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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Chemical Communications 57(23) 2899-2902 2021年A non-symmetric radical-type mechanophore (CF/ABF) was synthesized by molecular crossing between two radical-type mechanophores. The thermal stability and mechanoresponsiveness of CF/ABF were found to be tunable by altering the properties of the parent RMs. The CF/ABF-centred polymers showed mixed mechanochromism derived from the simultaneous generation of two radical species.
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Macromolecules 53(21) 9313-9324 2020年11月10日A rigid and brittle cross-linking structure was introduced into the flexible poly(n-hexyl methacrylate) (PHMA) network by the mechanochromic cross-linker difluorenylsuccinonitrile-containing methacrylate (DFMA), whose central C-C bond acted as a dynamic covalent bond and could generate pink radicals when fractured. PHMA with DFMA showed a remarkable hysteresis loop and mechanical enhancement. After deformation, the reassociation of dynamic covalent bonds and the reorganization of the network structure slowed down the recovery of the polymer to its initial state. The correlations between tension stimulation, energy dissipation, and mechanoresponsive color change were discussed. Under stress, the polymer changed from light gray to pink. The broad distribution of red channel intensity under large deformation detected on the surface confirmed that the rupture of dynamic covalent bonds occurred evenly throughout the polymer and suppressed stress concentration. The color showed a strong dependence on stress, which started to appear at around 1.5 to 2.0 MPa. The incorporation of DFMA promised mechanical enhancement and noncontact stress detection ability of the PHMA soft material.
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ACS Macro Letters 9(8) 1108-1113 2020年8月18日A difluorenylsuccinonitrile-(DFSN)-based linker, whose central C-C bond is readily cleaved under mechanical stress to generate a relatively stable pink radical species, was introduced into polymer networks. DFSN-based cross-linked polymers exhibit improved mechanical properties as compared to those of the corresponding covalently cross-linked polymers owing to the energy dissipation induced by cleavage of the central DFSN bond. The toughening mechanism of DFSN-based elastomers is qualitatively visualized by the intensity of the pink color and can be quantitatively characterized by electron paramagnetic resonance. These results demonstrate that the extent of DFSN cleavage is the main factor improving the mechanical properties of the polymer networks.
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Langmuir 36(18) 4855-4862 2020年5月12日 査読有り
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ACS Applied Polymer Materials 2020年3月13日
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Angewandte Chemie 132(11) 4620-4620 2020年3月9日
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Angewandte Chemie 132(11) 4324-4328 2020年3月9日
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Angewandte Chemie International Edition 59(11) 4590-4590 2020年3月9日
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Angewandte Chemie 132(11) 4299-4303 2020年3月9日
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Angewandte Chemie International Edition 59(11) 4269-4273 2020年3月9日A simple and efficient method to generate macrocyclic structures has been developed based on the dynamic behavior of the linker bis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide (BiTEMPS). The prime linear structure was transformed into a (macro)cycle using the following sequence: 1) thiol-ene reaction with a BiTEMPS derivative to afford the linear precursor, then 2) an entropy-driven transformation induced by diluting and heating. The radicals generated from BiTEMPS upon heating are highly tolerant toward a variety of chemical species, including oxygen and olefins, but they exhibit high reactivity in exchange reactions, which can be applied to the topology transformation of various skeletons. The advantages of the present method, namely, its procedural simplicity and substrate versatility, are demonstrated by the gram-scale synthesis of cyclic compounds with low and relatively high molecular weight.
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Angewandte Chemie International Edition 59(11) 4294-4298 2020年3月9日
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Macromolecular Rapid Communications 1900460-1900460 2020年1月8日 査読有り
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Soft Matter 16(48) 10869-10875 2020年<p>Characterization of <italic>N</italic>-phenylmaleimide-terminated poly(ethylene glycol)s and their application to a tetra-arm poly(ethylene glycol) gels</p>
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Chemical Communications 2020年 査読有り
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Journal of Polymer Science Part A: Polymer Chemistry 57(24) 2396-2406 2019年12月15日
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Mechanically Responsive Materials for Soft Robotics 307-325 2019年11月19日Mechanochromic materials that consist of polymer chains are expected to be good candidates for stress-sensing because their mechanical properties can be readily tuned by a judicious choice of the appropriate polymer composition. In this chapter, an approach for the development of functional polymers with mechanochromic properties and their characteristics are summarized with a focus on the dynamic covalent chemistry.
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MACROMOLECULAR RAPID COMMUNICATIONS 40(21) 2019年11月In this study, poly(delta-valerolactone) (PVL) axles bearing movable and fixed dibenzo-24-crown-8-ether wheels (rot-M and rot-F) are investigated for the first time in the terms of phase transition and nanoscale film morphology: PVL-rot-M and PVL-rot-F. Interestingly, the PVL axles reveal a strong tendency to form a horizontal lamellar structure with three different rotational crystal lattice domains in nanoscale films. The morphological structural parameters are discernibly varied by the movable and fixed rotaxane wheels. In particular, the rot-M wheel tends to be populated in both the interfacial and amorphous layers. The rot-M wheel is found to significantly influence the phase transition characteristics of the PVL axle because of its movability along the polymer backbone chain. In contrast, the rot-F wheel tends to be more localized in the interfacial layer rather than in the amorphous layer because of its immovability constrained at the polymer chain end. The rot-F wheel causes severe thermal instability in the PVL axle, which can be attributed mainly to the presence of its counter anion (PF6-).
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Macromolecules 52(14) 5325-5336 2019年7月23日 査読有りIn this study, poly(delta-valerolactone) (PVL) axles bearing movable and ionically fixed rotaxane wheels linked with polystyrene (rot-PS-M and rot-PS-F) have been investigated for the first time in the aspects of nanoscale film morphology by using synchrotron grazing incidence X-ray scattering: PVL-rot-PS-M and PVL-rot-PS-F. In addition, their thermal stabilities and phase-transition behaviors have been examined. PVL-rot-PS-M reveals a higher thermal stability than that of PVL-rot-PS-F, having an ionic character and a counter anion. The quantitative analyses of this study found that the mechanically linked rotaxane wheel could be able to enhance significantly the mobilities of the PVL axle and the PS block, which are essential for their phase separation and the PVL axle crystallization. With higher chain mobilities due to the movable rotaxane wheel, PVL-rot-PS-M always reveals a much better performance in the formation of the phase-separated PVL/PS lamellar structure as well as in the crystallization of the PVL axle chain, compared to PVL-rot-PS-F and the counter diblock copolymer. All morphology details as well as thermal stability and phase transition details are discussed, considering the nature of movable, ionically fixed, and covalent-bonded linkers between PVL and PS blocks.
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MACROMOLECULAR SYMPOSIA 385(1) 2019年6月 査読有りRotaxane-cross-linked polymers (RCP), which have rotaxane structures at the cross-link points, show unique physical properties originating from the movable cross-link points. Herein, poly(N,N-dimethylacrylamide) (PDMAAm) and poly(N-isopropylacrylamide) (PNIPAm) which are well known as hydrophilic polymers and whose glass transition temperatures are much higher than room temperature, were applied as matrix polymers for RCPs. These RCPs are easily and successfully synthesized by radical polymerization of vinyl monomers in the presence of small amounts of [2]rotaxane cross-linker (RC) comprising one wheel and one axle component with a methacrylate group on each component. As the result, PDMAAm-based RCP without any solvents and PNIPAm-based RCP swelled with water were much tougher than corresponding covalently cross-linked polymers. It is confirmed that RC endows both of the hard polymer networks and soft hydrogels with toughness.
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Angewandte Chemie - International Edition 58(9) 2765-2768 2019年2月25日Three component mobility controlling vinylic rotaxane crosslinkers with two radically polymerizable vinyl groups (RC_Rs) were synthesized to prove that the mobility of the components of the RC_Rs plays a crucial role in determining the properties of rotaxane-crosslinked polymers (RCPs). RC_Rs (R=H, Me, or Et) were obtained from living ring-opening polymerization. RCP_Et was prepared using RC_Et, which exhibits the lowest component mobility. The low component mobility is reflected in inferior mechanical strength and stretching ability in tensile stress tests compared to components with good (R=Me) and high (R=H) mobility. However, RCP_Et exhibited significantly higher stress and strain values than the corresponding covalently crosslinked polymers (CCP_Rs). These results indicate that a suitable component mobility substantially enhances the mechanical strength of RCPs. This behavior could serve as a guiding principle for the molecular design of advanced RCs.
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Journal of the American Chemical Society 2019年2月 査読有り
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Zeitschrift fur Naturforschung B 74(5) 421-425 2019年 査読有り
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日本レオロジー学会誌 47(2) 51-54 2019年 査読有り招待有り
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Materials Chemistry Frontiers 2019年 査読有り
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Chemical Communications 2019年 査読有り
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ACS Macro Letters 1 2019年1月 査読有り
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ACS Macro Letters 1359 2018年11月 査読有り
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Chemistry - An Asian Journal 13(7) 785-789 2018年4月4日 査読有りWe developed novel size-complementary molecular and macromolecular rotaxanes using a 2,6-dimethylphenyl terminal group as the axle-end-cap group in dibenzo-24-crown-8-ether (DB24C8)-based rotaxanes, where the 2,6-dimethylphenyl group was found to be less bulky than the 3,5-dimethylphenyl group. A series of molecular and macromolecular [2]rotaxanes that bear a 2,6-dimethylphenyl group as the axle-end-cap were synthesized using unsubstituted and fluorine-substituted DB24C8. Base-induced decomposition into their constituent components confirmed the occurrence of deslipping, which supports the size-complementarity of these rotaxanes. The deslipping rate was independent of the axle length but dependent on the DB24C8 substituents. A kinetic study indicated the rate-determining step was that in which the wheel is getting over the end-cap group, and deslipping proceeded via a hopping-over mechanism. Finally, the present deslipping behavior was applied to a stimulus-degradable polymer as an example for the versatile utility of this concept in the context of stimulus-responsive materials.
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Chemical Communications 2018年 査読有り
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Polymer Journal 50(1) 127-147 2018年 査読有り
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ACS Macro Letters 7(5) 556-560 2018年 査読有りMechanochromic polymers, which react to mechanical force by changing color, are expected to find applications in smart materials such as damage sensors. Although numerous types of mechanochromic polymers have been reported so far, developing mechanochromic polymers that can recognize different mechanical stimuli remains a formidable challenge. Materials that not only change their color in response to a mechanical stimulus but also detect its nature should be of great importance for practical applications. In this paper, we report our preliminary findings on multicolor mechanochromic polymer blends that can discriminate between two different mechanical stimuli, i.e., stretching and grinding, by simply blending two mechanochromic polymers with different architectures. The rational design and blending of two mechanochromic polymers with radical-type mechanochromophores embedded separately in positions adjacent to soft or hard domains made it possible to achieve multicolor mechanochromism in response to different stimuli. Electron paramagnetic resonance and solid-state UV-vis measurements supported the mechanism proposed for this discrimination.
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Chemistry - A European Journal 24(13) 3170-3173 2018年 査読有りMechanochromic polymers, that is, polymers sensitive to mechanical impact, promise great potential for applications in damage sensors. In particular, radical-type mechanochromic polymers, which produce colored radical species in response to mechanical stress, may enable not only the visualization of mechanical stress, but also its quantitative evaluation by electron paramagnetic resonance analysis. Herein, a radical-type mechanochromic polymer that exhibits a color change from white to green upon dissociation of a diarylbibenzothiophenonyl moiety at the mid-point of a polystyrene chain is presented, and its mechanochromic behavior is examined. Mechanochromic materials that show a variety of colors (“rainbow colors”) in response to mechanical stress were prepared by simply mixing radical-type mechanochromic polymers of primary colors.
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ChemistrySelect 3(2) 446-450 2018年 査読有りPalladium-complexing macrocyclic catalysts efficiently and chemoselectively catalysed the Suzuki coupling reaction of bromoarenes. Bromobenzene and 2-bromopyridine were efficiently monoarylated with 4-methoxyphenylboronic acid when catalysed by macrocyclic catalysts comprising cyclic pyridine-2,6-bisamide pincer-type ligands with palladium (II) located in the inner cavity (PdMCs). The Suzuki coupling of 2,6-dibromopyridine to aryl boronic acids catalysed by PdMCs afforded the corresponding monoarylpyridines with high selectivity and yield, whereas a mixture of mono- and di-arylpyridines was obtained when palladium chloride was used as the catalyst. Interestingly, the chemoselectivity increased as the cavity size of the PdMCs decreased. The high chemoselectivity seemed to arise from the steric effect of the macrocyclic ligand. Moreover, an unsymmetrical 2,6-diarylpyridine was successfully synthesised in high yield by two sequential couplings employing PdMCs followed by palladium chloride.
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Polymer 128 276-296 2017年10月 査読有りThis review article deals with the construction and function of dynamic macromolecular systems having mechanically linked polymer chains which can undertake a topology transformation to induce structure and property changes. Synthesis of a macromolecular [2] rotaxane (M2R) possessing a macromolecular switch function is first described, which is a structure-definite ideal polyrotaxane consisting of one polymer axle and one macrocycle wheel. Its application to the synthesis of rotaxane cross-linked polymers (RCP) and topology-transformable polymers is discussed along with their properties, where the rotaxane-linking of polymer chains plays a crucial role. The M2R-based cross-linker is prepared and applied to the synthesis of RCPs by adding it into radical polymerization systems of vinyl monomers. RCPs have high stretchability and toughness. Rotaxane-linked block copolymers and cyclic polymers synthesized by introducing polymer chains onto the wheel and axle components of M2R are subjected to the topology transformation using the switch function of M2R to cause remarkable structure and property changes. (C) 2017 Elsevier Ltd. All rights reserved.
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Chemistry - A European Journal 23(35) 8405-8408 2017年6月5日 査読有りCompared to rigid microspheres that consist, for example, of polystyrene or silica, soft and deformable elastomer microspheres can be used to generate colorless transparent films upon evaporating the solvent from microsphere-containing dispersions. To obtain tough films, a post-polymerization reaction to crosslink the microspheres is usually necessary, which requires extra additives during the drying process. This restriction renders this film-formation technology complex and rather unsuitable for applications in which impurities are undesirable. In the present study, it is demonstrated that tough elastomer microspheres that are crosslinked with rotaxanes can form tough bulk films upon evaporation of water from microsphere dispersions, so that post-polymerization reactions are not required. The results of this study should thus lead to new applications including coatings for biomaterials that need complete removal of all impurities from the materials prior to use.
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Macromolecular Symposia 372(1) 115-119 2017年4月 査読有りThe [2]rotaxane cross-linkers (RCs) comprising vinyl group-terminated axle component having different axle lengths and vinyl group-containing crown ether were synthesized, and applied to prepare the corresponding rotaxane cross-linked polymers (RCPs). The preparations of RCP were performed by the radical polymerizations of n-butyl acrylate in the presence of 0.5 mol% of RCs. Properties of the RCPs were evaluated by swelling ratio, clearly demonstrating that axle length of RC affects swelling ratio of RCPs.
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Journal of the American Chemical Society 139(20) 6791-6794 2017年4月 査読有りA simple and effective synthetic route to cyclic polymers has been developed based on the following sequence: (i) selective cyclization of two self-complementary sec-ammonium-containing crown ether monomers to afford [c2] daisy-chain bifunctional initiators, (ii) living polymerization to afford the corresponding linear polymers, and (iii) a topology transformation of these linear polymers to furnish cyclic polymers. The key step in this sequence is the quantitative cyclization via self assembly of two crown ether molecules with hydroxyl and sec-ammonium moieties. After the living polymerization, the linear polymers release the daisy-chain assembly to generate a cyclic topology. The specific advantages of the present synthetic protocol, i.e., procedural simplicity and concentration independence, are demonstrated by a gram scale synthesis.
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Kobunshi 66(5) 217-219 2017年 査読有り
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Angewandte Chemie - International Edition 56(48) 15393-15396 2017年 査読有りRotaxane cross-linked (RC) microgels that exhibit a decoupled thermo- and pH-responsive volume transition were developed. The pH-induced changes of the aggregation/disaggregation states of cyclodextrin in the RC networks were used to control the swelling capacity of the entire microgels. Different from conventional thermo- and pH-responsive microgels, which are usually obtained from copolymerizations involving charged monomers, the RC microgels respond to temperature as intended, even in the presence of charged functional molecules such as dyes in the microgel dispersion. The results of this study should lead to new applications, including drug delivery systems that require a retention of their smart functions even in environments that may contain foreign ions, for example, in invivo experiments.
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Polym. Chem. 8(12) 1878-1881 2017年 査読有りA [2] rotaxane cross-linker (RC) with one vinyl group in each component was designed and synthesized as a vinylic cross-linker for highly toughened network polymers, which were prepared from the radical polymerization of n-butyl acrylate and 2-ethylhexyl acrylate in the presence of 0.5 mol% of RC.
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
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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