Curriculum Vitaes

Fujita Masahiro

  (藤田 正博)

Profile Information

Affiliation
Professor, Faculty of Science and Technology, Department of Materials and Life Sciences, Sophia University
Degree
博士(工学)(Mar, 2002, 東京農工大学)

Contact information
masahi-fsophia.ac.jp
Other name(s) (e.g. nickname)
Yoshizawa
Researcher number
50433793
J-GLOBAL ID
200901014332520864
researchmap Member ID
6000003382

(Subject of research)
Developement of fast proton conductive plastic crystals


Papers

 192
  • T. Sato, M. Yoshizawa-Fujita, Y. Takeoka, M. Rikukawa
    Journal of Analytical & Bioanalytical Techniques, 8(6) 388, Dec, 2017  Peer-reviewed
  • Jun Ishii, Yuko Takeoka, Masahiro Rikukawa, Masahiro Yoshizawa-Fujita
    Kobunshi Ronbunshu, 74(6) 542-548, Nov 1, 2017  Last authorCorresponding author
    Colorless and transparent polybetainetype ion gels (PEG100CL2BTx (x = 0, 1, 3, 5, and 10)(the numbers indicate mole percent)) composed of poly(ethylene glycol) methyl ether methacrylate (PEGMA), [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide (BT) as the polymer matrix, N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)amide/lithium bis(trifluoromethylsulfonyl)amide (IL/Li) as the electrolyte, and a cross-linker (CL) were synthesized by in situ polymerization. These ion gels exhibited a glass transition temperature (Tg) at approximately -70°C, and their ionic conductivity was almost the same regardless of the x value. On the other hand, the oxidation stability of ion gels increased with increasing BT content. All ion gels exhibited a reduction peak for Li+ and an oxidation peak for Li. The current density and coulombic efficiency of PEG100CL2BT5 were higher than those of PEG100CL2BT0.
  • K. Akizuki, A. Ohma, S. Miura, T. Matsuura, M. Yoshizawa-Fujita, Y. Takeoka, M. Rikukawa
    Sustainable Energy & Fuels, 1(6) 1299-1302, Aug 1, 2017  Peer-reviewed
    Polyphenylene-based hydrophilic-hydrophobic diblock copolymers were developed and used as ionomers in the catalyst layers (CLs) of polymer electrolyte membrane fuel cells. The introduction of aliphatic side chains into the polymer backbone provided high oxygen transport properties in the CLs and high overall performance of the fuel cells.
  • Yundong Zhou, Xiaoen Wang, Haijin Zhu, Masahiro Yoshizawa-Fujita, Yukari Miyachi, Michel Armand, Maria Forsyth, George W. Greene, Jennifer M. Pringle, Patrick C. Howlett
    CHEMSUSCHEM, 10(15) 3135-3145, Aug, 2017  Peer-reviewed
    Organic ionic plastic crystals (OIPCs) are a class of solid-state electrolytes with good thermal stability, non-flammability, non-volatility, and good electrochemical stability. When prepared in a composite with electrospun polyvinylidene fluoride (PVdF) nanofibers, a 1:1 mixture of the OIPC N-ethyl-N-methylpyrrolidinium bis(fluorosulfonyl) imide ([C(2)mpyr][FSI]) and lithium bis( fluorosulfonyl) imide (LiFSI) produced a free-standing, robust solid-state electrolyte. These high-concentration Li-containing electrolyte membranes had a transference number of 0.37(+/- 0.02) and supported stable lithium symmetric-cell cycling at a current density of 0.13 m Acm(-2). The effect of incorporating PVdF in the Li-containing plastic crystal was investigated for different ratios of PVdF and [Li][FSI]/[C(2)mpyr][FSI]. In addition, Li jLiNi(1/3)Co(1/3)Mn(1/3)O(2) cells were prepared and cycled at ambient temperature and displayed a good rate performance and stability.
  • Shunsuke Horiuchi, Haijin Zhu, Maria Forsyth, Yuko Takeoka, Masahiro Rikukawa, Masahiro Yoshizawa-Fujita
    ELECTROCHIMICA ACTA, 241 272-280, Jul, 2017  Peer-reviewedLast authorCorresponding author
    Ionic liquids (ILs) containing zwitterions were studied as electrolytes for lithium-ion batteries. The effect of a pyrrolidinium zwitterion with a long ether side chain on the thermal and electrochemical properties of an IL and the charge/discharge properties of Li/LiCoO2, Li/LiNi1/3Mn1/3Co1/3O2 (NMC), and graphite/Li cells with IL/zwitterion electrolytes was investigated. The melting temperature of the IL-based electrolyte composed of N-methyl-N-methoxymethylpyrrolidinium bis(fluorosulfonyl) amide ([Pyr(1,101)] [FSA]) and lithium bis(fluorosulfonyl) amide (LiFSA) with 3-(1-(2-(2-methoxyethoxy)ethyl)pyrrolidin-1-ium-1-yl)propane-1-sulfonate (OE2pyps) as the zwitterionic additive was about -18 degrees C. The electrochemical window of [Pyr(1,101)][FSA]/LiFSA/OE2pyps was over 5 V vs. Li/Li+. Li|electrolyte| LiCoO2 cells containing the [Pyr(1,101)][FSA]/LiFSA/OE2pyps electrolyte system exhibited high capacity values in the cut-off voltage range of 3.0-4.3 V, even after 50 cycles. Moreover, increases of interfacial resistance between the electrolyte and cathode during cycling were suppressed. Li|electrolyte|NMC cells containing this electrolyte system also exhibited high capacities in a wide cut-off voltage range of 3.0-4.6 V, even after 50 cycles. In the cyclic voltammograms of cells employing a graphite electrode, the intercalation/deintercalation of lithium ions was observed between 0 and + 0.4 V vs. Li/Li+. Further, graphite|electrolyte|Li cells containing [Pyr(1,101)][FSA]/LiFSA/OE2pyps exhibited stable charge/discharge cycle behavior over 5 cycles. (C) 2017 Elsevier Ltd. All rights reserved.
  • Xiaoen Wang, Haijin Zhu, George W. Greene, Yundong Zhou, Masahiro Yoshizawa-Fujita, Yukari Miyachi, Michel Armand, Maria Forsyth, Jennifer M. Pringle, Patrick C. Howlett
    ADVANCED MATERIALS TECHNOLOGIES, 2(7) 1700046, Jul, 2017  Peer-reviewed
    Solid-state electrolytes have been identified as one of the most attractive materials for the fabrication of reliable and safe lithium batteries. This work demonstrates a facile strategy to prepare highly conductive organic ionic plastic crystal (OIPC) composites by combination of a low weight fraction of Li+ doped OIPC (N-ethyl-N-methylpyrrolidinium bis(fluorosulfonyl)amide, [C(2)mpyr][FSI]) with commercial poly(vinylidene difluoride) (PVDF) powder. Benefiting from the enhancement of lithium ion dynamics, as evidenced by the solid-state NMR measurements, the composite electrolyte shows an order of magnitude higher conductivity than that of the bulk material. Lithium metal/LiFePO4 cells incorporating the prepared composite electrolytes show impressively high specific capacity and good cycling stability (99.8% coulombic efficiency after 1200 cycles at 2 C, room temperature), which is the first demonstration of long-term cycling performance at such high rate for an OIPC-based electrolyte. The high voltage cathode, LiCo1/3Ni1/3Mn1/3O2 was tested and good rate performance and stable capacities have been achieved.
  • Su Chen, Jun Ishii, Shunsuke Horiuchi, Masahiro Yoshizawa-Fujita, Ekaterina I. Izgorodina
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 19(26) 17366-17372, Jul, 2017  Peer-reviewed
    Recent thermal runaways in lithium- ion batteries have reinforced the focus on the research of safer electrolytes based on ionic liquids. A simple switch from organic solvents to ionic liquids has been proven difficult due to the decreased efficiency of batteries caused by decreased conductivity and increased viscosity of ionic liquids upon addition of lithium salts. The new trend in replacing lithium salts with a cheaper alternative, sodium salts, has resulted in rather poor solubility of sodium salts in commonly used ionic liquids. This phenomenon has been left largely unexplained. Herein, we present a high-level quantum chemical study of the chemical bonding of lithium and sodium salts coupled with ionic liquid anions. Due to their proximity to the anion, the 1s2 electrons on the lithium cation are found to become strongly polarized by the presence of the anion such that they start participating in the bonding, making it more covalent than originally thought. In sodium salts the 2s(2) orbitals are rather removed from the anion, making its influence weaker. This polarization results in 90 kJ mol (-1) of difference in the interaction magnitude between lithium and sodium salts. Theoretical results have confirmed that increasing covalency in lithium salts results in their excellent solubility since these dissolve as ion-paired complexes. The downside of this ability is decreased conductivity as lithium salts are unlikely to easily dissociate in ionic liquids. Sodium salts are shown to maintain a high degree of ionicity, thus decreasing their chances of being solvated by ionic liquids as a result of their low concentration of ions per unit volume. The theoretical results are further underpinned by solubility studies of MX salts, where M = Li or Na and X = bis(trifluoromethylsulfonyl) imide (NTf2), BF4 -or PF6 (-), conducted in six different ionic liquids. Lithium salts consisting of BF4 -or PF6 -exhibited significantly better solubility than their sodium analogues by at least an order of magnitude. The findings of this work will have implications on the future direction of the development of safe electrolytes for lithium and sodium-ion secondary batteries.
  • R. Hamaguchi, M. Yoshizawa-Fujita, T. Miyasaka, H. Kunugita, K. Ema, Y. Takeoka, M. Rikukawa
    CHEMICAL COMMUNICATIONS, 53(31) 4366-4369, Apr, 2017  Peer-reviewed
    Formamidine (FA) and cesium (Cs) cations were introduced into quasi-two-dimensional (2D) perovskites as B site cations. The unique crystalline growth of the resulting (n-C6H13NH3)(2)FAPb(2)I(7), which promotes charge transport in photovoltaic solar cells, was confirmed, as was the stability of this material. The photovoltaic properties of (n-C6H13NH3)(2)FAPb(2)I(7) were found to be superior to those of other homologous quasi-2D perovskite compounds.
  • Koki Munakata, Masahiro Yoshizawa-Fujita, Masahiro Rikukawa, Toyonobu Usuki
    AUSTRALIAN JOURNAL OF CHEMISTRY, 70(6) 699-704, 2017  Peer-reviewed
    Lemon myrtle is the richest natural source of citral, which has potential medicinal applications. In this study, citral was extracted from lemon myrtle using cellulose-dissolving ionic liquids (ILs), 1-ethyl-3-methylimidazolium methylphosphonate ([C(2)mim][(MeO)(H)PO2]), N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium chloride ([DEME]Cl), and N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium 2-methoxyacetate ([DEME][MOAc]). The extraction yield of citral obtained using ILs was up to 2.1 times higher than that obtained using ethanol. The ILs could be recycled and reused nine times for the extraction of citral. The present method provides a greener process when compared with conventional approaches and may be applicable for the extraction of other natural products.
  • Arai, Ryosuke, Yoshizawa-Fujita, Masahiro, Takeoka, Yuko, Rikukawa, Masahiro
    ACS Omega, 2(5) 2333-2336, 2017  Peer-reviewed
    Two-dimensional perovskite compounds, ((RNH32PbX4)-Pb-), have attracted much attention as quantum confinement materials. To achieve suitable orientation and exciton properties for optical applications, carboxy groups were introduced into the ammonium cations of two-dimensional perovskite compounds, which formed dimer structures based on the hydrogen bonding by the carboxy moieties. This structural organization allowed control of the layer orientation for favorable solar cells and thermal stability of the perovskites, while maintaining quantum confinement effects.
  • Chihiro Murata, Masahiro Yoshizawa-Fujita, Masahiro Rikukawa, Toyonobu Usuki
    Asian Journal of Chemistry, 29(2) 309-312, 2017  Peer-reviewed
    Geranial [(E)-3,7-dimethyl-2,6-octadienal], neral [(Z)-3,7-dimethyl-2,6-octadienal] and geraniol [(E)-3,7-dimethyl-2,6-octadien-1-ol] are found in lemon grass and are attractive essential oils with potential medicinal applications. In this study, a new method for extracting these natural flavour substances from lemon grass using co-solvent systems consisting of methanol or ethyl acetate and the ionic liquids 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) or 1-ethyl-3-methylimidazolium methylphosphonate ([C2mim][(MeO)(H)PO2]) is described.
  • Tatsuya Oshima, Masahiro Yoshizawa-Fujita, Yuko Takeoka, Masahiro Rikukawa
    ACS Omega, 1(5) 939-942, Nov 30, 2016  Peer-reviewed
    Aromatic ionomers with perfluoroalkyl sulfonic acid groups for fuel cell applications have been prepared mostly by the post-functionalization method. Herein, we present a direct polymerization method using a novel monomer with a perfluorosulfonic acid group to control the amount and position of the sulfonic acid groups. A poly(p-phenylene)-based aromatic hydrocarbon ionomer bearing a pendant perfluorosulfonic acid group in a substituent at the 2-position is synthesized by Ni(0)-catalyzed coupling polymerization. The direct polymerization provides Mn values of up to 169 000 with a highly controlled molecular structure and allows the formation of thin membranes. These ionomers were found to combine the positive features of perfluorinated and aromatic hydrocarbon ionomers, and these thin membranes with a relatively high ion exchange capacity showed high proton conductivity and excellent fuel cell performance (907 mW cm-2 even at 80 °C and 30% RH) under low humidity conditions compared with other reported aromatic hydrocarbon ionomers.
  • Seitaro Yamaguchi, Masahiro Yoshizawa-Fujita, Yuko Takeoka, Masahiro Rikukawa
    JOURNAL OF POWER SOURCES, 331 308-314, Nov, 2016  Peer-reviewedCorresponding author
    Ionic liquids (ILs) containing zwitterions have been studied as electrolytes for lithium-ion batteries (LIBs). The effects of addition of a pyrrolidinium zwitterion in an IL electrolyte on the thermal and electrochemical stability and charge/discharge properties of Li/LiCoO2 and graphite/Li cells were investigated. The thermal decomposition temperature of the IL electrolyte composed of N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)amide ([P13][FSA])/lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) with 3-(1-butylpyrrolidinium)propane-1-sulfonate (Bpyps) as the zwitterionic additive, the thermal decomposition temperature was about 300 degrees C. The electrochemical window of [P13][FSA]/LiTFSA/Bpyps was 0 -+5.4 V vs. Li/Li+, which was almost identical to that of [P13][FSA]/LiTFSA. Li vertical bar electrolyte vertical bar LiCoO2 cells containing the IL/Bpyps electrolyte system exhibited high capacities in the cut-off voltage range of 3.0 -4.6 V, even after 50 cycles. The increase in the interfacial resistance between the electrolyte and cathode with cycling was suppressed. In the cyclic voltammograms of cells employing a graphite electrode, the intercalation/deintercalation of lithium ions were observed in the range of 0 and + 0.4 V vs. Li/Li+. Further, graphite vertical bar electrolyte vertical bar Li cells containing [P13][FSA]/LiTFSA/Bpyps exhibited stable charge/discharge cycle behaviour over 50 cycles. (C) 2016 Elsevier B.V. All rights reserved.
  • Y. Takeoka, K. Arai, M. Yoshizawa-Fujita, M. Aizawa, M. Rikukawa
    Research & Reviews: Journal of Microbiology and Biotechnology, 5(3) 1-4, Oct 27, 2016  Peer-reviewed
  • Shunsuke Horiuchi, Masahiro Yoshizawa-Fujita, Yuko Takeoka, Masahiro Rikukawa
    JOURNAL OF POWER SOURCES, 325 637-640, Sep, 2016  Peer-reviewedCorresponding author
    The ionic liquid (IL) N-Methyl-N-methoxymethylpyrrolidinium bis(fluorosulfonyl)amide ([Pyr(1,101)][FSA]) was synthesized, and its physicochemical and electrochemical properties were investigated with respect to its application as an electrolyte in lithium-ion secondary batteries operating over a wide temperature range. [Pyr(1,101)][FSA]/Li salt (0.34 mol kg) composites were prepared by adding lithium bis(tri-fluoromethylsulfonyl)amide (LiTFSA) into the IL. [Pyr(1,101)][FSA] and [Pyr(1,101)][FSA]/LiTFSA exhibited melting temperatures (T-m) below 30 degrees C. [Pyr(1,101)][FSA] exhibited a higher ionic conductivity value as compared with that of the corresponding IL with only alkyl substituents. The electrochemical window for both [Pyr(1,101)][FSA] and [Pyr(1,101)][FSA]/LiTFSA was 5.1 V. Stable lithium deposition and dissolution occurred on a Ni electrode at 25 degrees C. (C) 2016 Elsevier B.V. All rights reserved.
  • K. Okuda, M. Yoshizawa-Fujita, Y. Takeoka, M. Rikukawa
    The Journal of Fuel Cell Technology, 15(4) 77-81, Apr 30, 2016  Peer-reviewedInvited
  • Seitaro Yamaguchi, Masahiro Yoshizawa-Fujita, Haijin Zhu, Maria Forsyth, Yuko Takeoka, Masahiro Rikukawa
    ELECTROCHIMICA ACTA, 186(20) 471-477, Dec, 2015  Peer-reviewedCorresponding author
    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.
  • Shingo Onda, Toyonobu Usuki, Masahiro Yoshizawa-Fujita, Masahiro Rikukawa
    CHEMISTRY LETTERS, 44(11) 1461-1463, Nov, 2015  Peer-reviewed
    A protocol for extracting the terpene trilactone bilobalide from Ginkgo biloba leaves using the cellulose-dissolving ionic liquid 1-butyl-3-methylimidazolium chloride ([C(4)mim]Cl) was developed. Extraction with [C(4)mim]Cl/MeOH (1:1 w/w) at 80 degrees C afforded bilobalide with a yield of 0.14% w/w, which was 1.4 times higher than that achieved using conventional MeOH at 80 degrees C (0.098% w/w).
  • Mitsutake Suematsu, Masahiro Yoshizawa-Fujita, Haijin Zhu, Maria Forsyth, Yuko Takeoka, Masahiro Rikukawa
    ELECTROCHIMICA ACTA, 175 209-213, Sep, 2015  Peer-reviewedCorresponding author
    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.
  • 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.
  • Mitsutake Suematsu, Masahiro Yoshizawa-Fujita, Tetsuya Tamura, Yuko Takeoka, Masahiro Rikukawa
    INTERNATIONAL JOURNAL OF ELECTROCHEMICAL SCIENCE, 10(1) 248-258, Jan, 2015  Peer-reviewedCorresponding author
    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-reviewedLead authorCorresponding author
    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, Erina Kishi, Mitsutake Suematsu, Toshihiro Takekawa, Masahiro Rikukawa
    Chemistry Letters, 43(12) 1909-1911, 2014  Peer-reviewedLead authorCorresponding author
    A novel organic ionic plastic crystal, N-ethyl-N-methyl-pyrrolidinium bis(fluorosulfonyl)amide ([C2mpyr][FSA]), was synthesized, and its thermal properties and conductivity were investigated. [C2mpyr][FSA] showed a high melting point at 205°C and exhibited plastic crystalline behavior over a wide temperature range from -22°C to melting, which was also in a desirable temperature range for electrochemical devices. The ionic conductivity of [C2mpyr][FSA] was 1.23 × 10-6 S cm-1 at 25°C.
  • N. Sugiyama, Y. Yanagi, M. Yoshizawa-Fujita, M. Aizawa, Y. Takeoka, M. Rikukawa
    Chemistry Letters, 42(5) 465-467, May 5, 2013  
  • S. Miura, T. Oshima, K. Umezawa, M. Yoshizawa-Fujita, A. Ohira, Y. Takeoka, M. Rikukawa
    ECS Transaction, 50(2) 1081-1088, Mar 1, 2013  
  • T. Oshima, K. Umezawa, M. Yoshizawa-Fujita, A. Ohira, Y. Takeoka, M. Rikukawa
    ECS Transaction, 50(2) 1073-1079, Mar 1, 2013  
  • Osawa, A., Ide, K., Yoshida, M., Yoshizawa-Fwita, M., Takeoka, Y., Rikukawa, M.
    Kobunshi Ronbunshu, 70(1) 16-22, Jan 25, 2013  
  • 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.
  • Nami Sugiyama, Yusuke Yanagi, Masahiro Yoshizawa-Fujita, Mamoru Aizawa, Yuko Takeoka, Masahiro Rikukawa
    Chemistry Letters, 42(5) 465-467, 2013  
    Biphasic calcium phosphate (BCP) ceramics with wellcontrolled 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. © 2013 The Chemical Society of Japan.
  • 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, Tomoko Kinoshita, Yuta Ono, Yuko Takeoka, Masahiro Rikukawa
    Chemistry Letters, 42(10) 1185-1187, 2013  Peer-reviewedLead authorCorresponding author
    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 × 10-4 S cm-1 at 50 °C, with a high lithium ion transference number of over 0.5, owing to the anion-trapping effect of the boronic acid group. © 2013 The Chemical Society of Japan.
  • 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.
  • Yasuda Nanae, Yoshizawa-Fujita Masahiro, Rikukawa Masahiro, Usuki Toyonobu
    Symposium on the Chemistry of Natural Products, symposium papers, (54) 507-512, Sep 1, 2012  
    Shikimic acid was first isolated in 1885 by Eijkman from the fruit of the Japanese plant Illicium religiosum. Many natural plants contain shikimic acid for biosynthesis as an important intermediate. Roche pharmaceutical uses shikimic acid from star anise as a starting material for production of Tamiflu. However, isolation of star anise from natural resources has been limited. Here we report efficient and new isolation protocol of shikimic acid from Ginkgo biloba leaves utilizing an ionic liquid that dissolves cellulose. Shikimic acid was efficiently extracted and isolated from G. biloba leaves utilizing an ionic liquid 1-butyl-3-methylimidazolium chloride ([bmim]Cl), which is able to dissolve cellulose. Using the ionic liquid at 150 ℃ gave an extraction yield of 2.3% w/w for shikimic acid, which was 2.5 times higher than that for methanol at 80 ℃ (0.93% w/w). Meanwhile, an isolation protocol for obtaining shikimic acid in good yield from the IL phase using an anion-exchange resin Amberlite IRA-400 Cl form was established. The SEM micrograph of the leaves after extraction showed a significantly different morphology, with the larger features completely broken down into much smaller structures, indicating that the G. biloba leaves were much more highly dissolved in [bmim]Cl compared to in methanol The present procedure could lead to a convenient supply of shikimic acid, thus enabling production of greater amounts of the antiviral agent Tamiflu. The protocols are also likely to be applicable to other plant leaves, allowing for isolation of greater quantities of other natural products as well as unknown natural compounds.
  • 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.
  • Katagiri, M., Yoshizawa-Fujita, M., Takeoka, Y., Rikukawa, M.
    Advanced Materials Research, 409 502-507, Jan 4, 2012  
  • Hamaguchi, A., Yoshizawa-Fujita, M., Takeoka, Y., Rikukawa, M.
    Advanced Materials Research, 409 492-496, Jan 4, 2012  
  • Miru Yoshida, Yue Zhao, Masahiro Yoshizawa-Fujita, Akihiro Ohira, Yuko Takeoka, Satashi Koizumi, Msahiro Rikukawa
    ECS Transactions, 50(2) 1045-1053, 2012  Peer-reviewed
  • 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, Yoshizawa-FUJITA MASAHIRO, Yuko Takeoka, Masahiro Rikukawa
    Materials Science Forum, 706-709 1636-1641, Jan, 2012  
  • Takashi Hirahara, Masahiro Yoshizawa-Fujita, Yuko Takeoka, Masahiro Rikukawa
    Chemistry Letters, 41(9) 905-907, 2012  
    A chiral polyfluorenethiophene 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 100nm reached 0.2 at 505 nm. © 2012 The Chemical Society of Japan.
  • Ayumi Hamaguchi, Yoshizawa-FUJITA MASAHIRO, Yuko Takeoka, Masahiro Rikukawa
    Advanced Materials Research, 409 492-496, Nov, 2011  
  • Maki Katagiri, Yoshizawa-FUJITA MASAHIRO, Yuko Takeoka, Masahiro Rikukawa
    Advanced Materials Research, 409 502-507, Nov, 2011  
  • Fujita Masahiro, Rikukawa Masahiro
    Fine chemicals, 40(11) 18-23, Nov, 2011  
  • Shun Saito, Yuta Takami, Masahiro Yoshizawa-Fujita, Satoshi Yanase, Takao Oi
    PROGRESS IN NUCLEAR ENERGY, 53(7) 999-1004, Sep, 2011  
    Lithium was electrochemically inserted from a Li(+) ion containing ionic liquid into graphite or tin to observe lithium isotope effects that accompanied the insertion. While no preferential uptake of the lithium isotopes was detected with graphite, the lighter isotope, (6)Li, was preferentially fractionated into tin with the single-stage lithium isotope separation factors, S, ranging from 1.004 to 1.008 at 25 degrees C. It was speculated that a Li(+) ion was inserted into graphite together with an anionic component of the ionic liquid and, upon the reduction of the Li(+) ion to a lithium atom, the anion was released from graphite, while a Li(+) ion alone was inserted into tin. Molecular orbital calculations supported this speculation in a qualitative fashion. (C) 2011 Elsevier Ltd. All rights reserved.
  • Masahiro Yoshizawa-Fujita, Hiroyuki Ohno
    Electrochemical Aspects of Ionic Liquids: Second Edition, 403-408, Mar 2, 2011  Peer-reviewed
  • Masahiro Yoshizawa-Fujita, Hiroyuki Ohno
    Electrochemical Aspects of Ionic Liquids: Second Edition, 441-456, Mar 2, 2011  Peer-reviewed
  • Hiroyuki Ohno, Masahiro Yoshizawa-Fujita, Tomonobu Mizumo
    Electrochemical Aspects of Ionic Liquids: Second Edition, 87-93, Mar 2, 2011  Peer-reviewed
  • Masahiro Yoshizawa-Fujita, Asako Narita, Hiroyuki Ohno
    Electrochemical Aspects of Ionic Liquids: Second Edition, 301-316, Mar 2, 2011  Peer-reviewed
  • Hiroyuki Ohno, Masahiro Yoshizawa-Fujita, Wataru Ogihara
    Electrochemical Aspects of Ionic Liquids: Second Edition, 433-439, Mar 2, 2011  Peer-reviewed

Misc.

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  • 畠山歓, 藤田正博
    機能材料, 45(3) 56-64, Mar 7, 2025  InvitedLast authorCorresponding author
  • Takuto Ootahara, Kan Hatakeyama-Sato, Morgan L. Thomas, Yuko Takeoka, Masahiro Rikukawa, Masahiro Yoshizawa-Fujita
    ChemRxiv, May 13, 2024  Last authorCorresponding author
    Ionic plastic crystals (IPCs), which are soft crystals with plasticity and ionic conductivity, are expected to be applied as solid electrolytes in battery applications. Further improvement of ionic conductivity is necessary for practical use as an electrolyte for energy storage devices. Materials Informatics (MI) is a method of incorporating information science in materials development. In this research, MI is being used to develop IPCs with high ionic conductivity. By using informatics science in addition to chemical knowledge, this research can be carried out efficiently and innovatively. The synthesis of eight new compounds resulted in six of them being solid at room temperature, while two of them were in a liquid state, namely ionic liquids. We evaluated the phase transition temperatures and ionic conductivity for each compound. Notably, N-ethyl-N-methylpyrrolidinium trifluoromethyltrifluoroborate ([C2mpyr][CF3BF3]) exhibited a high ionic conductivity of 1.75×10-4 S cm-1 at 25 oC, which is one of the highest values reported among IPCs to date. The combination of an experimental and MI based approach revealed an improved understanding of the relationship between ion size and ionic conductivity for a series of pyrrolidinium-based IPCs, and it is expected that further improvements to this approach will yield greater understanding of structure-property relationships.
  • Yutaro Hayashi, Mariya Usami, Elisabeth R. D. Ito, Yuko Takeoka, Masahiro Rikukawa, Masahiro Yoshizawa-Fujita
    ChemRxiv, Feb 14, 2024  Last authorCorresponding author
    Cellulose is attracting attention for the development of environmentally friendly, carbon-neutral, sustainable materials. Cellulose derivatives with cationic groups have the potential for applications in various fields, e.g., electrolytes. However, the current situation is marked by a low degree of cationic group incorporation and a need for more efficient synthesis methods. In this study, cationic cellulose was synthesized using an epoxy derivative, 2,3-epoxypropyltrimethylammonium chloride (EPTMAC), in an aqueous pyrrolidinium hydroxide solution. Since an aqueous pyrrolidinium hydroxide solution is a strong alkaline solution, the solution not only exhibits a high cellulose solubility at room temperature but also facilitates the reaction between cellulose and the epoxy derivative. We investigated the influence of reaction time, temperature, cellulose concentration, cationic reagent concentration, and the selection of a precipitation solvent for purification on the degree of substitution (DS) value of cationic cellulose. The structure of the obtained cationic cellulose was examined using 1H NMR, 1H-1H TOCSY, 1H-13C HSQC measurements, and Fourier-transform infrared spectroscopy (FT-IR). As a result of increasing cellulose and EPTMAC concentrations, the DS value increased, reaching a maximum value of 1.9. Solubility tests indicated that the cationic cellulose with chloride counter-anions exhibited notable solubility even in ethanol when the DS values were over 1.2. Cationic cellulose with bis(trifluoromethylsulfonyl)amide (TFSA) anion synthesized with a view to battery applications was insoluble in water and exhibited a film-forming property. Thus, the solubility of cationic cellulose could be controlled by varying the anionic species.
  • Arata Matsui, Deandra Ayu Putri, Morgan L. Thomas, Yuko Takeoka, Masahiro Rikukawa, Masahiro Yoshizawa-Fujita
    ChemRxiv, Jan 17, 2024  Last authorCorresponding author
    Cellulose is one of the main components of plant cell walls, abundant on earth, and is a non-edible material that can be acquired at a low cost. Furthermore, there has been increasing interest in its use in environmentally friendly, carbon-neutral, sustainable materials. It is expected that the applications of cellulose will expand with the development of a simple processing method. Previously, it was demonstrated that cellulose can be dissolved in a non-heated, short-duration process using an aqueous pyrrolidinium hydroxide solution. In this study, we dissolved cellulose in aqueous N-butyl-N-methylpyrrolidinium hydroxide solution ([C4mpyr][OH]/H2O) and investigated the cellulose regeneration process based on changes in solubility upon application of CO2 gas. We investigated the effect of transformation of the anion chemical structure on cellulose solubility by flowing CO2 gas into [C4mpyr][OH]/H2O and conducted pH, FT-IR, and 13C NMR measurements. We observed that the changes in anion structure allowed for the modulation of cellulose solubility in [C4mpyr][OH]/H2O, thus establishing a simple and safe cellulose regeneration process. This regeneration process was also applied to enable the production of cellulose hydrogels. The hydrogel formed using this approach was revealed to be of a higher mechanical strength than that of an analogous hydrogel produced using the same dissolution solvent with addition of a cross-linker. The ability to produce cellulose-based hydrogels of different mechanical properties is expected to expand the possible applications.
  • 藤田正博
    液晶, 27(4) 240-244, Oct, 2023  InvitedCorresponding author

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