Nanorod‐Driven Orientational Control of Liquid Crystal for Polarization‐Tailored Electro‐Optic Devices

Abstract

Liquid-crystal display (LCD) devices are indispensable elements of modern life because of the ubiquity of their applications from wristwatch to personal-computer displays. Control over the longrange orientational order of the liquid crystal (LC) is critical for obtaining superior optical switching and display-device performance. [1][2][3][4][5][6][7] However, control of long-range alignment of LCs remains challenging because of the formation of unaligned dislocation regions, which is detrimental to LC device performance. Long-range alignment has been attempted by a variety of methods, including using alignment layers, modification of the LC cells, or using the interaction between nanosized aggregates of LC molecules. [7][8][9][10] Dispersion of nanoparticles as active-matrix components in LCs has been investigated to achieve long-range alignment, large scale orientation manipulation, and for faster switching speeds of LC devices. [10][11][12][13][14] However, incorporation of nanomaterials into an LC matrix gives rise to topological defects, due to deformations of the director field about the surface of the colloid species, breaking the continuous symmetry of the blend. [6,10,[12][13][14] For incorporation of nanomaterials in an LC matrix, the proper selection of size, shape, and crystallographic phase of the nanomaterials is critical for enhancing the performance of the blend. For example, spherical particles or centrosymmetric materials are less responsive to external fields, and tend to not form long-range ordered structures. On the other hand, elongated anisotropic nanomaterials possessing an inherent permanent dipole moment respond dramatically in an applied field, facilitating alignment along the direction of the field. [15,16] Anisotropic nanomaterials of proper dimensions coupled locally with the LC director field in a favorable energetic configuration should enhance long-range ordering and device performance. Additionally, the optical properties of the nanocrystals can be tuned by varying the size and shape of the nanocrystals, a feature which is useful for generating a range of spectral behaviors. [17,18] Anisotropic nanomaterials with ''parallel'' optical polarization axes have been used in attempts to control the state of polarization and viewing angle of LCs. [17][18][19] However, the parallel polarization axis coincides with the LC orientational order, thus restraining the viewing angle and contrast ratios to be tailored over wide angles. Moreover, the larger size of these materials limits device performance, requiring, in particular, higher operating voltages. Here, we show that dispersion of ultranarrow ZnS nanorods encapsulated by a fluid-like soft organic layer in the nematic LC ZLI-4792 results in a novel softmatter-type blend, with previously unachieved and robust electrooptic properties. The ultrasmall nanorods possess a strong inherent dipole moment, and show excellent miscibility in the LC host, forming well-organized locally aligned arrays. This local ordering affects significantly the glo...

Low-voltage electro-optical memory device based on NiO nanorods dispersed in a ferroelectric liquid crystal

“…Also, nanorods possessing inherent dipole moment can align faster with mesogens due to large torque experienced in external bias eld, which results in reduction in V sat . 55 When electric eld is switched on, the dipolar mesogens and nNiO get aligned along the direction of eld as shown in Fig. 8(b).…”

Electro-Optical Characteristics of ZrO2 Nanoparticle Doped Liquid Crystal on Ion-Beam Irradiated Polyimide Layer

“…[3][4][5][6] Other groups have studied ferromagnetic particles, ferroelectric particles, and metal nanoparticles such as Au, Ag, TiO 2 , and carbon nanotube and polymer-stablized domain structures as LC dopants. [7][8][9][10][11][12][13] Furthermore, crystallographic phase induced electro-optic properties of nanorod dispersed LC were studied by Acharya et al 14 15 Recently, Hwang et al Have shown that a good LC orientation can be achieved without an alignment layer and the pretilt angle of LCs can be controlled in polyhedral oligomeric silsesquioxanes (POSS)-doped LCD. [16][17][18] As a result, a colloidal system * Author to whom correspondence should be addressed.…”

Probing the Micro-Phase Separation of Thermo-Responsive Amphiphilic Polymer in Water/Ethanol Solution

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Among them, assemblies of functional polymeric materials sometimes result in smart and sophisticated functions. [20][21][22][23][24] For example, poly(vinyl methyl ether) (PVME) belongs to a group of so-called "smart" polymers.…”