Azomesogens with methoxyethyl tail: Synthesis and characterization

Prajapati, Akhilesh; Pandya, H. M.

doi:10.1007/bf02709295

Cited by 21 publications

(10 citation statements)

References 9 publications

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“…The tendency of rising transition curve has been considered to be a characteristic of low-melting mesogenic homologous series. Table 3 provides a comparison of smectic mesophase range, transition temperatures and molecular structure of representative compounds 10 and 22 (n512) of the present series I and II, respectively, as well as structurally related compounds A [32], B [23], C [27], D [33], E [25], F [28] and G [34]. The smectic range of compound 10 is about 39uC, whereas that of compound 22 is 47uC.…”

Section: Resultsmentioning

confidence: 99%

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Mesogenic cinnamates with a substituted ethyl terminal chain

Prajapati

Patel²

2007

Liquid Crystals

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Two new mesogenic homologous series of liquid crystalline cinnamates with substituted ethyl tails, b-methoxyethyl [4-(49-n-alkoxycinnamoyloxy)benzoates (I) and b-chloroethyl [4-(49-nalkoxycinnamoyloxy)benzoates (II), have been synthesized and characterized by a combination of elemental analysis and standard spectroscopic methods. In series I, lower-chain members exhibit nematic mesophase, middle members exhibit enantiotropic nematic as well as smectic A (SmA) mesophases, whereas higher members exhibit only an enantiotropic SmA mesophase. In series II, methoxy to n-butyloxy derivatives exhibit a monotropic nematic mesophase. The SmA mesophase commences from n-propyloxy derivative as monotropic and persists up to the last member synthesized. The mesomorphic properties of present series were compared with each other and with a structurally related mesogenic homologous series to evaluate the effects of substituted ethyl tail and cinnamoyloxy central linkage on mesomorphism.

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Section: Resultsmentioning

confidence: 99%

“…In order to further study the effect of broken alkyl terminal chains, four mesogenic homologous series of azoesters having methoxyethyl and ethoxyethyl terminal chain have been synthesized [25,26]. A literature survey also reveals that mesogenic homologous series with chloroethyl tail are very few.…”

Section: Introductionmentioning

confidence: 99%

Mesogenic cinnamates with a substituted ethyl terminal chain

Prajapati

Patel²

2007

Liquid Crystals

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“…Furthermore, while the methoxy and methyl-substituted analogues of III showed monotropic mesophases, the corresponding analogues in series I showed enantiotropic mesophases with high clearing temperatures. On the other hand, replacement of the ester group in IV [35] by an azo linkage in I has led to a decrease in T m and an increase in T C ; i.e. compounds I have greater mesomorphic ranges than those of the corresponding analogues in series IV.…”

Section: Liquid Crystals 1565mentioning

confidence: 94%

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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“…[1,2] From these structural investigations, one can mention the ester orientation within the rigid core, the position of azo/ester groups, lateral substitutions, as well as the terminal chain length. [3][4][5][6][7][8][9][10][11][12] In a liquid crystal compound, lateral substitution makes molecules broad, thus playing an effective role in the mesogenic properties of the resulting derivatives. Lateral substituent in rigid core can destroy the molecular closed packing, reduce liquid crystal melting point, thereby improving the solubility of liquid crystal effectively.…”

Section: Introductionmentioning

confidence: 99%

Mesophase behaviour of laterally di-fluoro-substituted four-ring compounds

Ahmed

Saad

2015

Liquid Crystals

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Four new groups of the di-fluoro-substituted 4-(2′-(or 3′)-fluoro phenylazo)-2-(or 3-) fluoro phenyl-4″-alkoxyphenylazo benzoates (In-IVn) were prepared and investigated for their mesophase behaviour. An alkoxy group of variable chain length (n = 6, 10 and 14 carbons) is attached to the terminal phenylazo benzoate moiety, and two lateral fluoro substituents are attached individually with different orientations to the other two adjacent rings. The molecular structures of the prepared compounds were confirmed by Fourier transform infrared spectroscopy and 1 H NMR spectroscopy. The study aims to investigate the steric effect of the spatial orientation and relative positions of the two lateral fluorine atoms on the mesomorphic properties in their pure states. The mesophase behaviour was investigated via differential scanning calorimetry and mesophases were identified by polarised light microscopy. The investigation shows that these compounds exhibit high enantiotropic mesophases (SmC and N) and broad mesophase temperature range. The type and stability of the mesophase depends on the length of the terminal alkoxy chain and the position the two fluoro substituents. A comparison between these investigated compounds with their corresponding three-ring analogues was discussed.

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Azomesogens with methoxyethyl tail: Synthesis and characterization

Cited by 21 publications

References 9 publications

Mesogenic cinnamates with a substituted ethyl terminal chain

Mesogenic cinnamates with a substituted ethyl terminal chain

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

Mesophase behaviour of laterally di-fluoro-substituted four-ring compounds

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