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In this investigation, we have reported some important electro-optical and dielectric parameters for pure nematic liquid crystal (NLC) and polymer-dispersed system. The used liquid crystal in the present investigation is NLC 1550C, consisting of 4′-(trans, trans-4-alkylbicyclohexyl) carbonates and 4′-(4-(trans, trans-4-alkyl)-4-cyanobicyclohexane w...
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In the present investigation optical, electro-optical and dielectric properties have been measured for nematic liquid crystal (NLC) material 1550C which is consisted of 4'-(trans, trans-4-alkylbicyclohexyl) carbonates and 4'-(4-(trans,trans-4-alkyl)-4-cyanobicyclohexane, dispersed with fluorescent dye (Benzo 2,1,3 Thiadiazole) in two different conc...
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... The same trend has been observed in the experimental measurement of response time in the present study. Increment in the temperature causes the decrement in the response time value [43]. Fig. 2 (A) shows the variation of optical response time with respect to temperature for the pure NLC and TiO 2 nanoparticles doped NLC. ...
In the present study, anatase TiO2 nanoparticles (NPs) have been doped in three different concentrations into nematic liquid crystal (NLC) 2020 (fluorinated 4’-alkylphenyl-4-isothiocyanatotolanes). The response time and contrast ratio has decreased and increased, respectively for the NLC-NPs composite system. Polarizing optical microscope images reveal that alignment has been improved after the doping of TiO2 NPs. Dielectric measurement study shows that the tan δ has been decreased and relaxation frequency shifted toward the lower frequency region for the doped system. The outcome of the present investigation may be very useful in the improvement of electro-optical features of liquid crystal displays.
... In the present work, to measure the electric field-induced optical response, we used optical switching method [20][21][22][23][24][30][31][32] in which linearly polarized laser beam makes an angle of 45° with the incidence plane of liquid crystal and input signal is a square wave of 4 Hz frequency and 10 V voltage (applied voltage > threshold voltage to get clear response). During measurement, first the laser light is turned on and then polarizer and analyzer are set in crossed position. ...
Graphene oxide is dispersed in negative dielectric anisotropy nematic liquid crystal p-methoxybenzylidene p-decylaniline (MBDA) in 0.2 wt/wt%, 0.4 wt/wt%, 0.6 wt/wt%, and 0.8 wt/wt% concentrations (abbreviated as MIX 1, MIX 2, MIX 3 and MIX 4). The paper proposes techniques to characterize and fill in the sample holder nematic–graphene oxide composites. The textures, electro-optical, dielectric as well as optical properties at 54 °C in nematic phase are investigated. X-ray diffraction result shows the particle size of graphene oxide to be 10–60 nm. The zeta potential of graphene oxide is around − 35 mV and its absolute value decreases from 31.5 mV in pure MBDA to 0.56 mV in MIX 4. Polarizing microscopy results display that MBDA and its composites in unaligned cell exhibit poor contrast with non-uniformity in bright state whereas aligned ones exhibit good contrast with uniformity. The observation reveals that switch-on time practically remains constant, while switch-off time and overall response time reduces from 25.8% (MIX 1) to 83.67% (MIX 4) and 25.69–83.074%, compared to pure MBDA. Rotational viscosity increases from 2.59 to 18.18%. The threshold voltage and splay elastic constant in pure MBDA and its composites increase from 2 to 3 V and 7.25 to 8.12 pN. Reduction in dielectric parameters has been observed. The magnitude of \(~\varepsilon {'_\parallel }\) and \(\varepsilon {'_ \bot }\) reduces from 44.2 to 76.1% and 24.6 to 72.8%, which shows \(\varepsilon {'_ \bot }\) is always greater than \(\varepsilon {'_\parallel }\). Therefore, absolute dielectric anisotropy reduces from 1.49 to 79.10%. The dielectric relaxation frequency reduces from 4.3 × 10⁵ Hz to 2.81 × 10⁵ Hz without bias voltage and 6.13 × 10⁵ Hz to 2.2 × 10⁵ Hz with bias voltage. UV–Vis absorbance study discloses π–π* transition with absorbance increase from 4.44 to 57.18% and corresponding blue shift in wavelength (249–194 nm). 7.23–65.90% quenching in photoluminescence study has been revealed. FTIR spectra are recorded on wavenumber range from 655 to 3500 cm⁻¹. This work has application in sensors, imaging functions, improved electro-optic display devices and colorful displays devoid of color filters.
... Liquid crystals (LCs) are functional soft materials between a liquid and a crystal with long orientation order [1,2]. Although LCs have been discovered by Friedrich Reinitzer in 1888, today LCs are attracting attention of researchers due to their importance in technology and potentials for applications mainly in LC displays, smartphones PCs tablet, optical and biological sensors [3][4][5][6][7][8]. Some thermal, electro-optical properties of LCs materials can be tuned by mainly two different approaches. ...
In this study, a novel liquid crystal mixture complex was designed and synthesized from the nematic liquid crystal mixture E7, hexylcyanobiphenyl (6CB) and hexylbenzoic acid (6BA). The thermal and morphological properties were investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The DSC and POM results show that the liquid crystal complexes exhibit liquid crystalline properties with smectic and nematic phase. While the E7 ratio is 80%, the mixture complex has the widest nematic range and exhibits E7 properties. When the E7 weight ratio is less than 80%, with the formation of hydrogen bonds the number of mesogenic phases increases and the nematic range decreases. The electrical properties of obtained samples were measured by impedance spectroscopy technique. The birefringence and contrast ratio of samples also investigated by the help of light transmittance experiment.
