Nanosize-confined nematic liquid crystals at slippery interfaces of polymer composites consisting of poly (hexyl methacrylate)

Park, Hyoung Soo; Lee, Da Yeon; Kim, Min Su; Lee, Seung Hee

doi:10.1016/j.molliq.2022.118540

Cited by 6 publications

(1 citation statement)

References 39 publications

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“…In liquid crystal (LC)-based devices, the interplay among confinement geometry, anchoring condition, and elastic constant is key to defining a system’s preferred orientation field and response behavior. − Understanding the orientation and ordering transitions within such materials in curved boundaries is therefore central to developing emerging LC-based miniaturized curved and flexible devices, including wearable sensors and flexible displays. Confinement within curved boundaries, as in micro- or nanodroplets, is known to distort the LC director field due to incompatibility between the preferred director field alignment and the curvature of the space, resulting in the emergence of new defect structures. − Depending on the type of surface anchoring, LC molecules in a spherical nematic microdroplet, for example, adopt two distinct director field configurations.…”

Section: Introductionmentioning

confidence: 99%

Director Distortion and Phase Modulation in Deformable Nematic and Smectic Liquid Crystal Spheroids

et al. 2022

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The growing interest in integrating liquid crystals (LCs) into flexible and miniaturized technologies brings about the need to understand the interplay between spatially curved geometry, surface anchoring, and the order associated with these materials. Here, we integrate experimental methods and computational simulations to explore the competition between surface-induced orientation and the effects of deformable curved boundaries in uniaxially and biaxially stretched nematic and smectic microdroplets. We find that the director field of the nematic LCs upon uniaxial strain reorients and forms a larger twisted defect ring to adjust to the new deformed geometry of the stretched droplet. Upon biaxial extension, the director field initially twists in the now oblate geometry and subsequently transitions into a uniform vertical orientation at high strains. In smectic microdroplets, on the other hand, LC alignment transforms from a radial smectic layering to a quasi-flat layering in a compromise between interfacial and dilatation forces. Upon removing the mechanical strain, the smectic LC recovers its initial radial configuration; however, the oblate geometry traps the nematic LC in the metastable vertical state. These findings offer a basis for the rational design of LC-based flexible devices, including wearable sensors, flexible displays, and smart windows.

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Section: Introductionmentioning

confidence: 99%

Director Distortion and Phase Modulation in Deformable Nematic and Smectic Liquid Crystal Spheroids

et al. 2022

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Field‐Induced Structural Transitions in Liquid Crystal Microemulsions

Kim

Manda

Lee

et al. 2022

Advanced Optical Materials

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Liquid crystal (LC) droplets have fascinating properties, such as anisotropic properties, in response to external stimuli. As LC droplet size may determine the proper application of soft composites, various results from numerical simulations and experimental observations of LC droplets are reported. Here, detailed topological responses of individual bipolar droplets to electric fields, are shown. The integration of each response influences the entire electro‐optic behavior. Monodispersed LC bipolar droplets are fabricated in a polyvinyl alcohol‐dissolved aqueous solution via a membrane‐emulsification method. The planar anchoring, provided by the polyvinyl alcohol surface, and surface elasticity, guide the entire LC director configuration, associated with topological defects, in the droplets. By simply blade‐coating the solution, bipolar axes of the droplets can be randomly placed on a flat substrate. Two different subsequential stages are found when applying voltages: 1) director reorientation, which is threshold‐less and 2) topological defect movement, which exhibits a threshold‐like behavior. Various initial directions of the bipolar axes with respect to the field direction provide the transition voltage between these two stages. It is believed that this study can provide important clues to handle several fundamental issues in electro‐optics of encapsulated LCs, such as the determination of response times, threshold, and operating voltages.

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Memorizable Electro‐Birefringence Effect Exhibited by Transparent Liquid Crystal/Polymer Composite Materials

Yamaguchi,

Okumura,

Nishikawa

et al. 2024

Adv Elect Materials

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Polymer‐dispersed liquid crystals (PDLCs) with nano‐phase‐separated structures, in which nanometer‐sized liquid crystal (LC) domains are dispersed within a polymer matrix (nano‐PDLCs), are transparent solid materials whose optical properties can be modulated by applying an electric field (E‐field). Because the proportion of LC that can respond to an electric field is small, the specific surface area of the phase‐separated interface of nano‐PDLCs is larger than that of conventional PDLCs, resulting in higher drive voltages than those of conventional PDLCs. To lower the driving voltage of nano‐PDLCs, highly polar LCs (C3DIO) are used with a large dielectric anisotropy (>10000), and prepared nano‐PDLCs using DIO mixtures obtained by mixing them with related compounds as the host LC. Nano‐PDLCs employing DIO mixtures exhibit higher E‐field responsivity than those using conventional LC. In addition, the electro‐optical Kerr coefficient at visible wavelength is significantly high, reaching 10−8 m V−2. Furthermore, nano‐PDLCs using the DIO mixture exhibit a memory effect in which the induced birefringence remains even after the removal of the in‐plane E‐field. Memorized birefringence can be erased by heating or applying an E‐field perpendicular to the substrate surface. Nano‐PDLCs using a DIO mixture can be rewritable electro‐birefringence‐responsive materials that can memorize arbitrary birefringence values.

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Nanosize-confined nematic liquid crystals at slippery interfaces of polymer composites consisting of poly (hexyl methacrylate)

Cited by 6 publications

References 39 publications

Director Distortion and Phase Modulation in Deformable Nematic and Smectic Liquid Crystal Spheroids

Director Distortion and Phase Modulation in Deformable Nematic and Smectic Liquid Crystal Spheroids

Field‐Induced Structural Transitions in Liquid Crystal Microemulsions

Memorizable Electro‐Birefringence Effect Exhibited by Transparent Liquid Crystal/Polymer Composite Materials

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