Liquid crystalline dimers containing a cholesteryl group: chiral smectic phases and TGBA* phase

2021 ◽  
pp. 1-17
Author(s):  
Hao-Zhou Huang ◽  
Yue-Hua Cong ◽  
An Du ◽  
Bing Hu ◽  
Bao-Yan Zhang
Keyword(s):  
Liquid Crystalline ◽  
Smectic Phases

scholarly journals Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline Mesophases

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 532
Author(s):  
Emily E. Pocock ◽  
Richard J. Mandle ◽  
John W. Goodby
Keyword(s):  
Liquid Crystalline ◽  
Computational Study ◽  
Structure Property ◽  
Correlation Lengths ◽  
Aspect Ratios ◽  
Smectic Phases ◽  
Out Of Plane ◽  
Lower Temperature ◽  
Soft Crystal ◽  
Optical Textures

Liquid crystalline dimers and dimesogens have attracted significant attention due to their tendency to exhibit twist-bend modulated nematic (NTB) phases. While the features that give rise to NTB phase formation are now somewhat understood, a comparable structure–property relationship governing the formation of layered (smectic) phases from the NTB phase is absent. In this present work, we find that by selecting mesogenic units with differing polarities and aspect ratios and selecting an appropriately bent central spacer we obtain a material that exhibits both NTB and intercalated smectic phases. The higher temperature smectic phase is assigned as SmCA based on its optical textures and X-ray scattering patterns. A detailed study of the lower temperature smectic ‘’X’’ phase by optical microscopy and SAXS/WAXS demonstrates this phase to be smectic, with an in-plane orthorhombic or monoclinic packing and long (>100 nm) out of plane correlation lengths. This phase, which has been observed in a handful of materials to date, is a soft-crystal phase with an anticlinic layer organisation. We suggest that mismatching the polarities, conjugation and aspect ratios of mesogenic units is a useful method for generating smectic forming dimesogens.

Collective fluctuation in chiral smectic phases of main‐chain liquid crystalline polymers

2007 ◽  
Vol 34 (3) ◽  
pp. 305-310 ◽  
Author(s):  
Kazuyuki Hiraoka ◽  
Takuhei Nose ◽  
Yoshiko Uematsu ◽  
Masatoshi Tokita ◽  
Junji Watanabe
Keyword(s):  
Liquid Crystalline ◽  
Main Chain ◽  
Liquid Crystalline Polymers ◽  
Crystalline Polymers ◽  
Smectic Phases

Effective control of optical purity by chiral HPLC separation for ester-based liquid crystalline materials forming anticlinic smectic phases

2020 ◽  
pp. 1-11
Author(s):  
Terézia Vojtylová-Jurkovičová ◽  
Petra Vaňkátová ◽  
Magdalena Urbańska ◽  
Věra Hamplová ◽  
David Sýkora ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Optical Purity ◽  
Effective Control ◽  
Chiral Hplc ◽  
Hplc Separation ◽  
Crystalline Materials ◽  
Smectic Phases ◽  
Liquid Crystalline Materials

Thermal and photo optical properties of azoxybenzene/alkyloxy-azobenzene–cholesterol dimesogens with alkyl diacetylene linker

2005 ◽  
Vol 20 (12) ◽  
pp. 3431-3438 ◽  
Author(s):  
Subramanian Kumaresan ◽  
V. Ajay Mallia ◽  
Yoshishige Kida ◽  
Nobuyuki Tamaoki
Keyword(s):  
Optical Properties ◽  
Liquid Crystalline ◽  
Visible Region ◽  
Blue Shift ◽  
Isotropic Phase ◽  
Benzene Derivatives ◽  
Smectic A ◽  
Smectic Phases ◽  
Reflected Light ◽  
Liquid Crystalline Material

Thermal and photo-optical properties of azoxybenzene/alkyloxy-azobenzene containing chiral dimesogens are presented. Alkyloxyazobenzene containing dimesogenic materials exhibited two kinds of smectic A phases. Photoirradiation at temperatures exhibiting smectic phases of pure materials in azobenzene linked dimesogens resulted in formation of the isotropic phase, and this was systematically studied at different liquid crystalline temperatures. The efficacy of these compounds as a dopant in the glassy liquid crystalline material was also explored. Increasing concentration to 4 wt%/5 wt% in azobenzene/azoxy-benzene derivatives caused a dramatic red-shift in the wavelength of reflected light by the host cholesteric glassy liquid crystal. Photo-isomerization of these dopants led to a blue-shift of the reflected light, and this effect could be used to tune the light reflectivity of these mixtures over the visible region.

Electron Nuclear Double Resonance (ENDOR) Investigations of Organic Doublet Radicals in the Nematic and Smectic Phase of Liquid Crystals

1980 ◽  
Vol 34 (3) ◽  
pp. 305-310 ◽  
Author(s):  
B. Kirste ◽  
H. Kurreck
Keyword(s):  
Liquid Crystals ◽  
Liquid Crystalline ◽  
Hyperfine Interactions ◽  
Double Resonance ◽  
Electron Nuclear Double Resonance ◽  
Smectic A ◽  
Smectic Phases ◽  
Anisotropic Hyperfine ◽  
Different Types ◽  
Nematic Phases

Different types of organic doublet radicals have been investigated in isotropic, nematic, and smectic phases of liquid crystals by performing electron nuclear double resonance (ENDOR), general TRIPLE and special TRIPLE experiments. For this purpose phenalenyls (perinaphthenyls), galvinoxyl, tetra- tert.-butylcarbazolyl, and bis(biphenylenyl)propenyl radicals have been chosen including some partially deuterated and 13C-labeled compounds. Anisotropic hyperfine interactions and deuterium quadrupole couplings could be determined. Smectic A phases have proved to be advantageous as compared to nematic phases in these studies. Detailed information about the orientation of the radicals within the liquid-crystalline solvent and about the conformations of the radicals could be obtained.

scholarly journals Thermotropic and lyotropic behaviour of new liquid-crystalline materials with different hydrophilic groups: synthesis and mesomorphic properties

2013 ◽  
Vol 9 ◽  
pp. 425-436 ◽  
Author(s):  
Alexej Bubnov ◽  
Miroslav Kašpar ◽  
Věra Hamplová ◽  
Ute Dawin ◽  
Frank Giesselmann
Keyword(s):  
Liquid Crystalline ◽  
Molecular Structures ◽  
Scanning Calorimetry ◽  
Crystalline Materials ◽  
Smectic Phases ◽  
Chiral Nematic ◽  
Nematic Phases ◽  
Liquid Crystalline Materials ◽  
Hydroxy Groups ◽  
Mesomorphic Properties

Several new calamitic liquid-crystalline (LC) materials with flexible hydrophilic chains, namely either hydroxy groups or ethylene glycol units, or both types together, have been synthesized in order to look for new functional LC materials exhibiting both, thermotropic and lyotropic behaviour. Such materials are of high potential interest for challenging issues such as the self-organization of carbon nanotubes or various nanoparticles. Thermotropic mesomorphic properties have been studied by using polarizing optical microscopy, differential scanning calorimetry and X-ray scattering. Four of these nonchiral and chiral materials exhibit nematic and chiral nematic phases, respectively. For some molecular structures, smectic phases have also been detected. A contact sample of one of the prepared compounds with diethylene glycol clearly shows the lyotropic behaviour; namely a lamellar phase was observed. The relationship between the molecular structure and mesomorphic properties of these new LCs with hydrophilic chains is discussed.

scholarly journals Nitrogen Nuclear Quadrupole Resonance Dips in the Proton Spin Relaxation Dispersion of Nematic and Smectic Thermotropic Liquid Crystals

1992 ◽  
Vol 47 (11) ◽  
pp. 1105-1114 ◽  
Author(s):  
D. J. Pusiol ◽  
R. Humpfer ◽  
F. Noack
Keyword(s):  
Spin Relaxation ◽  
Liquid Crystalline ◽  
Larmor Frequency ◽  
Quadrupole Coupling Constant ◽  
Proton Spin ◽  
Relaxation Dispersion ◽  
Coupling Constants ◽  
Smectic Phases ◽  
Nematic State ◽  
Quadrupole Coupling

Abstract The Larmor frequency dependence of the proton spin relaxation time, obtained by means of the fast field-cycling NMR technique, has been used to study the 14N quadrupole coupling constant K and its asymmetry parameter η in the nematic and smectic phases of some liquid crystalline azoxybenzenes (PAA, BAB, HAB, HpAB), cyanobiphenyls (8CB, 9CB, 11CB) and oxycyanobiphenyls (9 OCB). Due to fast molecular reorientations, the effective quadrupole coupling constants are relatively small, whereas surprisingly the asymmetry parameters are rather large. The temperature dependence of both K and η within the mesophases, as well as their discontinuities at the different mesophase transitions, can be interpreted by the anisotropy of molecular rotations. It is found that temperature effects are significantly more pronounced for the (biaxial) smectic-C phase of the heptyloxyazoxybenzene (HpAB) than for the (uniaxial) smectic-A phase of the various investigated cyano- and oxycyanobiphenyls. As a rule, η turned out smaller in the smectic than in the nematic state, whereas K has similar values in both phases

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