scholarly journals Photosensitive Bent-Core Liquid Crystals with Laterally Substituted Azobenzene Unit

Crystals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1265
Author(s):  
Diana Jágerová ◽  
Michal Šmahel ◽  
Anna Poryvai ◽  
Jan Macháček ◽  
Vladimíra Novotná ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Nematic Phase ◽  
Uv Light ◽  
Rapid Development ◽  
Functional Materials ◽  
Scanning Calorimetry ◽  
Isotropic Liquid ◽  
Relative Configuration ◽  
Azo Group ◽  
Optical Polarizing Microscopy

Photosensitive liquid crystals represent an important class of functional materials that experience rapid development. Hereby, we present novel bent-core liquid crystals bearing a lateral substitution on the central core and in the vicinity of the photosensitive unit—an azo group. The azo group enables fast (E)-to-(Z)-isomerization upon irradiation with UV-light and visible light, while the substitution facilitates the high stability of the photochemically formed (Z)-isomer. The effectiveness of the irradiation and the composition of photostationary states was determined by UV/Vis and 1H NMR spectroscopy. A nematic phase formed by the materials was characterized by differential scanning calorimetry and optical polarizing microscopy. We show that the materials easily change their relative configuration of the N=N double bond not only in solution, but also in the mesophase, which leads to fast isothermal phase transition from the nematic phase to isotropic liquid.

Synthesis of 4-Chloro-1,3-Diazobenzene Bent-Cores Liquid Crystal and Characterizations of Its Mesogenic Behaviors and Photosensitivity

2020 ◽  
Author(s):  
Jinying Lu ◽  
Zelong Zhang ◽  
Daoren Yan ◽  
Zhiyong Zhang ◽  
Jintao Guan ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Nematic Phase ◽  
Density Functional ◽  
Optical Switching ◽  
Density Functional Theory Calculations ◽  
Acetate Solution ◽  
Photochromic Properties ◽  
Scanning Calorimetry ◽  
Isotropic Liquid ◽  
Practical Applications

<p></p><p>Azobenzene-based bent-core liquid crystals demonstrate a variety of mesomorphic behaviors and photochromic properties which are desirable for optical switching. In this study, a novel compound was synthesized by adding azo functional groups and chlorine substituent to the central bent-cores to form a 4-chloro-1,3-dizaophenylene bent-core. This compound was characterized by fourier-transform infrared spectroscopy (FTIR), <sup>1</sup>H and <sup>13</sup>C nuclear magnetic resonance (NMR), mass spectrometry (MS), differential scanning calorimetry (DSC), polarized optical microscopy (POM), ultraviolet–visible spectroscopy (UV-Vis) to evaluate its structure, mesogenic properties, and photosensitivity. The experimental results show that compound <b>4c</b> exhibits a broad temperature window of 63.8 °C for nematic phase, rapid photoisomerization in seconds, and high <i>cis</i> fraction 0.81. At room temperature, compound <b>4c </b>dissolved in ethyl acetate solution can reach photostationary state in 10 seconds. At 95 °C, compound <b>4c</b> in nematic phase became isotropic liquid under UV-irradiation in 3 seconds due to the forward <i>trans – cis</i> photoisomerization and can be restored to be nematic under natural visible light in 5 seconds because of the backward <i>cis – trans</i> photoisomerization. Density functional theory calculations confirm that the diazo as the central linkages instead of esters can effectively reduce the molecular dipole moment, which promotes these favorable characteristics. This study provides valuable insights to improve future design of azobenzene bent-core liquid crystals for practical applications especially in photonic applications.</p><p></p>

scholarly journals Synthesis, Self-Assembly and Photoresponsive Behavior of Liquid Crystals Based on Azobenzene

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1560
Author(s):  
Yaming Wu ◽  
Yuhai Liu ◽  
Jianxiang Chen ◽  
Runmiao Yang
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Self Assembly ◽  
Driving Force ◽  
1H Nmr Spectroscopy ◽  
Uv Light ◽  
Light Exposure ◽  
Scanning Calorimetry ◽  
Stimulus Response ◽  
Cis Isomer

A new amphiphilic surfactant (C4-Azo-C5-HDA) was formed by liquid crystals (LCs) based on azobenzene, whose structures were characterized by 1H-NMR spectroscopy. The reversible hydrogelation upon changes in temperature and light exposure was also studied. Under the irradiation of UV light, the trans-isomer of C4-Azo-C5-HDA rapidly photoisomerized to the cis-isomer, resulting in rapid disruption of the gel. The thermotropic liquid crystal behavior of the gelator was investigated via Differential Scanning Calorimetry (DSC) and Polarizing Optical Microscopy (POM). The biocompatibility experiment of multi-stimulus response of the liquid crystal provides a potential driving force for the development of biomaterials.

Characterization and Thermal Behaviour of Polymer-Dispersed Liquid Crystals

2010 ◽  
Vol 152-153 ◽  
pp. 284-287 ◽  
Author(s):  
Xian Gen Han ◽  
Xian Yong Wei ◽  
Xing Yong Wang ◽  
Robert A. Shanks
Keyword(s):  
Liquid Crystals ◽  
Thermal Behaviour ◽  
Nematic Phase ◽  
Polarized Light ◽  
Nitrogen Atmosphere ◽  
Scanning Calorimetry ◽  
Polymer Dispersed Liquid Crystals ◽  
Polymer Dispersed ◽  
Clearing Temperature ◽  
Poly Ethylene

The thermal behaviour of polymer dispersed liquid crystals (PDLC), blends of poly(ethylene-co-methylacrylic acid) (PEMA) with 4-(n-hydroxypropoylxy)-4'-cyanobiphenyl (H3CB) prepared by solvent-induced phase separation (SIPS) method, has been characterized using differential scanning calorimetry (DSC) and polarized light microscopy (POM). Study shows that the concentration of the mixture of PEMA/ H3CB must be least 30%, which will exhibit nematic to isotropic transition phase during heating or cooling. Above 30 wt % 3CB the mixtures exhibited nematic phase, and this was detected as a splitting of the nematic-isotropic peak in the DSC thermograms. The clearing temperature of the PEMA/H3CB mixtures was higher than that of pure H3CB’s, the average increasing being 14°C, which is the evident that the polymer matrix could stable the nematic phase. This behaviour is in contrast with other reports about polymer-dispersed liquid crystals. In addition, thermal decomposition was also studied by thermogravimetry in nitrogen environments. A double-stage decomposition process was found in nitrogen atmosphere, and this was mainly due to H3CB for the first step and the PEMA decomposition for the second step.

EFFECT OF THICKNESS OF LIQUID CRYSTALLINE LAYER ON THE THERMOTROPIC AND THERMODYNAMICAL PROPERTIES OF NEMATIC-ISOTROPIC LIQUID AND ISTROPIC LIQUID-NEMATIC PHASE TRANSITIONS

2006 ◽  
Vol 20 (23) ◽  
pp. 3383-3394 ◽  
Author(s):  
ÖMER POLAT ◽  
ARIF NESRULLAJEV ◽  
ŞENER OKTIK
Keyword(s):  
Phase Transitions ◽  
Liquid Crystals ◽  
Interaction Energy ◽  
Nematic Phase ◽  
Liquid Crystalline ◽  
Isotropic Liquid ◽  
Crystalline Layer ◽  
Thermodynamical Properties ◽  
Work Effect

In this work, effect of thickness of the liquid crystalline layer on the morphologic, thermotropic and thermodynamical properties of the nematic–isotropic liquid and isotropic liquid–nematic phase transitions in Shiff based liquid crystals has been investigated. The shift of temperatures of the nematic–isotropic liquid and isotropic liquid–nematic phase transitions to the lower temperatures and the widening of linear and temperature widths of the heterophase regions of these phase transitions by the increase in the thickness of liquid crystalline layer have been found. The effect of thickness of liquid crystalline layer on morphologic, thermotropic and thermodynamical properties of liquid crystals under investigations is connected with change of interaction energy between liquid crystalline molecules and reference surfaces.

New Liquid Crystalline Material with an Azo Group in the Molecular Core

2011 ◽  
Vol 130-134 ◽  
pp. 1520-1522
Author(s):  
Si Chen ◽  
Si Pei Li ◽  
Xu Wang
Keyword(s):  
Nematic Phase ◽  
Liquid Crystalline ◽  
Polarized Light ◽  
Crystalline Material ◽  
Scanning Calorimetry ◽  
Chemical Structures ◽  
Phase Structures ◽  
Molecular Core ◽  
Azo Group ◽  
Liquid Crystalline Material

A new kind of liquid crystalline material with an azo group in the molecular core was synthesized successfully. The chemical structures of the compounds were confirmed by mass spectrometry and 1H NMR. Their phase structures and transitions were investigated by differential scanning calorimetry. And the liquid crystalline behaviors were researched with polarized light microscopy experiments. The experimental results suggested that the compounds with a azo group in the molecular core can develop into a well-defined nematic phase.

scholarly journals Phase Transitions of N-(4-methoxybenzylidene)-4-butylaniline (MBBA) Confined within Mesoporous Silica

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 792
Author(s):  
Takehisa Yoshimi ◽  
Ayumi Shima ◽  
Shoko Hagiwara-Norifusa ◽  
Takayuki Sugimoto ◽  
Atsushi Nagoe ◽  
...  
Keyword(s):  
Phase Transition ◽  
Nematic Phase ◽  
Three Dimensional ◽  
Porous Silica ◽  
Temperature Shift ◽  
Thermal Anomaly ◽  
Scanning Calorimetry ◽  
Isotropic Liquid ◽  
One Dimensional ◽  
Dsc Measurements

We have used differential scanning calorimetry (DSC) to investigate the phase transition of a liquid crystal, N-(4-methoxybenzylidene)-4-butylaniline (MBBA), confined within porous silica materials with one- and three-dimensional pore architectures. Each phase-transition temperature of the confined MBBA linearly decreased with the inverse pore size compared with that of bulk MBBA. However, the degree of temperature shift varied owing to differences in the pore architectures. In addition, when MBBA was confined within one-dimensional pores, the thermal anomaly associated with the phase transition from the nematic phase to the isotropic liquid phase was not observed in the DSC measurements.

scholarly journals Synthesis, Characterization and Study of Mesomorphic Behavior of New Bent and Liner Core Compounds Containing Heterocyclic

2017 ◽  
Vol 30 (3) ◽  
pp. 195
Author(s):  
Nisreen H. Karam ◽  
Alaa K. Shanshal
Keyword(s):  
Liquid Crystals ◽  
Schiff Bases ◽  
Aromatic Amines ◽  
Nematic Phase ◽  
Liquid Crystalline ◽  
Thioglycolic Acid ◽  
Melting Points ◽  
Scanning Calorimetry ◽  
Phosphorous Oxychloride ◽  
Compound Xvii

  We described herein the synthesized and characterized of new bent and liner core compounds containing thiazolidin-4-one ring[XI-XIII] and [XIV-XVI] respectively. These compounds synthesized by sequence reactions starting from reaction resorcinol or hydroquinone with chloracetyl chloride to yield compounds [I] and [II] ,then the later compounds reactant with 4-hydroxybenzylaldehyde to product dialdehyde compounds [III] and [IV] .The Schiff bases compounds[V-VII] and [VIII-X] synthesized from reaction the compound [III] or [IV] with different aromatic  amines, while the bent and liner core mesogens containing thiazolidin-4-one ring [XI-XIII] and [XIV-XVI] synthesized from reaction Schiff bases compounds[V-VII] or  [VIII-X] with thioglycolic acid. In addition estrfecation of cinnamic acid with methanol to yield ester compound[XVII]which was converted to their acid hydrazid[XVIII] and the acid hydrazid reacted with glysine in phosphorous oxychloride to yield (5-styryl-1,3,4-oxadiazol-2-yl) methanamine [XIX]. Then reactant the1,3,4-oxadiazol compound[XIX]    with dialdehyde compound [III] or  [IV] to product new Schiff bases compounds [XX] and [XXI]  , afterword added thioglycolic acid to give new thiazolidin-4-one derivatives [XXII] and [XXIII], respectively.        The synthesized compounds were characterized by melting points , FTIR ,1HNMR and mass spectroscopy (of some of them).The liquid crystalline properties were studied by hot stage polarized optical microscopy (POM) and differential scanning calorimetry(DSC).All the  Schiff bases compounds [V-X] showed liquid crystals phases while thiazolidin-4-one derivatives[XI-XIII],[XIV-XVI]and [XXIII] didn’t show any liquid crystals properties except the compound [XXII] showed enantiotropic nematic phase.

scholarly journals Thermal and Photocatalytic Performance of Unsaturated Polyester Resins Modified with TiO2 Nanoparticles as Panel Bodies for Vehicles

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2036
Author(s):  
Miren Blanco ◽  
Cristina Monteserín ◽  
Nerea Uranga ◽  
Estíbaliz Gómez ◽  
Estíbaliz Aranzabe ◽  
...  
Keyword(s):  
Tio2 Nanoparticles ◽  
Energy Use ◽  
Near Infrared ◽  
Uv Light ◽  
Unsaturated Polyester ◽  
Curing Kinetics ◽  
Pollutant Emissions ◽  
Transport Sector ◽  
Scanning Calorimetry ◽  
Photocatalytic Effect

The transport sector is the fastest growing contributor to climate emissions and experiences the highest growth in energy use. This study explores the use of TiO2 nanoparticles for obtaining photocatalytic nanocomposites with improved infrared reflectance properties. The nanocomposites were prepared by dispersing 0–20 wt% of TiO2 nanoparticles in an unsaturated polyester resin. The effect of TiO2 on the curing kinetics was studied by differential scanning calorimetry, showing a significant delay of the curing reactions. The thermal reflectance of the modified resins was characterized by UV-Vis-NIR spectrophotometry, measuring total solar reflectance (TSR). The TiO2 greatly increased the TSR of the resin, due to the reflectance properties of the nanoparticles and the change in color of the modified resin. These nanocomposites reflect a significant part of near-infrared radiation, which can contribute to a reduction of the use of heating, ventilation, and air conditioning. Moreover, the photocatalytic effect of the TiO2 modified nanocomposites was studied by monitoring the degradation of an organic model contaminant in an aqueous medium under UV light, and the reusability of the nanocomposites was studied with 5 cycles. The developed nanocomposites are proposed as a solution for reducing global warming and pollutant emissions.

scholarly journals Advanced Functional Materials Based on Nanocellulose for Pharmaceutical/Medical Applications

Pharmaceutics ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1125
Author(s):  
Raluca Nicu ◽  
Florin Ciolacu ◽  
Diana E. Ciolacu
Keyword(s):  
Rapid Development ◽  
Cellulose Nanofibrils ◽  
Functional Materials ◽  
Medical Applications ◽  
Bacterial Nanocellulose ◽  
Green Materials ◽  
Wide Range ◽  
In Vivo Cytotoxicity

Nanocelluloses (NCs), with their remarkable characteristics, have proven to be one of the most promising “green” materials of our times and have received special attention from researchers in nanomaterials. A diversity of new functional materials with a wide range of biomedical applications has been designed based on the most desirable properties of NCs, such as biocompatibility, biodegradability, and their special physicochemical properties. In this context and under the pressure of rapid development of this field, it is imperative to synthesize the successes and the new requirements in a comprehensive review. The first part of this work provides a brief review of the characteristics of the NCs (cellulose nanocrystals—CNC, cellulose nanofibrils—CNF, and bacterial nanocellulose—BNC), as well as of the main functional materials based on NCs (hydrogels, nanogels, and nanocomposites). The second part presents an extensive review of research over the past five years on promising pharmaceutical and medical applications of nanocellulose-based materials, which have been discussed in three important areas: drug-delivery systems, materials for wound-healing applications, as well as tissue engineering. Finally, an in-depth assessment of the in vitro and in vivo cytotoxicity of NCs-based materials, as well as the challenges related to their biodegradability, is performed.

Synthesis and characterisation of reactive liquid crystals containing an azo group

2013 ◽  
Vol 41 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Jianqiang Xie ◽  
Guangming Zhu ◽  
Yusheng Tang ◽  
Yongkun Wang
Keyword(s):  
Liquid Crystals ◽  
Azo Group ◽  
Reactive Liquid
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