研究者業績
基本情報
- 所属
- 千葉大学 大学院工学研究院 准教授
- 学位
- 博士（工学）(東京工業大学)
- ORCID ID
https://orcid.org/0000-0002-7272-0643- J-GLOBAL ID
- 201801020964389097
- researchmap会員ID
- B000300505
研究分野
1論文
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Organic & Biomolecular Chemistry 2024年
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Journal of the American Chemical Society 2023年11月1日
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Journal of Polymer Science 2023年9月
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Advanced Materials 2023年6月
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Polymer Chemistry 2023年4月11日
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Theoretical and Experimental Investigations of Stable Arylfluorene-Based Radical-Type Mechanophores.Chemistry (Weinheim an der Bergstrasse, Germany) 29(12) e202203249 2023年2月24日Radical-type mechanophores (RMs) can undergo homolytic cleavage of their central C-C bonds upon exposure to mechanical forces, which affords radical species. Understanding the characteristics of these radical species allows bespoke mechanoresponsive materials to be designed and developed. The thermal stability of the central C-C bonds and the oxygen tolerance of the generated radical species are crucial characteristics that determine the functions and applicability of such RM-containing mechanoresponsive materials. In this paper, we report the synthesis and characterization of two series of arylfluorene-based RM derivatives, that is, 9,9'-bis(5-methyl-2-pyridyl)-9,9'-bifluorene (BPyF) and 9,9'-bis(4,6-diphenyl-2-triazyl)-9,9'-bifluorene (BTAF). BPyF and BTAF derivatives were synthesized without generating any peroxides initially, albeit that BPyF slowly converted to the corresponding peroxide in solution. DFT calculations revealed the importance of the thermodynamic stability and the values of the α-SOMO levels of the corresponding radical species for their thermal stability and oxygen tolerance. Furthermore, the mechanochromism of BTAF was demonstrated by ball-milling a BTAF-centered polymer, which was synthesized by atom-transfer radical polymerization (ATRP).
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Theoretical and Experimental Investigations of Stable Arylfluorene-Based Radical-Type Mechanophores.Chemistry (Weinheim an der Bergstrasse, Germany) 29(12) e202300230 2023年2月24日Invited for the cover of this issue are the groups of Hideyuki Otsuka at the Tokyo Institute of Technology and Koichiro Mikami at the Sagami Chemical Research Institute. The image depicts theoretical and experimental investigations of stable arylfluorene-based radical-type mechanophores. Read the full text of the article at 10.1002/chem.202203249.
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Polymer Chemistry 2023年
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Chemical Science 2023年
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Polymer Chemistry 2023年The effect of chain length on ring-chain equilibria was investigated to both reveal their dynamic equilibrium reactions and expand the availability of bis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide (BiTEMPS)-based macrocyclic monomers.
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Advanced Materials 34(13) 2108818-2108818 2022年4月
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Advanced materials (Deerfield Beach, Fla.) 34(13) e2108818 2022年4月Dynamically crosslinked gels are appealing materials for applications that require time-dependent mechanical responses. DNA duplexes are ideal crosslinkers for building such gels because of their excellent sequence addressability and flexible tunability in bond energy. However, the mechanical responses of most DNA gels are complicated and unpredictable. Here, a DNA gel with a highly homogeneous gel network and well predictable mechanical behaviors is demonstrated by using a pair of star-polymer-DNA precursors with presimulated DNA sequences showing the two-state transition. The melting curve analysis of the DNA gels reveals the good correspondence between the thermodynamic potentials of the DNA crosslinkers and the presimulated values by DNA calculators. Stress-relaxation tests and dissociation kinetics measurements show that the macroscopic relaxation time of the DNA gels is approximately equal to the lifetime of the DNA crosslinkers over 4 orders of magnitude from 0.1-2000 s. Furthermore, a series of durability tests find the DNA gels are hysteresis-less and self-healable after the applications of repeated temperature and mechanical stimuli. These results demonstrate the great potential of star-polymer-DNA precursors for building gels with predictable and tunable viscoelastic properties, suitable for applications such as stress-response extracellular matrices, injectable solids, and soft robotics.
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Soft Matter 18(16) 3218-3225 2022年
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Nature Communications 12(1) 2021年12月<title>Abstract</title>The topology of polymers affects their characteristic features, i.e., their microscopic structure and macroscopic properties. However, the topology of a polymer is usually fixed during the construction of the polymer chain and cannot be transformed after its determination during the synthesis. In this study, topology-transformable block copolymers that are connected via rotaxane linkages are introduced. We will present systems in which the topology transformation of block copolymers changes their 1) microphase-separated structures and 2) macroscopic mechanical properties. The combination of a rotaxane structure at the junction point and block copolymers that spontaneously form microphase-separated structures in the bulk provides access to systems that cannot be attained using conventional covalent bonds.
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Nature Communications 12(1) 126-126 2021年12月The growth of lamellar crystals has been studied in particular for spherulites in polymeric materials. Even though such spherulitic structures and their growth are of crucial importance for the mechanical and optical properties of the resulting polymeric materials, several issues regarding the residual stress remain unresolved in the wider context of crystal growth. To gain further insight into micro-mechanical forces during the crystallization process of lamellar crystals in polymeric materials, herein, we introduce tetraarylsuccinonitrile (TASN), which generates relatively stable radicals with yellow fluorescence upon homolytic cleavage at the central C-C bond in response to mechanical stress, into crystalline polymers. The obtained crystalline polymers with TASN at the center of the polymer chain allow not only to visualize the stress arising from micro-mechanical forces during polymer crystallization via fluorescence microscopy but also to evaluate the micro-mechanical forces upon growing polymer lamellar crystals by electron paramagnetic resonance, which is able to detect the radicals generated during polymer crystallization.
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Macromolecules 54(21) 9992-10000 2021年11月9日
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Journal of the American Chemical Society 2021年10月27日
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Journal of the American Chemical Society 143(42) 17744-17750 2021年10月27日The exploration of mechanochemical reactions has brought new opportunities for the design of functional materials. We synthesized the novel organic peroxide mechanophore bis(9-methylphenyl-9-fluorenyl) peroxide (BMPF) and examined its mechanochromic properties. The mechanism behind its mechanofluorescence was clarified and harnessed in polymer networks that can release the small fluorescent molecule 9-fluorenone upon exposure to a mechanical stimulus. Additionally, polymer networks cross-linked with BMPF units are able to tolerate temperatures up to 110 °C without any change in optical properties or mechanical strength. As mechanophores based on organic peroxide have rarely been documented so far, these fascinating results suggest excellent potential for applications of BMPF in stress-responsive materials. The mechanochemical protocol demonstrated here may provide guiding principles to expand the field of mechanochromic peroxides.
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Journal of the American Chemical Society 143(42) 17744-17750 2021年10月27日The exploration of mechanochemical reactions has brought new opportunities for the design of functional materials. We synthesized the novel organic peroxide mechanophore bis(9-methylphenyl-9-fluorenyl) peroxide (BMPF) and examined its mechanochromic properties. The mechanism behind its mechanofluorescence was clarified and harnessed in polymer networks that can release the small fluorescent molecule 9-fluorenone upon exposure to a mechanical stimulus. Additionally, polymer networks cross-linked with BMPF units are able to tolerate temperatures up to 110 °C without any change in optical properties or mechanical strength. As mechanophores based on organic peroxide have rarely been documented so far, these fascinating results suggest excellent potential for applications of BMPF in stress-responsive materials. The mechanochemical protocol demonstrated here may provide guiding principles to expand the field of mechanochromic peroxides.
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Nature Communications 2021年10月26日
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Macromolecules 54(21) 9992-10000 2021年10月8日
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JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 143(42) 17744-17750 2021年10月The exploration of mechanochemical reactions has brought new opportunities for the design of functional materials. We synthesized the novel organic peroxide mechanophore bis(9-methylphenyl-9-fluorenyl) peroxide (BMPF) and examined its mechanochromic properties. The mechanism behind its mechano-fluorescence was clarified and harnessed in polymer networks that can release the small fluorescent molecule 9-fluorenone upon exposure to a mechanical stimulus. Additionally, polymer networks cross-linked with BMPF units are able to tolerate temperatures up to 110 degrees C without any change in optical properties or mechanical strength. As mechanophores based on organic peroxide have rarely been documented so far, these fascinating results suggest excellent potential for applications of BMPF in stress-responsive materials. The mechanochemical protocol demonstrated here may provide guiding principles to expand the field of mechanochromic peroxides.
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Macromolecules 54(17) 8154-8163 2021年9月14日
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ACS Macro Letters 10(6) 744-748 2021年6月15日
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ACS Macro Letters 10(6) 744-748 2021年6月15日
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Chemistry Letters 50(6) 1223-1225 2021年6月1日In solvent freezing, polyurethane gels cross-linked with tetraarylsuccinonitrile (TASN) moieties which can be cleaved to afford pink-colored and yellow-fluorescent radicals by mechanical stress, show mechano-Activated fluorescence based on dissociated TASN radicals and provide a consistent reaction field with vinyl monomers. We herein propose a toughening of a polymer network via freezing-induced mechanochemistry. Through the consistent reaction field, the toughness of resulting polymer networks can be changed by the number of repeated freeze-Thaw cycles and the concentration of dissociated TASN radicals.
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ACS Macro Letters 10(5) 558-563 2021年5月18日
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Angewandte Chemie 60(15) 8406-8409 2021年4月6日Mechanochromic elastomers that exhibit force-induced cross-linking reactions in the bulk state are introduced. The synthesis of segmented polyurethanes (SPUs) that contain difluorenylsuccinonitrile (DFSN) moieties in the main chain and methacryloyl groups in the side chains was carried out. DFSN was selected as the mechanophore because it dissociates under mechanical stimuli to form pink cyanofluorene (CF) radicals, which can also initiate the radical polymerization of methacrylate monomers. The obtained elastomers generated CF radicals and changed color by compression or extension; they also became insoluble due to the mechanically induced cross-linking reactions. Additionally, an SPU containing diphenylmethane units also exhibited highly sensitive mechanofluorescence. To the best of our knowledge, this is the first report to demonstrate damage detection ability and changes in the mechanical properties of bulk elastomers induced by simple compression or extension.
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Angewandte Chemie 60(15) 8406-8409 2021年4月6日Mechanochromic elastomers that exhibit force-induced cross-linking reactions in the bulk state are introduced. The synthesis of segmented polyurethanes (SPUs) that contain difluorenylsuccinonitrile (DFSN) moieties in the main chain and methacryloyl groups in the side chains was carried out. DFSN was selected as the mechanophore because it dissociates under mechanical stimuli to form pink cyanofluorene (CF) radicals, which can also initiate the radical polymerization of methacrylate monomers. The obtained elastomers generated CF radicals and changed color by compression or extension; they also became insoluble due to the mechanically induced cross-linking reactions. Additionally, an SPU containing diphenylmethane units also exhibited highly sensitive mechanofluorescence. To the best of our knowledge, this is the first report to demonstrate damage detection ability and changes in the mechanical properties of bulk elastomers induced by simple compression or extension.
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Polymer Journal 2021年2月19日
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ACS Applied Polymer Materials 2021年2月12日
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ACS Applied Polymer Materials 2021年2月12日
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Angewandte Chemie - International Edition 60(5) 2680-2683 2021年2月1日Since the beginning of polymer science, understanding the influence of mechanical stress on polymer chains has been a fundamental and important research topic. The detection of mechanoradicals generated by homolytic cleavage of the polymer chains in solution has been studied in many cases. However, the detection of mechanoradicals in the bulk is still limited owing to their high reactivity. Herein, we propose an innovative strategy to detect mechanoradicals visually and quantitatively using a chain-transfer agent that generates relatively stable fluorescent radicals as a molecular probe. Mechanoradicals generated by ball milling of polystyrene samples were successfully detected by using a diarylacetonitrile compound as a fluorescent molecular probe through this radical chain-transfer mechanism. This probe enables the visualization and quantitative evaluation of mechanoradicals generated by polymer-chain scission.
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Angewandte Chemie International Edition 2021年2月
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Macromolecular Rapid Communications 42(1) 2021年1月1日Mechanochromic polymers can be used as stress- and damage-detecting sensors in polymeric materials, given that mechanical stimuli can be visualized by color changes. Although many types of mechanochromic polymers have been reported so far, there are only few examples on their further functionalization based on multiple color changes (multicolor mechanochromism). Herein, preliminary results are reported on the use of multicolor mechanochromism to detect the duration of the mechanical stimulation by simply mixing white powders of two mechanochromic polystyrene samples that contain a different radical-type mechanochromophore at the midpoint of each polymer chain and thus exhibit different colors in response to mechanical stimuli. The mechanosensitivity can be tuned via the polymer length and shape, and a combination of these two types of mechanochromic polymers allows detecting the duration with multicolor mechanochromism, i.e., a color change from white to blue upon short exposure to grinding and a color change from white to gray upon longer exposure to grinding. Electron paramagnetic resonance and solid-state UV–vis measurements support the mechanism proposed for this multiple mechanochromism.
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Green Chemistry 23(22) 9030-9037 2021年A polymer is used as a source of fertilizer. To demonstrate the viability of this concept, the chemical recycling of poly(isosorbide carbonate) (PIC) is presented as a model for the next generation of plastic-recycling systems.
MISC
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高分子 = High polymers, Japan : polymers 66(5) 217-219 2017年5月
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日本ゴム協会誌 90(6) 283-289 2017年<p>This review summarizes the development of stimuli-responsive materials based on the topology transformable polymers from branched to linear. The junction point of the rotaxane components bearing plural polymer chains is the key for the topology transformation which cannot be attained by the fixed junction point formed by the covalent bond. Crown ether-containing macromolecular [2]rotaxane with both ammonium and urethane moieties (M2R) as the stations for the crown ether wheel on the axle polymer chain produces the controllable and movable junction point of the polymer chains via the control of the component interaction, which enables the construction of sophisticated dynamic polymer systems. The rotaxane-linked star polymers with a fixed rotaxane linkage owing to the ammonium/crown ether interaction were synthesized by the introduction of two additional polymer chains to the components of M2R. The star polymers altered their topology to linear by the <i>N</i>-acetylation of the ammonium moiety, which broke the ammonium/crown ether interaction and generated the urethane/crown ether interaction to move the wheel component to the polymer chain terminal, eventually affording the linear polymer. The change in physical property caused by the topology transformation was confirmed in hydrodynamic volume and viscosity, demonstrating an effective way to the development of novel stimuli-responsive materials.</p>
共同研究・競争的資金等の研究課題
5-
日本学術振興会 科学研究費助成事業 2021年7月 - 2023年3月
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日本学術振興会 科学研究費助成事業 2020年4月 - 2023年3月
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日本学術振興会 科学研究費助成事業 2018年4月 - 2021年3月
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日本学術振興会 科学研究費助成事業 2016年4月 - 2018年3月
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日本学術振興会 科学研究費助成事業 2014年8月 - 2016年3月