Chiral Photoresponsive Liquid Crystalline Materials Derived from Cyanoazobenzene Central Core: Effect of UV Light Illumination on Mesomorphic Behavior

One of the most frequently utilized liquid crystalline (LC) materials is a rod-like (calamitic) compound 4-cyano-4′-pentylbiphenyl (5-CB). The main objective of this work is to enhance its functionality by introducing a photoresponsive diazenyl spacer in the aromatic core and replace the non-chiral pentyl chain with various chiral alkyl carboxylate units. The mesomorphic properties of the prepared materials have been studied using polarizing optical microscopy and differential scanning calorimetry. It has been found that materials with an extended aromatic system possess the liquid crystalline behavior. The studied LC materials have shown mesophases at lower temperatures than previously reported analogous substances. Furthermore, one of them exhibits a chiral orthogonal frustrated twist grain boundary smectic phase, which has not been previously observed for this structural type of materials. We also investigated photoresponse of the mesophases under illumination with UV-light (365 nm) using a polarizing optical microscope. A non-conventional photoresponse of the prepared materials in a crystalline phase is presented and discussed.

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

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.9.45 ◽

2013 ◽

Vol 9 ◽

pp. 425-436 ◽

Cited By ~ 26

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.

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On resolving fine periodic microstructures in the optical microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153798 ◽

1989 ◽

Vol 47 ◽

pp. 364-365

Author(s):

W.S. Putnam ◽

C. Viney

Keyword(s):

Liquid Crystalline ◽

Numerical Aperture ◽

Polarized Light ◽

Normal Incidence ◽

Optical Microscope ◽

Angle Of Incidence ◽

Resolution Limit ◽

Crystalline Materials ◽

Periodic Microstructures ◽

Liquid Crystalline Materials

Many sheared liquid crystalline materials (fibers, films and moldings) exhibit a fine banded microstructure when observed in the polarized light microscope. In some cases, for example Kevlar® fiber, the periodicity is close to the resolution limit of even the highest numerical aperture objectives. The periodic microstructure reflects a non-uniform alignment of the constituent molecules, and consequently is an indication that the mechanical properties will be less than optimal. Thus it is necessary to obtain quality micrographs for characterization, which in turn requires that fine detail should contribute significantly to image formation.It is textbook knowledge that the resolution achievable with a given microscope objective (numerical aperture NA) and a given wavelength of light (λ) increases as the angle of incidence of light at the specimen surface is increased. Stated in terms of the Abbe resolution criterion, resolution improves from λ/NA to λ/2NA with increasing departure from normal incidence.

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Optical investigations and photoactive solar energy applications of new synthesized Schiff base liquid crystal derivatives

Scientific Reports ◽

10.1038/s41598-021-94533-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Fowzia S. Alamro ◽

Sobhi M. Gomha ◽

Mohamed Shaban ◽

Abeer S. Altowyan ◽

Tariq Z. Abolibda ◽

...

Keyword(s):

Solar Energy ◽

Liquid Crystalline ◽

Molecular Structures ◽

Light Illumination ◽

Electrical Measurements ◽

Scanning Calorimetry ◽

Energy Applications ◽

Meta Position ◽

Chain Group ◽

Liquid Crystalline Materials

AbstractNew homologues series of liquid crystalline materials namely, (E)-3-methoxy-4-[(p-tolylimino)methyl]phenyl 4-alkloxybenzoates (I-n), were designed and evaluated for their mesomorphic and optical behavior. The prepared series constitutes three members that differ from each other by the terminally attached alkoxy chain group, these vary between 6 and 12 carbons. A laterally OCH3 group is incorporated into the central benzene ring in meta position with respect to the ester moiety. Mesomorphic characterizations of the prepared derivatives are conducted using differential scanning-calorimetry (DSC), polarized optical-microscopy (POM). Molecular structures were elucidated by elemental analyses and NMR spectroscopy. DSC and POM investigations revealed that all the synthesized derivatives are purely nematogenic exhibiting only nematic (N) mesophase, except for the longest chain derivative (I-12) that is dimorphic possesses smectic A and N phases. Moreover, all members of the group have a wide mesomorphic range with high thermal nematic stability. A comparative study was established between the present derivative (I-6) and their previously prepared isomer. The results indicated that the location exchange of the polar compact group (CH3) influences the N mesophase stability and range. The electrical measurements revealed that all synthesized series I-n show Ohmic behaviors with effective electric resistances in the GΩ range. Under white light illumination, the effective electric conductivity for the compound I-8 is five times that obtained in dark conditions. This derivative also showed two direct optical band gaps in the UV and visible light range. In addition, I-6 has band energy gaps of values 1.07 and 2.79 eV, which are suitable for solar energy applications.

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The Role of Substitution in the Apex Position of the Bent-Core on Mesomorphic Properties of New Series of Liquid Crystalline Materials

Crystals ◽

10.3390/cryst10090735 ◽

2020 ◽

Vol 10 (9) ◽

pp. 735 ◽

Cited By ~ 1

Author(s):

Helena Skopalová ◽

Petr Špaček ◽

Václav Kozmík ◽

Jiří Svoboda ◽

Vladimíra Novotná ◽

...

Keyword(s):

Liquid Crystalline ◽

Structural Parameters ◽

Phase Identification ◽

Crystalline Materials ◽

X Ray ◽

Alkyl Chains ◽

Calorimetric Measurements ◽

Liquid Crystalline Materials ◽

Mesomorphic Properties

We present the synthesis and mesomorphic properties of the new series of bent-core liquid crystals based on 3-hydroxybenzoic acid bearing a lateral substituent in the apex position. Four different substituents of various sizes and electronic properties have been used. We have found that only compounds substituted with fluorine are mesogenic and exhibit one mesophase, whose type differs when prolonging the terminal alkyl chain. For homologues with shorter alkyl chains (octyl, decyl), a columnar B1-type of a mesophase was observed, while materials with longer terminal chains (dodecyl, tetradecyl) exhibited a switchable lamellar SmCAPA phase. Calorimetric measurements, texture observations under a polarizing microscope were performed and electro-optical properties studied. Additionally, dielectric measurements were realized to characterize the molecular dynamics in the SmCAPA phase. All mesogenic compounds were further studied by X-ray measurements to confirm phase identification and obtain more information about their structural parameters.

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Mesomorphism behaviour and photoluminescent properties of new asymmetrical 1,2-di(4-alkoxybenzylidene)hydrazines

Journal of Chemical Research ◽

10.1177/1747519819840715 ◽

2019 ◽

Vol 43 (1-2) ◽

pp. 67-77 ◽

Cited By ~ 1

Author(s):

Adil A Awad ◽

Al-Ameen Bariz OmarAli ◽

Ahmed Jasim M Al-Karawi ◽

Zyad Hussein J Al-Qaisi ◽

Samer Ghanim Majeed

Keyword(s):

Differential Scanning Calorimetry ◽

Liquid Crystal ◽

Liquid Crystalline ◽

Polarized Light ◽

Luminescent Properties ◽

Scanning Calorimetry ◽

Crystalline Materials ◽

X Ray ◽

Step Procedure ◽

Liquid Crystalline Materials

{1-[4-( n-Alkoxy)]-2-(4’-decyloxy)benzylidene}hydrazines ( n-alkoxy = O(CH2) nH, n = 1–9, 12, 16 or 18), an asymmetrical series of 1,2-disubstituted hydrazines, were prepared in a simple two-step procedure as a part of our continuing work in evaluating hydrophobic azine compounds as photoluminescent liquid crystalline materials. The compounds were characterized spectroscopically and their liquid crystalline behaviour and luminescent properties were evaluated using polarized light optical microscopy, differential scanning calorimetry and X-ray powder diffraction techniques. The studies revealed that all of these compounds are liquid crystalline materials exhibiting photoluminescent properties in the crystalline and liquid crystal states.

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Synthesis of Dendrimers Liquid Crystalline Materials based on 1,3,5-triphenylbenzene

International Journal of Drug Delivery Technology ◽

10.25258/ijddt.9.2.28 ◽

2019 ◽

Vol 9 (02) ◽

Author(s):

Linh I Awad ◽

Nasreen R Jber

Keyword(s):

Differential Scanning Calorimeter ◽

Liquid Crystalline ◽

Spectroscopic Method ◽

Optical Microscope ◽

Crystalline Materials ◽

Liquid Crystalline Phases ◽

Ft Ir ◽

Liquid Crystalline Materials ◽

New Compounds ◽

Liquid Crystalline Dendrimers

In this study, new compounds of discotic liquid crystalline dendrimers are prepared which is derived from 1,3,5-triphenylbenzene. The synthesis of these compounds shows the effect of dendrimer unit on the mesogenic properties. The structures of prepared compounds characterized by using spectroscopic method e.g. FT-IR and 1HNMR. The liquid crystalline phases of prepared compounds was identified by using the hot-stage polarizing optical microscope (POM) and differential scanning calorimeter (DSC).

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Perhydroazulene-based liquid-crystalline materials with smectic phases

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.8.44 ◽

2012 ◽

Vol 8 ◽

pp. 403-410 ◽

Cited By ~ 2

Author(s):

Zakir Hussain ◽

Henning Hopf ◽

S Holger Eichhorn

Keyword(s):

Liquid Crystalline ◽

X Ray Diffraction ◽

Core System ◽

Crystalline Materials ◽

Smectic Phases ◽

Differential Scanning Colorimetry ◽

Temperature Ranges ◽

Nematic Phases ◽

Liquid Crystalline Materials ◽

Mesomorphic Properties

New liquid-crystalline materials with a perhydroazulene core were synthesized and the stereochemistry of these compounds was investigated. The mesomorphic properties of the new LC compounds were investigated by differential scanning colorimetry, polarizing optical microscopy and X-ray diffraction. We report here on the LC properties of nonchiral materials, which predominantly exhibit smectic phases and display nematic phases only within narrow temperature ranges. The dependence of the mesogenic behavior of the new materials on the stereochemistry of the core system was also investigated. All newly synthesized compounds were fully characterized by the usual spectroscopic and analytical methods.

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