scholarly journals Chiral Liquid Crystal Lenses Confined in Microchannels

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3761
Author(s):  
Sean M. Hare ◽  
Beatrice Lunsford-Poe ◽  
MinSu Kim ◽  
Francesca Serra
Keyword(s):  
Phase Transition ◽  
Liquid Crystalline ◽  
Focal Length ◽  
Topological Defects ◽  
Experimental Conditions ◽  
Smectic A ◽  
Heating And Cooling ◽  
Chiral Nematic ◽  
Nematic Phases ◽  
Tunable Lenses

It is known that the liquid crystalline smectic-A phase has geometric defects, called focal conic domains, which can be used as gradient-index microlenses. Cholesteric (chiral nematic) phases also have topological defects with a central symmetry and a singularity at their center. We explore a weakly chiral system in which both types of defects can be present in the same material at different temperatures, and with this strategy we create lenses whose focal length is tunable with temperature. We measure the focal length of the tunable lenses, and we investigate the behavior of the defects near the phase transition. We identify the experimental conditions that make the simultaneous presence of the smectic focal conic domains and the circular cholesteric domains possible, such as the concentration of chiral dopant and the rate of heating and cooling. The transformation of focal conic domains into circular cholesteric domains is a new example of memory at the phase transition between smectic-A and nematic liquid crystals.

scholarly journals 2-Chloroalkoxy-Substituted Pentafluorinated Bistolanes as Novel Light-Emitting Liquid Crystals

Crystals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 195 ◽  
Author(s):  
Shigeyuki Yamada ◽  
Kazuya Miyano ◽  
Tomohiro Agou ◽  
Toshio Kubota ◽  
Tsutomu Konno
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Liquid Crystalline ◽  
Valuable Insight ◽  
The Novel ◽  
Light Emitting ◽  
Heating And Cooling ◽  
Chiral Nematic ◽  
Blue Phase ◽  
Insight Into

In this study, we designed and synthesized novel pentafluorinated bistolane derivatives with 2-chloropentyl or 2-chlorohexyl flexible units as novel light-emitting liquid crystals (LELCs). By measuring the phase-transition behaviors, all derivatives were found to display liquid-crystalline (LC) phases during both heating and cooling processes. Among the novel bistolanes, the S- and R-configured derivatives exhibited a chiral nematic (N*) phase with a typical Grandjean optical texture. Interestingly, the chiral derivatives also exhibited a blue phase with a typical platelet texture in a narrow temperature range (2–4 °C). Photophysical measurements revealed that the 2-chloroalkoxy-substituted pentafluorinated bistolanes exhibited intense photoluminescence (PL) both in solution and in crystalline phases. The PL characteristics, especially the maximum PL wavelength, were found to switch sensitively during the heating and cooling cycles depending on the molecular aggregates through the crystal (Cr) ⇄ N* phase transition. The 2-chloroalkoxy flexible units induced dynamic changes in the LC and PL properties, providing valuable insight into the potential of various LELCs as PL sensing materials.

scholarly journals Hexakis(terthiophenylthio)benzene as a Mew Class Liquid Crystalline Molecule

1999 ◽  
Vol 23 (10) ◽  
pp. 596-597
Author(s):  
Shinobu Inoue ◽  
Shoji Nishiguchi ◽  
Satoshi Murakami ◽  
Yoshio Aso ◽  
Tetsuo Otsubo ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Smectic A ◽  
Smectic C ◽  
Nematic Phases

A disk-like molecule, in which six α-linked terthiophenes are connected to a central benzene core via a thioether linkage, shows a sequence of calamitic liquid crystalline mesomorphism involving smectic C, smectic A and nematic phases.

Synthesis, characterisation and liquid-crystalline phase transition studies on two higher homologues of 4O.m (m=14 and 16) series

2001 ◽  
Vol 709 ◽  
Author(s):  
C. Rama Chandra Prabhu ◽  
V.G.K.M. Pisipati
Keyword(s):  
Phase Transition ◽  
Liquid Crystalline ◽  
Scanning Calorimetry ◽  
First Order ◽  
Smectic A ◽  
Phase Transition Temperatures ◽  
Crystalline Phase Transition ◽  
M 14 ◽  
Enthalpy Data ◽  
Transition Studies

ABSTRACTThe synthesis, characterization and phase transition studies of higher homologues of N(p-nbutoxybenzylidene)p-n-alkylanilines, Viz., 4O.m series (m=14 and 16) are carried out by thermal microscopy, differential scanning calorimetry and density. The compounds exhibit a phase variant of nematic and smectic-A. Density studies reveal a first order nature of IN transitions and a weak first order NA transitions. An estimate of pressure dependence of the phase transition temperatures using the volume and enthalpy data are presented. A comparison of these results with other reported results in nO.m and other compounds are presented.

Electroclinic effect around a smectic A-chiral nematic phase transition

2002 ◽  
Vol 29 (9) ◽  
pp. 1251-1251
Author(s):  
C. L. Folcia ◽  
J. Ortega ◽  
J. Etxebarria
Keyword(s):  
Phase Transition ◽  
Nematic Phase ◽  
Smectic A ◽  
Chiral Nematic

scholarly journals Synthesis and Characterization of Photoluminescence Liquid Crystals Based on Flexible Chain-Bearing Pentafluorinated Bistolanes

Crystals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 603
Author(s):  
Shigeyuki Yamada ◽  
Masaya Sato ◽  
Tsutomu Konno
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Oxygen Atom ◽  
Liquid Crystalline ◽  
Color Change ◽  
Photophysical Properties ◽  
Structure Property ◽  
Flexible Chain ◽  
Structure Property Relationships ◽  
Chiral Nematic

The liquid-crystalline (LC) and photophysical properties of molecules are very sensitive to their electronic and molecular aggregate structures. Herein, to shed light on the structure–property relationships of pentafluorinated bistolane-based photoluminescence (PL) liquid crystals (PLLCs) previously reported by our group, we synthesized pentafluorinated bistolanes with variable flexible chains and evaluated their LC and photophysical properties. The incorporation of an oxygen atom (to afford a 2-methoxyethoxy unit) or an oxygen atom and a methyl group (to afford a 1-methoxyprop-2-oxy unit) into the flexible butoxy chain significantly decreased the temperature of the crystalline-to-LC phase transition, and a chiral nematic phase comprising helical molecular aggregates was observed for the chiral 1-methoxyprop-2-oxy group–bearing bistolane. The synthesized bistolanes exhibited strong blue PL in both solution and crystalline phases; the featuring PL characteristics were maintained in the LC phase (produced by the crystalline-to-LC phase transition) except for a slight PL color change. Thus, it was concluded that the PL behavior of pentafluorinated bistolanes can be modulated by the choice of a suitable flexible chain, and the obtained insights are believed to facilitate the application of PLLCs in thermosensing PL materials.

Effects of the preparing condition of a polymer-stabilised liquid crystal with a smectic-A−chiral nematic phase transition on its properties

2009 ◽  
Vol 36 (2) ◽  
pp. 165-172 ◽  
Author(s):  
Guohui Pan ◽  
Yubo Cao ◽  
Renwei Guo ◽  
Huicong Cheng ◽  
Zhou Yang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Liquid Crystal ◽  
Nematic Phase ◽  
Smectic A ◽  
Chiral Nematic

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.

Thermal and Liquid Crystalline Properties of a Polymer with Amphiphilic-Mesogenic Side-Chains

2001 ◽  
Vol 709 ◽  
Author(s):  
Seiji Ujiie ◽  
Yumi Yano ◽  
Akira Mori
Keyword(s):  
Molecular Weight ◽  
Liquid Crystalline ◽  
Water Soluble ◽  
Low Molecular Weight ◽  
Side Chains ◽  
Columnar Phase ◽  
Smectic A ◽  
Smectic C ◽  
Heating And Cooling ◽  
Lyotropic Mesophases

ABSTRACTA low-molecular-weight liquid crystalline amphiphilic compound (Az6Bu) and a liquid crystalline polymethacrylate [P(Az6Bu)] with amphiphilic-mesogenic side-chains are reported in this present paper. A polyethyleneimine chain with 2-hydroxyethyl side-groups was used as the water-soluble spacer. Az6Bu exhibited a lyotropic columnar phase and no thermotropic mesophase. P(Az6Bu) showed thermotropic and lyotropic liquid crystalline properties. P(Az6Bu) formed thermotropic smectic A and C mesophases on the heating and cooling processes. The lyotropic systems consisting of P(Az6Bu) and water exhibited a smectic C lyomesophase with oilystreak and schlieren textures. The layered structures formed in the thermotropic and lyotropic mesophases are composed of a sublayer produced by the anisotropic alignment of aromatic-mesogenic groups and a sublayer of hydrophilic groups.

Sign in / Sign up

Export Citation Format

Share Document