NIPPON GOMU KYOKAISHI
Print ISSN : 0029-022X
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Special Issue for General Reviews “Progress in Self-healing Materials”
Introductory Remarks
General Reviews
  • Kazuaki SANADA, Yasuka NASSHO
    2021 Volume 94 Issue 2 Pages 26-32
    Published: 2021
    Released: April 20, 2021
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    Microscopic damage such as matrix crack, interlaminar fracture and interfacial debonding generates within carbon fiber reinforced polymers (CFRPs) and causes reduction in mechanical properties of CFRPs. Inspired by biological system, a concept of self-healing was proposed. Self-healing composites are designed to sense damage and repair automatically, thereby improving the reliability of CFRPs. Self-healing is accomplished by containers incorporating healing agents within matrix of CFRP, thus it is important to distribute containers throughout the matrix to obtain sufficient self-healing efficiency. In this paper, we present simply outline of self-healing CFRPs and report recently progress for self-healing spread carbon fiber (SCF)/ epoxy (EP) laminates.

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  • Hideyuki Hideyuki OTSUKA, Daisuke AOKI, Yasuhiro SHODA, Katsuhiko TSUN ...
    2021 Volume 94 Issue 2 Pages 33-38
    Published: 2021
    Released: April 20, 2021
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    In this review paper, the design of self-healing polymers and urethane-containing rubber materials based on dynamic covalent chemistry is described. This review is mainly divided into two parts. In the former part, the design of self-healing polymer networks with autonomously exchangeable C–C bonds or thermally exchangeable S–S bonds is introduced. The incorporation of such dynamic covalent bonds into polymer networks can endow polymer networks with structurally reorganizable properties. Not only self-healing property, but also reprocessability and adhesion capability were observed for the polymer networks with dynamic covalent bonds under appropriate conditions. In the latter part, the application of cross-metathesis reactions of C=C bonds between polybutadienes and olefin-containing polyurethanes to the synthesis of novel polybutadienes with urethane linkages as a source of hydrogen bonds is described. A series of polybutadienes copolymers with different contents of urethane linkages can be prepared by changing the feed ratios of the polybutadiene and olefin-containing polyurethanes in the cross-metathesis reactions. The aggregation structure of deuterated polybutadienes copolymers with different contents of urethane linkages are characterized by small-angle neutron scattering. Cured rubber materials prepared from polybutadienes copolymers with urethane linkages exhibit large energy dissipation at high strain.

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  • Ryota TAMATE, Masayoshi WATANABE
    2021 Volume 94 Issue 2 Pages 39-45
    Published: 2021
    Released: April 20, 2021
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    Ion gels, soft materials that contain ionic liquids (ILs), are promising soft solid electrolytes for use in various electrochemical devices. Due to the recent surge in demand for flexible and wearable devices, highly durable ion gels have attracted much attention. In this context, the introduction of a self-healing ability would significantly improve the longterm durability of ion gels subject to mechanical loading. Nevertheless, compared to hydrogels and organogels, the self-healing of ion gels has barely investigated. In this review, we address recent our development of functional ion gels that can heal themselves when mechanically damaged. Light-induced healing of ion gels are discussed as a stimuli-responsive healing strategy, after which self-healable ion gels based on supramolecular chemistry are addressed. Tough, highly stretchable, and self-healable ion gels can be fabricated through the judicious design of polymer nanostructures in ILs in which polymer chains and IL cations and anions interact.

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  • Shohei IDA
    2021 Volume 94 Issue 2 Pages 46-51
    Published: 2021
    Released: April 20, 2021
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    In order to develop highly functional hydrogel materials, elaborate design and precision construction of network structure are required. To this end, we are focusing on controlled/living radical polymerization techniques not only to synthesize defined precursor polymers but also to give a unique function by reversible activation-deactivation reaction mechanism. In this paper, a feature of living radical polymerization for gel synthesis is briefly described, and our recent results are outlined. In particular, the design of self-healable gel utilizing reversible addition-fragmentation chain transfer (RAFT) polymerization mechanism and amphiphilic conetworks with crosslinked domains capable of unique thermoresponsive swelling behavior and mechanical toughening are presented.

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  • Masayoshi NISHIURA, Zhaomin HOU
    2021 Volume 94 Issue 2 Pages 52-57
    Published: 2021
    Released: April 20, 2021
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    This article describes a new class of self-healing materials formed by the copolymerization of ethylene and anisyl-substituted propylenes using a sterically demanding half-sandwich scandium catalyst. The copolymerization proceeded in a controlled fashion, affording unique multi-block copolymers composed of relatively long alternating ethylene-alt-anisylpropylene sequences and short ethylene−ethylene units. By controlling the molecular weight and varying the anisyl substituents, a series of copolymers that show a wide range of glass-transition temperatures (Tg) and mechanical properties have been obtained. The copolymers with Tg below room temperature showed remarkable self-healability, being able to autonomously self-heal upon mechanical damage not only in a dry environment but also in water and aqueous acid and alkaline solutions, while those with Tg around or above room temperature exhibited excellent shape-memory property. The unique mechanical properties may be ascribed to the phase separation of the crystalline ethylene−ethylene nanodomains from the ethylene-alt-anisylpropylene matrix.

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  • Shintaro NAKAGAWA, Naoko YOSHIE
    2021 Volume 94 Issue 2 Pages 58-65
    Published: 2021
    Released: April 20, 2021
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    Mechanical performances are the most important aspect of elastomers consisting of a three-dimensionally cross-linked polymer network. Dynamic properties such as toughness, self-recoverability, and self-healing ability can be implemented by incorporation of physical crosslinks, which are weak and reversible bonds or interactions, into polymer networks. In this review, we focus on elastomers having hydrogen bonds (H-bonds) as the physical crosslinks and discuss the recent advances and directions in the field. After a general introduction to physical crosslinks and H-bonds in polymeric materials, our study on a tough and self-recoverable elastomer based on bioinspired phase-separated structure is reviewed. Application of this strategy to triblock copolymer-type thermoplastic elastomers is also discussed in the following section. Then, we turn our attention to the chemistry of H-bonds and introduce our recent findings on a tough and self-healable elastomer based on a new class of H-bonds, namely the entropy-driven H-bonds. Finally, the current and future directions of the H-bonded polymeric materials are discussed.

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  • Akihiro YABUKI, Ji Ha LEE
    2021 Volume 94 Issue 2 Pages 66-71
    Published: 2021
    Released: April 20, 2021
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    Corrosion protective coatings have been widely applied as a surface treatment to prevent corrosion of various metallic materials, such as carbon steels, aluminum alloys and magnesium alloys. One of the important characteristics which is required in the corrosion protective coatings is the self-healing ability. The self-healing coatings mean that when mechanical damage occurs and corrosive substances in the environment begin to degrade the bare metal surface, the damaged surface is repaired automatically by the chemical composition of the coating. This paper describes recent results which are developed self-healing coatings using the cellulose nanofibers and their network structure.

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