Effect of molecular structure on the phase behaviour of some liquid crystalline compounds and their binary mixtures VI[1]. The effect of molecular length

Saad, Gamal R.; Nessim, Refaat I.

doi:10.1080/026782999204679

Cited by 31 publications

(11 citation statements)

References 10 publications

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“…A change in the extent of conjugation alters the polarisability and resultant dipole moment of the molecule. It has also been shown [29] that the dipole moments of all members of a homologous series are virtually the same, irrespective of the alkoxy-chain length. This result is supported by the fact that alkoxy groups have similar polarity regardless of their length, and at the same time they do not affect the degree of conjugative interaction between the alkoxy oxygen and the ester carbonyl, as is confirmed by infrared measurements.…”

Section: Mesophase Behaviour Of the Investigated Compoundsmentioning

confidence: 97%

Polarity and steric effect of the lateral substituent on the mesophase behaviour of some newly prepared liquid crystals

et al. 2015

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Eight homologous series of 2-(or 3-) substituted phenyl 4ʹ-(4ʺ-alkoxy phenylazo) benzoates (In a-h ) were prepared in which, within each homologous series, the length of the terminal alkoxy group varies between 6, 8, 10 and 12 carbons, while the other substituent, X, is a laterally attached polar group that alternatively changed from CH 3 , H, F, Br and CN. Compounds prepared were characterised by infrared and 1 H-NMR spectroscopy, and their mesophase behaviour investigated by differential scanning calorimetry and identified by polarised light microscopy. The results were discussed in terms of polarity and steric effects. The stability of the mesophase was correlated once with the dipolar anisotropy of the whole molecule and another with the dipolar anisotropy of the substituent, X. A comparative study was made between the investigated compounds and their previously prepared linear 4-substituted isomers, namely 4-substituted phenyl 4ʹ-(4ʺ-alkoxy phenylazo) benzoates (In i-k ).

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Section: Mesophase Behaviour Of the Investigated Compoundsmentioning

confidence: 97%

Polarity and steric effect of the lateral substituent on the mesophase behaviour of some newly prepared liquid crystals

et al. 2015

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“…A change in the extent of conjugation alters the polarisability and resultant dipole moment of the molecule. It has also been shown [4] that the dipole moments of all the members of a homologous series are virtually identical, irrespective of the length of the alkoxy chain. This result is supported by the fact that the alkoxy groups have similar polarity regardless of their length and at the same time do not affect the degree of conjugative interaction between the alkoxy oxygen and the ester carbonyl, as is confirmed by infrared measurements.…”

Section: Mesophase Behaviour Of Compounds Investigatedmentioning

confidence: 98%

“…This can be investigated by comparing compounds, In a-f , with the correspondingly substituted 4-aryl-4′-alkoxybenzoates, III, [4] and 1,4-phenylene-bis-4′-substituted benzoates, IV, [34] with respect to the crystal-mesophase (T m ) and mesophase-isotropic (T C ) transition temperatures, as well as the mesomorphic ranges,…”

Section: Liquid Crystals 1565mentioning

confidence: 99%

“…The study revealed that the introduction of a phenylazo moiety into the phenyl benzoate molecule [4] in III to form I results in an increase of the intermolecular forces and consequently of the stability of the solid and mesophase; i.e. results in an increase in the melting and clearing temperatures.…”

Section: Liquid Crystals 1565mentioning

confidence: 99%

“…Attempts to correlate the mesophase stability with molecular structure are based on considerations of the nature and magnitude of the intermolecular forces that favour the lateral association of their rod-shaped molecules. However, intermolecular forces due dipoledipole interactions have shown [1][2][3][4][5][6][7] not to be the only factors important in promoting mesophase stability. Linking groups that maintain rigidity and linearity of the molecule are satisfactory in this respect.…”

Section: Introductionmentioning

confidence: 99%

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Effect of exchange of terminal substituents on the mesophase behaviour of some azo/ester compounds

et al. 2014

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Six homologous series of 4-(4′-alkoxy phenylazo) phenyl 4″-substituted benzoates (In a-f ) were prepared in which, within each homologous series, the length of the terminal alkoxy chain varies between 6, 8, 10, and 12 carbons, while the other terminal substituent, X, is a polar group that alternatively changed from CH 3 O, CH 3 , H, Br, NO 2 and CN. Compounds prepared were characterised by spectroscopic methods, and their mesophase behaviour investigated by differential scanning calorimetry (DSC) and polarised optical microscopy (POM). The results were discussed in terms of mesomeric and polarisability effects. In each group of compounds, bearing the same alkoxy substituent, the nematic-to-isotropic transition temperatures (T C ) were successfully correlated with the polarisability anisotropy of bonds to the substituent X. A comparative study was made between the investigated compounds and their previously prepared isomers, namely, 4-(4′-substituted phenylazo) phenyl 4″-alkoxybenzoates (IIn a-f ) in which the two terminal (alkoxy-and X) groups are exchanged.

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The influence of molecular flexibility on the mesogenic behavior of a new homologous series based on azo-azomethine: Synthesis, characterization, photoisomerization and DFT study

Nakum

Katariya

Savani

et al. 2022

Journal of Molecular Structure

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Effect of molecular structure on the phase behaviour of some liquid crystalline compounds and their binary mixtures VI[1]. The effect of molecular length

Cited by 31 publications

References 10 publications

Polarity and steric effect of the lateral substituent on the mesophase behaviour of some newly prepared liquid crystals

Polarity and steric effect of the lateral substituent on the mesophase behaviour of some newly prepared liquid crystals

Effect of exchange of terminal substituents on the mesophase behaviour of some azo/ester compounds

The influence of molecular flexibility on the mesogenic behavior of a new homologous series based on azo-azomethine: Synthesis, characterization, photoisomerization and DFT study

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