Recovery of UV-degraded electrical properties of nematic liquid crystals doped with TiO2 nanoparticles

Wu, Po Chang; Yang, Shun Yi; Lee, Wei

doi:10.1016/j.molliq.2016.02.029

Cited by 26 publications

(6 citation statements)

References 36 publications

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“…25,29 Both of these frequently used fabrication methods are associated with major drawbacks. While UV and thermal curing may cause unavoidable changes in the properties of LCs, 30,31 the preparation of polymer particles requires advanced experimental procedures. Hence, there is a need to use a relatively simpler noninvasive approach to fabricate PFLCs.…”

Section: Introductionmentioning

confidence: 99%

“…Most of the PFLCs reported in the literature are exclusively formed either by ultraviolet (UV) exposure and thermal curing of monomer units or by filling sterically stabilized polymer particles in the host LC. , Both of these frequently used fabrication methods are associated with major drawbacks. While UV and thermal curing may cause unavoidable changes in the properties of LCs, , the preparation of polymer particles requires advanced experimental procedures. Hence, there is a need to use a relatively simpler noninvasive approach to fabricate PFLCs.…”

Section: Introductionmentioning

confidence: 99%

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Pseudopeptidic Polymer Microsphere-Filled Liquid Crystals as High-Performance Light-Scattering Switches

Kumari

Dhawan

Singh

et al. 2021

ACS Appl. Polym. Mater.

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We, herein, report the fabrication of light-scattering switches from polymer microsphere-filled liquid crystals (PFLCs) using pseudopeptidic bottlebrush polymers. A simple method of precipitation of a polymer using the 4-cyano-4′-pentylbiphenyl (5CB) nonsolvent is employed for the preparation of PFLC devices. For this, a series of phenylalanine (Phe)-based bottlebrush polymers having different chain lengths are synthesized by ring-opening metathesis polymerization (ROMP) using the Grubbs second-generation ruthenium catalyst and used in a nematic liquid crystal (LC) matrix. The developed PFLC devices are well-characterized using various ultramicroscopic techniques such as field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and polarizing optical microscopy (POM). For the first time, the effect of the molecular weight of a polymer on electro-optic (E-O) properties of PFLC is investigated. PFLCs show significant differences in microsphere size, required operating voltage, transmittance, contrast ratio (CR ratio), memory effect, and switching speed upon subtle variation of the dopant polymer units. Overall, we demonstrated that the chain length of a polymer plays a crucial role in controlling the performance of PFLC devices. The presented methodology offers promising possibilities for the fabrication of PFLC-based switchable scattering devices with improved performance for optoelectronic applications.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Pseudopeptidic Polymer Microsphere-Filled Liquid Crystals as High-Performance Light-Scattering Switches

Kumari

Dhawan

Singh

et al. 2021

ACS Appl. Polym. Mater.

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“…In addition, TiO 2 has a high refractive index of 2.6, and thus the optical transmittance of the device can be increased by the closely matched refractive index of the PI layer (1.6) with that of the ITO substrate (1.8). Moreover, the screening effect can be prevented because of the ability of the TiO 2 NPs to trap the free ions of the LC [ 20 , 21 , 22 ]. The effects of the TiO 2 NPs introduced into PI were evaluated by using two sizes of NPs (15 and 300 nm) and different NP contents.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of TiO2-Embedded Polyimide Layer with High Transmittance and Improved Reliability for Liquid Crystal Displays

Son

Choi

et al. 2021

Polymers

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Construction of liquid crystal (LC) alignment by introducing polyimide (PI) to indium tin oxide (ITO) electrodes is one of the main methods to realize high-resolution images in liquid crystal displays (LCD). However, the loss of transmittance caused by the difference in refractive index between ITO and PI leads to direct degradation of LCD performance. Thus, we herein fabricated a functional hybrid PI alignment layer that reduces the difference in refractive index and greatly increases the transmittance of the device by introducing inorganic titanium dioxide (TiO2) nanoparticles (NP) to the organic PI. The highly refractive TiO2 NPs were surface-treated with stearic acid comprising long alkyl chains to improve their dispersibility and uniformly dispersed in the PI matrix by simply stirring the mixture. The hybrid PI mixture was spin-coated on the ITO substrate, and the resulting LC cell exhibited excellent electro-optical properties. In addition, the reliability of the LC cells was enhanced by the inclusion of the TiO2 NPs, which was confirmed through the evaluation of voltage holding ratio, residual direct current, and LC cell reliability. Overall, functional hybrid PI can be used in advanced display technology for next-generation LC devices that require high transmittance and reliability.

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“…Organic optical materials are used to construct many elements of optical devices operating in various spectral ranges, from ultraviolet [ 1 , 2 , 3 , 4 , 5 ] through visible [ 6 , 7 ] to infrared [ 8 , 9 , 10 , 11 , 12 , 13 ]. Most organic materials are passive elements; however, one group—mesomorphic materials—constitute the heart of active elements, where the wide tunable abilities of these materials are used.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Mesomorphism and the Optical Properties of Alkyl-deuterated Nematogenic 4-[(2,6-Difluorophenyl)ethynyl]biphenyls

et al. 2021

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The synthesis and characterization of new deuterated liquid crystal (LC) compounds based on phenyl tolane core is described in this paper. The work presents an alternative molecular approach to the conventional LC design. Correlations between molecular structure and mesomorphic and optical properties for compounds which are alkyl-hydrogen terminated and alkyl-deuterium, have been drawn. The compounds are characterized by mass spectrometry (electron ionization) analysis and infrared spectroscopy. They show enantiotropic nematic behavior in a broad temperature range, confirmed by a polarizing thermomicroscopy and differential scanning calorimetry. Detailed synthetic procedures are attached. Synthesized compounds show a significantly reduced absorption in the near-infrared (NIR) and medium-wavelength infrared (MWIR) radiation range, and stand as promising components of medium to highly birefringent liquid crystalline mixtures.

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Recovery of UV-degraded electrical properties of nematic liquid crystals doped with TiO2 nanoparticles

Cited by 26 publications

References 36 publications

Pseudopeptidic Polymer Microsphere-Filled Liquid Crystals as High-Performance Light-Scattering Switches

Pseudopeptidic Polymer Microsphere-Filled Liquid Crystals as High-Performance Light-Scattering Switches

Fabrication of TiO2-Embedded Polyimide Layer with High Transmittance and Improved Reliability for Liquid Crystal Displays

Synthesis, Mesomorphism and the Optical Properties of Alkyl-deuterated Nematogenic 4-[(2,6-Difluorophenyl)ethynyl]biphenyls

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