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Dr. Rebecca Walker Dr. Magdalena Majewska Dr. Damian Pociecha Dr. Anna Makal Prof. John MD Storey Prof. Ewa Gorecka Prof. Corrie T. Imrie 《Chemphyschem》2021,22(5):461-470
A selection of pyrene-based liquid crystal dimers have been prepared, containing either methylene-ether or diether linked spacers of varying length and parity. All the diether linked materials, CBOnO.Py (n=5, 6, 11, 12), exhibit conventional nematic and smectic A phases, with the exception of CBO11O.Py which is exclusively nematic. The methylene-ether linked dimer, CBnO.Py, with an even-membered spacer (n=5) was solely nematogenic, but odd-members (n=6, 8, 10) exhibited both nematic and twist-bend nematic phases. Replacement of the cyanobiphenyl fragment by cyanoterphenyl giving CT6O.Py, gave elevated melting and nematic-isotropic transition temperatures, and SmA and SmCA phases were observed on cooling the nematic phase. Intermolecular face-to-face associations of the pyrene moieties drive glass formation, and all these materials have a glass transition temperature at or above room temperature. The stability of the glassy twist-bend nematic phase allowed for its study using AFM, and the helical pitch length, PTB, was measured as 6.3 and 6.7 nm for CB6O.Py and CB8O.Py, respectively. These values are comparable to the shortest pitch of a twist-bend nematic phase measured to date. 相似文献
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Wongi Park Minyong Yang Hyewon Park Dr. Joanna M. Wolska Dr. Hyungju Ahn Prof. Dr. Tae Joo Shin Prof. Dr. Damian Pociecha Prof. Dr. Ewa Gorecka Prof. Dr. Dong Ki Yoon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(24):7108-7113
Herein, it is reported that the polymorphism in the helical nanofilament (HNF, B4) liquid-crystalline phase depends on the fabrication methods, that is, UV-driven formation and template-assisted self-assembly in the nanoconfined geometry. As a result, uniaxially oriented HNFs with different helical structures were obtained, in which generation of the twisted-ribbon and cylindrical-ribbon polymorphs showed that even the molecular lattice has a different orientation. The detailed structures were directly observed by SEM and grazing-incidence X-ray diffraction with synchrotron radiation. The resultant polymorphs could be used in chiro-optical applications due to the capability for fine control of the helical structures. 相似文献
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J. Szydlowska K. Trzcinska P. Bilkova J. Mieczkowski D. Pociecha E. Gorecka 《Liquid crystals》2006,33(3):335-339
Doping a photoconductive mesogenic material with a small amount of functionalized fullerene significantly increases the photocurrent. LESR studies show the appearance of a long-lived charge-separated state under light illumination, with a negative charge on the fullerene moiety. This confirms that in the system studied the fullerene unit acts as an electron trap. In the lamellar structure of the liquid crystalline phase the fullerene units and mesogenic cores are separated, which ensures better space separation between negative and positive charges. As a result the charge recombination is slowed and the photocurrent is amplified. 相似文献
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The supramolecular approach was applied to obtain a thermotropic liquid crystalline phase from the smallest possible molecules. Diaminobenzene derivatives are able to form smectic layers through a network of interconnected hydrogen bonded rings. The observed smectic A phase exhibits unusually small optical birefringence, comparable with that of lyotropic lamellar phases. 相似文献
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Assuming that a pulse of excitation corresponds to the logical "true" state one can use a chemical medium for information processing and construct devices that execute the basic binary logical operations. Here we discuss direct chemical realizations of four argument logical functions equivalent to special types of McCulloch-Pitts neuron. We demonstrate that if a proper geometrical arrangement of excitable and nonexcitable areas is used then the construction of the considered devices can be much simpler than in the case where they are composed of chemical binary logical gates. 相似文献
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We present a synthesis and mesomorphic properties of a new series of rod-like mesogens. All the compounds possess a substituted 2-aminothiophene unit as a main element in the structure attached to a stilbene moiety with a terminal alkyloxy chain (OR1, OR2 where R1=CnH2n+1, R2=CmH2m+1; n, m ranging from 6 to 12). The synthesis of alkyloxybiphenyl substituted 2-aminothiophenes was carried out by the Gewald reaction and the appropriate reaction conditions were investigated. The liquid–crystalline properties were studied via polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction. These materials exhibit nematic and/or smectic A phases. The influence of structural changes (variation in alkyloxy chain length and symmetry of the molecule) on mesogenic behaviour is discussed. Evaluation of UV–vis, fluorescent and electrochemical properties are also included. 相似文献
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Guan-Yeow Yeap Tze-Nee Chan Wan-Sinn Yam Damian Pociecha Ewa Gorecka 《Liquid crystals》2013,40(9):1041-1047
A new series of non-symmetric chiral isoflavone-based liquid crystalline dimers, α-(2-methylbutyl-4′-(4″-phenyloxy)benzoate)-ω-(3-(4′-decyloxyphenyl)-4H-1-benzopyran-4-one-7-oxy)alkanes, with 3–12 carbon atoms in the alkyloxy spacer, have been synthesised. A pronounced odd–even effect for the phase transition temperatures upon varying the spacer length was observed. The short dimers exhibited monolayer smectic A (SmA) and smectic C (SmC*) phases while for longer homologues a chiral nematic (N*) phase was found. The temperature range of the nematic phase was broadened with elongation of the alkyl spacer. Stabilisation of the nematic phase resulted from competition between the monolayer and intercalated smectic structures. The SmA–SmC* phase transition was second order for all studied compounds with a cross over to the de Vries type behaviour for the shortest homologue. 相似文献
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Vladimíra Novotná Věra Hamplová Milada Glogarová Lubor Lejček Ewa Gorecka 《Liquid crystals》2018,45(4):634-640
New lactic acid derivatives have been prepared and studied and found that they form cholesteric phase with the helix pitch length in interval 120–200 nm within a broad temperature range. Due to the positive dielectric anisotropy and the short pitch, the applied electric field causes reversible optical changes in planar cell, in which the applied electric field reorients the long molecular axis. Presence of short pitch and possibility to effectively affect electro-optical properties are promising from the point of view of specific applications. 相似文献