| 1. |
B. Hwang, S. Kondo, T. Kikuchi, K. Sasaki, A. Hayashi, M. Nishihara, Silicone-containing polymer blend electrolyte membranes for fuel cell applications, Journal of Applied Polymer Science
, DOI: 10.1002/app.50328, 138, 18, 50328, 2021.03. |
| 2. |
S. Feng, S. Kondo, T. Kikuchi, L. Christiani, B. Hwang, K. Sasaki, M. Nishihara, Development of a Heat-Treated PolymerPolymer Type Charge-Transfer Blend Membrane for Application in Polymer Electrolyte Fuel Cells, ACS Applied Energy Materials, 10.1021/acsaem.9b01697, 2, 8715-8723, 2019.12. |
| 3. |
Shiyan Feng, Shoichi Kondo, Takahiro Kaseyama, Taichi Nakazawa, Takamasa Kikuchi, Roman Selyanchyn, Shigenori Fujikawa, Liana Christiani, Kazunari Sasaki, Masamichi Nishihara, Characterization of polymer-polymer type charge-transfer (CT) blend membranes for fuel cell application, Data in Brief, 10.1016/j.dib.2018.02.031, 18, 22-29, 2018.06, The data presented in this article are related to polymer-polymer type charge-transfer blend membranes for fuel cell application. The visible spectra of the charge-transfer (CT) blend membranes indicated formation of CT complex in the blend membranes, and behavior of CT complex formation by polymers was clarified by Job plot of the visible spectra. The effect of fluorine for membrane property and fuel cell performance of CT blend membranes were evaluated by 19F NMR and overvoltage analysis, respectively.. |
| 4. |
Liana Christiani, Kazunari Sasaki, Masamichi Nishihara, Aliphatic SPI charge-transfer complex hybrid films for high temperature polymer electrolyte membrane fuel cells, Journal of Applied Polymer Science, 10.1002/app.46087, 135, 14, 2018.04, A new method to synthesize polymer electrolyte membranes based on charge-transfer (CT) complexes for high temperature fuel cells is investigated. Aliphatic sulfonated polyimide (SPI) CT complex hybrid films are prepared. Aliphatic units are introduced into the SPI main chain to increase the elasticity compared with aromatic SPI films. Electron-donating compounds are included to form a CT complex, resulting in improved control over mechanical strength, water uptake, and thermal stability. The resulting thermal properties of the SPI CT films are sufficient to operate at elevated temperature (up to 120 °C), and the proton conductivity is comparable to that of Nafion 115. These films are thus promising alternative membranes for high temperature polymer electrolyte fuel cell applications.. |
| 5. |
Masamichi Nishihara, Y. Terayama, T. Haji, Stephen Matthew Lyth, S. Satokawa, Hiroshige Matsumoto, Proton-conductive nano zeolite-PVA composite film as a new water-absorbing electrolyte for water electrolysis, Express Polymer Letters, 10.3144/expresspolymlett.2018.23, 12, 3, 256-264, 2018.03, In this study, organic-inorganic composite electrolyte membranes are developed for a novel water-absorbing porous electrolyte water electrolysis cell. As the materials of the composite electrolyte membrane, 80 wt% of a proton-con-ducting nano zeolite (H-MFI) as an electrolyte and 20 wt% of poly(vinyl alcohol) (PVA) as a cross-linkable matrix are used. The nano zeolite is prepared by a milling process. The nano zeolite-PVA composite membrane precursors are prepared by spraying onto a substrate, followed by cross-linking. The resulting nano zeolite-cross-linked PVA composite films are then evaluated for their properties such as proton conductivity as electrolyte membranes for the water-absorbing porous electrolyte water electrolysis cell. It is confirmed that conventional materials such as zeolites and PVA can be used for the water electrolysis as an electrolyte.. |
| 6. |
Shiyan Feng, Shoichi Kondo, Takahiro Kaseyama, Taichi Nakazawa, Takamasa Kikuchi, Roman Selyanchyn, Shigenori Fujikawa, Liana Christiani, Kazunari Sasaki, Masamichi Nishihara, Development of polymer-polymer type charge-transfer blend membranes for fuel cell application, Journal of Membrane Science, 10.1016/j.memsci.2017.11.025, 548, 223-231, 2018.02, We have prepared new charge-transfer (CT) complex polymer blend membranes (CT membranes), for use as high performance polymer electrolyte membranes (PEMs); with a simple and easy preparation method for application in PEFCs. In this study, electron-accepting sulfonated polyimide (SPI) and electron-donating polyether (PE), were used to develop polymer-polymer type CT membranes. The formation of CT complex in the obtained SPI/PE membranes was confirmed by visible spectroscopy. The use of flexible spacers in the PE and heat treatment of the CT membranes, enhanced the CT complex formation. SPI/PE CT membranes showed 1.9–2.2 times higher mechanical strength than the original SPI, while SPI/PE 0.33 CT membrane with heat treatment at 130 °C for 2 h showed 4.3 times higher mechanical strength than the original SPI. Hydrogen permeability through SPI/PE CT membranes was 4.1–5.4 times lower than Nafion 212 and 1.4–1.9 times lower than the original SPI membrane. We have prepared a thin SPI/PE CT membrane (10 µm thickness), that showed comparable OCV (0.88 V), similar resistance compared to Nafion 212 and demonstrated more than 10 h of durability in a fuel cell test; suggesting that SPI/PE thin CT membrane can be applied for PEFC application.. |
| 7. |
Yuki Terayama, Shoichi Furukawa, Munemitsu Nomura, Takamasa Haji, Masamichi Nishihara, Omar Mendoza, Yoshitsugu Sone, Hiroshige Matsumoto, Preparation of hydrophobic electrocatalyst layer and inorganic porous electrolyte layer for water absorbing porous electrolyte electrolysis cell, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2018.04.137, 2018.01, A water-absorbing porous electrolyte electrolysis cell is presented consisting of a hydrophobic gas diffusion layer (GDL), a controlled-hydrophobicity electrocatalyst layer, and a hydrophilic porous electrolyte layer. The specific character of this cell is that high-pressure water is injected directly into the porous electrolyte layer and is resisted by the electrocatalyst layer and GDL, which have strong water support force. In this study, the preparation method of the electrocatalyst layer and the porous inorganic electrolyte layer, and the evaluation of water electrolysis using the prepared layers were investigated. The optimized conditions and preparation methods of each layer of the MEA (i.e. the GDL, electrocatalyst layer, electrolyte layer) were determined. The assembly method and conditions of these three layers were also determined for fabricating MEAs for water electrolysis. The evaluation of water electrolysis tests using this MEA showed that the hydrogen evolution rate obeyed Faraday's Law in the low current density region (−2).. |
| 8. |
Yuki Terayama, Takamasa Haji, Shoichi Furukawa, Munemitsu Nomura, Masamichi Nishihara, Stephen Matthew Lyth, Yoshitsugu Sone, Hiroshige Matsumoto, Carbon black / PTFE composite hydrophobic gas diffusion layers for a water-absorbing porous electrolyte electrolysis cell, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2017.12.045, 2017.01, The characteristics of a water-absorbing porous electrolyte electrolysis cell, in which pressurized water is injected directly into the electrolyte layer, are investigated. High water support force is required for the gas diffusion layer (GDL) in this novel cell design, and therefore here we report a new type of hydrophobic GDL comprising an acetylene black (AB) and poly(tetrafluoroethylene) (PTFE) composite film. The method of preparation of the AB/PTFE slurry, film formation methods, and the AB/PTFE weight ratio were investigated and optimized. The ball-milling and transfer method were suitable for preparing uniform AB/PTFE slurry and successfully covering AB/PTFE film without any cracks on micro-porous layer coated carbon paper, respectively. An investigation about different PTFE weight ratios against AB from 0.1 to 6 showed a serious trade-off character between electrical resistance R, gas permeability V', and water support force P lim. The 1/2.5 of AB/PTFE weight ratio was most optimal, which showed to have most equivalent R (2.5 Ω cm-2), V'(136 mL atm-1 cm-2 min-1), and P lim (0.25 MPa). We also confirmed that fabricated GDL with optimal condition was worked as the blocking layer against water injected through electrolyte layer and pressurized by nitrogen gas, and as gas-permeation layer for generated hydrogen gas in water electrolysis test.. |
| 9. |
M. Okumura, Z. Noda, Junko Matsuda, Yuya Tachikawa, Masamichi Nishihara, Stephen Matthew Lyth, Akari Hayashi, Kazunari Sasaki, Correlating cathode microstructure with PEFC performance using FIB-SEM and TEM, Journal of the Electrochemical Society, 10.1149/2.0581709jes, 164, 9, F928-F934, 2017.01, The cathode electrocatalyst layers of polymer electrolyte membrane fuel cells (PEFCs) are quantitatively investigated for different ratios of Nafion ionomer. This is achieved using focused-ion-beam coupled scanning electron microscopy (FIB-SEM) to reconstruct the three-dimensional microstructure via tomography. Parameters such as the porosity and pore size distribution were calculated from this data. The distributions of Nafion ionomer, carbon support, and platinum nanoparticles were then further clarified using transmission electron microscopy (TEM). Changes in the PEFC performance (notably the I-V characteristics, the electrochemical surface area, the activation overvoltage, and the concentration overvoltage) are thus correlated to electrode microstructure.. |
| 10. |
Keigo Kitamura, Hiroyuki Honda, Shinosuke Takaki, Masamichi Nishihara, Kenneth T. Christensen, Yasuhiro Mitani, Experimental Study of Two-phase Fluid Flow in the Porous Sandstone by P-wave Velocity and Electrical Impedance Measurement, Energy Procedia, 10.1016/j.egypro.2017.03.1636, 114, 4948-4953, 2017.01, Two-phase flow is important to discuss the displacement mechanism between brine and super critical CO2 in the reservoir. The capillary number (Ca) is essential parameter to control the CO2 flow in porous sandstone. In this study, we try to estimate the effect of Ca on CO2 behavior by CO2 injection experiment. The CO2 is injected porous sandstone with changing flow rate (FR) and measure P-wave velocity (Vp) and electrical impedance (Z), simultaneously. The CO2 produces very low Ca-flow in porous sandstone. Vp indicates rapidly reduction with increasing Ca under this CO2-flow condition. On the other hand, Z shows clearly increment with increasing Ca. Both of parameters mean the increasing CO2 saturation (SCO2) with increasing Ca.. |
| 11. |
Shiyan Feng, Kazunari Sasaki, Masamichi Nishihara, Effect of Sulfonation Level on Sulfonated Aromatic Poly(ether sulfone) Membranes as Polymer Electrolyte for High-Temperature Polymer Electrolyte Membrane Fuel Cells, Macromolecular Chemistry and Physics, 10.1002/macp.201600397, 217, 24, 2692-2699, 2016.12, Sulfonated poly(ether sulfone)s (SPESs) are developed which have different sulfonation level as a polymer electrolyte membrane for high-temperature operation. The sulfonation level of SPESs is calculated by 1H NMR, and the molecular structure and crystalline structure of SPESs are evaluated by Fourier transform infrared and X-ray diffraction. SPES membranes are thermally stable up to 250 °C. SPES membranes can keep their shapes at 120 °C and 23%RH. Water uptake at 120 °C and 23%RH is 5.7–6.4 wt%, while Nafion 212 shows 2.4 wt%. Proton conductivity measurements of SPESs are carried out from 30 to 120 °C at different relative humidity. With increasing sulfonation level of SPES, proton conductivity increases in all humidity. The proton conductivity obtained from all SPESs is more than 100 mS cm–1 at 120 °C in high humidity (>90%RH), and high-sulfonation SPES shows higher conductivities than Nafion 212 at 120 °C, 20%RH. (Figure presented.).. |
| 12. |
Thomas Bayer, Benjamin V. Cunning, Roman Selyanchyn, Masamichi Nishihara, Shigenori Fujikawa, Kazunari Sasaki, Stephen Matthew Lyth, High temperature proton conduction in nanocellulose membranes
Paper fuel cells, Chemistry of Materials, 10.1021/acs.chemmater.6b01990, 28, 13, 4805-4814, 2016.07, Polymer electrolyte membrane fuel cells are an efficient and clean alternative power source, but high cost impedes widespread commercialization. The fuel cell membrane, e.g., Nafion, contributes significantly to this cost, and therefore, novel alternatives are required. Temperature is also an important factor; high temperature operation leads to faster reaction kinetics, lower electrocatalyst loading, and improved water management, thereby further reducing cost. However, higher temperature puts greater demands on the membrane. Conductivity is related strongly to humidification, and therefore, this generally decreases above 100 °C. Nanocellulose membranes for fuel cells in which the proton conductivity increases up to 120 °C are reported here for the first time. The hydrogen barrier properties are far superior to conventional ionomer membranes. Fuel cells with nanocellulose membranes are successfully operated at 80 °C. Additionally, these membranes are environmentally friendly and biodegradable.. |
| 13. |
Thomas Bayer, Benjamin V. Cunning, Roman Selyanchyn, Takeshi Daio, Masamichi Nishihara, Shigenori Fujikawa, Kazunari Sasaki, Stephen Matthew Lyth, Alkaline anion exchange membranes based on KOH-treated multilayer graphene oxide, Journal of Membrane Science, 10.1016/j.memsci.2016.02.017, 508, 51-61, 2016.06, A novel class of alkaline anion exchange membrane (AAEM) is presented, in the form of KOH-modified multilayer graphene oxide paper (GOKOH). Such membranes can be easily fabricated at large scale with varying thickness using conventional filtration techniques, and have high tensile strength (24.5 MPa). However, a large degree of swelling is observed. SEM investigations show that the morphology of GO changes after KOH-treatment, whilst XPS measurements and XRD analysis confirm successful chemical modification. The hydrogen gas permeability is several orders of magnitude lower than conventional polymer-based ionomer membranes. The maximum anion conductivity is 6.1 mS/cm at 70 °C, and the dominant charge carrier is confirmed to be OH- by utilization of anion and proton-conducting blocking layers. The ion exchange capacity is 6.1 mmol/g, measured by titration. A water-mediated reverse Grotthuss-like mechanism is proposed as the main diffusion mode of OH- ions. Finally, a prototype AAEM fuel cell is fabricated using a GOKOH membrane, confirming the applicability to real systems.. |
| 14. |
Liana Christiani, Kazunari Sasaki, Masamichi Nishihara, Development of Charge-Transfer Complex Hybrid Films as Polymer Electrolyte Membrane for High Temperature PEFC Operation, Macromolecular Chemistry and Physics, 10.1002/macp.201500320, 217, 5, 654-663, 2016.03, Novel charge-transfer (CT) complex hybrid films for high temperature polymer electrolyte fuel cell (PEFC) application based on sulfonated polyimide (SPI) with hydrophobic unit (4,4 (sulfonylbis(4,1-phenylene)bis(oxy)dianyline (BAPPS)) are synthesized and characterized. In this study, property changes of the polymer electrolytes prepared by a unique CT complex postmodification process are evaluated. The effect of the CT complex formation in the obtained films on the properties of the polymer films is evaluated, because the CT complex can work as a binder between SPIs. Water uptake of the CT complex hybrid films shows a lower value than that of the original SPI film. The CT complex hybrid films also exhibit comparable proton conductivity to Nafion 115 under high-temperature operational conditions (100-120 °C). These results suggest that the CT complex hybrid films developed are promising alternatives for high temperature PEFC application.. |
| 15. |
M. Okumura, Z. Noda, Junko Matsuda, Masamichi Nishihara, Akari Hayashi, Kazunari Sasaki, An FIB-SEM study on correlations between PEFC electrocatalyst microstructure and cell performance, Symposium on Polymer Electrolyte Fuel Cells 16, PEFC 2016 - PRiME 2016/230th ECS Meeting
Polymer Electrolyte Fuel Cells 16, PEFC 16, 10.1149/07514.0347ecst, 75, 347-354, 2016, The electrocatalyst layer of the polymer electrolyte fuel cells (PEFCs) has a complicated porous microstructure. Since the porous nanostructure allows the transport of reactant gas, water vapor, protons, and electrons, cell performance depends strongly on their 3D microstructure. Understanding the correlations between the electrocatalyst microstructure and the cell performance is therefore essential for further improving the PEFC electrochemical performance. In this study, these correlations are quantitatively considered by using the focused-ion-beam coupled scanning electron microscopy (FIB-SEM) technique. In particular, while it is difficult to distinguish between the solid and the pore of the electrocatalyst layer due to the complicated porous nanostructure, this problem has been solved by the auto-image thresholding technique.. |
| 16. |
Keiichi Imato, Takeshi Kanehara, Tomoyuki Ohishi, Masamichi Nishihara, Hirofumi Yajima, Masayoshi Ito, Atsushi Takahara, Hideyuki Otsuka, Mechanochromic Dynamic Covalent Elastomers
Quantitative Stress Evaluation and Autonomous Recovery, ACS Macro Letters, 10.1021/acsmacrolett.5b00717, 4, 11, 1307-1311, 2015.11, Stress evaluation in polymeric materials is important in order to not only spot danger in them before serious failure, but also precisely interpret the destructive mechanism, which can improve the lifetime and durability of polymeric materials. Here, we are able to visualize stress by color changes, as well as quantitatively estimate the stress in situ, in segmented polyurethane elastomers with diarylbibenzofuranone-based dynamic covalent mechanophores. We prepared films of the segmented polyurethanes, in which the mechanophores were incorporated in the soft segments, and efficiently activated them by mechanical force. Cleavage of the mechanophores during uniaxial elongation and their recovery after the removal of the stress were quantitatively evaluated by in situ electron paramagnetic resonance measurements, accompanied by drastic color changes.. |
| 17. |
Liana Christiani, Sandra Hilaire, Kazunari Sasaki, Masamichi Nishihara, Erratum
Evaluation of proton conductivity of sulfonated polyimide/dihydroxy naphthalene charge-transfer complex hybrid membranes, Journal of Polymer Science, Part A: Polymer Chemistry, 10.1002/pola.27419, 53, 6, 828, 2015.09. |
| 18. |
Keiichi Imato, Atsushi Irie, Takahiro Kosuge, Tomoyuki Ohishi, Masamichi Nishihara, Atsushi Takahara, Hideyuki Otsuka, Mechanophores with a reversible radical system and freezing-induced mechanochemistry in polymer solutions and gels, Angewandte Chemie - International Edition, 10.1002/anie.201412413, 54, 21, 6168-6172, 2015.05, Visualization and quantitative evaluation of covalent bond scission in polymeric materials are highly important for understanding failure, fatigue, and deterioration mechanisms and improving the lifetime, durability, toughness, and reliability of the materials. The diarylbibenzofuranone-based mechanophore radical system enabled, through electron paramagnetic resonance spectroscopy, in situ quantitative evaluation of scission of the mechanophores and estimation of mechanical energy induced along polymer chains by external forces. The coagulation of polymer solutions by freezing probably generated force but did not cleave the mechanophores. On the other hand, cross-linking led to efficient propagation of the force of more than 80 kJ?mol-1 to some mechanophores, resulting their cleavage and generation of colored stable radicals. This mechanoprobe concept has the potential to elucidate other debated issues in the polymer field as well.. |
| 19. |
Kazunari Sasaki, Shunsuke Taniguchi, Yusuke Shiratori, Akari Hayashi, T. Oshima, Masamichi Nishihara, Yuya Tachikawa, T. Daio, T. Kawabata, M. Fujita, A. Zaitsu, Smart fuel cell demonstration project
A challenge to realize SOFC-powered campus, 14th International Symposium on Solid Oxide Fuel Cells, SOFC 2015; held as part of the Electrochemical Society, ECS Conference on Electrochemical Energy Conversion and Storage
Solid Oxide Fuel Cells 14, SOFC 2015, 10.1149/06801.0171ecst, 68, 171-178, 2015, This paper introduces a challenge to realize a fuel-cell-powered campus at Kyushu University where SOFC technology plays a major role. The Smart Fuel Cell Demonstration Project, supported by Cabinet Secretariat/Office of Japan, enables us to install one 250 kW SOFC power generation system, other SOFC units, and the world-first university-owned fuel cell vehicle to which renewable hydrogen gas is supplied from the hydrogen refueling station on the campus using electrolyzers. The experience in this demonstrative project is described along with related efforts to accelerate industry-academia collaborations and fundamental scientific studies using advanced analytical facilities.. |
| 20. |
T. Bayer, S. R. Bishop, Masamichi Nishihara, Kazunari Sasaki, Stephen Matthew Lyth, Characterization of a graphene oxide membrane fuel cell, Journal of Power Sources, 10.1016/j.jpowsour.2014.08.071, 272, 239-247, 2014.12, The electrical, mechanical, and compositional characterization of a graphene oxide membrane is presented, and its application as an electrolyte material in a polymer electrolyte membrane fuel cell is explored. Self-supporting graphene oxide membranes were prepared by a simple vacuum filtration process and, for the first time, characterized as the electrolyte in a fuel cell operating in an elevated temperature range (30-80 °C), with a maximum power density of ∼34 mW cm-2, approaching that of a Nafion electrolyte based cell prepared and tested under similar conditions. Evidence for partial membrane reduction was found at higher temperatures and is believed to originate from more easily released, higher energy oxide groups, such as epoxides. We also discuss the morphology, the mechanical properties, chemical composition, and electrical conductivity of the graphene oxide membranes, with comparisons made to conventional Nafion membranes.. |
| 21. |
Liana Christiani, Sandra Hilaire, Kazunari Sasaki, Masamichi Nishihara, Evaluation of proton conductivity of sulfonated polyimide/dihydroxy naphthalene charge-transfer complex hybrid membranes, Journal of Polymer Science, Part A: Polymer Chemistry, 10.1002/pola.27343, 52, 20, 2991-2997, 2014.10, Sulfonated polyimide (SPI)/dihydroxynaphthalene (DHN) charge-transfer (CT) complex hybrid films were investigated as possible alternative for polymer electrolyte membranes in polymer electrolyte fuel cells. SPI/DHN CT complex hybrid films include CT complexes, which might work as electronic conductors, and sulfonic acid units, which could work as proton conductors. Therefore, the origin of the conductivity of SPI/DHN complex hybrid films was evaluated by four-probe impedance measurements in the through-plane direction of the films. The obtained conductivity of the CT complex hybrid films increased with the increase of ion exchange capacity of the CT films and the decrease of CT complex concentration in the films. These results indicated that proton transfer dominantly occurred in the CT complex hybrid films. Proton conductivity of the CT complex hybrid films consisting of 2,6- or 1,5-DHN showed the similar values, although the molecular geometries of the CT complex were different. The activation energy values for proton conductivity in the CT films were approximately the same as that of Nafion 212. Water uptake (WU) results were also conducted and suggest that CT complex formation could control the degree of WU of the films and prevent dissolution of SPI.. |
| 22. |
Keiichi Imato, Tomoyuki Ohishi, Masamichi Nishihara, Atsushi Takahara, Hideyuki Otsuka, Network reorganization of dynamic covalent polymer gels with exchangeable diarylbibenzofuranone at ambient temperature, Journal of the American Chemical Society, 10.1021/ja5065075, 136, 33, 11839-11845, 2014.08, Reversible bonds and interactions have been utilized to build stimuli-responsive and reorganizable polymer networks that show recyclability, plasticity, and self-healing. In addition, reorganization of polymer gels at ambient temperature, such as room or body temperature, is expected to lead to several biomedical applications. Although these stimuli-responsive properties originate from the reorganization of the polymer networks, not such microscopic structural changes but instead only macroscopic properties have been the focus of previous work. In the present work, the reorganization of gel networks with diarylbibenzofuranone (DABBF)-based dynamic covalent linkages in response to the ambient temperature was systematically investigated from the perspective of both macroscopic and microscopic changes. The gels continued to swell in suitable solvents above room temperature but attained equilibrium swelling in nonsolvents or below room temperature because of the equilibrium of DABBF linkages, as supported by electron paramagnetic resonance measurements. Small-angle X-ray scattering measurements revealed the mesh sizes of the gels to be expanded and the network structures reorganized under control at ambient temperature.. |
| 23. |
Masamichi Nishihara, Liana Christiani, Aleksandar Tsekov Staykov, Kazunari Sasaki, Experimental and theoretical study of charge-transfer complex hybrid polyimide membranes, Journal of Polymer Science, Part B: Polymer Physics, 10.1002/polb.23411, 52, 4, 293-298, 2014.02, The nanostructure of sulfonated polyimide (SPI)/dihydroxynaphthalene (DHN) derivative charge-transfer (CT) complex hybrid films, which are noble alternative polymer electrolyte membranes (PEMs), is determined by a combined visible spectroscopy/quantum mechanical approach. From the visible spectra of SPI/2,6-dihydroxynaphthalene (2,6-DHN) and 1,5-dihydroxynaphthalene (1,5-DHN) CT complex hybrid films, it is confirmed that these films have different maximum wavelength, although difference of the molecular structure is small. From the calculation based on the experimental result, SPI and DHNs form multiple interactions consisting of not only CT interaction, but also hydrogen bonding in multilayered structures. CT interaction between SPI and DHN defines the DHN position in the SPI matrix, with DHN sitting in the cavity formed between SPIs. The molecular structure of the CT films derived from the multiple and complex interactions can recognize small differences in the structural isomers and bring changes of the optical property. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 293-298 Many sulfonated polyimides (SPIs) have been actively investigated as polymer electrolyte membranes (PEMs) for polymer electrolyte fuel cells (PEFCs) as alternatives to Nafion. In this work, the molecular geometry of (SPI)/dihydroxynaphthalene (DHN) derivative charge-transfer complex hybrid films is determined by a combined visible spectroscopy/quantum mechanical approach. From the experimental and calculated results for SPI/2,6-DHN and 1,5-DHN, while the structural difference is small, different molecular geometries and optical properties can be seen.. |
| 24. |
T. Bayer, S. R. Bishop, Masamichi Nishihara, Kazunari Sasaki, Stephen Matthew Lyth, Graphene oxide membrane fuel cells
Utilizing of a new class of ionic conductor, 14th Polymer Electrolyte Fuel Cell Symposium, PEFC 2014 - 226th ECS Meeting
Polymer Electrolyte Fuel Cells 14, 10.1149/06403.0441ecst, 64, 441-448, 2014, The characterization and application of graphene oxide membranes as fuel cell electrolytes is explored and presented. Morphology, chemical composition, mechanical and electrochemical properties of vacuum-filtration prepared graphene oxide membranes and their performance as fuel cell electrolytes are discussed. Our graphene oxide membrane fuel cell (GOMFC) showed a maximum power density of ∼ 6 mW/cm2 at 30 °C. Power density exhibited a decrease with increasing temperature and operation time, possibly due to partial loss of oxygen through reduction, and a resulting decrease in water-mediated proton transport.. |
| 25. |
Ryohei Watari, Masamichi Nishihara, Hiroo Tajiri, Hideyuki Otsuka, Atsushi Takahara, Preparation of novel polyimide hybrid materials by multi-layered charge-transfer complex formation, Polymer Journal, 10.1038/pj.2012.222, 45, 8, 839-844, 2013.08, A versatile method for the post-modification of sulfonated polyimides by charge-transfer (CT) complex formation between electron-deficient naphthalenediimide units in polyimide and electron-rich dihydroxynaphthalene was developed. CT complex hybrid films whose physicochemical properties, such as mechanical strength, differed from those of the original polyimide films were successfully fabricated.. |
| 26. |
Masamichi Nishihara, Keiichi Imato, Atsushi Irie, Takeshi Kanehara, Arihiro Kano, Atsushi Maruyama, Atsushi Takahara, Hideyuki Otsuka, Reversibly crosslinked polymeric micelles formed by autonomously exchangeable dynamic covalent bonds, Chemistry Letters, 10.1246/cl.121289, 42, 4, 377-379, 2013, We report the preparation of amphiphilic block copolymer micelles with dynamic covalent bonds as autonomously exchangeable crosslinkers with high tolerance against oxygen. Diarylbibenzofuranone (DABBF) was employed as a crosslinker owing to its durability to oxygen and autonomous exchangeability at ambient temperature. It was confirmed that the amphiphilic block copolymer containing the DABBF unit has the capability to form micelles and can form a crosslinking with an exchangeable structure in the presence of oxygen.. |
| 27. |
Keiichi Imato, Masamichi Nishihara, Takeshi Kanehara, Yoshifumi Amamoto, Atsushi Takahara, Hideyuki Otsuka, Self-healing of chemical gels cross-linked by diarylbibenzofuranone-based trigger-free dynamic covalent bonds at room temperature, Angewandte Chemie - International Edition, 10.1002/anie.201104069, 51, 5, 1138-1142, 2012.01, Linked: Polymers cross-linked with diarylbibenzofuranone units have been prepared by polyaddition. The exchange of bonds of the gels and their macroscopic self-healing were accomplished under air at room temperature in the dark. The macroscopic fusion of completely separated parts was successful (see picture).. |
| 28. |
Kouichi Shiraishi, Reiko Endoh, Hiroshi Furuhata, Masamichi Nishihara, Ryo Suzuki, Kazuo Maruyama, Yusuke Oda, Jun Ichiro Jo, Yasuhiko Tabata, Jun Yamamoto, Masayuki Yokoyama, A facile preparation method of a PFC-containing nano-sized emulsion for theranostics of solid tumors, International Journal of Pharmaceutics, 10.1016/j.ijpharm.2011.10.006, 421, 2, 379-387, 2011.12, Theranostics means a therapy conducted in a diagnosis-guided manner. For theranostics of solid tumors by means of ultrasound, we designed a nano-sized emulsion containing perfluoropentane (PFC5). This emulsion can be delivered into tumor tissues through the tumor vasculatures owing to its nano-size, and the emulsion is transformed into a micron-sized bubble upon sonication through phase transition of PFC5. The micron-sized bubbles can more efficiently absorb ultrasonic energy for better diagnostic images and can exhibit more efficient ultrasound-driven therapeutic effects than nano-sized bubbles. For more efficient tumor delivery, smaller size is preferable, yet the preparation of a smaller emulsion is technically more difficult. In this paper, we used a bath-type sonicator to successfully obtain small PFC5-containing emulsions in a diameter of ca. 200 nm. Additionally, we prepared these small emulsions at 40 °C, which is above the boiling temperature of PFC5. Accordingly, we succeeded in obtaining very small nano-emulsions for theranostics through a very facile method.. |
| 29. |
Takahiro Yano, Weng On Yah, Hiroki Yamaguchi, Yuki Terayama, Masamichi Nishihara, Motoyasu Kobayashi, Atsushi Takahara, Precise control of surface physicochemical properties for electrospun fiber mats by surface-initiated radical polymerization, Polymer Journal, 10.1038/pj.2011.80, 43, 10, 838-848, 2011.10, Non-woven fiber mats were fabricated with the electrospinning method using poly(methyl methacrylate)-co-poly(2-(2-bromoisobutyryloxy)ethyl methacrylate) in various solvents. The surface morphology of the electrospun fibers depended on the solvent vapor pressure and polymer concentration. Surface-initiated atom transfer radical polymerization (ATRP) with 3-(N-2-methacryloyloxyethyl-N,N- dimethyl) ammonatopropanesulfonate), 2-hydroxyethyl methacrylate or 2-(perfluorooctyl)ethyl acrylate generated surface-grafted polymers, as determined by X-ray photoelectron spectroscopy. Scanning electron microscopic observation revealed that the apparent fiber morphology did not change upon modification. The atomic force microscopic images of the grafted fiber cross-sections indicated that monomers and solvents penetrated slightly into the fibers and polymerization occurred at both internal and external initiation sites. Physicochemical properties, such as contact angle, hydrophobicity and hydrophilicity, and wettability, could be altered by the proper selection of substrates (spin-coated flat films or the variously prepared non-woven fiber mats). We have successfully prepared hydrophilic and hydrophobic fiber surfaces by a combination of the electrospinning protocol and surface-initiated ATRP.. |
| 30. |
Jing Su, Yoshifumi Amamoto, Masamichi Nishihara, Atsushi Takahara, Hideyuki Otsuka, Reversible cross-linking of hydrophilic dynamic covalent polymers with radically exchangeable alkoxyamines in aqueous media, Polymer Chemistry, 10.1039/c1py00176k, 2, 9, 2021-2026, 2011.09, Reversible cross-linking of alkoxyamine-containing hydrophilic dynamic covalent polymers in aqueous media has been accomplished. Water-soluble polymers with alkoxyamine units in the side chains were synthesized by radical copolymerization of 2-(dimethylamino)ethyl methacrylate and methacrylic esters with alkoxyamine units, and subsequent protonation of dimethylaminoethyl groups by hydrochloric acid. By heating the polymers in water at 100 °C in a closed system, hydrogels were formed by radical exchange reactions. Because the radical reactions are tolerant of water, the exchange reactions of alkoxyamine units in the side chain caused the cross-linking reaction even in aqueous media. Cross-linking behaviors depended on the amounts of alkoxyamine units in the polymers and the reaction concentrations. A de-cross-linking reaction was also accomplished by radical exchange reaction between the cross-linked polymer and added hydrophilic alkoxyamine compound. This dynamic cross-linking nature in aqueous media provides a foundation for a wide range of polymer reactions, and it can be applied to environmentally benign dynamic materials.. |
| 31. |
Michiko Yokosawa, Yukihiko Sonoda, Shin ichiro Sugiyama, Ryuta Saito, Yoji Yamashita, Masamichi Nishihara, Taku Satoh, Toshihiro Kumabe, Masayuki Yokoyama, Teiji Tominaga, Convection-enhanced delivery of a synthetic retinoid Am80, loaded into polymeric micelles, prolongs the survival of rats bearing intracranial glioblastoma xenografts, Tohoku Journal of Experimental Medicine, 10.1620/tjem.221.257, 221, 4, 257-264, 2010.07, Prognosis for the patients with glioblastoma, the most common malignant brain tumor, remains dismal. A major barrier to progress in treatment of glioblastoma is the relative inaccessibility of tumors to chemotherapeutic agents. Convection-enhanced delivery (CED) is a direct intracranial drug infusion technique to deliver chemotherapeutic agents to the central nervous system, circumventing the blood-brain barrier and reducing systemic side effects. CED can provide wider distribution of infused agents compared to simple diffusion. We have reported that CED of a polymeric micelle carrier system could yield a clinically relevant distribution of encapsulated agents in the rat brain. Our aim was to evaluate the efficacy of CED of polymeric micellar Am80, a synthetic agonist with high affinity to nuclear retinoic acid receptor, in a rat model of glioblastoma xenografts. We also used systemic administration of temozolomide, a DNA-alkylating agent, which has been established as the standard of care for newly diagnosed malignant glioma. U87MG human glioma cells were injected into the cerebral hemisphere of nude rats. Rats bearing U87MG xenografts were treated with CED of micellar Am80 (2.4 mg/m2) on day 7 after tumor implantation. Temozolomide (200 mg/m2/day) was intraperitoneally administered daily for 5 days, starting on day 7 after tumor implantation. CED of micellar Am80 provided significantly longer survival than the control. The combination of CED of micellar Am80 and systemic administration of temozolomide provided significantly longer survival than single treatment. In conclusion, temozolomide combined with CED of micellar Am80 may be a promising method for the treatment of malignant gliomas.. |
| 32. |
Katsuyoshi Hori, Masamichi Nishihara, Kouichi Shiraishi, Masayuki Yokoyama, The combretastatin derivative (Cderiv), a vascular disrupting agent, enables polymeric nanomicelles to accumulate in microtumors, Journal of Pharmaceutical Sciences, 10.1002/jps.22038, 99, 6, 2914-2925, 2010.01, A previous study found almost no leakage of polymeric nanomicelles from vessels in microtumors. If such vessels become leaky, sufficient nanomedicines may be delivered to microtumors and large tumors. To create leaky vessels, a combretastatin derivative (Cderiv), a vascular disrupting agent, was used. Via vital microscopy with fluorescein isothiocyanate (FITC)-labeled nanomicelles, the effect of Cderiv pretreatment on changes in micelle extravasation was investigated. Whether such treatment would prolong microtumor retention of micelles was also examined. FITC-albumin was used for comparison. The degree of extravasation from intact vessels in microtumors (rat sarcoma LY80) was extremely low and comparable to that from normal vessels. Cderiv pretreatment (1 or 3 days before administration of FITC-labeled compounds) markedly enhanced extravasation of such nanomicelles and albumin from vessels that survived treatment and had restored blood flow. A high concentration of extravasated macromolecules remained even 24 h later in tissue areas whose microcirculatory function had collapsed. Tumors receiving 10 Gy irradiation 3 days before the macromolecules evidenced gradual removal of extravasated macromolecules, which did not accumulate in those areas, despite extravasation from tumor vessels. Our results strongly suggest that pretreatment with Cderiv is quite effective for maintaining microtumor concentrations of nanomicelles and albumin associated with anticancer or diagnostic drugs.. |
| 33. |
Katsuyoshi Hori, Masamichi Nishihara, Masayuki Yokoyama, Vital microscopic analysis of polymeric micelle extravasation from tumor vessels
Macromolecular delivery according to tumor vascular growth stage, Journal of Pharmaceutical Sciences, 10.1002/jps.21848, 99, 1, 549-562, 2010.01, Particles larger than a specific size have been thought to extravasate from tumor vessels but not from normal vessels. Therefore, various nanoparticles incorporating anticancer drugs have been developed to realize selective drug delivery to solid tumors. However, it is not yet clear whether nanoparticles extravasate readily from all tumor vessels including vessels of microtumors. To answer this question, we synthesized new polymeric micelles labeled with fluorescein isothiocyanate (FITC) and injected them into the tail vein of rats with implanted skinfold transparent chambers. We also analyzed, by means of time-lapse vital microscopy with image analysis, extravasation of FITC micelles from tumor vessels at different stages of growth of Yoshida ascites sarcoma LY80. Polymeric micelles readily leaked from vessels at the interface between normal and tumor tissues and those at the interface between tumor tissues and necrotic areas. The micelles showed negligible extravasation, however, from the vascular network of microtumors less than 1mm in diameter and did not accumulate in the microtumor. Our results suggest that we must develop a novel therapeutic strategy that can deliver sufficient nanomedicine to microtumors.. |
| 34. |
Takahiro Yano, Weng On Yah, Hiroki Yamaguchi, Yuki Terayama, Masamichi Nishihara, Motoyasu Kobayashi, Atsushi Takahara, Preparation and surface characterization of surface-modified electrospun poly(methyl methacrylate) copolymer nanofibers, Chemistry Letters, 10.1246/cl.2010.1110, 39, 10, 1110-1111, 2010, We developed a surface modification of electrospun nonwoven nanofiber mat by surface-initiated atom transfer radical polymerization (ATRP). Nanofibers of poly(methyl methacryIate)-co-poly[2-(2-bromoisobutyryloxy)ethyl methacrylate] were prepared by electrospinning to form a nonwoven nanofiber mat containing bromoalkyl groups, which initiated ATRP of 3-[dimethyl(methacryloyloxyethyl) ammonio]propanesulfonate (DMAPS) and 2-(perfluorooctyl)ethyl acrylate (FA-C 8), respectively, without deformation of nanofiber structure. The surface of the obtained electrospun nonwoven nanofiber mat was characterized by XPS, SEM, AFM, and contact angle measurement before and after surface modification.. |
| 35. |
T. Mashimo, M. Ichikawa, E. Omurzak, Masamichi Nishihara, H. Ihara, Graded oxide glasses in binary systems (Si-Ti, Si-V, and Si-Zr) prepared by the sol -gel and centrifugal process, Chemistry of Materials, 10.1021/cm801864g, 21, 12, 2339-2343, 2009.06, Graded oxide glasses in binary oxide systems (Si-Ti, Si-V, and Si-Zr) had been prepared by means of a sol -gel method combined with centrifugal processing. In the Si-Ti and Si-V oxide systems, the graded oxide glasses, whose composition continuously changed with dimension in molecular scale, were prepared. The FT-IR analysis showed that infrared absorption peaks of Si-O-Si stretching and bending shifted, and Ti-O-Si or V-O-Si bands appeared with increasing the concentration of Ti or V, respectively. In the Si-Zr oxide system, the graded oxide glass in which the ZrO 2 nanocrystals appeared in the high gravity region was prepared.. |
| 36. |
Takanori Kawaguchi, Takashi Honda, Masamichi Nishihara, Tatsuhiro Yamamoto, Masayuki Yokoyama, Histological study on side effects and tumor targeting of a block copolymer micelle on rats, Journal of Controlled Release, 10.1016/j.jconrel.2009.02.011, 136, 3, 240-246, 2009.06, Histological examinations were performed with polymeric micelle-injected rats for evaluations of possible toxicities of polymeric micelle carriers. Weight of major organs as well as body weight of rats was measured after multiple intravenous injections of polymeric micelles forming from poly(ethylene glycol)-b-poly(aspartate) block copolymer. No pathological toxic side effects were observed at two different doses, followed only by activation of the mononuclear phagocyte system (MPS) in the spleen, liver, lung, bone marrow, and lymph node. This finding confirms the absence of - or the very low level of - in vivo toxicity of the polymeric micelle carriers that were reported in previous animal experiments and clinical results. Then, immunohistochemical analyses with a biotinylated polymeric micelle confirmed specific accumulation of the micelle in the MPS. The immunohistochemical analyses also revealed, first, very rapid and specific accumulation of the micelle in the vasculatures of tumor capsule of rat ascites hepatoma AH109A, and second, the micelle's scanty infiltration into tumor parenchyma. This finding suggests a unique tumor-accumulation mechanism that is very different from simple EPR effect-based tumor targeting.. |
| 37. |
Tomoo Inoue, Yoji Yamashita, Masamichi Nishihara, Shinichiro Sugiyama, Yukihiko Sonoda, Toshihiro Kumabe, Masayuki Yokoyama, Teiji Tominaga, Therapeutic effcacy of a Polymeric micellar doxorubicin infused by Convection-enhanced delivery against intracranial 9L brain tumor models, Neuro-Oncology, 10.1215/15228517-2008-068, 11, 2, 151-157, 2009.04, Convection-enhanced delivery (CED) with various drug carrier systems has recently emerged as a novel chemotherapeutic method to overcome the problems of current chemotherapies against brain tumors. Polymeric micelle systems have exhibited dramatically higher in vivo antitumor activity in systemic administration. This study investigated the effectiveness of CED with polymeric micellar doxorubicin (DOX) in a 9L syngeneic rat model. Distribution, toxicity, and effcacy of free, liposomal, and micellar DOX infused by CED were evaluated. Micellar DOX achieved much wider distribution in brain tumor tissue and surrounding normal brain tissue than free DOX. Tissue toxicity increased at higher doses, but rats treated with micellar DOX showed no abnormal neurological symptoms at any dose tested (0.1-1.0 mg/ml). Micellar DOX infused by CED resulted in prolonged median survival (36 days) compared with free DOX (19.6 days; p 5 0.0173) and liposomal DOX (16.6 days; p 5 0.0007) at the same dose (0.2 mg/ml). This study indicates the potential of CED with the polymeric micelle drug carrier system for the treatment of brain tumors. Neuro-Oncology 11, 151-157, 2009 (Posted to Neuro- Oncology [serial online], Doc. D08-00039, August 28, 2008. URL http://neuro-oncology.dukejournals.org;. |
| 38. |
Masamichi Nishihara, Kenji Imai, Masayuki Yokoyama, Preparation of perfluorocarbon/fluoroalkyl polymer nanodroplets for cancer-targeted ultrasound contrast agents, Chemistry Letters, 10.1246/cl.2009.556, 38, 6, 556-557, 2009, Perfluorocarbon (PFC) nanodroplets formed from PEG-bpoly(fluoroheptyl aspartate) were developed for a cancer-targeted ultrasound (US) contrast agent. 10% esterifed fluoroalkyl polymer (F10) was the optimal composition for PFC solubilization in aqueous solution. PFC/F10 nanodroplets showed echogenicity with US irradiation, and long-term stability of PFC nanodroplets at 4 °C was confirmed.. |
| 39. |
Hiroyuki Koide, Tomohiro Asai, Kentaro Hatanaka, Takeo Urakami, Takayuki Ishii, Eriya Kenjo, Masamichi Nishihara, Masayuki Yokoyama, Tatsuhiro Ishida, Hiroshi Kiwada, Naoto Oku, Particle size-dependent triggering of accelerated blood clearance phenomenon, International Journal of Pharmaceutics, 10.1016/j.ijpharm.2008.06.004, 362, 1-2, 197-200, 2008.10, A repeat-injection of polyethylene glycol-modified liposomes (PEGylated liposomes) causes a rapid clearance of them from the blood circulation in certain cases that is referred to as the accelerated blood clearance (ABC) phenomenon. In the present study, we examined whether polymeric micelles trigger ABC phenomenon or not. As a preconditioning treatment, polymeric micelles (9.7, 31.5, or 50.2 nm in diameter) or PEGylated liposomes (119, 261 or 795 nm) were preadministered into BALB/c mice. Three days after the preadministration [3H]-labeled PEGylated liposomes (127 nm) as a test dose were administered into the mice to determine the biodistribution of PEGylated liposomes. At 24 h after the test dose was given, accelerated clearance of PEGylated liposomes from the bloodstream and significant accumulation in the liver was observed in the mice preadministered with 50.2-795 nm nanoassemblies (PEGylated liposomes or polymeric micelles). In contrast, such phenomenon was not observed with 9.7-31.5 nm polymeric micelles. The enhanced blood clearance and hepatic uptake of the test dose (ABC phenomenon) were related to the size of triggering nanoassemblies. Our study provides important information for developing both drug and gene delivery systems by means of nanocarriers.. |
| 40. |
Hirotaka Ihara, Yasuyuki Abe, Akihiro Miyamoto, Masamichi Nishihara, Makoto Takafuji, Masao Ono, Satoru Okayasu, Tsutomu Mashimo, Chemistry in mega-gravity
Preparation of molecular-scaled graded materials from radical copolymerization, Chemistry Letters, 10.1246/cl.2008.200, 37, 2, 200-201, 2008.02, The molecular-graded structures have been realized through direct copolymerization of halogenated styrene and 2-ethylhexyl methacrylate under ultra-strong gravitational field. The graded structures were clearly confirmed by EPMA and NMR spectroscopy.. |
| 41. |
Masamichi Nishihara, Yoshihiko Murakami, Takashi Shinoda, Jun Yamamoto, Masayuki Yokoyama, Synthesis and characterization of a temperature-responsive amphiphilic block copolymer containing a liquid crystalline unit, Chemistry Letters, 10.1246/cl.2008.1214, 37, 12, 1214-1215, 2008, To create a stimuli-responsive micelle, we synthesized a novel temperature-responsive amphiphilic block copolymer, poly(ethylene glycol)-block-poly{6-[4-(4-pyridylazo)phenoxy]-hexyl methacrylate} [PEG-b-P(AzoPyl)], by undertaking the RAFT polymerization of an AzoPyl monomer with a PEG mac-ro-RAFT reagent. This block copolymer possesses a liquid crystalline unit derived from a hydrophobic AzoPyl/carboxylic acid complex. The PEG-b-P(AzoPyl/decanoic acid (C 9COOH)) complex formed a micelle structure (weight-average diameter = 68 nm). DSC results confirmed that the PEG-b-P(AzoPyl/C 9COOH) micellar solution exhibited thermodynamic phase-transition behavior.. |
| 42. |
Tomohiro Miyatake, Masamichi Nishihara, Stefan Matile, A cost-effective method for the optical transduction of chemical reactions. Application to hyaluronidase inhibitor screening with polyarginine-counteranion complexes in lipid bilayers, Journal of the American Chemical Society, 10.1021/ja064732o, 128, 38, 12420-12421, 2006.09, We report the systematic elaboration of a cost-effective, interference-minimized assay for the label-free optical transduction of chemical reactions. Recently, we have found that certain complexes formed by arginine-rich cell-penetrating peptides (CPPs) and amphiphilic counteranions can act as synergistic anion carriers in lipid bilayer membranes. Application of this discovery to rapid and reversible cytosolic CPP delivery has been described (Futaki, S.; et al. ACS Chem. Biol. 2006, 1, 299). Here, we report the complementary use of polyarginine (pR)-counteranion complexes as general optical transducers of chemical reactions. Counterion screening revealed dodecyl phosphate (DP) as an ideal pR activator. Carboxyfluorescein (CF)-loaded vesicles with a shelf life of 3.5 years served best for the detection of fluorogenic CF release by pR-DP complexes with the naked eye. Inactivation of pR-DP complexes by counterion exchange with hyaluronan (HA) caused no CF emission, while HA removal by hyaluronidase (HAase) did. pR-DP complexes were further compatible with the optical detection of HA immobilization on solid support as well as inhibitor screening for HAase (cromolyn, heparin) with and without substrate immobilization. Controls concerning binary ATP/ADP discrimination for naked-eye kinase detection are mentioned to delineate scope but also limitations of this simple and quite universal method.. |
| 43. |
Yoann Baudry, Guillaume Bollot, Virginie Gorteau, Svetlana Litvinchuk, Jiri Mareda, Masamichi Nishihara, Dario Pasini, Florent Perret, Dawn Ronan, Naomi Sakai, M. Raza Shah, Abhigyan Som, Nathalie Sordé, Pinaki Talukdar, Duy Hien Tran, Stefan Matile, Molecular recognition by synthetic multifunctional pores in practice
Are structural studies really helpful?, Advanced Functional Materials, 10.1002/adfm.200500198, 16, 2, 169-179, 2006.01, This account summarizes five years of research devoted to the development of the concept of synthetic multifunctional pores. The objective is to complement a comprehensive graphical summary of molecular recognition with a survey of structural studies on the same topic. The relevance of the latter for research focusing on creation and application of supramolecular functional materials is discussed briefly in a subjective manner.. |
| 44. |
Yoann Baudry, Dario Pasini, Masamichi Nishihara, Naomi Sakai, Stefan Matile, The depth of molecular recognition
Voltage-sensitive blockage of synthetic multifunctional pores with refined architecture, Chemical Communications, 10.1039/b509610c, 38, 4798-4800, 2005.10, Voltage-sensitive blockage by ADP, ATP and phytate (IP6) demonstrates that active-site contraction toward the middle of newly synthesized rigid-rod β-barrels provides a general strategy to rationally create and modulate the voltage sensitivity (and to increase the efficiency) of molecular recognition by synthetic multifunctional pores.. |
| 45. |
Masamichi Nishihara, Florent Perret, Toshihide Takeuchi, Shiroh Futaki, Adina N. Lazar, Anthony W. Coleman, Naomi Sakai, Stefan Matile, Arginine magic with new counterions up the sleeve, Organic and Biomolecular Chemistry, 10.1039/b501472g, 3, 9, 1659-1669, 2005.05, The elusive questions how arginine-rich sequences allow peptides and proteins to penetrate cells or to form voltage-gated ion channels are controversial topics of current scientific concern. The possible contributions of exchangeable counterions to these puzzling processes remain underexplored. The objective of this report is to clarify scope and limitations of certain counteranions to modulate cellular uptake and anion carrier activity of oligo/polyarginines. The key finding is that the efficiency of counteranion activators depends significantly on many parameters such as activator-membrane and activator-carrier interactions. This finding is important because it suggests that counteranions can be used to modulate not only efficiency but also selectivity. Specifically, activator efficiencies are found to increase with increasing aromatic surface of the activator, decreasing size of the transported anion, increasing carrier concentration as well as increasing membrane fluidity. Efficiency sequences depend on membrane composition with coronene > pyrene ≫ fullerene > calix[4]arene carboxylates in fluid and crystalline DPPC contrasting to fullerene > calix[4]arene ≈ coronene > pyrene carboxylates in EYPC with or without cholesterol or ergosterol. In HeLa cells, the efficiency of planar activators (pyrene) exceeds that of spherical activators (fullerenes, calixarenes). Polyarginine complexes with pyrene and coronene activators exhibit exceptional excimer emission. Decreasing excimer emission with increasing ionic strength reveals dominant hydrophobic interactions with the most efficient carboxylate activators. Dominance of ion pairing with the inefficient high-affinity sulfate activators is corroborated by the reversed dependence on ionic strength. These findings on activator-carrier and activator-membrane interactions are discussed as supportive of arene-templated guanidinium-carboxylate pairing and interface-directed translocation as possible origins of the superb performance of higher arene carboxylates as activators.. |
| 46. |
Florent Perret, Masamichi Nishihara, Toshihide Takeuchi, Shiroh Futaki, Adina N. Lazar, Anthony W. Coleman, Naomi Sakai, Stefan Matile, Anionic fullerenes, calixarenes, coronenes, and pyrenes as activators of oligo/polyarginines in model membranes and live cells, Journal of the American Chemical Society, 10.1021/ja043633c, 127, 4, 1114-1115, 2005.02, We report that the efflux of 5(6)-carboxyfluorescein anions from neutral egg yolk phosphatidylcholine vesicles is mediated by oligo/polyarginines only in the presence of activating amphiphilic anions. Screening of anion activators reveals best synergism for amphiphilic carboxylates (fullerene ≫ calix[4]arene ≈ coronene > pyrene > calix[6]arene ≫ alkyl), whereas amphiphilic sulfates show less satisfactory activation despite often lower effective concentrations. The analogous alcohols and one calix[4]arene diphosphate were inactive. These results are discussed in the context of a tentative anion carrier mechanism, where interactions with bilayer (interface-directed translocation) and carrier (arene-templated carboxylate-guanidinium pairing) contribute to activator efficiencies. Applied to HeLa cells, pyrenebutyrate is shown to significantly increase the uptake of a fluorescently labeled octaarginine in a concentration-dependent manner.. |
| 47. |
Hirotaka Ihara, Taisuke Yamada, Masamichi Nishihara, Toshihiko Sakurai, Makoto Takafuji, Hiroshi Hachisako, Takashi Sagawa, Reversible gelation in cyclohexane of pyrene substituted by dialkyl L-glutamide
Photophysics of the self-assembled fibrillar network, Journal of Molecular Liquids, 10.1016/S0167-7322(03)00263-0, 111, 1-3, 73-76, 2004.04, L-Glutamic acid-derived compound with pyrenyl group was able to form organic gels in benzene, cyclohexane, and so on. The gels were produced through the formation of highly oriented aggregates and a remarkable development of their fibrous polymer networks. Our scopes of this study are to present the salient features of the photophysics of pyrene in the highly oriented fibrillar network in cyclohexane and to describe spectroscopic measurements used either to detect pyrene association prior to excitation or to confirm the absence of aggregated pyrenes. The concentration and the temperature affected the gel-formation. The sol in the concentration below critical gel concentration includes nanoassemblies with highly oriented aggregates of the compound. Functionalization of L-glutamide derivative with different head groups using electron accepting pyrene and electron-donating N,N-dimethylaniline (DMA) chromophores was also performed to detect the exciplex formation as the mimicry of the photoinduced electron transfer process in the photosynthesis. Upon cooling from 60 to 10 °C, red shifted fluorescence from 446 to 456 nm ascribed to the charge transfer from DMA to pyrene was observed in the mixed system of pyrene- and DMA-containing L-glutamide derivatives in cyclohexane.. |
| 48. |
H. Ihara, W. Dong, T. Mimaki, Masamichi Nishihara, T. Sakurai, M. Takafuji, S. Nagaoka, Poly(4-vinylpyridine) as novel organic phase for RP-HPLC. Unique selectivity for polycyclic aromatic hydrocarbons, Journal of Liquid Chromatography and Related Technologies, 10.1081/JLC-120023796, 26, 15, 2491-2503, 2003.09, Subsidiary weak interaction such as π-π interaction shows us unique separation even in RP-HPLC. This communication shows the first example that poly(4-vinylpyridine) on silica provides extremely large selectivity with specificity for polycyclic aromatic hydrocarbons in methanol-water as a mobile phase. It also describes that the selectivity mode does not always obey those in conventional π-electron-containing stationary phases.. |
| 49. |
Masamichi Nishihara, Koji Teramoto, Toshihiko Sakurai, Makoto Takafuji, Tsutomu Mashimo, Hirotaka Ihara, Enhancement of isotacticity in bulk radical polymerization of poly(methyl methacrylate) under strong gravity field, Polymer Journal, 10.1295/polymj.35.276, 35, 3, 276-279, 2003.06, A novel method for preparing stereoregular polymer under strong gravity field was proposed. As such, the most isotactic-rich polymer was the polymer prepared by using a benzylmercaptan and this value showed 2.0 times higher than that of the controlled polymer. It indicates that it was possible to control the stereoregularity by polymerization under strong gravity field.. |
| 50. |
Tsutomu Mashimo, Xinsheng Huang, Toyotaka Osakabe, Masao Ono, Masamichi Nishihara, Hirotaka Ihara, Masanori Sueyoshi, Koji Shibasaki, Shiro Shibasaki, Nobuo Mori, Advanced high-temperature ultracentrifuge apparatus for mega-gravity materials science, Review of Scientific Instruments, 10.1063/1.1527718, 74, 1 I, 160-163, 2003.01, The development of an advanced high-temperature ultracentrifuge apparatus for mega-gravity materials science was presented. The apparatus consisted of an air turbine motor with ceramic ball bearings and dumper section, a sample rotor, a vacuum chamber and a heating system. The double-structural dumper bushing and the nonbored rotor raised the maximum rotational speed and improved the stability.. |
| 51. |
T. Mashimo, R. Nishimura, S. Matsuzaki, Masamichi Nishihara, T. Sagawa, H. Ihara, Preparation of functionally graded oxide glass in molecular scale, Journal of Materials Science Letters, 10.1023/A:1020885028287, 21, 21, 1691-1693, 2002.11, The preparation of functionally graded oxide galss in molecular scale was discussed. A transparent SiO2-TiO2 glass of a mm scale that had a graded structure was obtained by controlling sol-gel processing times before the centrifugation. The method has several advantages. The specimen size can be increased up to cm scale.. |
| 52. |
Masamichi Nishihara, Takashi Sagawa, Hirotaka Ihara, Rika Nishimura, Susumu Matsuzaki, Tsutomu Mashimo, Preparation of SiO2-TiO2 graded glass by using high gravity field combined with sol-gel method, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.47.1201, 47, 11, 1201-1204, 2000.01, A method to prepare the multi-component oxide glass with graded structure was proposed. This method is based on the facts that colloid particles can sediment during a sol-gel transition process under comparatively low gravity field, and the resultant gel can be converted into glass at lower temperature treatment than a conventional method. The graded structure was formed by centrifuging (10,000 g level) the Si and Ti mixed colloids, and immobilized by removal of solvent at 90 °C. This graded precursor gel was heated to 900 °C to convert into a glass state. The proper condition to prepare the graded glass was examined especially focusing on the growth time of colloids before the centrifugation. A transparent SiO2-TiO2 glass with molecular-scale graded structure was obtained in many trials.. |
