Calculation on frequency and temperature properties of birefringence of nematic liquid crystal 5CB in terahertz band

Chen, Zezhang; Jiang, Lijuan; Ma, Heng

doi:10.1016/j.cplett.2016.01.004

Cited by 20 publications

(5 citation statements)

References 40 publications

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“…Moreover, BNA doping decreases the T NI and hence the associated order parameter S and Δn of the LC mixture according to Eq. ( 2 ) and ( 3 ) 41 – 43 . where S is the order parameter, T is ambient temperature, T 0 is the melting point of the LC mixture, m is an exponent, a i are proportionality, Δn 0 is the birefringence of the LC mixture at 0 K, k b is the Boltzmann constant, β is a material parameter, and E is the activation energy of molecule rotation.…”

Section: Resultsmentioning

confidence: 99%

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Selvaraj

Karthick

Brahadeeswaran

et al. 2020

Sci Rep

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The dispersion of organic N-benzyl-2-methyl-4-nitroaniline (BNA) in nematic liquid crystals (LCs) is studied. BNA doping decreases the threshold voltage of cell because of the reduced splay elastic constant and increased dielectric anisotropy of the LC mixture. When operated in the high voltage difference condition, the BNA-doped LC cell has a fall time that is five times faster than that of the pure one because of the decrements in the threshold voltage of the cell and rotational viscosity of the LC mixture. The additional restoring force induced by the BNA's spontaneous polarization electric field (SPEF) also assists to decrease the fall time of the LC cell. The decreased viscosity can be deduced from the decrements in phase transition temperature and associated order parameter of the LC mixture. Density functional theory calculation demonstrates that the BNA dopant strengthens the absorbance for blue light, enhances the molecular interaction energy and dipole moment, decreases the molecular energy gap, and thus increases the permittivity of the LC mixture. The calculation also shows that the increased dipole moment, polarizability, and polarizability anisotropy increase the dielectric anisotropy of the LC mixture, which agrees with the experimental results well. BNA doping has a promising application to the fields of LC devices and displays. Nematic liquid crystals (LCs) are extraordinarily responsive and optically uniaxial materials. Nematic LCs have been extensively used in diverse applications, such as optical nonlinearity, optical phase modulators, microdisplays, flat panel displays, optical antennas, and optical switching, due to their electro-optical property and other admirable features 1-5. LCs with a fast response are vital in removing motion blur in moving pictures and resolving cross-talk in 3D displays 6-9. The response time of LCs should be less than 3 ms to diminish motion blur and cross-talk. Several techniques have been proposed to resolve this issue, and they include tuning the viscosity of materials 10 , varying the anchoring energy 11 , changing the electrode shape and driving scheme 12 , changing the cell gap 13 , modifying the guest-host material 14 , and applying new switching modes 15. The improvements in the electro-optical properties of LCs with the dispersion of different gust entities were presented recently. For example, Y. Dai et al. demonstrated that the incorporation of γ-Fe 2 O 3 nanoparticles into LCs results in a response time of 4.75 ms with the application of the overdriving scheme, which is three times faster than pure LCs 16. A response time of around 4 ms was obtained with the addition of a small amount of dye to a polymer-dispersed liquid crystal (PDLC) or functionalized carbon nanotubes dispersed in optically isotropic LCs. However, in this case, the excellent response speed is valid only for operation at a relatively high voltage 17,18. Blue-phase LCs have a response time of 0.5 ms, but they still have drawbacks, such as hysteresis, high operation voltage, and narrow t...

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Section: Resultsmentioning

confidence: 99%

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Selvaraj

Karthick

Brahadeeswaran

et al. 2020

Sci Rep

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“…The validity of the above equation is that the ambient temperature ( T ) is sufficiently lesser than that of the anisotropic temperature ( T NI ). , Since the Ga 2 O 3 microrod doping significantly increased the T NI (measured by POM), the associated Δ n and S of pure and Ga 2 O 3 microrod-doped LC cells also increased according to eqs and . − …”

Section: Resultsmentioning

confidence: 90%

“…Table shows that Ga 2 O 3 microrod doping increased the T NI of the LC mixture, measured by POM on heating the nematic to the isotropic phase at the rate of 0.25 °C/min using a temperature controller. Moreover, Ga 2 O 3 microrod doping increased the associated order parameter S and Δ n of the LC mixture according to eqs and . − The concentration dependence of the birefringence (Δ n ), the nematic–isotropic temperature ( T NI ), and the estimated second-order orientational order parameter ( S ) of pure LC composites are listed in Table . The birefringence increases with the dispersion of Ga 2 O 3 microrods in the nematic LC (up to 0.5 wt %).…”

Section: Resultsmentioning

confidence: 92%

Nematic Liquid Crystals Dispersed with Thermoelectric Gallium Oxide (Ga₂O₃) Microrods: A Perspective for Improving the Response Time of Electro-Optical Devices

Singh

Sikarwar

Pandey³

et al. 2022

J. Phys. Chem. C

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Electro-optic properties of nematic liquid crystals (LCs) based on thermoelectric gallium oxide (Ga 2 O 3 ) microrod doping have been reported for the first time. Ga 2 O 3 -microroddoped LC cells result in a 5-fold faster response time than pristine LC cell. Doping microrods increases the dielectric anisotropy and remarkably decreases the rotational viscosity of LC. The decreased rotational viscosity and increased dielectric anisotropy are explained by the increased nematic−isotropic phase-transition temperature of the LC mixture. The experimental result discloses that the 0.1 wt % Ga 2 O 3 -microrod doped LC cell delivers a response time of 2.46 ms at room temperature, indicating Ga 2 O 3 doping as a promising method for different LC-based display applications.

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“…Table 5 shows that MWCNT dispersiong has increased the T N I of the LC mixture, measured by POM from N → Iso (nematic to isotropic) phase with a heating rate of 0.25 • C/min. Moreover, MWCNT dispersion in the E7 LC has increased the order parameter S and ∆n of composites following to Equations (1) and ( 5) [56,57]. The concentration dependence of the birefringence (∆n), nematic-isotropic temperature (T N I ), and estimated second order orientational order parameter (S) of the pure LC composites are listed in Table 5.…”

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confidence: 99%

“…Equation ( 12) is only valid when, T T N I [48,49]. Though, MWCNT dispersion has significantly increased the T N I (measured by POM) and hence the associated ∆n and S of the pure and MWCNT doped LC have also been increased according to Equations ( 11) and ( 12) [56,57]. The birefringence ∆n is linked with the order parameter (S) of LC as follows:…”

mentioning

confidence: 99%

Carbon Nanotubes Blended Nematic Liquid Crystal for Display and Electro-Optical Applications

Singh

Sikarwar

Pandey³

et al. 2021

Electronic Materials

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In this paper, we investigate a commercial nematic liquid crystal (LC) mixture namely E7 dispersed with small concentrations of multi-walled carbon nanotubes (MWCNTs). The dielectric and electro-optical characterizations have been carried out in the homogeneously and vertically aligned LC cells. The electro-optical response of LC molecules has been enhanced by 60% after the addition of MWCNTs, which is attributed to the reduced rotational viscosity in the composites. MWCNTs act like barricades for ionic impurities by reducing them up to ∼34.3% within the dispersion limit of 0.05 wt%. The nematic–isotropic phase transition temperature (TNI) of the E7 LC has also been shifted towards the higher temperature, resulting in a more ordered nematic phase. The enhanced birefringence and orientational order parameter in the LC-MWCNTs are attributed to π-π electron stacking between the LC molecules and the MWCNTs. The outlined merits of the LC-MWCNTs composites evince their suitability for ultrafast nematic-based electro-optical devices.

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Calculation on frequency and temperature properties of birefringence of nematic liquid crystal 5CB in terahertz band

Cited by 20 publications

References 40 publications

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Nematic Liquid Crystals Dispersed with Thermoelectric Gallium Oxide (Ga₂O₃) Microrods: A Perspective for Improving the Response Time of Electro-Optical Devices

Carbon Nanotubes Blended Nematic Liquid Crystal for Display and Electro-Optical Applications

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Calculation on frequency and temperature properties of birefringence of nematic liquid crystal 5CB in terahertz band

Cited by 20 publications

References 40 publications

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Nematic Liquid Crystals Dispersed with Thermoelectric Gallium Oxide (Ga2O3) Microrods: A Perspective for Improving the Response Time of Electro-Optical Devices

Carbon Nanotubes Blended Nematic Liquid Crystal for Display and Electro-Optical Applications

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Product

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Nematic Liquid Crystals Dispersed with Thermoelectric Gallium Oxide (Ga₂O₃) Microrods: A Perspective for Improving the Response Time of Electro-Optical Devices