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228 results on '"Takeoka, Yuko"'

2. Phase transition and ionic conductivity of pyrrolidinium-based ionic plastic crystals with magnesium salts.

Author

Hirotsu, Yoshifumi, Sekiguchi, Ryotaro, Takeoka, Yuko, Rikukawa, Masahiro, and Yoshizawa-Fujita, Masahiro

Subjects
IONIC conductivity, PLASTIC crystals, MAGNESIUM salts, SOLID electrolytes, ELECTROCHEMISTRY
Abstract

Despite being safe for use in secondary Mg batteries, solid electrolytes exhibit lower ionic conductivities than those of traditional liquid electrolytes. Organic ionic plastic crystals—soft crystals with excellent thermal and electrochemical stabilities and ionic conductivities—are promising solid electrolytes. Herein, we investigated the effects of various anion species and Mg salt concentrations on the properties of pyrrolidinium-based organic ionic plastic crystals (N , N -diethylpyrrolidinium bis(fluorosulfonyl)amide [[C2epyr][FSA]] and N , N -diethylpyrrolidinium bis(trifluoromethylsulfonyl)amide [[C2epyr][TFSA]]) upon Mg(TFSA)2 addition. The Mg-ion transference number (t Mg2 + ) was measured using the Vincent–Bruce method; ionic conductivity via impedance measurements; and phase transition via differential scanning calorimetry. The phase transition behavior, dissociation state of the Mg salt, and electrochemical properties varied with the organic ionic plastic crystal anionic structure. The FSA system became liquid when the Mg salt concentration exceeded 15 mol%. The ionic conductivity of the pyrrolidinium-based organic ionic plastic crystals increased substantially with the Mg salt concentration. In the solid state, [C2epyr][FSA]/Mg(TFSA)2 (5 mol%) (FT5) showed the highest ionic conductivity (2.9 × 10−4 S cm−1 at 25 °C). The t Mg2 + of FT5 at 60 °C was 0.29. Mg exhibited redox behavior in FT5 but not in [C2epyr][TFSA]/Mg(TFSA)2 (5 mol%). The FSA− structure is suitable for Mg electrochemistry and will aid in developing high-performance secondary Mg batteries. [ABSTRACT FROM AUTHOR]

Published
2024
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6. Evaluation of alginate‐coated β‐tricalcium phosphate fiber scaffold for cell culture.

Author

Kawamura, Satoshi, Furuya, Kozue, Sasaki, Nene, Takeoka, Yuko, Aizawa, Mamoru, and Kanzawa, Nobuyuki

Subjects
CELL culture, TISSUE culture, TISSUE scaffolds, CARTILAGE diseases, TISSUE engineering
Abstract

Ex vivo tissue engineering is an effective therapeutic approach for the treatment of severe cartilage diseases that require tissue replenishment or replacement. This strategy demands scaffolds that are durable enough for long‐term cell culture to form artificial tissue. Additionally, such scaffolds must be biocompatible to prevent the transplanted matrix from taking a toll on the patient's body. From the viewpoint of structure and bio‐absorbability, a β‐tricalcium phosphate (β‐TCP) fiber scaffold (βTFS) is expected to serve as a good scaffold for tissue engineering. However, the fragility and high solubility of β‐TCP fibers make this matrix unsuitable for long‐term cell culture. To solve this problem, we developed an alginate‐coated β‐TCP fiber scaffold (βTFS‐Alg). To assess cell proliferation and differentiation in the presence of βTFS‐Alg, we characterized ATDC5 cells, a chondrocyte‐like cell line, when grown in this matrix. We found that alginate coated the surface of βTFS fiber and suppressed the elution of Ca2+ from β‐TCP fibers. Due to the decreased solubility of βTFS‐Alg compared with β‐TCP, the former provided an improved scaffold for long‐term cell culture. Additionally, we observed superior cell proliferation and upregulation of chondrogenesis marker genes in ATDC5 cells cultured in βTFS‐Alg. These results suggest that βTFS‐Alg is suitable for application in tissue culture. [ABSTRACT FROM AUTHOR]

Published
2024
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30. Ion Conductive Behavior of Oligoether/Zwitterion Diblock Copolymers Containing Magnesium Salt.

Author

Yoshizawa‐Fujita, Masahiro, Ota, Ryoma, Ishii, Jun, Takeoka, Yuko, and Rikukawa, Masahiro

Subjects
ZWITTERIONS, DIBLOCK copolymers, MAGNESIUM salts, POLYELECTROLYTES, GLASS transition temperature, ATOMIC force microscopes, SOLID electrolytes, IONIC conductivity
Abstract

Rechargeable magnesium (Mg) batteries are envisioned as next generation batteries. The development of solid polymer electrolytes with high ionic conductivity will contribute to realize not only high performance Mg batteries but also reliable and safe devices. In this study, diblock copolymers (PPEGMAm‐b‐SPBn) with oligoether (PEGMA) and zwitterionic (SPB) side‐chains are synthesized in order to develop novel Mg‐ion electrolytes. PPEGMAm‐b‐SPBn copolymers with various unit ratios are synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization. PPEGMAm‐b‐SPBn exhibited two distinct glass transition temperatures. Phase‐separated structures are observed by atomic force microscope (AFM) measurements. PPEGMAm‐b‐SPBn/Mg‐salt composites exhibited a glass transition temperature due to the mixture formation of PEGMA and SPB blocks. When the unit numbers of m and n are 44 and 75, respectively, PPEGMAm‐b‐SPBn/Mg‐salt ([EO]: [Mg] = 6: 1) exhibits the highest ionic conductivity of over 10−4 S cm−1 at 60 °C among 11 composites prepared in this study. [ABSTRACT FROM AUTHOR]

Published
2022
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