Research Theme
Tough Materials
Cross-linking design of tough materials using radical polymerizable CD monomers
Toughening of Inorganic Polymeric Materials by Movable Cross-Linking
Inorganic polymers such as polydimethylsiloxane (PDMS) have poorer mechanical properties than organic polymers. We prepared mobile crosslinked PDMS (PDMS-TAcγCD) by modifying thiol-modified PDMS with acrylamide-modified total acetylated γ-cyclodextrin (TAcγCD) via a thiol-ene reaction (Figure a). 100 times higher than that of chemically crosslinked PDMS. It is considered that TAcγCD, which forms a movable crosslink, slides on the PDMS main chain as it is stretched, alleviating the stress concentration at the crosslink point and contributing to the toughening (Figure b).
Yoshida, D. ;Park, J.; Yamashita, N.; Ikura, R.; Kato, N.; Kamei, M.; Ogura, K.; Igarashi, M.; Nakagawa, H.; Takashima, Y.,
Preparation of Mechanically Tough Poly(dimethyl siloxane) through the Incorporation of Acetylated Cyclodextrin-Based Topologically Movable Cross-links
Polym. Chem. 2023, 14, 3277-3285.
Composite of multiple movable networks and glassy polymers by braiding
The mobility crosslinking design was found to be effective not only in organic polymers but also in inorganic polymers, and we attempted to combine two mobility networks and improve the compatibility and toughness of the polymers. Several movable crosslinked network polymers with different glass transition temperatures were combined (Figure). The resulting composite material exhibited toughness with both hardness and elongation. The toughening mechanism was elucidated by simultaneous tensile test and small-angle X-ray scattering (SAXS) measurements at SPring-8, a large synchrotron radiation facility. It was found that the hard and soft components were independently deformed in multiple steps during the drawing process.
Kawai, Y.; Park, J.; Murayama, S.; Ikura, R.; Osaki, M.; Konishi, T.; Matsuba, G.; Takashima, Y.,
Hybridizing a dual-cross network and a linear glassy polymer for dynamic contributions to high mechanical toughness based on phase-separated structures
Macromolecules 2023, 56, 4503-4512.
Cross-linking Design of Tough Materials Using Heavily Additive CD Derivatives
Formation of a composite via dynamic crosslinking between multiple types of polymers
We developed a polymer composite material through molecular threading, in which solvent-free polymerization of main-chain monomers was conducted in the presence of linear polymers modified with cyclodextrins (CDs). This resulted in dynamic crosslinking structures where the polymer main chains are threaded through CD rings (see figure). The resulting material exhibited enhanced toughness due to efficient stress dissipation enabled by the long-range mobility of the crosslinks. By applying this molecular threading design, we successfully connected two immiscible polymers, poly(ethyl acrylate) (PEA) and polystyrene (PS), via dynamic crosslinks, which led to further improvements in toughness and Youngfs modulus. In the resulting mixed-phase system, the PEA phase contributed to stress dissipation owing to its high chain mobility, while the PS phase acted as a hard domain, allowing for synergistic mechanical reinforcement through the cooperation of the two distinct phases.
Ikura, R.; Murayama, S.; Park, J.; Ikemoto, Y.; Osaki, M.; Yamaguchi, H.; Harada, A.; Matsuba, G.; Takashima, Y.,
Fabrication and Mechanical Properties of Knitted Dissimilar Polymeric Materials with Movable Cross-Links.
Molecular Systems Design & Engineering 2022, 7, 733-745.
Toughening via Dynamic Crosslinking Formed During Solvent-Free Polymerization
An acetylated hydrophobic cyclodextrin (CD) monomer was dissolved in the liquid main-chain monomer, ethyl acrylate (EA), and bulk radical copolymerization was carried out. As a result, an elastomeric single movable cross-network (SC) was obtained, in which the EA main chains are threaded through the CD rings, forming dynamic crosslinks (see figure). This method of forming dynamic crosslinking is applicable to various liquid main-chain monomers, provided they are of suitable size for the CD cavity, and has also been successfully applied to the development of movable crosslinked hydrogels. Tensile testing of the SC elastomer revealed high strength and elongation. It is considered that the CD rings in the SC elastomer can "slide" along the polymer main chain, enabling effective stress dissipation and thereby contributing to the enhanced toughness.
Ikura, R.; Park, J.; Osaki, M.; Yamaguchi, H.; Harada, A.; Takashima, Y.,
Supramolecular Elastomers with Movable Cross-Linkers Showing High Fracture Energy Based on Stress Dispersion
Macromolecules 2019, 52(18), 6953-6962.
