Highly Self-Healable Polymeric Coating Materials Based on Charge Transfer Complex Interactions with Outstanding Weatherability.

In this study, we prepare highly self-healable polymeric coating materials using charge transfer complex (CTC) interactions. The resulting coating materials demonstrate outstanding thermal stability (1 wt% loss thermal decomposition temperature at 420 °C), rapid self-healing kinetics (in 5 min), and high self-healing efficiency (over 99%), which is facilitated by CTC-induced multiple interactions between the polymeric chains. In addition, these materials exhibit excellent optical properties, including transmittance over 91% and yellow index (YI) below 2, and show enhanced weatherability with a ΔYI value below 0.5 after exposure to UV light for 72 h. Furthermore, the self-healable coating materials developed in this study show outstanding mechanical properties by overcoming the limitations of conventional self-healing materials.

Ink-Lithography for Property Engineering and Patterning of Nanocrystal Thin Films.

Next-generation devices and systems require the development and integration of advanced materials, the realization of which inevitably requires two separate processes: property engineering and patterning. Here, we report a one-step, ink-lithography technique to pattern and engineer the properties of thin films of colloidal nanocrystals that exploits their chemically addressable surface. Colloidal nanocrystals are deposited by solution-based methods to form thin films and a local chemical treatment is applied using an ink-printing technique to simultaneously modify (i) the chemical nature of the nanocrystal surface to allow thin-film patterning and (ii) the physical electronic, optical, thermal, and mechanical properties of the nanocrystal thin films. The ink-lithography technique is applied to the library of colloidal nanocrystals to engineer thin films of metals, semiconductors, and insulators on both rigid and flexible substrates and demonstrate their application in high-resolution image replications, anticounterfeit devices, multicolor filters, thin-film transistors and circuits, photoconductors, and wearable multisensors.

Residual Image Suppression Through Annealing Process of Amorphous Indium Gallium Zinc Oxide Thin Film Transistor for Plastic Organic Light-Emitting Diode Display.

For the evaluation of the residual image suppression, the amorphous indium-gallium-zinc-oxide thin film transistor was manufactured with electric field shield metal on silicon oxide multi-buffer layer, without the need for a silicon crystallization process through the excimer laser process, and is advantageous for the manufacture of large-scale plastic organic light-emitting display. We conducted a study on the propensity to suppress a residual image according to the temperature of the annealing process in amorphous indium gallium zinc oxide. The evaluation divided by the ambient process temperature conditions to measure the change and restoration tendency of the gray current by the black/white current of thin film transistors, and for precise measurement of the current change intervals, the current was analyzed in 0.004 seconds per point. Through the study, residual image of amorphous Indium Gallium Zinc Oxide transistor was found to be suppressed as the temperature of the annealing crystallization increased from 250°C to 325°C, and there was no improvement effect on the 325°C or higher. The trend of threshold voltage shift of thin film transistors according to the two process temperature conditions, 250°C and 325°C, was analyzed by Two sample T analysis method, and the analysis confirmed that the trend of current deterioration is different through p-value 0.007.

Residual Image Reduction Using Electric Field Shield Metal in Plastic Organic Light-Emitting Diode Display.

A plastic organic light-emitting diode display is a device that emits light in an organic layer in proportion to the amount of current applied from a thin film transistor, which constitutes a pixel. However, it was confirmed that the residual image was shown by the operation of the thin film transistor. To suppress residual image, the effect of electric field was studied in operation of a-IGZO thin film transistor. The a-IGZO thin film transistor, in which a polyimide film was used as a substrate, was applied as a driving thin film transistor for pixel circuits in a plastic organic light-emitting diode display, and the effect of the electric field behavior inside the film on residual images was studied. Residual images were strongly connection with the electric field distribution characteristics inside the polyimide substrate, and they were reduced by introducing an electric field shield metal layer in the a-IGZO thin film transistor. The correlation between residual image generation and the operation of the a-IGZO thin film transistor was further explained through technology computer-aided design simulation (Silvaco Group Inc.).

Spatiotemporally Controlled Plasticity and Elasticity in 3D Multi-Shape Memory Structures Enabled by Elemental Sulfur-Derived Polysulfide Networks with Intrinsic NIR Responsiveness.

Thermadapt shape memory polymers (SMPs), utilizing a variety of dynamic covalent bond exchange mechanisms, have been extensively studied in recent years but it is still challenging to address several constraints in terms of limited accuracy and complexity for constructing 3D shape memory structures. Here, an effective and facile preparation of thermadapt SMPs based on elemental sulfur-derived poly(phenylene polysulfide) networks (PSNs) is presented. These SMPs possess intrinsic near-infrared (NIR)-induced photothermal conversion properties for spatiotemporal control of their plasticity and elasticity. The NIR-controllable plasticity and elasticity of the PSNs enable versatile shape manipulation of 3D multi-shape memory structures, including building block assembly, reconfiguration, shape fixing/recovery, and repair.

Synthesis of Poly(phenylene polysulfide) Networks from Elemental Sulfur and p-Diiodobenzene for Stretchable, Healable, and Reprocessable Infrared Optical Applications.

The synthesis and characterization of poly(phenylene polysulfide) networks (PSNs) with controlled average sulfur ranks, from elemental sulfur (ES) and p-diiodobenzene (DIB), are investigated. The PSN films, prepared via simple hot pressing, are found to possess large extensibility up to around 300% and complete recovery of shape and mechanical properties after deformation, which are attributed to the loosely cross-linked network structures mainly consisting of linear poly(phenylene polysulfide) chains. The covalent polysulfide linkages in the PSNs also exhibit dynamic behaviors under ultraviolet (UV) or thermal treatment, thus, enabling self-healing and reprocessing of the films when scratched and broken, respectively. Combined with the unique mechanical properties of the PSNs, their high refractive index and excellent infrared (IR) transparency contribute to the preparation of stretchable, healable, and reprocessable IR transmitting materials for potential deformable and stretchable optical applications.

Effects of Y2O3 Additive on Mechanical and Thermal Properties of Cordierite-Mullite Ceramics.

Cordierite is an alumina-magnesia-silica compound widely used as a thermal shock resistant material due to its high thermal shock resistance, low coefficient of thermal expansion (CTE), low dielectric constant, and good electrical insulation. However, its narrow sintering temperature range and low mechanical strength hinder its application in ceramic heaters. Although mullite shows excellent thermal and chemical stability, heat resistance, and mechanical strength, it has the disadvantages of high sintering temperatures (1600-1700 °C) and poor thermal shock resistance. In this study, a composite phase was prepared by mixing cordierite and mullite to expand the narrow sintering temperature range of cordierite and adjust its CTE to be similar to that of Si. Furthermore, Y2O3 was added to reduce the sintering temperature and to increase the mechanical strength. Therefore, the composite showed the highest density of 2.5 g/cm³ at 1380 °C when the ratio of mullite to cordierite was 20 wt%. When 11 wt% Y2O3 was added to this composition, the highest density was 2.8 g/cm³ for a sintering temperature of 1320 °C, and the mechanical strength was relatively good as 180 MPa of 3-points bending strength was comparatively good. The CTE was 2.6×10-6.K-1, which was similar to that of Si.

Molybdenum-Doped PdPt@Pt Core-Shell Octahedra Supported by Ionic Block Copolymer-Functionalized Graphene as a Highly Active and Durable Oxygen Reduction Electrocatalyst.

Development of highly active and durable electrocatalysts that can effectively electrocatalyze oxygen reduction reactions (ORR) still remains one important challenge for high-performance electrochemical conversion and storage applications such as fuel cells and metal-air batteries. Herein, we propose the combination of molybdenum-doped PdPt@Pt core-shell octahedra and the pyrene-functionalized poly(dimethylaminoethyl methacrylate)-b-poly[(ethylene glycol) methyl ether methacrylate] ionic block copolymer-functionalized reduced graphene oxide (Mo-PdPt@Pt/IG) to effectively augment the interfacial cohesion of both components using a tunable ex situ mixing strategy. The rationally designed Mo-PdPt@Pt core-shell octahedra have unique compositional benefits, including segregation of Mo atoms on the vertexes and edges of the octahedron and 2-3 shell layers of Pt atoms on a PdPt alloy core, which can provide highly active sites to the catalyst for ORR along with enhanced electrochemical stability. In addition, the ionic block copolymer functionalized graphene can facilitate intermolecular charge transfer and good stability of metal NPs, which arises from the ionic block copolymer interfacial layer. When the beneficial features of the Mo-PdPt@Pt and IG are combined, the Mo-PdPt@Pt/IG exhibits substantially enhanced activity and durability for ORR relative to those of commercial Pt/C. Notably, the Mo-PdPt@Pt/IG shows mass activity 31-fold higher than that of Pt/C and substantially maintains high activities after 10 000 cycles of intensive durability testing. The current study highlights the crucial strategies in designing the highly active and durable Pt-based octahedra and effective combination with functional graphene supports toward the synergetic effects on ORR.

Rational Design of Multiamphiphilic Polymer Compatibilizers: Versatile Solubility and Hybridization of Noncovalently Functionalized CNT Nanocomposites.

The design of amphiphilic polymer compatibilizers for solubility manipulation of CNT composites was systematically generalized in this study. Structurally tailored multiamphiphilic compatibilizer were designed and synthesized by applying simple, high-yield reactions. This multiamphiphilic compatibilizer was applied for noncovalent functionalization of CNTs as well as provided CNTs with outstanding dispersion stability, manipulation of solubility, and hybridization with Ag nanoparticles (NPs). With regard to the dispersion properties, superior records in maximum concentration (2.88-3.10 mg/mL in chloroform), and mass ratio of the compatibilizer for good CNT dispersion (36 wt %) were achieved by MWCNTs functionalized with a multiamphiphilic block copolymer compatibilizer. In particular, the solubility limitations of MWCNT dispersion in solvents ranging from toluene (nonpolar) to aqueous solution (polar) are surprisingly resolved by introducing this multiamphiphilic polymer compatibilizer. Furthermore, this polymer compatibilizer allowed the synthesis of the hybrid CNT nanocomposites with Ag nanoparticles by an in situ nucleation process. As such, the multiamphiphilic compatibilizer candidate as a new concept for the noncovalent functionalization of CNTs can extend their use for a wide range of applications.

Inkjet-printing of antimony-doped tin oxide (ATO) films for transparent conducting electrodes.

Antimony-doped Tin oxide (ATO) films have been prepared by inkjet-printing method using ATO nanoparticle inks. The electrical and optical properties of the ATO films were investigated in order to understand the effects of rapid thermal annealing (RTA) temperatures. The decrease in the sheet resistance and resistivity of the inkjet-printed ATO films was observed as the annealing temperature increased. The film annealed at 700 degrees C showed the sheet resistance of 1.7 x 10(3) Omega/sq with the film thickness of 350 nm. The optical transmittance of the films remained constant regardless of their annealing temperatures. In order to further reduce the sheet resistance of the films as well as the annealing temperature, Ag-grid was printed in between two layers of inkjet-printed ATO. With 1.5 mm Ag line spacing, the Ag-grid embedded ATO film showed the sheet resistance of 25.6 Omega/sq after RTA at 300 degrees C.

Synthesis of Cu nanoparticles with self-assembled monolayers via inert-gas condensation.

Cu nanoparticles with vaporized self-assembled monolayers (SAMs) for the prevention of oxidation were synthesized via inert-gas condensation (IGC). When processing the nanoparticles, the convection in the vacuum chamber was controlled using carrier gases such as Ar and He. Cu shots (2-8 mm) were used as raw materials and were evaporated via resistance heating. Octanethiol (CH3(CH2)7SH) was used for the SAMs and was introduced with the carrier gases during the process. The prepared samples were examined via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to determine the particle sizes, the coating thicknesses of the SAMs, and the particle distribution states. The ingredients were confirmed via X-ray photoelectron spectroscopy (XPS) and energy-dispersive spectroscopy (EDS). The particle size and morphology were controlled by introducing various combinations of carrier gases, such as He, Ar and H2. Finally, stabilized Cu nanoparticles stably coated with octanethiol were successfully fabricated.

Electrical properties of imidazole-modified MWNT/polyphenylenesulfide composites prepared by melt mixing.

The electrical conductivity of surface-modified multiwalled carbon nanotubes (MWNTs)/poly-phenylenesulfide (PPS) composites prepared by melt processing is measured as a function of frequency with the MWNTs content and evaluated in terms of percolation behavior. The imidazoledithiocarboyxlic acid (imidazole) is grafted from the oxidized MWNTs, and the results of surface analysis, HRTEM and thermal analysis reveal that the MWNTs are successfully modified by imidazole. Although the imidazole-modified MWNTs are most damaged during the modification reaction of imidazole with carboxylic group onto the MWNTs as well as during the oxidation, so that the modified MWNTs are significantly shortened, the imidazole modification of MWNTs enables the PPS composites to have the lower percolation threshold and the higher electrical conductivity than the oxidized MWNTs/PPS composites. It is recognized that the better dispersion of MWNTs derived from the compatibility of PPS with sulfur moiety in the imidazole and the presence of N-H groups which may act as an assistor of the electronic conduction and/or decrease the energy barrier required for the charge carriers to hop from conducting clusters to neighbors contribute to the enhancement of the electrical properties of the imidazole-modified MWNTs/PPS composites.