the classical approaches, the main part focuses on recent developments of new concepts for designing biaxial nematics. First, the major theoretical concepts are outlined, including the classification to different symmetries, the importance of cooperativity and cluster formation for the development of biaxial order and the conditions for the establishment of field induced and spontaneous biaxiality in nematic phases. These new concepts also require the re-evaluation of the tools used for the identification of phase biaxiality, which are discussed briefly. In the second part, recent progress in the design of potential biaxial nematic materials, especially focussing on bent-core molecules with nematic phases, is reported and, finally, comparisons with phase biaxiality as observed in smectic liquid crystals are made.

299 citations

Journal ArticleDOI
TL;DR: In this article, a review of various ways of preparation of liquid crystal/polymer blends and composites leading to their required applications is presented. But the most important features of polymers which can be used as components of blends or composites with liquid crystals include: their film formation ability, high transparency, amorphicity, inertness in relation to a liquid crystal, good miscibility with liquid state and immiscibility in a solid state.

274 citations