Nitro substitution in achiral calamitic liquid crystals

Petrov, Vladimir F.; Shimizu, Yo

doi:10.1080/02678290110074625

Cited by 11 publications

(8 citation statements)

References 261 publications

(78 reference statements)

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“…Moreover, there was, as usual, no regular change of melting temperatures with the increase of the terminal alkoxy chain length ( n ). It was previously reported that the position of the lateral NO 2 group within the molecular structure also increases the melting transition temperature [ 28 ]. Their SmA stability and range also increases gradually with n .…”

Section: Resultsmentioning

confidence: 99%

“…The strong mesomeric property of the NO 2 moiety induces a positive charge on the N atom, and thus, increases the electronegativity of the group [ 17 , 18 ]. The resonance approach has been supported by dipole moment investigations [ 25 ], NMR, and the chemical electron-withdrawing character of the nitro group, which affects the measurements [ 26 , 27 , 28 ]. For the development of the mesomorphic range and mesophase stabilities of the prepared materials, an effective strategy for modification of the architectures of compounds is necessary.…”

Section: Introductionmentioning

confidence: 99%

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New Nitro-Laterally Substituted Azomethine Derivatives; Synthesis, Mesomorphic and Computational Characterizations

et al. 2021

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Two new homologues series, based on two rings of the azomethine central group bearing the terminal alkoxy group of various chain lengths, were prepared. The alkoxy chain length varied between 6 and 16 carbons. The other terminal wing in the first series was the F atom, and the compound is named N-4-florobenzylidene-4-(alkoxy)benzenamine (In). The second group of compounds included a lateral NO2 substituent in addition to the terminal F atom, named N-(4-fluoro-3-nitrobenzylidene)-4-(alkyloxy)aniline (IIn). Mesomorphic and optical properties were carried out via differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Elemental analyses, FT-IR, and NMR spectroscopy were carried out to elucidate the molecular structures of the synthesized groups. Mesomorphic investigations indicated that all the synthesized homologues (In) were monomorphic, possessing the smectic A (SmA) phase monotropically, while the second group (IIn) members were non-mesomorphic. The experimental data indicated that the formation of the mesophase is affected by the protrusion of the lateral nitro group. The disruption of the mesophase in the second group was attributed to the increase of its molecular width, which affects its lateral intermolecular interactions. The computational simulations were in agreement with the experimental data. On the other hand, the location of NO2 group within the molecular geometry increased the melting temperature of the molecule, and thus, affected their thermal and physical properties. By discussing the estimated parameters, it was found that the molecular architecture, the dipole moment, and the polarizability of the investigated compounds are highly affected by the electronic nature and position of the terminal and lateral substituents as well as their volumes.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

New Nitro-Laterally Substituted Azomethine Derivatives; Synthesis, Mesomorphic and Computational Characterizations

et al. 2021

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“…We introduced a pendant nitro group on the aromatic ring because it has been suggested that (i) LCs with a nitro group at the ortho position to a linkage ester group typically form a nematic phase with a relatively low phase transition temperature (31) and, more importantly, (ii) the introduction of a polar (e.g., nitro) or polarizable group into the chemical structure often results in an increase of molecular polarity, affecting molecular packing and, in turn, the phase stability of LCs (31). In particular, aromatic ester-based mesogens could achieve a stable nematic phase through strong intermolecular dipoledipole interactions between carbonyl groups of adjacent molecules, an effect that increases with the strength of the molecular interaction (32,33).…”

Section: Resultsmentioning

confidence: 99%

Direct mapping of local director field of nematic liquid crystals at the nanoscale

Xia

Serra

Kamien

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Liquid crystals (LCs), owing to their anisotropy in molecular ordering, are of wide interest in both the display industry and soft matter as a route to more sophisticated optical objects, to direct phase separation, and to facilitate colloidal assemblies. However, it remains challenging to directly probe the molecular-scale organization of nonglassy nematic LC molecules without altering the LC directors. We design and synthesize a new type of nematic liquid crystal monomer (LCM) system with strong dipole-dipole interactions, resulting in a stable nematic phase and strong homeotropic anchoring on silica surfaces. Upon photopolymerization, the director field can be faithfully "locked," allowing for direct visualization of the LC director field and defect structures by scanning electron microscopy (SEM) in real space with 100-nm resolution. Using this technique, we study the nematic textures in more complex LC/colloidal systems and calculate the extrapolation length of the LCM.nematic liquid crystal polymers | dipole-dipole interactions | topological defects | photo-cross-linking | nanoscale imaging

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“…Because of its linear structure, such effects would be less important with the cyano group. Petrov and Shimizu [59] have shown that the introduction of a nitro group into the liquid crystalline system, in the place of the cyano group, usually leads to a decrease of the clearing temperatures and nematic ranges, but there were also cases where the same substituent increased the melting points.…”

Section: Comparison Of the Thermal Properties Of Lcsmentioning

confidence: 98%

End Group Effect on the Thermal and Gas Chromatographic Properties of Some para-Substituted Non-Symmetrical Nematogens

et al. 2016

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Nitro substitution in achiral calamitic liquid crystals

Cited by 11 publications

References 261 publications

New Nitro-Laterally Substituted Azomethine Derivatives; Synthesis, Mesomorphic and Computational Characterizations

New Nitro-Laterally Substituted Azomethine Derivatives; Synthesis, Mesomorphic and Computational Characterizations

Direct mapping of local director field of nematic liquid crystals at the nanoscale

End Group Effect on the Thermal and Gas Chromatographic Properties of Some para-Substituted Non-Symmetrical Nematogens

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