Dielectric and electro-optic properties of cybotactic nematic phase in hydrogen-bonded liquid crystals

Missaoui, Tayssir; Amor, Ikram Ben; Soltani, Taoufik; Ouada, H. Ben; Jeanneau, Erwann; Chevalier, Yves

doi:10.1016/j.molliq.2020.112726

Cited by 28 publications

(15 citation statements)

References 47 publications

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“…This behavior is consistent with the results on hydrogen-bonded liquid crystals reported by Saccone et al [33], which reveal that increasing chain length enhances the stability of the assemblies of smectic phases and lowers both the clearing and melting points. In addition, our previous work disclosed that the monofluorinated compounds nOBAF displayed nematic and SmC phases and that TI-N decreased as n increased [19].…”

Section: Phase Behavior Of Mixed Nobaff/8obamentioning

confidence: 95%

“…The impact of the fluorination of the phenyl ring on the mesomorphic behavior and LCs properties has been investigated by several groups [19][20][21][22]. It has been found that the properties of hydrogen-bonded materials such as melting point, mesophase morphology, transition temperatures and dielectric properties as well as optical anisotropy are significantly influenced by fluorination.…”

Section: Introductionmentioning

confidence: 99%

“…Conversely, fluorination of the alkyl chain increases the melting point and mesophase range compared to the nonfluorinated compounds [24]. We have recently reported the interesting electric and electro-optic properties of monofluorinated benzoic acids (nOBAF; n is the carbon number) [19,21].…”

Section: Introductionmentioning

confidence: 99%

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Synthesis, thermal, dielectric and electro-optic properties of new series of fluorinated hydrogen-bonded liquid crystals

Derbali

Soltani

Guesmi

et al. 2022

Journal of Molecular Liquids

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Section: Phase Behavior Of Mixed Nobaff/8obamentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Synthesis, thermal, dielectric and electro-optic properties of new series of fluorinated hydrogen-bonded liquid crystals

Derbali

Soltani

Guesmi

et al. 2022

Journal of Molecular Liquids

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“…Влиять на величину анизотропии диэлектрической проницаемости можно на стадии молекулярного дизайна мезогена, вводя различные функциональные группы. Также анизотропия диэлектрической проницаемости может значительно изменяться в жидкокристаллических композициях и смесях в зависимости от типа межмолекулярных взаимодействий и составов исследуемых смесей [13][14][15][16][17][18][19].…”

Section: Introductionunclassified

Dielectric properties of the system: 4-n-pentyloxybenzoic acid– N-(4-n-butyloxybenzylidene)-4᾽-methylaniline

Syrbu

Fedorov

Лапыкина

et al. 2021

Fine Chem. Technol.

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Objectives. Our aim was to study the dielectric properties of the 4-n-pentyloxybenzoic acid– N-(4-n-butyloxybenzylidene)-4’-methylaniline system and reveal how different concentrations of N-(4-n-butyloxybenzylidene)-4’-methylaniline additives affect the dielectric properties of 4-n-pentyloxybenzoic acid.Methods. System properties were investigated using polarization thermomicroscopy and dielcometry.Results. We found that dielectric anisotropy changes its sign from positive to negative at the transition temperature of the high-temperature nematic subphase to the low-temperature one. The anisotropy of the dielectric constant of N-4-n-butoxybenzylidene-4’-methylaniline has a positive value and increases as to the system approaches the crystalline phase. The crystal structure of the 4-n-pentyloxybenzoic acid contains dimers formed by two independent molecules due to a pair of hydrogen bonds. The crystal structure of N-(4-n-butoxybenzylidene)-4’-methylaniline contains associates formed by orientational interactions of two independent molecules. 4-n-Pentyloxybenzoic acid dimers (270 nm) and associates of N-4-n-butoxybenzylidene-4’- methylaniline (250 nm) proved to have approximately the identical length. Considering the close length values of the structural units of both compounds and the dielectric anisotropy sign, we assume that the N-4-n-butoxybenzylidene-4’-methylaniline associates are incorporated into the supramolecular structure of the 4-n-pentyloxybenzoic acid. The specific electrical conductivity of the compounds under study lies between 10−7 and 10−12 S∙cm−1. The relationship between the specific electrical conductivity anisotropy and the system composition in the nematic phase at the identical reduced temperature, obtained between 100 and 1000 Hz is symbatic. However, the electrical conductivity anisotropy values of the system obtained at 1000 Hz are lower compared to those obtained at 100 Hz. At N-(4-n-butoxybenzylidene)-4’-methylaniline concentrations between 30 and 60 mol %, the electrical conductivity anisotropy values are higher than those of the individual component.Conclusions. A change in the sign of the dielectric constant anisotropy of the 4-n-pentyloxybenzoic acid during nematic subphase transitions was established. We showed that the system has the highest dielectric constant anisotropy value when components have an equal number of moles. Highest electrical conductivity anisotropy values are observed when the concentration of the N-4-n-butoxybenzylidene-4᾽-methylaniline system lies between 30 and 60 mol %.

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“…Nowadays, materials forming liquid crystal (LC) phases have found wide application in the manufacturing of displays [ 1 ], spatial light modulators [ 2 ], optical connectors [ 3 ], switches [ 4 ], and molecular sensors and detectors [ 5 , 6 ]. The strong demand for new LC applications has led to the synthesis of a wide range of molecules—in particular, thermotropic LC molecules [ 7 , 8 ].…”

Section: Introductionmentioning

confidence: 99%

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

2020

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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.

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Dielectric and electro-optic properties of cybotactic nematic phase in hydrogen-bonded liquid crystals

Cited by 28 publications

References 47 publications

Synthesis, thermal, dielectric and electro-optic properties of new series of fluorinated hydrogen-bonded liquid crystals

Synthesis, thermal, dielectric and electro-optic properties of new series of fluorinated hydrogen-bonded liquid crystals

Dielectric properties of the system: 4-n-pentyloxybenzoic acid– N-(4-n-butyloxybenzylidene)-4᾽-methylaniline

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

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