Dielectric Behaviour of EBBA in Nematic Phase at Radio-Frequencies

Arora, V. P.; Agarwal, V.K.

doi:10.1143/jpsj.45.1360

Cited by 9 publications

(2 citation statements)

References 16 publications

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“…The nematic liquid crystal (NLC) materials used were EBBA (Tokyo Chemical Industry) and MBBA (Tokyo Chemical Industry), both of which have negative dielectric anisotropy. EBBA exhibits the nematic-to-isotropic phase transition at 79.3°C [24], and the dielectric anisotropy ε is −0.26 at 50°C [25]. We prepared the following three EBBA samples with different conductivities by doping with an ionic compound (tetrabutylammonium benzoate, Sigma-Aldrich): pure EBBA [EBBA(P)], low-doped EBBA [EBBA(L)], and high-doped EBBA [EBBA(H)].…”

Section: Methodsmentioning

confidence: 99%

Negative viscosity of liquid crystals in the presence of turbulence: Conductivity dependence, phase diagram, and self-oscillation

et al. 2020

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Recently, we reported the discovery of enormous negative viscosity of a nematic liquid crystal in the presence of turbulence induced by ac electric fields, which enabled us to observe unique phenomena related to the negative viscosity, such as spontaneous shear flow, hysteresis in flow curves, and self-oscillation [Orihara et al., Phys. Rev. E 99, 012701 (2019)]. In the present paper, we report the rheological properties of another nematic liquid crystal, which is a homologue of the previous one. The properties of the present liquid crystal are strongly dependent on electrical conductivity. Three samples with different conductivities were prepared by changing the amount of an ionic dopant. It was found that the lowest-conductivity sample without dopant shows no negative viscosity whereas the other ion-doped samples exhibit negative viscosity with strong dependence on the frequency of the ac electric field, consistent with microscopic observations. Phase diagrams of the negative-and positive-viscosity states in the amplitude and frequency plane are constructed to show the conductivity effect. Furthermore, we propose a model to reproduce another type of self-oscillation found in the present study.

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Section: Methodsmentioning

confidence: 99%

Negative viscosity of liquid crystals in the presence of turbulence: Conductivity dependence, phase diagram, and self-oscillation

et al. 2020

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“…The experimental set-up and the measuring techniques were the same as described earlier [13]. An electromagnet (pole pieces 9 cni diameter) provided a uniform magnetic field of 3.0 kG (greater than saturation value) across the cell acting parallel to the rf electric field.…”

Section: Methodsmentioning

confidence: 99%

Dielectric behaviour of nematic phase OHMBBA at radio frequencies

Arora

Agarwal

1978

Phys. Stat. Sol. (a)

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Dielectric measurements in the frequency range 0.7 to 3.0 MHz are made in the isotropic phase and in the nematic phase of OHMBBA magnetically aligned with the long molecular axis parallel to both the magnetic and rf electric fields. Measurements in the nematic phase indicate a Debyetype dispersion with a relaxation time of 7.4 × 10−8 s at 47 °C and an activation energy of 14 kcal/mol. The results can be explained by assuming the molecular rotation about a transverse axis occuring under hindering nematic potential. The dielectric permittivity (ϵ′⊥), measured with the magnetic field acting perpendicular to rf electric field, does not vary with the magnetic field intensity, which indicates that OHMBBA probably prefers homogeneous alignment with the electrodes.

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Dielectric Properties of Nematic Liquid Crystals

Kresse¹

1998

Handbook of Liquid Crystals Set

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Dielectric Behaviour of EBBA in Nematic Phase at Radio-Frequencies

Cited by 9 publications

References 16 publications

Negative viscosity of liquid crystals in the presence of turbulence: Conductivity dependence, phase diagram, and self-oscillation

Negative viscosity of liquid crystals in the presence of turbulence: Conductivity dependence, phase diagram, and self-oscillation

Dielectric behaviour of nematic phase OHMBBA at radio frequencies

Dielectric Properties of Nematic Liquid Crystals

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