scholarly journals Synthesis and Determination of Thermotropic Liquid Crystalline Behavior of Cinnamaldehyde-Based Molecules with Two Schiff Base Linking Units

Molecules ◽  
2020 ◽  
Vol 25 (17) ◽  
pp. 3780
Author(s):  
Zuhair Jamain ◽  
Nor Faizawani Omar ◽  
Melati Khairuddean
Keyword(s):  
Schiff Base ◽  
Liquid Crystal ◽  
Nematic Phase ◽  
Liquid Crystalline ◽  
Condensation Reaction ◽  
Structure Property ◽  
Scanning Calorimetry ◽  
Crystal Properties ◽  
Structure Property Relationship

A series of liquid crystal molecules with two Schiff base linking units and a cinnamaldehyde core with different terminal groups were synthesized and characterized. The intermediates of 4-heptyloxybenzaldehyde (1a) and 4-dodeyloxybenzaldehyde (1b) were synthesized through the alkylation of 4-hydroxybenzaldehyde with a series of bromoalkane. A condensation reaction of cinnamaldehyde, 1,4-phenylenediamine and a series of substituted benzaldehydes with different terminal groups such as bromo, chloro, hydroxy, cinnamaldehyde, hydrogen, methoxy, heptyloxy and dodecyloxy produced a series of new cinnamaldehyde-based compounds, 2–9, respectively. All these compounds were characterized using Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and CHN elemental analysis. The liquid crystal properties of these compounds were determined using polarized optical microscopy (POM), and their transitions were further confirmed using differential scanning calorimetry (DSC). Compounds with chloro, bromo, methoxy, heptyloxy, and dodecyloxy substituents are mesogenic compounds with nematic phase behavior. However, the other compounds were found to be non-mesogenic without any mesophase transitions. The structure–property relationship was investigated in order to study the effect of different terminal groups and Schiff base linking units on the liquid crystalline behavior of these compounds.

scholarly journals Liquid-Crystal and Fire-Retardant Properties of New Hexasubstituted Cyclotriphosphazene Compounds with Two Schiff Base Linking Units

Molecules ◽  
2020 ◽  
Vol 25 (9) ◽  
pp. 2122 ◽  
Author(s):  
Zuhair Jamain ◽  
Melati Khairuddean ◽  
Tay Guan-Seng
Keyword(s):  
Schiff Base ◽  
Liquid Crystal ◽  
Polyester Resin ◽  
Fire Retardant ◽  
Terminal Group ◽  
Scanning Calorimetry ◽  
Limiting Oxygen Index ◽  
Crystal Properties ◽  
Fire Retardant Properties ◽  
Good Agreement

A series of new hexasubstituted cyclotriphosphazene compounds (4a–j) consisting of two Schiff base linking units and different terminal substituents was successfully synthesized and characterized. The structures of these compounds were confirmed using Fourier Transform Infra-Red (FTIR), Nuclear Magnetic Resonance (NMR), and CHN elemental analysis. Polarized optical microscopy (POM) was used to determine their liquid-crystal behavior, which was then further confirmed using differential scanning calorimetry (DSC). Compounds 4a–i with heptyl, nonyl, decyl, dodecyl, tetradecyl, hydroxy, 4-carboxyphenyl, chloro, and nitro terminal ends, respectively, showed the liquid-crystal properties, whereas compound 4j with the amino group was found to be non-mesogenic. The attachment of an electron-donating group in 4j eventually give a non-mesogenic product. The study of the fire-retardant properties of these compounds was done using the limiting oxygen index (LOI). In this study, polyester resin (PE) was used as a matrix for moulding, and the LOI value of pure PE was 22.53%. The LOI value increased to 24.71% when PE was incorporated with 1 wt.% of hexachlorocyclotriphosphazene (HCCP), thus indicating that HCCP has a good fire-retardant properties. The result showed that all the compounds have good agreement in their LOI values. Compound 4i with a nitro terminal group gave the highest LOI value of 28.37%.

scholarly journals The use of isoxazoline and isoxazole scaffolding in the design of novel thiourea and amide liquid-crystalline compounds

2020 ◽  
Vol 16 ◽  
pp. 175-184 ◽  
Author(s):  
Itamar L Gonçalves ◽  
Rafaela R da Rosa ◽  
Vera L Eifler-Lima ◽  
Aloir A Merlo
Keyword(s):  
Liquid Crystal ◽  
Relative Position ◽  
Liquid Crystalline ◽  
Condensation Reaction ◽  
Ammonium Thiocyanate ◽  
The Other ◽  
Amide Derivatives ◽  
Crystal Properties ◽  
Benzoyl Chlorides ◽  
Membered Heterocycle

A series of novel thiourea and amide liquid crystals containing 5-membered isoxazoline and isoxazole rings were synthetized and the liquid crystal properties studied. Thioureas were obtained using a condensation reaction of benzoyl chlorides, arylamines and ammonium thiocyanate. The amides, on the other hand, were the byproduct of a quantitative reaction which used potassium cyanate as the starting material. Thiourea and amide derivatives were predominantly SmA mesophase inductors. A nematic mesophase was observed only for thioureas and amides containing an isoxazole ring. Additionaly, the liquid crystal behavior was also dependent on the relative position of nitrogen and oxygen atoms on the 5-membered heterocycle.

scholarly journals Synthesis, liquid crystalline behaviour and structure–property relationships of 1,3-bis(5-substituted-1,3,4-oxadiazol-2-yl)benzenes

2020 ◽  
Vol 16 ◽  
pp. 149-158
Author(s):  
Afef Mabrouki ◽  
Malek Fouzai ◽  
Armand Soldera ◽  
Abdelkader Kriaa ◽  
Ahmed Hedhli
Keyword(s):  
Differential Scanning Calorimetry ◽  
Liquid Crystalline ◽  
Dipole Moments ◽  
Structure Property ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Rigid Core ◽  
X Ray ◽  
Structure Property Relationships ◽  
Crystal Properties

Two series containing 1,3-bis(1,3,4-oxadiazol-2-yl)benzene as a rigid core (RC) and alkyl or perfluoroalkyl as terminal chains were synthesized and characterized. Liquid crystal properties of the synthesized compounds have been investigated by polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction techniques. Conformation effects of the synthesized products on the dipole moments were also investigated.

scholarly journals An unsymmetrical porphyrin and its metal complexes: Synthesis, spectroscopy, thermal analysis and liquid crystal properties

2009 ◽  
Vol 74 (10) ◽  
pp. 1097-1104 ◽  
Author(s):  
Changfu Zhuang ◽  
Xuexin Tang ◽  
Dong Wang ◽  
Aiqing Xia ◽  
Wenhui Lian ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Liquid Crystalline ◽  
Thermal Studies ◽  
Luminescent Properties ◽  
Quantum Yields ◽  
Scanning Calorimetry ◽  
Crystal Properties

The synthesis and characterization of a new unsymmetrical porphyrin liquid crystal, 5-(4-stearoyloxyphenyl)phenyl-10,15,20-triphenylporphyrin (SPTPPH2) and its transition metal complexes (SPTPPM, M(II) = Zn, Fe, Co, Ni, Cu or Mn) are reported. Their structure and properties were studied by elemental analysis, and UV-Vis, IR, mass and 1H-HMR spectroscopy. Their luminescent properties were studied by excitation and emission spectroscopy. The quantum yields of the S1 ? S0 fluorescence were measured at room temperature. According to thermal studies, the complexes have a higher thermal stability (no decomposition until 200?C). Differential scanning calorimetry (DSC) data and an optical textural photograph, obtained using a polarizing microscope (POM), indicate that the porphyrin ligand had liquid crystalline character and that it exhibited more than one mesophase and a low-lying phase transition temperature, with transition temperatures of 19.3 and 79.4?C; the temperature range of the liquid crystal (LC) phase of the ligand was 70.1?C.

scholarly journals Synthesis, characterization and structure-property relationships of 1,3-bis(5-substituted-1,3,4-oxadiazol-2-yl)benzenes

2019 ◽  
Author(s):  
Afef Mabrouki ◽  
Malek Fouzai ◽  
Armand Soldera ◽  
Abdelkader Kriaa ◽  
ahmed hedhli
Keyword(s):  
Differential Scanning Calorimetry ◽  
Liquid Crystal ◽  
Dipole Moments ◽  
Structure Property ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Rigid Core ◽  
X Ray ◽  
Structure Property Relationships ◽  
Crystal Properties

Two series containing 1,3-bis(1,3,4-oxadiazol-2-yl)benzene as a rigid core (RC) and alkyl or perfluoroalkyl as terminal chains were synthesized and characterized. Liquid Crystal properties of the synthesized compounds have been investigated by Polarizing Optical Microscopy, Differential Scanning Calorimetry and X-ray Diffraction techniques. Conformation effects of the synthesized products on the dipole moments were also investigated.

Synthesis and Properties of Novel Thiophene-Based Liquid Crystalline Conducting Polymers

2017 ◽  
Vol 25 (9) ◽  
pp. 669-676 ◽  
Author(s):  
Danesh Roudini
Keyword(s):  
Magnetic Field ◽  
Differential Scanning Calorimetry ◽  
Liquid Crystal ◽  
Optical Microscopy ◽  
Electronic Properties ◽  
Liquid Crystalline ◽  
Side Chain ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Crystal Properties

Side-chain liquid crystalline polythiophenes were synthesised and the effects of the mesogenic units on the structure and electronic properties of the polymers were studied. The liquid crystal properties of the polymer films were studied using polarised hot-stage optical microscopy and differential scanning calorimetry, and X-ray diffractometry was used to investigate the effect of a magnetic field on the monomers and polymers.

scholarly journals New azobenzene liquid crystal with dihydropyrazole heterocycle and photoisomerization studies

2020 ◽  
Vol 7 (7) ◽  
pp. 200474
Author(s):  
Xiaoxuan Wang ◽  
Zhaoxia Li ◽  
Haiying Zhao ◽  
Shufeng Chen
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystalline ◽  
Ester Group ◽  
Azo Compounds ◽  
Scanning Calorimetry ◽  
Polarizing Microscopy ◽  
Mesogenic Unit ◽  
Crystal Properties ◽  
Azobenzene Derivatives ◽  
Long Chain

New azobenzene derivatives with dihydropyrazole heterocycle have been prepared and characterized. According to thermal polarizing microscopy and differential scanning calorimetry studies, the compounds consisting of four linearly linked rings and a long alkoxy chain on the azobenzene side ( 3a-8 and 3a-14 ) displayed no liquid crystal properties. When the length of mesogenic unit increased to five rings, except for compound 5a-8 , all compounds from 5a-10 to 5a-16 containing a long chain of 10–16 carbon atoms on the side of ester group displayed liquid crystalline properties, and the mesogenic domain gradually narrowed with increase of the chain length. However, in the case of the molecule with long alkoxy chains on both sides, only 5c-16 with a long chain of 16 carbon atoms exhibited liquid crystal behaviour. In addition, these azo compounds underwent isomerization from E to Z under ultraviolet irradiation and then thermal back relaxation slowly in the dark, which can be recycled many times.

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