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The hermetic sealing of optoelectronic devices has attracted much attention because it can endow the devices with long-term operation reliability and high mechanical resistance. Herein, we present a facile and efficacious strategy for fabrication of water-resistant and highly adhesive acrylate-based sealing materials for hermetic optical devices using oxime-based photoinitiators. Compared with conventional sealing materials containing ketone-based photoinitiator, those embedded with oxime-based photointiators afforded a strong UV absorption in the effective wavelength range, a high UV curing conversion of 99.5% at a low radiant energy of 1.0 J cm−2, a remarkable adhesion strength of 42.2 kgf cm−2, an improved water impermeability of 5.3 g m−2 day−1, and a reduced internal pollution length of 104.9 µm. These excellent properties of the fabricated sealing materials are attributed to the fragmentation mechanism of oxime-based photoinitiators which can generate numerous initiating radicals through multi-step decomposition reactions, resulting in the efficient initiation for photoreaction with acrylate resins. This study provides promising sealing materials based on the oxime-based photoinitiators for ultra-slim and flexible optoelectronic applications.

A new type of highly flexible and transparent adhesive film embedded with elastic hybrid nanoparticles was fabricated using simple roll-to-roll coating and UV curing process. The elastic organic-inorganic nanoparticles comprising a hard SiO2 core and spring-like aliphatic shell were synthesized using a surface-modification reaction and then applied to acrylic adhesives. The facile and large-scale roll-to-roll coating and subsequent UV curing process produced a highly flexible optical adhesive film, wherein the elastic nanoparticles were chemically crosslinked to the acrylic resin. Compared with a conventional film, the proposed adhesive film exhibited high optical transmittance, high adhesion strength, and excellent relaxation and recovery characteristics.

Hierarchical self-assembled nanoarchitectures based on peculiar self-assembly of block copolymers are advantageous for the nanofabrication of functionally versatile materials with a wide range of potential applications from bioelectronic devices to flexible displays. Herein, we developed a simple yet efficient, cost-effective, scalable strategy for the fabrication of an ultrafast responsive and highly reliable self-constructed polymer nanolayer for automatic control of molecular alignment by using the template-assisted interfacial self-assembly of amphiphilic poly(ethylene oxide)–poly(propylene oxide)-based triblock copolymers. A new type of ultrathin polymer nanolayer was facilely fabricated on polar electrode surface using simple doping in liquid crystal (LC) medium and in situ interfacial self-assembly of a small amount of amphiphilic triblock copolymers in the closed LC cell. A hydrophobic and ultrathin polymer nanolayer with dense nanoneedle arrays formed by interfacial hydrogen bonding between hydrophilic poly(ethylene oxide) block and hydrophilic indium tin oxide electrode induces a spontaneous homeotropic alignment of LCs during programmed self-assembly process. Moreover, this facile approach endows the polymer nanolayer with ultrafast electro-optical switching and high molecular alignment force characteristics, as well as an excellent alignment stability during long-term operation. Compared to commercial polyimide layer, our polymer nanolayer accomplishes the ultrafast falling response time with an improvement of 55.3% and fast rising response time with a reduction of 36.4%.

Functional ultrathin nanoarchitectures are commonly based on hierarchical molecular self-assemblies that are structurally tunable and facilely fabricable, and have found a broad range of potential applications from nanoelectronics to biosensors. Here, we demonstrate a simple and elegant approach for the rational design of ultrathin molecular nanoarchitectures for tunable interfacial orientation of liquid crystals (LCs) using the surface-confinement of functional amphiphilic copolymers. The surface-confined nanostructured self-assemblies are simply prepared by introducing common functional polymers into amphiphilic systems. The surface-confined copolymeric nanoalignment layer, which is constructed from the simple doping and molecular self-assembly of comb-shaped amphiphilic copolymers in a confined LC medium, comprises a hydrophobic polyacrylate segment with a long side chain moiety capable of uniformly controlling the LC alignment and a hydrophilic polyacrylic acid segment with a carboxylic acid group confined to the hydrophilic surface of indium tin oxide substrate. The combination of structural variations on amphiphilic copolymer system and tunability of molecular orientation makes the surface-confined copolymeric nano-assemblies highly attractive ultrathin nanoarchitectures. The resulting nanostructured self-assemblies exhibit a spontaneous and uniform vertical orientation of LC molecules, simultaneously providing the LC device with a superfast electro-optical switching time and a strong surface anchoring control.

Hierarchical ultrathin nanoarchitectures are structurally stable and functionally versatile, which are supramolecular building blocks with a broad range of applications from optoelectronic devices to tunable biosensors. Here, we present a facile and scalable strategy to fabricate an ultrathin polymer nanoarchitecture with islands of alkyl chains for spontaneous interfacial molecular orientation by using the hierarchical and automatic self-assembly of amphiphilic comb-like copolymers. The intriguing self-constructed nanoarchitecture is achieved by facile doping and interfacial self-assembly of amphiphilic poly(dodecyl acrylate)–poly(acrylic acid) comb-like copolymers on hydrophilic indium tin oxide substrate. It is experimentally revealed that an ultrathin and spiky polymer nanoarchitecture with a hydrophobic segment surface formed by hydrophilic and cooperative interactions of amphiphilic copolymers ensures an automatic vertical molecular alignment of liquid crystals during hierarchical self-construction process. Furthermore, this effective approach affords a fast responsive and low-voltage driving polymer nanoarchitecture with an enhanced electro-optical performance compared to common polyimide layer.

Graphene oxide (GO) is one of the thinnest two-dimensional (2D) organic materials and has been investigated for application in various fields due to its excellent mechanical and optical properties. The unique planar structure and hydrophilic functional groups allow GO to spontaneously form various nanoarchitectures. Herein, we report an unprecedented methodology to achieve the homeotropic alignment of nematic liquid crystals (NLCs) using surface-anchored alkylated graphene oxide (AGO). The GO is functionalized by amino reactions with dodecylamine to impart amphiphilic characteristics. This AGO spontaneously forms a 2D-alignment layer on indium tin oxide surface via polar affinity, and the hydrophobic alkyl chains of AGO guide the constant direction of the NLCs. Furthermore, a study on the effect of the alkylation ratio of AGO on the NLC orientation was conducted, and the achievement of a 2D-alignment layer based on the optimal AGO successfully resulted in the initial homeotropic orientation of the NLCs without any defects. Compared to a conventional polymer alignment layer, it showed a comparable alignment ability, and exhibited an improved optical transmittance due to the ultrathin nature of the AGO alignment layer. This new modus of NLC vertical alignment based on the use of AGO can expand the utility of functionalized GO.

An interfacial molecular array of octadecylamine-functionalized graphene quantum dots (GQDs) was fabricated to simultaneously realize photoluminescence characteristics and molecular orientation for liquid crystals (LCs). The functionalized GQDs were synthesized using a simple bottom-up method by first grafting them with octadecylamine. The subsequent interfacial self-assembly of these functionalized GQDs in an LC medium formed a nanostructured molecular array on an indium tin oxide (ITO) electrode. Experiments revealed that the hydrophobic GQDs spontaneously covered the hydrophilic ITO surface through polar intermolecular interactions, and the resulting GQD layer induced the uniform vertical orientation of the LC molecules at the ITO interface owing to van der Waals interactions of long side chains. In addition, the unique photoluminescence of pure GQDs in the blue region was maintained even in an LC mixture with a low concentration of functionalized GQDs. A new type of homeotropically oriented LC device based on the nanostructured layer of functionalized GQDs exhibited superior electro-optical properties and a 375% improvement in response time for turn-off switching of the device relative to those of a conventional polymer layer. This functionalized GQD-based device simultaneously achieved the spontaneous alignment of the LCs, blue photoluminescence emission, and high-speed response performance for turn-off switching of the device. In addition, our method is cost-effective and encompasses a simple fabrication process for developing functional controllable surfaces without requiring a tedious multi-step manufacturing process.

In the development of high temperature superconducting (HTS) power machines, HTS bushing is one of core technologies. In particular, the insulation body with sheds and electrical insulation at cryogenic temperature have attracted a great deal of interest from the view point of the size, weight and efficiency of bushing. In this study, the electrical and mechanical characteristics of various insulators for body in liquid nitrogen (LN2) were investigated. And the surface discharge distance, collar length of GFRP sheds were studied. To emit bubbles between sheds, the shape and arrangement of shed were studied. The shed structure for 60 kV class HTS bushing were designed with regular arrangement.

For the operation of high temperature superconducting (HTS) power equipments, it is necessary to develop insulating materials a nd high voltage (HV) insulation technology at cryogenic temperature of bushing. In this paper, the surface flashover characteristics of various insulating materials in LN 2 are studied. These results are studied at both AC and impulse voltage under a non-uniform field. The negative impulse breakdown voltage of GFRP is slightly higher than the positive impulse breakdown voltage. The use of glass fiber reinforced plastic(GFRP) and polytetrafluoroethylene (PTFE, Teflon) as insulation body for HTS bushing should be much desirable. Especially, GFRP is excellent material not only surface flashover characteristics but also mechanical characteristics at cryogenic temperature. The surface flashover is most serious problem for the shed design in LN 2 and operation of superconducting equipment. 1. INTRODUCTION Recently, HTS power equipments such as HTS cable, fault current limiter, transformer and others have attracted much interest from the view point of energy. In order to commercialize HTS power equipments, it is necessary to develop HTS conductor, cooling system, insulation and materials technology and high voltage (HV) bushing. Especially, HV bushing is a very important because it must supply the high voltage to the cable or winding of the transformer. The HV bushing is basically a hollow insulator that allowing a conductor to pass along its center.

DC high-temperature superconducting(HTS) cable system has attracted a great deal of interest from the view point of low loss, dense structure and large capacity. A HTS cable system is made of cable and termination. The insulating materials and insulation technology must be solved for the long life, reliability and compact of cable system. In this paper, we will report on the dielectric breakdown characteristics of insulating materials for HTS cable and termination. The AC, DC and lightning impulse breakdown strength of laminated polypropylene paper(PPLP) and glass fiber reinforced plastic(GFRP) have been measured under nitrogen pressures in the range of 0.l-0.4MPa. PPLP and GFRP are found to have a significantly higher DC breakdown strength. Also, DC surface flashover voltage of negative polarity is slightly higher than that of positive polarity in GFRP.

Superconducting magnetic energy storage (SMES) has attracted a great deal of interest from the viewpoint of energy saving. The magnet of conduction-cooled high temperature superconducting (HTS) SMES is cooled down by a cryocooler. One of the most important problems to be assured the protection of magnet and cryocooler is breakdown at cryogenic temperature. In this study, we investigated insulation materials such as Kapton, Aluminum Nitride(AIN), Alumina(), glass fiber reinforced plastics(GFRP) and vacuum in cryogenic temperature. Also, we analyzed statistically the Weibull distribution of breakdown voltage.