Magnetic Properties of Liquid Crystals

The conoscopic method for investigating the optical properties of a liquid crystal cell is studied with the aim of determining the effects of the approximations used in the calculation on the results. We confirm that the chiral liquid crystal cell forming a helical structure can be regarded as a single biaxial plate for analyzing the conoscopic image only if the helical pitch is less than several multiples of the wavelength of light. This approximation implies that the square of the refractive index along a direction is averaged over all the layers. An incorrectly chosen value for one of the principal refractive indices to be used in the analysis of the conoscopic data can lead to an incorrect conclusion, especially for the case when the wavelength dispersion of the refractive index is neglected. A thicker cell and a longer wavelength of the incident light can minimize these limitations of the conoscopic method. We propose a novel simulation method to find the molecular distribution in a liquid crystal cell based on the average-refractive-index approximation and the conoscopic data. This is shown to be a fast, more efficient, and useful method for estimating the director distributions.

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“…In the approximation of the isotropic local field, the principal refractive indices ͑n i ͒ of the uniform media can be written as [14,15] …”

Section: B Single-biaxial-plate Approximationmentioning

confidence: 99%

Conoscopy of chiral smectic liquid crystal cells

2008

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“…Recent studies have been conducted on syntheses and research activities in this area [8,[21][22][23][24][25]. On the other hand, a wide range of terminal substituents, such as small polar compact substituents and alkoxy chains, are employed [26][27][28][29][30]. Variable mesomorphic properties can be promoted by polar substituents with strong dipole moments [31].…”

Section: Introductionmentioning

confidence: 99%

Wide Nematogenic Azomethine/Ester Liquid Crystals Based on New Biphenyl Derivatives: Mesomorphic and Computational Studies

et al. 2022

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The thermal stability and mesomorphic behavior of a new biphenyl azomethine liquid crystal homologues series, (E)-4-(([1,1’-biphenyl]-4-ylmethylene)amino)phenyl 4-(alkoxy)benzoate, In, were investigated. The chemical structures of the synthesized compounds were characterized using FT-IR, NMR, and elemental analyses. Differential scanning calorimetry (DSC) and polarized optical microscopy were employed to evaluate the mesomorphic characteristics of the designed homologues. The examined homologues possessed high thermal stability and broad nematogenic temperature ranges. Furthermore, the homologues were covered by enantiotropic nematic phases. The experimental measurements of the mesomorphic behavior were substantiated by computational studies using the density functional theory (DFT) approach. The reactivity parameters, dipole moments, and polarizability of the studied molecules are discussed. The theoretical calculations demonstrated that as the chain length increased, the polarizability of the studied series increased; while it did not significantly affect the HOMO–LUMO energy gap and other reactivity descriptors, the biphenyl moiety had an essential impact on the stability of the possible geometries and their thermal as well as physical parameters.

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“…Liquid crystals (LCs) are fascinating soft materials that can easily change the molecular orientation or superstructure by the application of external stimuli, such as heat, light, and electric or magnetic field [1][2][3][4]. Magnetic LCs have been considered to become novel advanced soft materials that can combine the optical and electrical properties of conventional LCs with the magnetic and electronic properties of magnetic compounds [5][6][7]. Furthermore, endowing the magnetic LCs with chirality is expected to result in the emergence of unconventional magneto-electric [8][9][10] or magneto-optical [11][12][13] properties, intriguing magnetic interactions and so on in the chiral liquid crystalline (LC) state.…”

Section: Introductionmentioning

confidence: 99%

Electric Field Dependence of Molecular Orientation and Anisotropic Magnetic Interactions in the Ferroelectric Liquid Crystalline Phase of an Organic Radical Compound by EPR Spectroscopy

Suzuki

Uchida

Tamura

et al. 2012

Advances in Science and Technology

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To confirm whether chiral organic radical compound 1, which showed the generation of a sort of spin glass-like inhomogeneous ferromagnetic interactions (the average spin-spin interaction constant J > 0) in the bulk liquid crystalline state under weak magnetic fields, has a spin easy axis or exhibits anisotropic magnetic interactions in the SmC* or SmC phase, we have measured the temperature dependence of g-value and relative paramagnetic susceptibility (χrel) for the ferroelectric SmC* phase of (2S,5S)-1 confined in a thin sandwich cell by EPR spectroscopy.

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Magnetic Properties of Liquid Crystals

Cited by 4 publications

References 27 publications

Conoscopy of chiral smectic liquid crystal cells

Conoscopy of chiral smectic liquid crystal cells

Wide Nematogenic Azomethine/Ester Liquid Crystals Based on New Biphenyl Derivatives: Mesomorphic and Computational Studies

Electric Field Dependence of Molecular Orientation and Anisotropic Magnetic Interactions in the Ferroelectric Liquid Crystalline Phase of an Organic Radical Compound by EPR Spectroscopy

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