Details of a Researcher - Koike, Yasuhiro

Papers - Koike, Yasuhiro

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Preparation of A Zero-Birefringence Polymer Doped with A Birefringent Crystal and Analysis of Its Characteristics

OHKITA HISANORI, TAGAYA AKIHIRO, KOIKE YASUHIRO

Macromolecules Vol. 37 ( No. 22 ) pp. 8342-8348 2004.11

Research paper (scientific journal), Joint Work

We proposed the “birefringent crystal dopant method” in order to compensate the birefringence of polymers. In this method, the birefringence was compensated by homogeneous doping with a needlelike crystal which has the opposite birefringence to that of the polymers. Strontium carbonate (SrCO3) was selected for this purpose because it has a large birefringence and a needlelike shape. SrCO3 was synthesized, with a length of about 200 nm and a width of about 20 nm, and doped into a poly-(MMA/BzMA)78/22(w/w)) film. The film was drawn at 130 °C and 4 mm/min. The orientational birefringence of the drawn polymer film at a wavelength of 633 nm was compensated by doping with 0.3 wt % SrCO3 without losing its transparency and thermostability. The analysis of infrared dichroism of the films showed that the birefringence of the films was compensated at a low concentration of SrCO3 because of its orientation-inhibition effect and its high orientation degree as compared with that of the polymer main chains.

Synthesis and Properties of Partially Fluorinated Amorphous Ring Containing Polymers: Poly[bis(2,2-difluorovinyl) formal], Poly[bis(2,2-difluorovinyl) difluoroformal], and Poly[bis(1-deutorio-2,2- difluorovinyl)difluoroformal]

YANG YU, MIKES FRANTISEK, KOIKE YASUHIRO, OKAMOTO YOSHIYUKI

Macromolecules Vol. 37 ( No. 21 ) 7918-7923 2004.10

Research paper (scientific journal), Single Work, Accepted

Three novel partially fluorinated monomers, bis(2,2-difluorovinyl)formal (I), bis(2,2-difluorovinyl)difluoroformal (II), and bis(1-deutrio-2,2-difluorovinyl)difluoroformal (III) , were prepared. These monomers were polymerized in bulk via free radical mechanism. Monomer I produced a cross-linked polymer, but monomers II and III yielded amorphous polymers (II-P and III-P) having five – and six- membered rings along the backbone. Polymers II-P and III-P were soluble not only in fluorinated solvents but also in nonfluorinated solvents such as THF, 1, 4-dioxane, DMF, and DMSO. They have good thermal stability, high glass transmission temperature, and low dielectric constant. Furthermore, these polymers are completely amorphous and possess outstanding optical clarity extending from visible to near-IR region. The refractive indices of both polymers were measured at various wavelengths to evaluate material dispersion. The material dispersion of II-P and III-P were similar and had low values, which are comparable to perfluorinated polymers and much lower than perdeuterioPMMA. The unique optical properties of these polymers make them attractive for use optical materials.

私にとってのファンダメンタルズ

KOIKE YASUHIRO

若手社員のための高分子基礎講座 (社団法人高分子学会関東支部) 2004.10

Single Work

Free-Radical Polymerization of Dioxolane and Dioxane Derivatives: Effect of Fluorine Substituents on the Ring Opening Polymerization

LIU WEIHONG, MIKES FRANTISEK, GUO YINZHONG, KOIKE YASUHIRO, YOSHIYUKI OKAMOTO

Journal of Polymer Science: Part A: Polymer Chemistry Vol. 42 ( Issue 20 ) 5180-5188 2004.09

Research paper (scientific journal), Single Work, Accepted

Partially fluorinated and perfluorinated dioxolane and dioxane derivatives have been prepared to investigate the effect of fluorine substituents on their free-radical polymerization products. The partially fluorinated monomer 2-difluoromethylene-1,3-dioxolane (I) was readily polymerized with free-radical initiators azobisisobutyronitrile or tri (n-butyl) borane-air and yielded a vinyl addition product. However, the hydrocarbon analogue, 2-methylene-1,3-dioxolane (II), produced as much as 50% ring opening product at 60 °C by free-radical polymerization. 2-Difluoromethylene-4-methyl-1,3-dioxolane (III) was synthesized and its free-radical polymerization yielded ring opening products: 28% at 60 °C, decreasing to 7 and 4% at 0 °C and -78 °C, respectively. All the fluorine-substituted, perfluoro-2-methylene-4-methyl-1,3-dioxolane (IV) produced only a vinyl addition product with perfluorobenzoylperoxide as an initiator. The six-membered ring monomer, 2-methylene-1,3-dioxane (V), caused more than 50% ring opening during free-radical polymerization. However, the partially fluorinated analogue, 2-difluoromethylene-1,3-dioxane (VI), produced only 22% ring opening product with free-radical polymerization and the perfluorinated compound, perfluoro-2-methylene-1,3-dioxane (VII), yielded only the vinyl addition polymer. The ring opening reaction and the vinyl addition steps during the free-radical polymerization of these monomers are competitive reactions. We discuss the reaction mechanism of the ring opening and vinyl addition polymerizations of these partially fluorinated and perfluorinated dioxolane and dioxane derivatives.

High-Bandwidth Plastic Optical Fiber with W-Refractive Index Profile

ISHIGURE TAKAAKI, ENDO HIDEKI, OHDOKO KUNIHIRO, KOIKE YASUHIRO

IEEE Photonics Technology Letters Vol. 16 ( No. 9 ) pp. 2081-2083, 2004.09

Research paper (scientific journal), Joint Work, Accepted

A plastic optical fiber having a W-shaped refractive index profile [W-shaped plastic optical fiber (POF)] was prepared for the first time to realize a higher bit rate transmission than those of the conventional silica-based multimode fiber and graded-index (GI) POF links. Since the W-shaped POF has a valley of the refractive index at the boundary of the core and cladding of the conventional GI POF, the group delay of higher order modes is strongly influenced, thus compensating the modal dispersion that exists in the GI POF. The modal dispersion compensation effect by the W-shaped index profile was theoretically and experimentally confirmed.

Plastic Optical Fiber

KOIKE YASUHIRO, KONDOU ATSUSHI

Chemical Engineering of Japan (The Society of Chmical Engineers, Japan) Vol. 68 ( No. 8 ) 442-444 2004.08

Research paper (scientific journal), Joint Work

Stereochemistry of The Radical Polymerization of Vinyl Pentafluorobenzoate

WRIHONG LIU, KOIKE YASUHIRO, OKAMOTO YOSHIYUKI

Polymer Vol. 45 ( Issue 16 ) pp. 5491-5495 2004.07

Research paper (scientific journal), Joint Work, Accepted

The free-radical polymerization of vinyl pentafluorobenzoate (VPBz) was carried out under various conditions in order to compare its stereochemistry to that of the vinyl benzoate (VBz) polymerization using similar conditions. Contrary to the stereochemistry of the radical polymerization of VBz, VPBz favors syndiotactic propagation. The poly(VPBz) obtained in hexafluoroisopropanol (HFIP) with nBu3B–air at −30 °C has a triad syndiotacticity (rr) of 52% which achieved the highest syndiotacticity reported for the radical polymerization of vinyl esters. The stereochemistry difference for the VPBz polymerization was ascribed to the electron-withdrawing effect of the fluorine on the aromatic ring. The solvent effect of enhancing the rr specificity in HFIP may be related to the hydrogen-bonding between HFIP and VPBz or the growing species. It was also found that the glass transition temperatures (Tg) of the VPBz polymers apparently increased with an increase in their diad syndiotacticities (r): the Tg of poly(VPBz) with r=72% was 79 °C, which was 25 °C higher than that of poly(VPBz) with r=56% obtained in toluene.

Zero-birefringence photonics polymer films

TAGAYA AKIHIRO, KOIKE YASUHIRO

Chemistry and Chemical Industry (The Chemical Society of Japan) 57 ( 7 ) 749-751 2004.07

Research paper (scientific journal), Joint Work

Birefringence Reduction Method for Optical Polymers by The Orientation-Inhibition Effect of Silica Particles

OHKITA HISANORI, ABE YASUYUKI, KOJIMA HIROSHI, TAGAYA AKIHIRO, KOIKE YASUHIRO

Applied Physics Letters Vol. 84 ( No. 18 ) 3534-3536 2004.05

Research paper (scientific journal), Joint Work

A method for reducing the orientational birefringence of polymers by doping with optically isotropic silica particles is reported. Particles with a diameter of 16 nm were selected and their surface was treated with dimethyldichlorosilane. Doping with 1 wt% of the particles reduced about 15% of the orientational birefringence of polycarbonate and poly(methylmethacrylate) films regardless of the sign and the magnitude of their birefringence. The analysis of the infrared dichroic ratio confirmed an effect in which the particles reduced the orientation of polycarbonate main chains. The effect that caused the reduction of birefringence was named "the orientation-inhibition effect."

ITを支えるフォトニクスポリマーとその展開

KOIKE YASUHIRO

先端通信技術　新技術説明会 (Japan Science and Technology Agency (JST)) 2004.02

Single Work

Face-to-Faceコミュニケーションの実現へブロードバンド社会を拓くフォトニクスポリマー

KOIKE YASUHIRO

化学経済 ( 2月 ) 2004.02

Research paper (scientific journal), Single Work

A Novel Thermally and Chemically Stable Polymer: Poly (2-difluoromethylene-1,3-dioxolane)

W. LIU, Y. GUO, KOIKE YASUHIRO, OKAMOTO YOSHIYUKI

Macromolecules (American Chemical Society) Vol. 37 ( 2 ) 254-255 2004.02

Research paper (scientific journal), Joint Work, Accepted

Fluorinated polymers have become of increasing interest in the development of advanced materials having superior thermal and chemical stability, excellent electrical insulating ability, and unique optical properties. Perfluoropolymers such as Teflon AF and Cytop have been commercialized by DuPont and Asahi Glass, respectively.2,3 These polymers have high chemical and thermal stability and are soluble in selected fluorinated solvents. However, the polymers are quite expensive due to the high manufacturing costs for their monomers.3 Here, we report that a partially fluorinated polymer, poly(2-difluoromethylene-1,3-dioxolane) (P1), is thermally and chemically stable and is soluble in fluorinated alcohols.

大量な情報を伝達するソフトマテリアル

KOIKE YASUHIRO

学術月報 Vol.57 ( No, 2 ) 125-129 2004.02

Research paper (other academic), Single Work

ゼロ複屈折光学ポリマー－複屈折性結晶による光学ポリマーの複屈折相殺－

TAGAYA AKIHIRO, OOKITA HISANORI, KOIKE YASUHIRO

O Pluse E (新技術コミュニケーションズ) Vo. 26 ( No. 2 ) 113-114 2004.02

Research paper (scientific journal), Joint Work

Synthesis of A Zero-Birefringence Optical Polymer by The Birefringent Crystal Dopant Method and Analysis of Its Characteristics

OHKITA HISANORI, TAGAYA AKIHIRO, KOIKE YASUHIRO

Transactions of The Materials Research Society of Japan (Transactions of The Materials Research Society of Japan) Vol. 29 ( No. 1 ) 259-262 2004.02

Research paper (conference, symposium, etc.), Joint Work

Birefringence induced by the orientation of polymer mainchains during an injection- molding or extrusion processing restricts the application of optical polymer to optical devices that require maintaining the polarization state of incident light. We propose the "birefringent crystal dopant method" to compensate the birefringence of polymers by homgeneous doping with an opposite birefringent needle-like crystal. SrCO3 was selected for this method and synthesised, with a length of about 200nm and a width of about 20nm. SrCO3 was doped into PMMA/BzMA film. The film was uniaxcially drawn at 130℃ and 4mm/min. For the first time, the positive birefringence of the drawn coplymer film at a wavelength of 633nm was compensated by doing with 0.3we.% of SrCO3 without losing transparency and thermostability. The orientational birefringence of the zero-birefringence film was lower than that of blank copolymer film at any angle of incidence of light.

複屈折ゼロの光学ポリマーを開発液晶テレビの大幅コストダウンに道拓く

KOIKE YASUHIRO

JST基礎研究最前線 ( No. 4 ) 2-3 2004.01

Research paper (other academic), Single Work

Graded-Index Plastic Optical Fiber with High Mechanical Properties Enabling Easy Network Installations. I

ISHIGURE TAKAAKI, HIRAI MIKI, SATO MASATAKA, KOIKE YASUHIRO

Journal of Applied Polymer Science Vol. 91 ( No.1 ) 404-409 2004.01

Research paper (scientific journal), Joint Work, Accepted

A doped poly(methyl methacrylate) (PMMA)-based graded-index plastic optical fiber (GI POF) with high mechanical strength is reported for the first time. Although the POF is generally believed to have a good mechanical flexibility even if it has a large-core diameter, such a high mechanical strength has been provided by making the polymer chains in the POF highly oriented in its axial direction. If such an orientation of polymer chains is eliminated, the POF becomes brittle, which is similar to silica-based fibers. On the other hand, too high an orientation of the polymer chains induces fiber deformation in a high-temperature atmosphere resulting from orientation relaxation. This study reports how high mechanical strengths such as the tensile strength and the large elongation are provided to the GI POF. By selecting the optimum heat-drawing conditions, the GI POF has a mechanical strength comparable to that of the commercially available step index (SI) POF.

Graded-Index Plastic Optical Fiber with High Mechanical Properties Enabling Easy Network Installations. II

ISHIGURE TAKAAKI, HIRAI MIKI, SATO MASATAKA, KOIKE YASUHIRO

Journal of Applied Polymer Science Vol. 91 ( No.1 ) 410-416 2004.01

Research paper (scientific journal), Joint Work, Accepted

It was shown how high mechanical strength should be provided in the high numerical aperture (NA) graded-index plastic optical fiber (GI POF). In this newly developed GI POF, a copolymer of methyl methacrylate (MMA) and 2,2,2-trifluoroethyl methacrylate (3FMA) was used to increase the NA. The GI POF we proposed previously was composed of a PMMA homopolymer cladding and a doped PMMA core. It was previously shown that substituting the copolymer P(MMA-3FMA) for the PMMA as the cladding material made little change in the fiber's light-transmission characteristics. This study focused on mechanical flexibility, which is one of the most important advantages of the POF. It was found that the P(MMA-3FMA)-clad GI POF had almost the same or superior mechanical strength in addition to the excellent light-propagation characteristics. It was also found that such excellent mechanical properties were achieved using a small dopant concentration and optimum heat-drawing conditions.

Train Communication System Using Graded-Index Leaky Plastic Optical Fiber

A. Shimura, Y. Sugawara, S. Haruyama, M. Nakagawa, H. Suzuki, A. Kondo, T. Ishigure, and Y. Koike

2004 IEEE International Conference on Industrial Conference on Industrial Technology (ICIT), Vols. 1-3 78 2004

Research paper (international conference proceedings), Joint Work, Accepted

High-Definition Projection Screen Based on Multiple Light Scattering Technique

T. Okumura, H. Suzuki, A. Tagaya, Y. Koike, and E. Higuchi

Liquid Crystal Materials, Devices, and applications X and Projection Displays X 5289 294 2004

Research paper (international conference proceedings), Joint Work, Accepted

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