Curriculum Vitaes

Takeoka Yuko

  (竹岡 裕子)

Profile Information

Affiliation
Professor, Faculty of Science and Technology, Department of Materials and Life Sciences, Sophia University
Degree
博士(工学)(東京大学)

J-GLOBAL ID
200901054354018811
researchmap Member ID
5000041377

Papers

 158
  • 奥田寛大, 藤田正博, 竹岡裕子, 陸川政弘
    燃料電池, 15(4) 77-81, Apr 30, 2016  Peer-reviewed
  • Seitaro Yamaguchi, Masahiro Yoshizawa-Fujita, Haijin Zhu, Maria Forsyth, Yuko Takeoka, Masahiro Rikukawa
    ELECTROCHIMICA ACTA, 186(20) 471-477, Dec, 2015  Peer-reviewed
    Zwitterions with a cyano group on the side chain (CZ) were synthesized. Although the addition of CZ caused a slightly negative effect on viscosity, ionic conductivity, limiting current density, and lithium transference number, the oxidation limit of PEGDME/lithium bis(trifluoromethylsulfonyl) amide (LiTFSA) composites was improved to over 5 V. For charge/discharge testing using Li vertical bar electrolyte vertical bar LiCoO2 cells, the cycle stability of PEGDME/LiTFSA with CZ in the voltage range of 3.0-4.6 V was much higher than that of PEGDME/LiTFSA. Incorporating a small mole fraction of CZ into PEGDME-based electrolytes prevented an increase in the interface resistance between the electrolyte and cathode with increasing numbers of the cycle. (C) 2015 Elsevier Ltd. All rights reserved.
  • Mitsutake Suematsu, Masahiro Yoshizawa-Fujita, Haijin Zhu, Maria Forsyth, Yuko Takeoka, Masahiro Rikukawa
    ELECTROCHIMICA ACTA, 175 209-213, Sep, 2015  Peer-reviewed
    Solid polymer electrolytes show great potential in electrochemical devices. Poly(ethylene oxide) (PEO) has been studied as a matrix for solid polymer electrolytes because it has relatively high ionic conductivity. In order to investigate the effect of zwitterions on the electrochemical properties of poly (ethylene glycol) dimethyl ether (G5)/lithium bis(fluorosulfonyl) amide (LiFSA) electrolytes, a liquid zwitterion (ImZ2) was added to the G5-based electrolytes. In this study, G5, which is a small oligomer, was used as a model compound for PEO matrices. The thermal properties, ionic conductivity, and electrochemical stability of the electrolytes with ImZ2 were evaluated. The thermal stabilities of all the G5-based electrolytes with ImZ2 were above 150 degrees C, and the ionic conductivity values were in the range of 0.8-3.0 mS cm(-1) at room temperature. When the electrolytes contained less than 5.5 wt% ImZ2, the ionic conductivity values were almost the same as that of the electrolyte without ImZ2. The electrochemical properties were improved with the incorporation of ImZ2. The anodic limit of the electrolyte with 5.5 wt% ImZ2 was 5.3 V vs. Li/Li+, which was over 1 V higher than that of G5/LiFSA. (C) 2014 Elsevier Ltd. All rights reserved.
  • Hideyuki Kunugita, Tsubasa Hashimoto, Yuki Kiyota, Yosuke Udagawa, Yuko Takeoka, Yuiga Nakamura, Junro Sano, Tomonori Matsushita, Takashi Kondo, Tsutomu Miyasaka, Kazuhiro Ema
    CHEMISTRY LETTERS, 44(6) 852-854, Jun, 2015  Peer-reviewed
    We have measured the temperature dependence of the reflection and photoluminescence spectra of a lead bromide hybrid material (CH3NH3PbBr3) using high-quality macroscopic single crystals. Single crystals provide clear and sample-independent reflection spectra that permit discussion of the properties of the photoexcited carriers. We have found that excitons still exist in CH3NH3PbBr3, even at room temperature. We have also determined the temperature dependence of the exciton resonance energy and the line width.
  • Yuko Takeoka, Miki Hayashi, Nami Sugiyama, Masahiro Yoshizawa-Fujita, Mamoru Aizawa, Masahiro Rikukawa
    POLYMER JOURNAL, 47(2) 164-170, Feb, 2015  Peer-reviewed
    Poly(L-lactic acid-co-glycolic acid)/hydroxyapatite (PLGA/HAp) composites were fabricated by the in situ polymerization of L-lactide and glycolide in porous HAp disks, using lipase MM, derived from Mucor miehei, as a catalyst. Various PLGA/HAp composites were obtained by changing the feed ratio of L-lactide and glycolide. The fourier transform infrared spectroscopy, scanning electron microscopy and porosity measurements showed that the porous HAp was completely filled with PLGA after polymerization at 100 degrees C for 9 days. Lactyl unit fractions (FL) of obtained PLGA calculated from the 1H nuclear magnetic resonance were consistent with the feed fraction of L-lactide (fL). The PGA/HAp, PLGA20/HAp, PLGA50/HAp, PLGA80/HAp and PLLA/HAp composites showed maximum bending strengths of 91.1 MPa, 78.8 MPa, 73.4 MPa, 54.3 MPa and 67.0 MPa, respectively. These values were 4.7-2.8 times greater than that of the untreated porous HAp disks and were suitable for artificial bone materials. The cell adhesion and proliferation properties of these materials with osteoblast-like MC3T3-E1 cells suggest that these PLGA/HAp composites have suitably bioactive surfaces. The PLGA/HAp composites showed higher alkaline phosphatase activity after cultivation of rat bone marrow stromal cells.
  • Kiyota Y., Udagawa Y., Nakamura Y., Sano J., Matsushita T., Kunugita H., Takeoka Y., Kondo T., Ema K.
    Meeting Abstracts of the Physical Society of Japan, 70 1284-1284, 2015  
  • Mitsutake Suematsu, Masahiro Yoshizawa-Fujita, Tetsuya Tamura, Yuko Takeoka, Masahiro Rikukawa
    INTERNATIONAL JOURNAL OF ELECTROCHEMICAL SCIENCE, 10(1) 248-258, Jan, 2015  Peer-reviewed
    In order to investigate the effects of lithium salt species and concentration on the electrochemical properties of a liquid zwitterion (LZw), composites of a LZw with lithium bis(fluorosulfonyl) amide (LiFSA) or lithium bis(trifluoromethylsulfonyl) amide (LiN(Tf)(2)) were prepared at various lithium salt concentrations. The majority of LZw/LiFSA and LZw/LiN(Tf)(2) composites with lithium salt mole fractions in the range of 0.2 to 0.8 were obtained as colorless liquids and exhibited glass transitions only during DSC measurements. The dissociation state of the lithium salts in the composites was discussed by means of FT-IR measurements. The interactions between the imidazolium cation and the amide anions were demonstrated. The LZw/LiFSA composite with a LiFSA mole fraction of 0.8 (corresponding to a concentration of 13.7 mol kg(-1)) exhibited the highest ionic conductivity (1.2 x 10(-5) S cm(-1)) as well as the greatest lithium transference number (0.46) at 40 degrees C.
  • Masahiro Yoshizawa-Fujita, Kensuke Shimada, Yuko Takeoka, Masahiro Rikukawa
    KOBUNSHI RONBUNSHU, 72(10) 624-629, 2015  Peer-reviewed
    We synthesized new polymer electrolytes containing zwitterions [P(MEO-co-Zw)] by reacting an imidazole derivative with the p-chloromethylstyrene groups in a random methacryloyl oligo(ethylene oxide) (MEO/p-chloromethylstyrene (CMS) copolymer [P(MEO-co-CMS)]. The weight-average molecular weight of P(MEO-co-CMS) was about 200,000 g mol(-1), and P(MEO-co-Zw) formed flexible films. P(MEO-co-Zw)/LiTFSA composites exhibited two glass transition temperatures at around -70 degrees C and -10 degrees C. Contrary to usual polyether electrolytes, the ionic conductivity and lithium ion transference number of P(MEO-co-Zw)/LiTFSA composites remained constant even at high lithium salt concentration, because the high dipole moment of the zwitterions leads to a strong solvation of lithium salt through the electrostatic interaction.
  • Y. Takeoka, K. Umezawa, T. Oshima, M. Yoshida, M. Yoshizawa-Fujita, M. Rikukawa
    POLYMER CHEMISTRY, 5(13) 4132-4140, 2014  Peer-reviewed
    Diblock copolymer ionomers SP1-P2(m-n) with ion exchange capacity (IEC) of 0.96-2.42 meq g(-1) were prepared. The parent diblock copolymers P1-P2(m-n) having various block lengths (m, n) were synthesized via successive catalyst-transfer polymerization of 1,4-dibromo-2,5-di[4-(2,2-dimethylpropoxysulfonyl)phenyl]butoxybenzene (1) and 1,4-dibromo-2,5-hexyloxybenzene (2). The molecular weights were successfully controlled by the feed ratio of the monomer and catalyst, and the molecular weight distribution values were less than 1.32, irrespective of the polymerization degree or polymerization order. Preliminary morphological studies showed that the diblock copolymer ionomers SP1-P2(m-n) had a clear phase separation that could be controlled by the ratios and lengths of the hydrophilic and hydrophobic units. The ionomers showed high proton conductivities with a small humidity dependence, indicating that the clear phase separation formed by the precisely controlled molecular weight and polydispersity index (PDI) of the diblock copolymers enhanced the ionic connectivity and proton conductivity.
  • Masahiro Yoshizawa-Fujita, Tomoko Kinoshita, Yuta Ono, Yuko Takeoka, Masahiro Rikukawa
    CHEMISTRY LETTERS, 42(10) 1185-1187, Oct, 2013  Peer-reviewed
    A new ionic liquid was prepared by introducing a boronic acid group to an imidazolium cation with a hydrophobic anion. The boronic acid-containing ionic liquid showed the best ionic conductivity of 6.5 x 10(-4) S cm(-1) at 50 degrees C, with a high lithium ion transference number of over 0.5, owing to the anion-trapping effect of the boronic acid group.
  • Yuko Takeoka, Fumihiko Saito, Masahiro Rikukawa
    LANGMUIR, 29(27) 8718-8727, Jul, 2013  Peer-reviewed
    Regioregular polythiophenes containing an optically active substituent in the third position of the thiophene ring, head-to-tail poly(3-[2-((S)-1-methyloctyloxy)ethyl]thiophene)s (HT-P(S)MOETs), were synthesized using highly reactive zinc. For comparison, HT-P(R)MOET and achiral HT-P(+/-)MOET also were synthesized from R-type monomers and racemic monomers, respectively. The HT-PMOET possessed greater than 95% head-to-tail coupling with a weight-average molecular weight (M-w) between 1.96 x 10(4) and 2.94 x 10(4). The polymers were characterized using H-1 and C-13 NMR, optical rotatory power measurements, circular dichroism (CD), and UV-vis spectroscopy. X-ray diffraction patterns of the cast films demonstrated that regioregular HT-PMOET possessed a strong tendency to self-assemble into highly ordered, crystalline structures. The HT-P(S)MOET and HT-P(R)MOET showed strong Cotton effects, while HT-P(+/-)MOET showed very weak Cotton effects. The presence of a circular dichroism effect indicated that the side chain chirality induced optical activity in poly(thiophene) main chains. The monolayer formation of HT-PMOET spread on the water surface was characterized using a pressure-area (pi-A) isotherm. The molecular areas of HT-P(S)MOET and HT-P(R)MOET molecules on the water surface were 33.5 and 32.9 angstrom(2), respectively, at 10 degrees C, which were larger than that of HT-P(+/-)MOET (27.9 angstrom(2)), suggesting that optically active HT-PMOET expanded because of the chiral repulsion between side chains. Multilayer films of HT-PMOET were prepared by repeating horizontal deposition of the monolayer on the water surface. The multilayer films of optically active HT-PMOET obtained showed stronger Cotton effects than did the cast films. In addition, electrical conductivities of HT-PMOET multilayer films were superior to those of spin-coated films. Head-to-tail poly(3-[2-((S)-1-methylpropyloxy)ethyl]thiophene) (HT-P(S)MPET), which contained shorter side chain lengths compared to HT-P(S)MOET, also was synthesized. The CD intensities of HT-P(S)MPET multilayer films were smaller than those of HT-P(S)MOET multilayer films, suggesting that the optically active side-chain length is critically important to the optically active self-assembly.
  • 杉山奈未, 大野達也, 國分玲子, 相澤守, 竹岡裕子, 陸川政弘
    高分子論文集, 70(5) 185-192, Apr, 2013  Peer-reviewed
  • N. Sugiyama, Y. Yanagi, Masahiro Yoshizawa-Fujita, M. Aizawa, Y. Takeoka, M. Rikukawa
    Chemistry Letters, 42(5) 465-467, Mar 19, 2013  Peer-reviewed
    Biphasic calcium phosphate (BCP) ceramics with well-controlled pores were fabricated by sintering mixtures of synthetic hydroxyapatite (HAp) and deoxyribonucleic acid (DNA). BCP ceramics with macro- and micropores revealed excellent cell proliferation as a result of suitable surface topography and phase composition.
  • Nami Sugiyama, Tatsuo Ohno, Kunibu Ryoko, Mamoru Aizawa, Yuko Takeoka, Masahiro Rikukawa
    KOBUNSHI RONBUNSHU, 70(5) 185-192, 2013  Peer-reviewed
    Poly(L-lactic acid)/hydroxyapatite (PLLA/HAp) composites were fabricated by in situ polymerization of L-lactide in porous HAp disks, using lipase as a catalyst. The effect of using various lipase species on the molecular weight of the resulting PLLA was investigated, as was the effect of varying the lipase concentration. Lipase CA, derived from Candida antarctica, was found to promote the polymerization of L-lactide in bulk form as well as within porous HAp disks. The in situ polymerization of L-lactide within lipase CA-coated HAp disks at 130 degrees C for 7 days resulted in PLLA/HAp composites with a PLLA content in the range of 16 to 19 wt.%. The weight average molecular weights of the PLLAs formed in these composites were in the range of 1.6 x 10(4) to 3.0 x 10(4) g mo1-1 and varied with the lipase CA concentration. The PLLA/HAp composites exhibited a maximum bending strength of 72 MPa and a fracture toughness value of 0.93 MPa m(1/2), as estimated by three point bending tests. The cell adhesion and proliferation properties of these materials with osteoblast-like MC3T3-E1 cells suggest that these PLLA/HAp composites have suitably bioactive surfaces.
  • Hidetsugu Takagi, Mikio Sato, Yuko Takeoka, Hideyuki Kunugita, Kazuhiro Ema
    PHYSICS OF SEMICONDUCTORS, 1566 435-+, 2013  Peer-reviewed
    We have investigated experimentally excitonic properties in organic-inorganic hybrid multi quantum well crystals, (C4H9NH3)(2)PbBr4 and (C6H5-C2H4NH3)(2)PbBr4, by measuring photoluminescence, reflectance, photoluminescence excitation spectra. In these materials, the excitonic binding energies are enhanced not only by quantum confinement effect (QCE) but also by image charge effect (ICE), since the dielectric constant of the barrier layers is much smaller than that of the well layers. By comparing the 1s-exciton and 2s-exciton energies, we have investigated the influence of ICE with regard to the difference of the Bohr radius.
  • Azusa Osawa, Kotaro Ide, Miru Yoshida, Masahiro Yoshizawa-Fujita, Yuko Takeoka, Masahiro Rikukawa
    KOBUNSHI RONBUNSHU, 70(1) 16-22, 2013  Peer-reviewed
    We synthesized sulfonated poly[(4-phenoxybenzoyl)-1,4-phenylene-co-anthraquinone] copolymers (S-P(PBP-co-ANQ)s) in order to investigate the effect of polycyclic units on the water uptake, dimensional stability, and proton conductivity. The effect of the binding positions of anthraquinone (ANQ) was also investigated by preparing S-P(PBP-co-1,4ANQ) and S-P(PBP-co-1,5ANQ), each with 5 mol% ANQ. Number-average molecular weights and thermal decomposition temperatures of S-P(PBP-co-ANQ)s were about 50-70 kgmol(-1) and 220 degrees C, which were sufficient for polymer electrolyte fuel cell (PEFC) applications. S-P(PBP-co-1,5ANQ) membranes showed higher dimensional stability and proton conductivity than S-P(PBP-co-1,4ANQ) and S-PPBP membranes. The maximum current densities and power densities of S-P(PBP-co-1,5ANQ) fuel cells were 2200mA cm(-1) and 800 mW cm(-2) at 80 degrees C and 100% relative humidity. These results suggest that the improvement of dimensional stability and electrochemical properties is due to strong aggregation of the copolymer chains induced by ANQ at an appropriate coupling position.
  • 大澤あずさ, 井出光太郎, 吉田実留, 藤田正博, 竹岡 裕子, 陸川政弘
    高分子論文集, 70(1) 16-22, Jan 1, 2013  
  • Azusa Osawa, Takuyuki Ishizuka, Masahiro Yoshizawa-Fujita, Yuko Takeoka, Masahiro Rikukawa
    KAGAKU KOGAKU RONBUNSHU, 39(3) 224-230, 2013  
    Poly(p-phenylene) derivatives with pendant-type side chains of various lengths were synthesized in order to investigate the effect of side chain structure on properties such as sulfonation, thermal stability, mechanical strength, water uptake, dimensional stability, proton conductivity, and polymer electrolyte fuel cell (PEFC) properties. The sulfonation reactions were affected by the electron density of side chains. All sulfonated polymers showed thermal stabilities up to 240 degrees C, which is sufficient for polymer electrolyte membranes used in PEFC. Although the glass transition temperatures were about 200 degrees C regardless of the side chain structure, the mechanical strength was influenced by the side chain length. The number of adsorbed water molecules per sulfonic acid group (X) decreased with increasing side chain length, resulting in a lower swelling ratio. The proton conductivity increased with an increase in ion exchange capacity and lambda, and S-P1(2.79), Which has the shortest side chain, showed the highest proton conductivity. All the sulfonated polymer membranes exhibited sufficient cell performance, but S-P2(2.27) showed the highest performance, revealing a different order of performance among the membranes from that of proton conductivity. It is suggested that the higher water uptake of S-P1 provides not only higher proton conductivity but also lower carrier density, resulting in increased membrane resistance in fuel cell tests.
  • Masahiro Yoshizawa-Fujita, Yu Kakegawara, Yuko Takeoka, Masahiro Rikukawa
    KOBUNSHI RONBUNSHU, 70(10) 612-615, 2013  Peer-reviewed
    Poly(L-lactic acid) was synthesized in ionic liquids by lipase-catalyzed ring-opening polymerizations. A lower molecular weight poly(L-lactic acid) (PLLA) and a higher molecular weight PLLA were obtained in the same batch. When up to 5 wt. % water was added, the ratio of the higher molecular weight PLLA increased with increasing water content. Also, the specific rotation of PLLAs increased, indicating that PLLAs with a high optical purity were obtained by the lipase-catalyzed polymerization of L-lactide in hydrated ILs.
  • Yuko Takeoka, Mitsuyasu Kawahara, Masahiro Rikukawa
    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 73(11) 1401-1403, Nov, 2012  
    Novel organic-inorganic hybrid compounds, C16H44N4Pb3I10 and C14H34N2Pb2I6, were synthesized by solvent diffusion recrystallization from the dimethylsulfoxide solution containing PbI2 and gemini ammonium surfactants with different head groups. The results of single crystal X-ray structural analysis showed that the inorganic region of C16H44N4Pb3I10 has quasi one-dimensional chains of [Pb3I10](4-) units, whereas that of C12H30N2Pb2I6 has one-dimensional chains of face-sharing PbI6 octahedra. The absorption and fluorescence spectra of these compounds also indicate the formation of one-dimensional inorganic chains and quantum-confined structures. (C) 2012 Elsevier Ltd. All rights reserved.
  • Takashi Hirahara, Masahiro Yoshizawa-Fujita, Yuko Takeoka, Masahiro Rikukawa
    CHEMISTRY LETTERS, 41(9) 905-907, Sep, 2012  
    A chiral polyfluorene-thiophene derivative incorporating two different chiral side chains was synthesized via the Suzuki coupling reaction. Upon photoexcitation, thin films of the polymer exhibited efficient circularly polarized luminescence in the visible range, even without thermal annealing. The dissymmetry factor, g(lum), of films with thicknesses less than 100 nm reached 0.2 at 505 nm.
  • Kensuke Umezawa, Tatsuya Oshima, Masahiro Yoshizawa-Fujita, Yuko Takeoka, Masahiro Rikukawa
    ACS MACRO LETTERS, 1(8) 969-972, Aug, 2012  
    Hydrophilichydrophobic block copolymer ionomers based on polyphenylenes with controlled the block lengths were synthesized for the first time by a catalyst-transfer polycondensation of a dibromo phenylene derivative having a neopentyl ester protected sulfonic acid group, followed by the polycondensation of hydrophobic dibromo hexyloxybenzene. The diblock copolymer ionomers were obtained by the removal of neopentyl groups, resulting in clear phase separation dependent on the block lengths. The well-developed microphase separation provided controlled water uptake and sufficiently high proton conductivity, especially at low relative humidity conditions. The fine block copolymerization by using catalyst transfer polycondensation is a promising strategy for the development of hydrocarbon ionomers having well-defined ordered structures with reasonable proton conductivity for fuel cell applications.
  • RIKUKAWA MASAHIRO, Katagiri Maki, Yoshizawa-Fujita Masahiro, Takeoka Yuko
    Advanced Materials Research, 409 502-507, Jan 4, 2012  
  • RIKUKAWA MASAHIRO, Hamaguchi Ayumi, Yoshizawa-Fujita Masahiro, Takeoka Yuko
    Advanced Materials Research, 409 492-496, Jan 4, 2012  
  • RIKUKAWA MASAHIRO, Hirahara Takashi, Fujita Masahiro-Yoshizawa, Takeoka Yuko
    Materials Science Forum, 706-709(3) 1636-1641, Jan 4, 2012  
  • Ayumi Hamaguchi, Masahiro Yoshizawa-Fujita, Yuko Takeoka, Masahiro Rikukawa
    Advanced Materials Research, 409 492-496, 2012  
    Layered perovskite (RNH 3)2PbI 4 (R = organic cation), which contained the fullerene derivatives, [ethyl-3-tert- butoxycarbonylaminopropyl (1,2-methanofullerene C 60)]-61,61-di carboxylate iodide (EAF-I) and di[3-tert-butoxycarbonylaminopropyl (1,2-methanofullerene C 60)]- 61,61-dicarboxylate diiodide (DAF-I 2) in the organic layers were fabricated and compared with previously reported perovkite compound containing N-methyl-2-(4-aminophenyl)- fulleropyrrolidine iodide (AmPF-I). Because the solvent solubilities of EAF-I and DAF-I 2 to N,N-dimethylformamide (DMF) were higher than AmPF-I, the film processability of EAF-I and DAF-I 2 was improved compared with AmPF-I. The X-ray diffraction patterns proved the construction of the perovskite structure in (EAF) 2PbI 4 and (AmPF) 2PbI 4 cast films. EAF was well-organized and closer-packing than AmPF in the perovskite structure. For the diamine-type fullerene, DAF-I 2, it is difficult to form layered structure by spin-coated or cast methods. New sharp X-ray diffraction peaks were observed for DAF-I 2 films dipped in PbI 2 solution. The intercalations and formation of perovskite structure of (DAF)PbI 4 were studied. © (2012) Trans Tech Publications, Switzerland.
  • Maki Katagiri, Masahiro Yoshizawa-Fujita, Yuko Takeoka, Masahiro Rikukawa
    Advanced Materials Research, 409 502-507, Jan, 2012  
  • Mikio Sato, Masahiro Yoshizawa-Fujita, Yuko Takeoka, Masahiro Rikukawa
    Advanced Materials Research, 409 538-543, 2012  
    Oligothiophene derivatives, 4,4′-bis-(2-aminoethylthienyl)-3,4- ethylenedioxythiophene dihydrohalide (AET-EDOT·HX: X = I, Br), were synthesized by Grignard coupling reactions. The hybrid films of oligothiophene and lead halide were fabricated by casting and spin-coating methods. The effect of halogen species on the optical properties of the perovskites was investigated. The X-ray diffraction profiles of (AET-EDOT)PbX 4 cast films indicated that the layered structures were formed by the self-organization. After hybridization of AET-EDOT·HX with PbX 2, new absorption peaks due to the confined excitons were observed at 400 nm for (AET-EDOT)PbBr 4 film, and at 395 nm for (AET-EDOT)PbI 4 film. These results indicated that the diamino-type oligothiophenes were successfully incorporated into the organic-inorganic layered perovskites. AFM images of (AET-EDOT)PbX 4 cast films showed polycrystalline grains, indicating that the polycrystalline structures covered on the substrate surface. © (2012) Trans Tech Publications, Switzerland.
  • Takashi Hirahara, Masahiro-Yoshizawa Fujita, Yuko Takeoka, Masahiro Rikukawa
    THERMEC 2011, PTS 1-4, 706-709 1636-+, 2012  
    Fluorene-thiophene copolymers having chiral and azobenzene substituents, PAzB4-T, were synthesized by the Pd-catalyzed Suzuki coupling method. We studied the aligning organization of the main chain of PAzB4-T with the activation of the attached functional groups by thermal annealing and photo-annealing processes. Circular dichroism (CD) measurements revealed that the thermally annealed PAzB4-T spin-coated films exhibited bisignate Cotton effects over the absorption regions of the polymer main chains and the azobenzene side chains due to the formation of chiral assemblies. After the photo-annealing process, which means linearly polarized light irradiation accompanied by thermal annealing, the PAzB4-T spin-coated films showed linear dichroism over the absorption region of the main chains, due to the alignment of azobenzene side chains against the electric field of the linearly polarized light. These results suggested that rigid conjugated polymers were successfully aligned by the alignment of functional groups with the external stimuli.
  • Miru Yoshida, Yue Zhao, Masahiro Yoshizawa-Fujita, Akihiro Ohira, Yuko Takeoka, Satoshi Koizumi, Masahiro Rikukawa
    ECS Transactions, 50(2) 1045-1053, 2012  
    We employed the pulsed field gradient nuclear magnetic resonance (PFG-NMR) technique to investigate the self-diffusion coefficient of water, D NMR, in newly designed cation exchange membranes, made of sulfonated poly(p-phenylene)-poly(ether ketone) multiblock copolymers, which are denoted by S-6H (n) x:y. The DNMR value was measured as a function of the gradient strength, g, from 0.1 to 11.0 T m-1. S-6H (14) 1:1 showed the DNMR value of 2.35 × 10-10 m2 s -1 at 30 °C and 90% RH, which are about 10 times lower than the value in bulk liquid water. Small angle neutron scattering (SANS) measurements showed two peaks in S-6H (14) 1:1. The low q peak is attributed to the formation of microdomains and the high q peak is due to the formation of ionic clusters in the swollen microdomains.
  • Satoshi Miura, Tatsuya Oshima, Kensuke Umezawa, Masahiro Yoshizawa-Fujita, Akihiro Ohira, Yuko Takeoka, Masahiro Rikukawa
    ECS Transactions, 50(2) 1081-1088, 2012  
    We synthesized a new sulfonated phenylene block copolymer (S-PPBP-PES) by a Ni(0) coupling reaction. Membrane electrode assemblies (MEAs) were fabricated with the S-PPBP-PES ionomer and a Nafion 112 membrane. Five alcohols (methanol, ethanol, 1-propanol, 2-propanol, or mixed propanol) were used as the dispersion solvent for catalyst ink, and the effect of solvents on the fuel cell performance was investigated. These MEAs prepared with mixed propanol exhibited the highest power density among them due to the larger electrochemically active area and smooth surfaces of the catalytic layer compared with others. © The Electrochemical Society.
  • Tatsuya Oshima, Kensuke Umezawa, Masahiro Yoshizawa-Fujita, Akihiro Ohira, Yuko Takeoka, Masahiro Rikukawa
    ECS Transactions, 50(2) 1073-1079, 2012  
    A poly(p-phenylene)-based diblock copolymer P2-P1 was synthesized with a hydrophilic monomer, 2,5-dibromo-1,4-di[4-(2, 2-dimethylpropoxysulfonyl)phenyl] butoxybenzene, and a hydrophobic monomer, 2,5-dibromo-1,4-dihexyloxybenzene, via a catalyst transfer polycondensation. Deprotection of the neopentyl groups using diethylamine hydrobromide and subsequent acidic hydrolysis provided a sulfonated diblock copolymer SP2-P1. The diblcok copolymer SP2-P1 showed similar hydration numbers λ to the random copolymer SP2-RAN-P1 in the rage of 30-90% RH at 80°C. The proton conductivity of the SP2-P1 was higher than that of SP2-RAN-P1 membranes at 80°C despite of the lower IEC and the comparable λ. © The Electrochemical Society.
  • Isao Tonozuka, Miru Yoshida, Keiichi Kaneko, Yuko Takeoka, Masahiro Rikukawa
    POLYMER, 52(26) 6020-6028, Dec, 2011  
    Ni(0)-catalyzed coupling polymerization of 2,5-dichloro-4'-phenoxybenzophenone was investigated by varying the ligand and coligand, temperature, reaction time, and solvent. The weight-average molecular weight (M-w) of poly(4-phenoxybenzoyl-1,4-phenylene)s (PPBPs) could be controlled by the polymerization conditions and reached a maximum of 4.4 x 10(5) g mol(-1). Sulfonated PPBPs (S-PPBPs) with various M(w)s were prepared with sulfuric acid to study the effect of molecular weight on the chemical and electrical properties of PPBP-based electrolytes. The strong molecular interactions in S-PPBP provided an ion exchange capacity of 2.9 meq g(-1) without loss of high mechanical properties. High molecular weight S-PPBPs had more desirable properties for fuel cell applications. While the swelling ratios and hydration numbers of S-PPBPs decreased with increasing molecular weight, the mechanical strength, proton conductivity, and fuel cell performance increased. S-PPBP also showed anisotropic behavior in the swelling and proton conductivity; such behavior is caused by the rigid-rod nature and the liquid-crystal structure. (C) 2011 Elsevier Ltd. All rights reserved.
  • Takemasa Miura, Yuko Takeoka, Mikio Sato, Hideyuki Kunugita, Kazuhiro Ema
    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 9, 8(9) 2752-2755, 2011  
    Optical properties in a single crystal of the organic-inorganic hybrid perovskite quantum-well material (C4H9NH3)(2)(CH3NH3)Pb2Br7 have been investigated. This material has double-layer sheets of corner-sharing [PbBr6](4-) octahedrons constituting the inorganic well. The estimated longitudinal-transverse (LT) splitting, exciton exchange energy, and biexciton binding energy are about 60 meV, 17 meV and 26 meV respectively. We can also study well-width dependence in angstroms by comparing with (C4H9NH3)(2)PbBr4 which has single-layer sheets comprising the inorganic well. This is the first time the well-width dependence of excitonic properties in hybrid organic-inorganic quantum materials is investigated. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • T. Yoshimi, N. Sugiyama, Y. Takeoka, M. Rikukawa, K. Oribe, M. Aizawa
    JOURNAL OF THE AUSTRALIAN CERAMIC SOCIETY, 47(1) 18-22, 2011  
    We have developed the porous HAp ceramics with bi-modal pore structure. Using the porous HAp ceramics, HAp/poly-L-lactide (PLLA) hybrids were fabricated by introducing PLLA into the porous HAp ceramics via enzyme polymerization of L-lactide using lipase (lipase PS) as an enzyme. The amount of lipase PS was added 1 and 3 mass% to weight of L-lactide. In order to examine the changes of material properties before and after immersing into the simulated body fluid (SBF), we fabricated three kinds of specimens: i) Porous HAp, ii) HAp/PLLA(1%), iii) HAp/PLLA(3%). The bending strength of the hybrids decreased during immersing SBF up to 28 days. Furthermore, when the hybrids were immersed into the SBF for 4 days, the formation of bone-like apatite occurred on the surface of the specimens.
  • Masahiro Yoshizawa-Fujita, Tetsuya Tamura, Yuko Takeoka, Masahiro Rikukawa
    CHEMICAL COMMUNICATIONS, 47(8) 2345-2347, 2011  
    An imidazolium-based zwitterion containing two oxyethylene units was obtained as a colorless liquid at room temperature. The equimolar mixture of the liquid zwitterion and lithium bis(trifluoromethylsulfonyl) amide showed an ionic conductivity of over 10(-4) S cm(-1) at 80 degrees C, which was higher than those of mixtures composed of analogous solid zwitterions.
  • Masahiro Yoshizawa-Fujita, Yuri Kousa, Koh Kidena, Akihiro Ohira, Yuko Takeoka, Masahiro Rikukawa
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 13(29) 13427-13432, 2011  
    An ionic liquid having a hydroxyl group, choline bis(trifluoromethylsulfonyl)amide ([N-111(2OH)][N(Tf)(2)]), was synthesized to investigate the effect of hydroxyl groups on the proton transport. 1,1,1-Trifluoro-N-(trifluoromethylsulfonyl)methanesulfoneamide (HN(Tf)(2)) as a proton source was mixed with the choline derivative at various molar ratios. Their thermal properties, viscosities, and ionic conductivities were investigated. [N-111(2OH)][N(Tf)(2)] showed a melting point at 27 degrees C, and its thermal stability was higher than 400 degrees C. The viscosity of [N-111(2OH)][N(Tf)(2)]/HN(Tf)(2) mixtures increased as the acid molar fraction increased. The ionic conductivity of [N-111(2OH)][N(Tf)(2)] was 2.1 x 10(-3) S cm(-1) at 25 degrees C; the ionic conductivity monotonously decreased as the acid molar fraction increased. There was a clear correlation between the ionic conductivity and the viscosity for the mixtures of the choline derivative and the acid. PFG-NMR measurements were carried out to investigate the diffusion behavior of protons. Although the acid and the hydroxyl group were indistinguishable by H-1 NMR, the self-diffusion coefficient of the H-1 of the hydroxyl group and the acid was larger than those of other H-1 nuclei. This difference suggests that a fast intermolecular proton transfer exists between the hydroxyl group and the acid.
  • Takemasa Miura, Yuko Takeoka, Mikio Sato, Hideyuki Kunugita, Kazuhiro Ema
    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 9, 8(9) 2752-2755, 2011  
    Optical properties in a single crystal of the organic-inorganic hybrid perovskite quantum-well material (C4H9NH3)(2)(CH3NH3)Pb2Br7 have been investigated. This material has double-layer sheets of corner-sharing [PbBr6](4-) octahedrons constituting the inorganic well. The estimated longitudinal-transverse (LT) splitting, exciton exchange energy, and biexciton binding energy are about 60 meV, 17 meV and 26 meV respectively. We can also study well-width dependence in angstroms by comparing with (C4H9NH3)(2)PbBr4 which has single-layer sheets comprising the inorganic well. This is the first time the well-width dependence of excitonic properties in hybrid organic-inorganic quantum materials is investigated. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • Yuko Takeoka
    KOBUNSHI RONBUNSHU, 67(8) 440-446, Aug, 2010  
    Lead halide-based layered perovskites, (H(3)N-Cr,H(2n)-NH(3))PbX(4)(X: I, Br), have attracted much attention because of their exceptional properties and quantum well structure. The tunable optical properties and high crystallinilty of pi-conjugated oligomers make them promising candidates as advanced materials for the optelectronic applications. In this study, pi-conjugated oligomer derivatives, 4,4'-bis-[5-(2-aminoethyl)thienyl]biphenylene hydrohalides (AETP center dot HX; X =Br and I) and 2,7-bis-[5-(2-aminoethyl}thienyl]-9H-fluorene dihydrohalides (AETF center dot HX; H = I), were incorporated into the organic layer of the layered perovskites, as shown by the XRD profile pf hybrid films. The UV-vis absorption spectra of the oligomers were not dependent on the halogen. The specta of the (AETP)PbI(4) and (AETF) PbI(4) films showed a sharp and intense absorption at 516 nm and 514 nm, respectively, while the (AETP)PbBr(4) film exhibited an absorption peak at 400 nm. In the photoluminescence spectrum of the (AETP)PbI(4) film, an exciton emission at 516 nm was observed. On the contrary, (AETP)PbBr(4) and (AETF)PbI(4) films showed characteristic peaks at other wavelengths. These results suggest that a novel energey interaction between organic and inorganic layers was formed in the layered perovskite films.
  • Miho Kamiya, Masahiro Yoshizawa-Fujita, Yuko Takeoka, Masahiro Rikukawa
    ELECTROCHIMICA ACTA, 55(4) 1385-1388, Jan, 2010  
    Multilayer-type polymer electrolyte membranes composed of a sulfonated poly(4-phenoxybenzoyl-1,4-phenylene) (S-PPBP) layer and a mono[ poly(propylene oxide)methacrylate] phosphate ester (PPHP) layer were fabricated by solution-casting procedure (Method 1) and hot-pressing procedure (Method 2) in order to suppress methanol permeability of electrolyte membranes. No delamination was observed by SEM measurements of S-PPBP/PPHP interfaces, indicating that PPHP had good adhesive properties to S-PPBP surfaces. The methanol permeability of S-PPBP/PPHP membranes was lower than that of S-PPBP membranes and decreased with increasing the thickness of PPHP layers. The bilayer membrane with 12 mu m PPHP and 40 mu m S-PPBP layers showed a methanol permeability of 2.97 x 10(-7) cm(2) s(-1) in 1 mol dm(-3) methanol aqueous solution at 25 degrees C, which was 13% less than that ofthe S-PPBP membranes. The conductivity of this membrane reached its optimum with values as high as 1.57 x 10(-1) S cm(-1) at 80 degrees C and 90%RH. (C) 2009 Elsevier Ltd. All rights reserved.
  • K. Esashika, M. Yoshizawa-Fujita, Y. Takeoka, M. Rikukawa
    SYNTHETIC METALS, 159(21-22) 2184-2187, Nov, 2009  
    Poly[9,9-dihexylfluorene-co-(benzothiazol-2-yl)thiophene-co-9,9'-spirobifluorene] (PF(x)B(y)S(z)) were synthesized by palladium-catalyzed Suzuki coupling reaction. PE(x)B(y)S(z) were characterized by FT-IR,elemental analysis, and (1)H NMR. All the copolymers showed decomposition temperatures above 400 degrees C and glass transition points above 180 degrees C. suggesting that these materials had excellent thermal stability. As the benzothiazolylthiophene content in copolymers was increased, the band gaps of copolymers decreased. All the copolymers exhibited fluorescence peaks in the visible region, and the energy transfer from fluorene to benzothiazolylthiophene units were observed. (C) 2009 Elsevier B.V. All rights reserved.
  • T. Hirahara, M. Yoshizawa-Fujita, Y. Takeoka, M. Rikukawa
    SYNTHETIC METALS, 159(21-22) 2180-2183, Nov, 2009  
    A series of alternating copolymers consisting of chiral thiophene and fluorene, poly[9,9-dihexylfluorene-alt-(3-{2-[(S)-(+)-1-methyloctyloxy]ethyl}thiophene)] (P1), and poly[9,9-dihexylfluorene-alt-(3-{2-[(S)-(+)-1-methyloctyloxy]ethyl}-2,2'-bithiophene)] (P2), were synthesized by Suzuki coupling method. P1 and P2 were characterized by (1)H NMR spectra and elemental analyses. Both of the copolymers showed clear solvatochromism and circular dichroism in methanol/chloroform mixed solutions. These two polymers had different spacer lengths between the chiral side chains along the main chain. and accordingly the circular dichroism spectra were apparently different. (C) 2009 Elsevier B.V. All rights reserved.
  • TAKEOKA YUKO, Y. Iwamoto, Y. Shigemitsu, K. Oribe, N. Sugiyama, M. Rikukawa, M. Matsumoto, H. Morisue, M. Aizawa
    Bioceramics, 22 639, Oct 1, 2009  
  • TAKEOKA YUKO, T. Yoshimi, Y. Tanaka, N. SUgiyama, Y. Takeoka, M. Rikukawa, M. Aizawa
    Bioceramics, 22 643, Oct 1, 2009  
  • H. Ohmori, M. Yoshizawa-Fujita, Y. Takeoka, M. Rikukawa
    Polymer Preprints, 50(2) 662, Aug, 2009  
  • M. Hatanaka, M. Yoshizawa-Fujita, Y. Takeoka, M. Rikukawa
    Polymer Preprints, 50(2) 641, Aug, 2009  
  • M. Yoshida, M. Yoshizawa-Fujita, Y. Takeoka, M. Rikukawa
    Polymer Preprints, 50(2) 537, Aug, 2009  
  • A. Yamada, M. Yoshizawa-Fujita, Y. Takeoka, M. Rikukawa
    Polymer Preprints, 50(2) 518, Aug, 2009  
  • Y. Kawabata, M. Yoshizawa-Fujita, Y. Takeoka, M. Rikukawa
    SYNTHETIC METALS, 159(9-10) 776-779, May, 2009  
    Novel lead iodide-based layered perovskite compounds, which contain fullerene derivatives, N-methyl-2-(4-ammoniumphenyl)-fulleropyrrolidine iodide (AmPF) and N-(n-dodecyl)-2-(4-ammoniumphenyl)fulleropyrrolidine iodide (C12AmPF), in their organic layers were fabricated as thin solid films by spin-coating. The XRD profiles showed that (AmPF)Pbl(4) molecules were arranged in a closer-packing form, compared with (C12AmPF)Pbl(4). The photoluminescence spectra of thin films suggested the presence of energy transfer between C(60) moiety and lead(II) iodide layers, which led to the disappearance of fluorescence peak at 517 nm and the appearance of a new fluorescence peak at 780 nm.(AmPF)Pbl(4) and (C12AmPF)Pbl(4) films exhibited photoconductivity when ultraviolet light was irradiated, and the photocurrent values with applying 1.0 V bias voltage were 1.77 mu A and 1.48 x 10(-2) mu A, respectively. (C) 2009 Elsevier B.V. All rights reserved.
  • Naohiko Takimoto, Libin Wu, Akihiro Ohira, Yuko Takeoka, Masahiro Rikukawa
    POLYMER, 50(2) 534-540, Jan, 2009  
    The relationships between morphology and proton conduction for Nafion membranes and hydrocarbon-type proton exchange membranes, namely, sulfonated poly(arylene ether ether ketone) (S-PEEK) and sulfonated poly(arylene ether sulfone) (S-PES), were investigated by small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). The direct simultaneous observation of surface morphology and active regions of proton conduction on membranes by combined high-resolution AFM phase imaging and an electrochemical technique at controlled humidity provided significant morphological information, particularly for the hydrocarbon-type membranes that exhibit few or no features on SAXS profiles. For the Nafion membranes, the active proton paths became denser and congregated with each other at over 60% RH, resulting in the formation of well-connected networks. For the hydrocarbon-type membranes, however, only the relatively small and dispersed proton paths were observed, which showed no significant change even as water content increased. We have demonstrated that the differences in microscopic morphology between the Nafion and hydrocarbon-type membranes are associated with the differences between their macroscopic proton conductivities. (C) 2008 Elsevier Ltd. All rights reserved.

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