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Copolymer films of photoalignable liquid crystalline (LC) copolymethacrylates comprised of a phenyl benzoate mesogen connected with N-benzylideneaniline end moiety (NBA2) and benzoic acid (BA) side groups exhibit a photoinduced reorientation behavior. Significant thermally stimulated molecular reorientation attains a dichroism (D) greater than 0.7 for all copolymer films and a birefringence of 0.113–0.181. In situ thermal hydrolysis of the oriented NBA2 groups decreases the birefringence to 0.111–0.128. However, the oriented structures of the film are maintained, demonstrating a photo-durability, even though the NBA2 side groups photo-react. The hydrolyzed oriented films show higher photo-durability without changing their optical properties.

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. Herein, emerging applications of luminescent semiconductor nanocrystals are addressed with a focus on anisotropic quantum rods as down‐conversion materials for liquid crystal displays (LCDs). Techniques for the quantum rod alignment, with a focus on the photoalignment approach, and different configurations of LCDs are considered.

The accurate and controlled alignment of liquid crystals (LCs) in modern optical devices is of great importance. Photoalignment is one of the most appealing approaches for achieving more versatile alignment in designs. One of the most important parameters of these devices is the thickness and the homogeneity in the photoaligned area, especially in devices that introduce retardance. In this work, we propose a novel polarimetric-based method for the measurement of thickness of homogeneous liquid crystal cells that considers diattenuation effects and how they affect the retardance generated by a liquid crystal variable retarder (LCVR). We experimentally demonstrate the production of dye-doped liquid crystal (DDLC) devices, photoaligned in the visible range with a 532 nm laser light, of two different thicknesses with a very high spatial homogeneity. Thinner devices can be used across the whole visible spectrum despite the residual diattenuation at shorter wavelengths, whereas thicker ones achieve the best degree of polarization (DOP) in the transmitted wavefronts, close to 100%, at longer wavelengths.

In this paper, we present a novel approach for advanced, three-dimensional patterned ordering of nematic liquid crystals. Our method allows for simultaneous control of azimuth and tilt of molecules by using a two-step process based on patterned photoalignment (used to define azimuth) followed by selective polymer stabilization of molecules reorientated with an electric field (used to define tilt). We demonstrate that those two subsequent processes, realized with high-resolution patterned illumination with UV light, allow us to obtain multiple microdomains with independently controlled tilt and azimuth. It opens possibilities to create complex three-dimensional distributions of director within a single liquid crystal cell, which is impossible with any other technique so far. Moreover, although the polymer-stabilization process is used, it is still possible to retune the tilt of the molecules; however, the electric field intensity needed for tuning is slightly higher than in the non-polymerized areas of the sample.

Tunable diffraction gratings and phase filters are important functional devices in optical communication and sensing systems. Polarization gratings, in particular, capable of redirecting an incident light beam completely into the first diffraction orders may be successfully fabricated in liquid crystalline cells assembled from substrates coated with uniform transparent electrodes and orienting layers that force a specific molecular distribution. In this work, the diffraction properties of liquid crystal (LC) cells characterized by a continually rotating cycloidal director pattern at the cell substrates and in the bulk, are studied theoretically by solving a relevant set of the Euler-Lagrange equations. The electric tunability of the gratings is analyzed by estimating the changes in liquid crystalline molecular distribution and thus in effective birefringence, as a function of external voltage. To the best of our knowledge, such detailed numerical calculations have not been presented so far for liquid crystal polarization gratings showing a cycloidal director pattern. Our theoretical predictions may be easily achieved in experimental conditions when exploiting, for example, photo-orienting material, to induce a permanent LC alignment with high spatial resolution. The proposed design may be for example, used as a tunable passband filter with adjustable bandwidths, thus allowing for potential applications in optical spectroscopy, optical communication networks, remote sensing and beyond.

Thermally stimulated photoinduced reorientation of liquid crystalline (LC) polymethacrylate composed of a phenyl benzoate mesogen connected with N-benzylideneaniline (NBA2) end moiety exhibits a significant molecular reorientation (D > 0.7) when the film is exposed to linearly polarized 313 nm light and subsequently annealed in the LC temperature range of the material. Hydrolysis of the NBA2 end moieties yields an oriented mesogen with phenylamine moieties without distorting the oriented structure. In situ condensation of 2-hydroxybenzaldehyde derivatives and phenylamine moieties yields oriented N-salicylideneaniline side groups. The resultant film displays a polarized fluorescence with a polarization ratio up to 3.4.

Photoalignment technology is serving as an emerging technology for programming liquid crystalline polymer (LCP) materials due to its advantages including noncontact, high resolution, spatial control, programmability, and high efficiency. In this review, we report the research progress in implementing polarized light to design the anisotropy of LCPs, which is categorized based on the photoalignment mechanisms. The alignment approaches and the different stimulus‐responsive behaviors of the materials after photoalignment are discussed. Additionally, we have summarized the applications of photoaligned LCPs such as liquid crystal displays, optical components, intelligent soft actuators, and beyond. Finally, the challenges and future directions of the technology are outlined. In this review, we report the research progress in liquid crystalline polymer‐based photoalignment technology via polarized light. We categorize the technology according to the mechanism, focusing on the alignment strategies and applications including liquid crystal displays, optical components, and intelligent soft actuators.

We compare photoaligning properties of polymer layers fabricated from the same constituents: polymethyl-methacrylate (PMMA) and azo-dye Disperse Red 1 (DR1), either chemically attached to the PMMA main-chain, or physically mixed with it. Photoaligning properties depend on the preparation method drastically. Photoalignment was found to be far more efficient when PMMA is functionalized with DR1 compared to the case of physically mixing the constituents. This finding is supported by atomic force microscope (AFM) scans monitoring the light-induced changes at the polymer–air interface, and revealing a photoinduced mass transfer, especially in the case of functionalized PMMA.

We demonstrate a physical model of photoalignment and photopatterning based on rotational diffusion in solid azo-dye nanolayers. We also highlight the new applications of photoalignment and photopatterning in display and photonics such as: (i) liquid crystal (LC) E-paper devices, including optically rewritable LC E-paper on flexible substrates as 3D E-paper, as well as optically rewritable technology for photonics devices; (ii) photonics LC devices, such as LC Switches, polarization controllers and polarization rotators, variable optical attenuators, LC filled photonic crystal fiber, switchable diffraction grating; (iii) patterned micro-polarizer array using photo-alignment technology for image sensor; (iv) electrically tunable liquid crystal q-plates; (v) electrically switchable liquid crystal Fresnel lens; (vi) liquid crystal optical elements with integrated Pancharatnam-Berry phases. We are sure, that in the field of (LC), the main point is no longer display research, but new photonic applications of LC are emerging in telecommunication, fiber optical communication systems, sensors, switchable lenses, LC light converters and other LC photonics devices.

In this communication, we summarise our results related to light-induced orientational phenomena at liquid crystal–polymer interfaces. We investigated photoalignment for various nematics at the interface with the photosensitive polymer layer polymethyl methacrilate functionalised with azo dye Disperse Red 1. It was found that the efficiency of photoalignment exhibits marked differences depending on the structure of the rigid core of the liquid crystal molecules. It was demonstrated that the photo-orientation process is also significantly affected by the type of mesophase in which irradiation is carried out. The observations highlight the importance of the mutual influence of the polymer and the liquid crystal in light-induced processes.