scholarly journals Photosensitive Bent-Core Compounds with Azo-Group Attached to the Central Ring

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1030
Author(s):  
Martin Cigl ◽  
Věra Hamplová ◽  
Damian Pociecha ◽  
Vladimíra Novotná
Keyword(s):  
Liquid Crystalline ◽  
Uv Light ◽  
Structural Parameters ◽  
Structural Motif ◽  
Isotropic Phase ◽  
Phase Identification ◽  
Scanning Calorimetry ◽  
Dsc Measurements ◽  
Disubstituted Benzene ◽  
Phase Transition Temperatures

We prepared and studied bent-core liquid crystalline (LC) compounds based on 1,3-disubstituted benzene in a central part and azo-linkage attached directly to this bent core. We designed three structures and checked their mesogenic properties, as well as photosensitivity. We found that two studied compounds revealed columnar LC mesophases, which we transformed to the isotropic phase under the illumination of UV light. We concluded that only one type of structural motif was not mesogenic. For LC compounds, we established phases and phase transition temperatures based on differential scanning calorimetry (DSC) measurements and observations in a polarizing microscope. To confirm phase identification, X-ray studies were performed and structural parameters describing the columnar phases supplied.

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

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 735 ◽  
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.

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.

Analytical Models for the Systematic Errors of Differential Scanning Calorimetry Instruments

Volume 1 ◽  
2004 ◽  
Author(s):  
Adrian S. Sabau ◽  
Wallace D. Porter
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Change ◽  
Computational Analysis ◽  
Systematic Errors ◽  
Analytical Models ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
Heating And Cooling ◽  
Dsc Measurements ◽  
Phase Transition Temperatures

Differential Scanning Calorimetry (DSC) measurements are routinely used to determine enthalpies of phase change, phase transition temperatures, glass transition temperatures, and heat capacities. In order to obtain data on the amount of phases during phase change, time-temperature lags, which are inherent to the measurement process, must be estimated through a computational analysis. An analytical model is proposed for the systematic error of the instrument. Numerical simulation results are compared against experimental data obtained at different heating and cooling rates.

SYNTHESIS AND CHARACTERIZATION OF NEW THERMOTROPIC LIQUID CRYSTALLINE POLYURETHANES WITH BIPHENYL MOIETY

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4487-4492 ◽  
Author(s):  
JONG BACK LEE ◽  
SANG PILL LEE ◽  
JIN KYUNG LEE
Keyword(s):  
Liquid Crystalline ◽  
Gravimetric Analysis ◽  
Scanning Calorimetry ◽  
Infrared Study ◽  
H Nmr ◽  
X Ray Scattering ◽  
Phase Transition Temperatures ◽  
No Weight Loss ◽  
Ft Ir ◽  
Tolylene Diisocyanate

A new series of thermotropic polyurethanes containing biphenyl units was synthesized by polyaddition reaction of diisocyanates such as 2,6-tolylene diisocyanate, 2,5-tolylene diisocyanate, 2,4-tolylene diisocyanate, and 1,4-phenylene diisocyanate, with 4,4□-bis(9-hydroxynonoxy)biphenyl (BP9). Structures of the monomer and the corresponding polymers were identified using FT-IR and 1 H NMR spectroscopic methods. BP9 exhibited a smectic type mesophase, however, nematic phase was found for all synthesized liquid crystalline polyurethanes except for 1,4-phenylene diisocyanate/BP9 based polyurethane. Their phase transition temperatures and thermal stability were investigated by differential scanning calorimetry (DSC), optical polarizing microscopy, and X-ray scattering. The infrared study indicated that the hydrogen bonding among urethane linkages attributed to the mesomorphism. Thermal gravimetric analysis (TGA) of synthesized polyurethanes showed that no weight loss of the polymers observed up to 280°C.

Dilatometric Study on Phase Transitions of Benzylidene-p-n-hexadecyl /Hexadecyloxy Anilines (5.O16, 5O.O16 and 5.16)

2011 ◽  
Vol 181-182 ◽  
pp. 67-70
Author(s):  
M. Ramakrishna Nanachara Rao ◽  
P.V. Datta Prasad ◽  
D. Madhavi Latha ◽  
V.G.K.M. Pisipati
Keyword(s):  
Phase Transition ◽  
Schiff Base ◽  
Phase Transitions ◽  
Liquid Crystalline ◽  
The Body ◽  
Phase Identification ◽  
Transition Temperatures ◽  
Phase Transition Temperatures ◽  
Characterization Studies ◽  
Density Results

Synthesis, characterization and phase transition studies (Dilatometry) have been carried out on three mesomorphic Schiff base compounds viz., N-(p-n-pentyl benzylidene)-p-n-hexadecyloxy aniline, 5.O16, N-(p-n-pentyloxy benzylidene)-p-n-hexadecyloxy aniline 5O.O16 and N-(p-n-pentyl benzylidene)-p-n-hexadecyl aniline, 5.16. The liquid crystalline phase identification and the phase transition temperatures have been carried out using SDTECHS polarising microscope attached with temperature controller with accuracy of ± 0.1 °C and for the conformation of the phase identification and the textures observed are compared with the standard textures. Further, the phase transition temperatures and the corresponding heats of transition across the phase transitions are recorded using DSC (Perkin Elmer). The characterization studies reveal that these compounds exhibit NG, N and A phase variants respectively. The nature of the phase transitions are studied through density results using dilatometric technique. The phase transitions exhibit first order nature in all the cases as expected. The results are discussed in the light of the body of the data available on other Schiff base compounds and on 5O.16.

Effects of Cyclic Heating and Cooling on the Banana-Phase Growing Behaviors of Banana-Shaped Liquid Crystal 1,3-Phenylene-bis[4-(4-octyl phenylimino)methyl]benzoate

2010 ◽  
Vol 428-429 ◽  
pp. 322-325 ◽  
Author(s):  
Yuan Ming Huang ◽  
Qing Lan Ma ◽  
Bao Gai Zhai
Keyword(s):  
Liquid Crystal ◽  
Nucleation And Growth ◽  
Methyl Benzoate ◽  
Isotropic Phase ◽  
Cyclic Heating ◽  
Phase Growth ◽  
Scanning Calorimetry ◽  
Polarized Optical Microscopy ◽  
Heating And Cooling ◽  
Phase Transition Temperatures

The effects of cyclic heating and cooling on the banana-phase growth behaviors of the prototype banana-shaped liquid crystal 1,3-phenylene-bis[4-(4-octylphenylimino)methyl]benzoate were investigated with differential scanning calorimetry and polarized optical microscopy, respectively. Cyclic heating and cooling can reduce the phase transition temperatures and increase the domain sizes of the banana phases of the banana-shaped liquid crystal. These results can be interpreted in terms of the nucleation and growth of the banana phases out of its isotropic phase of the banana-shaped liquid crystal.

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

Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1161
Author(s):  
Anna Poryvai ◽  
Alexej Bubnov ◽  
Michal Kohout
Keyword(s):  
Liquid Crystalline ◽  
Uv Light ◽  
Structural Type ◽  
Optical Microscope ◽  
Light Illumination ◽  
Aromatic System ◽  
Scanning Calorimetry ◽  
Crystalline Materials ◽  
Liquid Crystalline Materials ◽  
Mesomorphic Properties

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.

Preparation and Characterization of Oligopeptide/M-Pluronic F127 Composite Membranes

2020 ◽  
Vol 996 ◽  
pp. 59-63
Author(s):  
Chuan Jun Xia ◽  
Ping Deng Ming ◽  
Ya Song Hu ◽  
Cong Cong Zhan ◽  
An Duo Zhou ◽  
...  
Keyword(s):  
Self Assembly ◽  
Structural Parameters ◽  
Composite Films ◽  
Composite Membranes ◽  
Intermolecular Forces ◽  
Pluronic F127 ◽  
Scanning Calorimetry ◽  
Dsc Measurements ◽  
Assembly Behavior

In the present study, oligopeptide (TEA) and modified Pluronic F127 (M-Pluronic F127) with different mass fraction composited by intermolecular forces. And the oligopeptide/M-Pluronic F127 composite membranes were prepared and investigated. The structural parameters of the membranes were characterized by fourier transform-infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) measurements. It was found that there had strong interaction between TEA and M-Pluronic F127 and the composite films with different proportions had different surface morphology and thermal stability. The characteristics of the membranes were related to the significant changes of the self-assembly behavior of the TEA modified by M-Pluronic F127.

Synthesis and properties of new aromatic-aliphatic homo-and copoly(ester-imide)s based on 3,4,3',4'-diphenylsulphone tetracarboxdiimide

1995 ◽  
Vol 7 (3) ◽  
pp. 347-355 ◽  
Author(s):  
Moriyuki Sato ◽  
Tomohiro Hirata ◽  
Tomoaki Kamrnita ◽  
Ken-ichi Mukaida
Keyword(s):  
Thermal Analysis ◽  
Liquid Crystalline ◽  
Analysis Data ◽  
Dichloroacetic Acid ◽  
Scanning Calorimetry ◽  
Phase Transition Temperatures ◽  
Elemental Analyses ◽  
Nematic Phases ◽  
Chain Lengths ◽  
Tetracarboxylic Dianhydride

New aromrnatic-aliphatic homo-and copoly(ester-imide)s were prepared by the melt polytransesterification of a dihexanol derivative of 3,4,3',4'-diphenylsulphone tetra-carboxdiimide and'/or a dioxydihexanol of biphenyl with aliphatic dimethyl esters of various chain lengths (m=6, 8 and 18) in the presence of zinc acetate. The tetracarboxdiimide derivative was prepared by the methanolysis of the corresponding diacetylated compound derived from 3,4,3',4'-diphenylsulphone tetracarboxylic dianhydride and 6-amino-1-hexanol with acetic anhydride. The structures of the polymers were confirmed by means of FTIR and 13C NMR spectra, and elemental analyses. They had very good solubility in organic solvents such as chloroform and dichloroacetic acid. The thermal properties of the polymers were investigated by differential scanning calorimetry (DSC), and thermogravimetry and differential thermal analysis (TG-DTA) measurements. The thermal analysis data indicated that the polymers were thermally stable up to near 300C in air and had low phase transition temperatures based on glass transition, and melting and/or isotropization below 200C. Two biphenyl-rich copolymers were recognized to show thermotropic liquid crystalline nematic phases by optical texture observation and x-ray analyses at various temperatures.

Electron microscopy of crystalline structure in thermotropic random copolymers

1991 ◽  
Vol 49 ◽  
pp. 1054-1055
Author(s):  
Afzana Anwer ◽  
S. Eilidh Bedford ◽  
Richard J. Spontak ◽  
Alan H. Windle
Keyword(s):  
Electron Microscopy ◽  
Crystalline Structure ◽  
Liquid Crystalline ◽  
Elevated Temperatures ◽  
Random Copolymers ◽  
Molecular Characteristics ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Identical Monomer ◽  
Periodic Layer

Random copolyesters composed of wholly aromatic monomers such as p-oxybenzoate (B) and 2,6-oxynaphthoate (N) are known to exhibit liquid crystalline characteristics at elevated temperatures and over a broad composition range. Previous studies employing techniques such as X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) have conclusively proven that these thermotropic copolymers can possess a significant crystalline fraction, depending on molecular characteristics and processing history, despite the fact that the copolymer chains possess random intramolecular sequencing. Consequently, the nature of the crystalline structure that develops when these materials are processed in their mesophases and subsequently annealed has recently received considerable attention. A model that has been consistent with all experimental observations involves the Non-Periodic Layer (NPL) crystallite, which occurs when identical monomer sequences enter into register between adjacent chains. The objective of this work is to employ electron microscopy to identify and characterize these crystallites.

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