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High-density Azobenzene Side Chain Polymer Brush for Azimuthal and Zenithal Orientation Photoswitching of Nematic Liquid Crystal
摘要： The azimuthal and zenithal orientation switching of nematic liquid crystals (NLCs) can be performed by photoresponsive azobenzene alignment layers called command surfaces. Such photoresponsive layers have been prepared by molecular assembly methods or spincast of polymer materials. This work reports on the photo-switching orientation behavior of NLC on a high-density brush of an azobenzene-containing side chain liquid crystalline polymer. On the high-density polymer brush surface, the zenithal homeotropic/planar photoalignment switching modes triggered by UV/visible light irradiation are reversed from those observed for traditional command surface systems, reflecting the azobenzene side chain orientation directing parallel with the substrate surface. Because the thermally stable trans-azobenzene provides the in-plane orientation of NLC, irradiation with linearly polarized visible light readily switches the azimuthal direction to an arbitrary direction, and the resulting orientation is retained persistently. This paper discusses the features of the architecture of high-density polymer brush as the command surface for NLC orientation.
关键词： azobenzene,photoalignment,photoresponsive surface,nematic liquid crystal,polymer brush
更新于2025-09-23 15:23:52
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Photoactive Functional Soft Materials (Preparation, Properties, and Applications) || Photoinduced Liquid Crystal Domain Engineering for Optical Field Control
摘要： Liquid crystals (LCs) have attracted considerable attention due to their pronounced high optical anisotropy/transparency over a wide electromagnetic spectrum, high sensibility to various external field stimuli (such as electric/magnetic field, light irradiation, and heat) and strong capability for matter and electromagnetic field interactions. Thanks to their large birefringence and reconfigurable director (i.e. local optical axis) orientation, LCs have become one of the most attractive candidates for making optical devices requiring versatile functionalities. Particularly, liquid crystal display (LCD) holds a dominant position in the flat panel display market nowadays. Essentially, they are composed of a huge number of separate light intensity modulators in the visible range. In addition to amplitude, LCs can freely manipulate other spatial degrees of light, such as polarization and phase. Through specifical designing of the director distribution of LC domains, one could arbitrarily manipulate the optical field. Optical field control is a key requirement for optics and photonics. Structured light, also known as shaped light or tailored light, is a light beam that has customized intensity, polarization, and phase. Recently, specific beams including vortex beams, vector beams (VBs), and Airy beams have been studied intensively due to their fantastic properties and diverse applications in optical trapping, laser processing, high‐resolution imaging, etc. Generally, these beams can be directly generated from Gaussian beams by spatially manipulating the amplitude or phase of light. Such manipulations could be accomplished by lens or plates with specific curvature radius, photoresist masks, or metasurfaces with delicately designed structures. However, their optical characteristics are static once the respective device is fabricated, which severely restricts corresponding applications. Thanks to the electro‐optical tunability of LCs, structured LC domains make these devices dynamic and more efficient.
关键词： vector beams,Airy beams,photoalignment,vortex beams,optical field control,structured light,Liquid crystals
更新于2025-09-23 15:21:01
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Enhanced Ordering and Efficient Photoalignment of Nanostructures in Block Copolymers Enabled by Halogen Bond
摘要： Fabrication and manipulation of macroscopically ordered nanostructures in polymer ?lms via supramolecular self-organization are fascinating from the viewpoints of science and technology. Here, a halogen bond (XB) was introduced into a block copolymer to facilitate its microphase separation process upon XB-driven supramolecular self-assembly. To the best of our knowledge, this is an extremely rare example to elegantly maneuver nanostructures of polymers by the emerging supramolecular interaction, XB. The nonmesogenic block copolymer composed of poly(ethylene oxide) and azopyridine-containing polymethacrylate was transformed into a supramolecular liquid-crystalline polymer through the halogen-bonded interaction between 1,2-diiodo-3,4,5,6-tetra?uorobenzene and the azopyridine group with the optimal molar ratio of 1:1. For comparison, one hydrogen-bonded liquid-crystalline polymer was also fabricated but no such ordering enhancement was acquired, indicating that both the high directionality of XB and the resulting supramolecular mesogenic ordering played key roles in the enhanced ordering of nanostructures in polymer ?lms. In addition, e?cient photoalignment and photoreorientation of nanostructures coinciding with the oriented direction of the supramolecular mesogens were also obtained by manipulating photoirradiation of linearly polarized light for the present XB-involved liquid-crystalline block copolymer, which is promising for the development of a novel generation of advanced composite liquid crystal (LC) materials.
关键词： halogen bond,supramolecular self-assembly,photoalignment,block copolymer,nanostructures
更新于2025-09-23 15:19:57
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Liquid-Crystal-Mediated Active Waveguides toward Programmable Integrated Optics
摘要： Optics, playing an ever-important role in life, is developing toward miniaturization and integration. Particularly, the field programming of integrated optics will benefit its functionality and durability, thus is highly pursued. Here, through precisely controlling the space-variant orientations of anisotropic liquid crystals (LCs), various graded-index waveguides are demonstrated in a homogeneous medium. Straight/bending waveguides and ring resonators are fabricated via LC photopatterning. They exhibit pronounced polychromatic light-guiding performance. Thanks to their intrinsic external-stimuli responsivity, the thermal switchability and polarization tunability are verified. By selectively polymerizing, robust functional components and active connecting waveguides can be realized on the same chip. It provides a practical and universal solution to programmable integrated optics, and extends the applications of microstructured soft matter even in wearable photonics.
关键词： integrated optics,photoalignment,waveguides,liquid crystals
更新于2025-09-23 15:19:57
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Luminescent Down‐Conversion Semiconductor Quantum Dots and Aligned Quantum Rods for Liquid Crystal Displays
摘要： Herein, emerging applications of luminescent semiconductor nanocrystals are addressed, such as quantum dots and quantum rods as down-conversion materials used in liquid crystal displays (LCD). Their precisely tunable emission wavelengths and narrow emission bandwidths offer high color purity resulting in a wide color gamut with vivid colors for LCDs. Anisotropic materials, such as quantum rods, have the additional advantage of polarized emission, which can bring a significant improvement to the efficiency of LCD displays. The basic optical properties of these nanomaterials are considered, with a focus on quantum rods, and the challenges and progress in their assembly are discussed. Different techniques for quantum rod alignment are introduced such as shear-oriented, electric field and magnetic field assisted assembly, mechanical rubbing, stretching, and electrospinning. The photoalignment approach allows for an easy arrangement of quantum rods in-plane, and the implications of this method to patterning are considered. Different configurations of LCDs utilizing semiconductor quantum dots and quantum rods as down-conversion layers are also presented, and the potential applications that are enabled by the wide range of emerging materials are highlighted.
关键词： quantum dots,liquid crystal displays,photoalignment,quantum rods,luminescent semiconductor nanocrystals,down-conversion materials,polarized emission
更新于2025-09-19 17:13:59
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Ligand Shell Engineering to Achieve Optimal Photoalignment of Semiconductor Quantum Rods for Liquid Crystal Displays
摘要： The photoalignment process to align semiconductor quantum rods (QRs) in the liquid crystal monomer (LCM) matrix is a flexible technology; however, the optical quality of the resulting enhancement films drops at high concentrations of the QRs. The compatibility between the ligand shell on the QRs and the LCM plays an important role in avoiding this issue. Herein, several kinds of ligand shells on the rod-in-rod CdSe/CdS QRs are designed, without affecting the optical properties of QRs, and their compatibility with LCM molecules is studied. Promesogenic dendritic ligands in combination with relatively short alkylphosphonic acids are found to provide the highest optical quality, without QR aggregation, and so the high brightness of the resulting enhancement films, even at higher concentrations of QRs in LCM, which is perfectly suitable for the application in liquid crystal displays.
关键词： photoalignment,enhancement films,ligand design,quantum rods,liquid crystal displays
更新于2025-09-10 09:29:36
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22.1: Fabrication of Broadband Quarter Wave Plate by Combination of Two Retardation Films Using Coating Technique
摘要： Broadband quarter waveplate can be treated as a circular polarizer providing true dark in the display system. Broadband quarter wave plate consists of two waveplates with different alignment direction using coating technique is proposed and fabricated. The reflection spectrum shows a good dark state
关键词： Broadband waveplate,Photoalignment,Dark state
更新于2025-09-09 09:28:46