| POLYMERS Vol.64 No.7 |
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COVER STORY
New Polymeric Materials to Replace Glass |
| COVER STORY: Highlight Reviews |
| Highly Transparent Technologies for Polymer Materials | Toshitaka KANAI |
| <Abstract> In order to obtain highly transparent isotactic PP sheets by an industrial process, various factors contributing to transparency were analyzed. The higher order structure of the high tacticity PP sheets was investigated. After the heat treatment of quick quenched sheets, the matrix was transformed from smectic structure to α-monoclinic crystal phase. The density and refractive index differences between spherulite and matrix were decreased, and the transparency was drastically improved. Additionally, the influence of the isotacticity, crystallization control material and multilayer extrusion process were analyzed. The lower tacticity PP generated a smaller number and a smaller size of spherulites and showed improved behavior on transparency by heat treatment. In the case of addition of L-LDPE with the specific density to PP, the transparency was markedly improved by heat treatment. This phenomenon could be explained by the refractive index difference of PP matrix and the fine distribution of L-LDPE particles. The shear stress was reduced by laminating resin with low melt viscosity on both surfaces, and therefore it can be surmised that the stress induced crystallization was restrained. Keywords: Polypropylene / Transparency / Spherulite / Crystallization / Heat Treatment / Multilayer |
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| COVER STORY: Topics and Products |
| Development of Crystalline Cycloolefin Polymer | Shigetaka HAYANO |
| <Abstract> Crystalline Cycloolefin Polymer was developed for the first time as a means to enhance thermal properties of conventional Cycloolefin Polymer. Stereocontrol of ROMP of norbornene(NB), dicyclopentadiene(DCP) and tetracyclododecene(TCD) was achieved by Mo- and W-based binary catalysts. Hydrogenated poly(NB)s were crystalline polymers irrespective of their tacticities, but melting of isotactic polymer was much higher than atactic and syndiotactic ones. Isotactic and Syndiotactic hydrogenated poly(DCP)s were clarified to be crystalline polymers of which meltings were extremely high. Syndiotactic hydrogenated poly(TCD) was entirely amorphous. On the other hand, atactic and isotactic polymers were revealed to be crystalline. Keywords: Cycloolefin / Metathesis / Stereoselective / Dicyclopentadiene / Norbornene / Crystalline Polymer / Polyolefin |
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| Development of Thermally Stable and Colorless Polymer Substrate Materials, Past and Present | Shinji ANDO |
| <Abstract> Recently, colorless and transparent polymer films exhibiting high thermal stability and good mechanical properties attract much of interests as substrate materials for flexible organic light-emitting diode (OLED) displays. A colorless fluorinated polyimide was firstly invented by DuPont in 1965, and it has been tried out for aerospace and optical communication applications. In the last decade, Japanese chemical companies have developed various kinds of colorless polyimides (PIs) for flexible display applications using fluorinated and/or alicyclic source materials, of which the coefficients of thermal expansion (CTE), refractive indices, birefringence, glass transition temperatures, electric resistance and film thickness are precisely controlled. In particular, control of CTE for reducing residual stress at the surface between PI substrate and inorganic layers of ITO and/or IGZO is of special importance, and it was achieved by judicious choice of molecular structure and processing conditions. However, the high moisture uptake and significant transmission of oxygen and moisture compared with inorganic glass are still the challenging task. Keywords: Flexible Display / Film Substrate / Colorless Polyimide / Thermal Stability / Thermal Expansion |
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| Development of Glass Alternative Material Using Clay | Takeo EBINA |
| <Abstract> A smectite-based gas barrier coating film was developed. In the coating layer, thin smectite crystals are orderly and densely stacked and an added organic polymer acts as a binder. Purified bentonite and synthetic smectite were used because of their good film formability. The film is prepared by a solution-casting method. The film has superior heat-resistance and gas barrier performance. Transparent films were also successfully made from synthetic smectite and transparent organic polymer. Such a gas barrier film is prepared using a water-soluble polymer and a synthetic smectite clay. The film also has high visible light transparency and it is stable up to 350 degree Celsius. This film is expected to be applied for glass-alternative flexible films. Keywords: Clay / Nanocomposite / Gas Barrier / Visible Light Transparency |
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| Organic-Inorganic Hybrid Hardcoat | Koji KURAOKA |
| <Abstract> Organic-inorganic hybrid flexible hardcoat layers on poly(ethylene terephtalate) (PET) and polycarbonate (PC) were prepared by sol-gel method. The prepared hardcoats were homogenous and transparent, and light transmittance of the hardcoats was high. This transparency is important for applications, such as touch panel and packaging materials. Pencil hardness of the prepared hardcoats were 3H on PET and B on PC, respectively. The prepared hardcoats indicated a high degree of flexibility (Diameter of Mandrel was 10 mm on flexibility test). This flexibility combined with hardness is a novel property of the organic-inorganic hybrid hardcoat film due to dispersion of inorganic segments and organic segments at the molecular level and the effect of phenyl groups. Keywords: Organic-Inorganic Hybrid / Hardcoat / Silica |
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| Cellulose Nanoaterials | Masaya NOGI |
| <Abstract> This topics presented optically transparent nanopaper using cellulose nanofibers only without any polymers. The nanopaper have high optical transparency and low coefficient of thermal expansions like glass, higher thermal resistance than plastics, and high foldability like traditonal paper. This topics have also brief introductions about electronic device applications such as transparent electrodes, transistor arrays, ultra flexible nonvolatile memory, foldable antenna. Thus, the nanopaper is one of the best candidate for future flexible electronic device materials. Keywords: Cellulose Nanofiber / Paper Electronics |
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| The High Reliability Optical Material Based on the Isocyanuric Acid | Kentaro OHMORI |
| <Abstract> The curable resin for advanced electronic materials is required to excellent workability and heat resistance and transparency. For such application field, we have developed a novel epoxy resin having high thermal stability and low absorption to visible light. The material is designed to UV and/or Thermal curable resin, and soluble to popular organic solvents. From these properties, the developed epoxy resin is expected to be beneficial for the transparent sealing material for optical semiconductor such as LED and the clear film substrate. Keywords: Multifunctional Epoxy Monomer / Isocyanuric Acid / Optical Materials |
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| Polymer Science and I: A Personal Account |
| Let’s Think about the Feelings of Molecules | Naoki OUSAKA |
| <Abstract> When I was a graduate student, I have read a wide variety of scientific papers that helped me to enhance not only my knowledge but also the ability of logical thinking. |
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| Front-Line Polymer Science |
| Molecular Self-Assembly and Photon Upconversion | Nobuhiro YANAI, Nobuo KIMIZUKA |
| <Abstract> Photon upconversion (UC) is the key technology to overcome the thermodynamic efficiency limits in solar energy conversion devices. Triplet-triplet annihilation (TTA)-based UC has drawn increasing attention in recent years, primarily because of its occurrence with low-intensity, noncoherent light as the excitation source. To date, efficient TTA-UC has been achieved in solution because diffusion of triplet molecules is essential for energy transfer processes. However, the use of volatile organic solvents and deactivation of triplet states by molecular oxygen significantly disturb their practical applications. Although recently the TTA-based UC has been investigated in solid polymer films, the slow molecular diffusion limits the efficiency of TTA-UC. To solve these problems, we are proposing a paradigm shift from molecular diffusion to energy migration. Assemblies of donor and acceptor display a sequence of efficient donor-to-acceptor triplet-triplet energy transfer (TTET), triplet energy migration, and TTA in the self-assembled state. Keywords: Photon Upconversion / Self-Assembly / Energy Migration |
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