Mesophase behavior and DFT conformational analysis of new symmetrical diester chalcone liquid crystals

Hagar, Mohamed; Ahmed, Hoda A.; El-Sayed, Taghreed H.; Alnoman, Rua B.

doi:10.1016/j.molliq.2019.04.083

Cited by 64 publications

(49 citation statements)

References 55 publications

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“…Liquid crystalline materials are classified into three distinct types: polymeric, lyotropic, and thermotropic. Thermotropic liquid crystals have been widely studied and used for their linear and nonlinear optical properties [2,[6][7][8][9][10][11][12][13][14][15][16][17][18]. Usually, this type of liquid crystal is represented as rigid rods, which can interact with one another and form characteristic ordered structures.…”

Section: Introductionmentioning

confidence: 99%

Binary Liquid Crystal Mixtures Based on Schiff Base Derivatives with Oriented Lateral Substituents

et al. 2020

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Binary mixtures of the laterally substituted Schiff base/ester derivatives, namely 4-((2- or 3-) substituted phenyl imino methyl) phenyl-4”-alkoxy benzoates, Ia–d, were prepared and mesomorphically studied by differential scanning calorimetry (DSC) and their mesophases identified by polarized optical microscopy (POM). The lateral group (1-naphthyl, 2-F, 2-Br, 3-F in Ia–d, respectively) is attached to different positions of the phenyl Schiff moiety. The mixtures investigated were made from two differently shaped compounds that differ from each other in the polarity, size, orientation, and relative positions of the lateral group. The results revealed that the binary mixture Ia/Ib (bearing the naphthyl and 2-flouro substituents) exhibited the SmA phase, which covered the whole composition range. For the mixtures Ib/Id (2-F and 2-Br), the isomeric lateral F-group in compound Ib distributed the SmA arrangement of Id. In the Ic/Id mixture bearing two positionally and structurally different substituents, the addition of Ic to Id resulted in solid binary mixtures where its behavior may be attributed to the negligible steric effect of the small electronegative fluorine atom compared to the Br atom. Density functional theory (DFT) theoretical calculations were carried out to estimate the geometrical parameters of individual components and to show the effect of these parameters in the mesophase behavior of the binary system, where the higher dipole moment of Id (6 Debye) may be the reason for its high π–π molecular stacking, which influences its mesophase range and stability.

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Section: Introductionmentioning

confidence: 99%

Binary Liquid Crystal Mixtures Based on Schiff Base Derivatives with Oriented Lateral Substituents

et al. 2020

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“…Moreover, the H-bonded formation of the complex enhanced the calculated thermal energy. The number of aromatic rings of the carboxylic acid affected the stability of the H-bonding complexes, where, as the number of aromatic rings increased the packing of the molecules by stacking of the aromatic rings increased, and this resulted in an increment in the thermodynamic stability of the molecules [63,66,67,[76][77][78][79]. It is noteworthy that there was no effect of the H-bond formation on the dipole moment.…”

Section: Dft Calculationsmentioning

confidence: 99%

Optical and Geometrical Characterizations of Non-Linear Supramolecular Liquid Crystal Complexes

et al. 2020

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Nonlinear architecture liquid crystalline materials of supramolecular 1:1 H-bonded complexes (I/II and I/III) were prepared through a self-assembly intermolecular interaction between azopyridine (I) and 4-n-alkoxybenzoic acid (II) as well as 4-n-alkoxyphenylazo benzoic acid (III). The H-bond formation of the prepared supramolecular hydrogen bonded (SMHB) complexes was confirmed by Fourier-transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). Optical and mesomorphic behaviors of the prepared complexes were studied by polarized optical microscopy (POM) as well as DSC. Theoretical calculations were performed by the density functional theory (DFT) and used to predict the molecular geometries of the synthesized complexes, and the results were used to explain the experimental mesomorphic and optical properties in terms of their estimated thermal parameters. Ordinary and extraordinary refractive indices as well as birefringence at different temperatures were investigated for each sample using an Abbe refractometer and modified spectrophotometer techniques. Microscopic and macroscopic order parameters were calculated for individual compounds and their supramolecular complexes.

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“…Calamitic molecules are linear, with two terminals; these groups may be similar or not. Many-wing units have been designed in the generation of LCs, but the most general route [33], is to use either an alkyl/alkoxy chain or a small compact polar substituent [34][35][36][37]. The role of these groups is to act as dipolar parts to introduce anisotropy in physical characteristics.…”

Section: Introductionmentioning

confidence: 99%

“…The role of these groups is to act as dipolar parts to introduce anisotropy in physical characteristics. Azobenzene moiety is considered to be a good fragment to develop and design a new molecular shape of thermally stable phase transitions, often with very interesting polymorphisms [5,[36][37][38][39][40][41]. Liquid crystals containing an azo group in the mesogenic core are attractive for studying their electro-optical properties [39].…”

Section: Introductionmentioning

confidence: 99%

Thermal and Photophysical Studies of Binary Mixtures of Liquid Crystal with Different Geometrical Mesogens

et al. 2020

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Three binary systems were prepared by mixing of two different mesogenic derivatives, homologues, the first is azo/ester, namely 4-alkoxyphenylazo-4′-phenyl-4″-alkoxybenzoates (IIn+m) and the second is Schiff base/ester, namely 4-(arylideneamino)phenyl-4″-alkoxy benzoates (In+m). The two corresponding analogues from both series in the binary mixtures investigated are of the same terminal alkoxy chain length. Mesomorphic properties were investigated by differential scanning calorimetry (DSC) and phases identified by polarized optical microscope (POM). Photophysical studies were investigated by UV spectroscopy connected to a hot stage. Results were discussed based on constructed binary phase diagrams. All mixtures were found to exhibit eutectic compositions, with linear or slightly linear nematic and smectic A stability/composition dependences. Geometrical parameters were predicted applying density functional theory (DFT) calculations. Twist angle (θ), aspect ratio, dipole moment and the polarizability of the individual compounds were discussed and correlated with the experimental results to illustrate the enhanced the mesophase stability and the mesophase range of the mixture at the eutectic composition compared with those of their individual components.

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Mesophase behavior and DFT conformational analysis of new symmetrical diester chalcone liquid crystals

Cited by 64 publications

References 55 publications

Binary Liquid Crystal Mixtures Based on Schiff Base Derivatives with Oriented Lateral Substituents

Binary Liquid Crystal Mixtures Based on Schiff Base Derivatives with Oriented Lateral Substituents

Optical and Geometrical Characterizations of Non-Linear Supramolecular Liquid Crystal Complexes

Thermal and Photophysical Studies of Binary Mixtures of Liquid Crystal with Different Geometrical Mesogens

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