Strain-responsive mechanical properties of polymeric materials, Koichi Mayumi
The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
Polymeric materials that exhibit strain-responsive mechanical properties are attracting increasing attention as a class of adaptive and functional materials capable of dynamically adjusting their behavior under external deformation. In such systems, mechanical characteristics such as stiffness, strength, and energy dissipation evolve in response to applied strain, often driven by reversible changes in molecular conformation, network architecture, or intermolecular interactions. Understanding and controlling these strain-coupled processes enable the design of polymers with tunable and programmable mechanical performance, which are promising for applications in soft robotics, flexible electronics, and biomedical devices. In the seminar, I will introduce several topics on the strain-responsive mechanical properties of polymeric materials: (i) tough and elastic polymer gels reinforced by strain-induced crystallization, (ii) shear-induced gelation of polymer/nanoparticle solutions, (iii) fracture of cross-linked epoxy resins with different network structures.
Recently, we have successfully developed tough polymer gels utilizing strain-induced crystallization (SIC) [1-6]. In order to realize SIC in polymer gels, the polymer chain orientation under stretching should be homogeneous. We have discovered that SIC occurs in polymer gels with homogeneous polymer networks and sufficiently high polymer concentrations: slide-ring (SR) hydro gels [1], SR ion gels [2, 3], Tri-branched PEG gels [4], and Tetra-branched PEG gels [5]. From in-situ wide-angle X-ray scattering (WAXS) experiments on the gels under repeated tensile deformation, we found that nanocrystals of PEG in the gels forms at large strains and disappears quickly when applied stress is reduced. The reversible strain-induced crystallization yields the high toughness and elasticity. A similar concept can be applied to bio-based polysaccharide hydrogels to improve their mechanical toughness [7].
References:
[1] Liu C., Morimoto N., Jiang L., Kawahara S., Noritomi T., Yokoyama H., Mayumi K.*, Ito K.* Science 2021, 372, 1078.
[2] Hashimoto K., Shiwaku T., Aoki H., Yokoyama H., Mayumi K.*, Ito K.* Sci. Adv. 2023, 9, eadi8505.
[3] Enoki T., Hashimoto K., Oda T., Ito K., Mayumi K.* Macromolecules 2024, 57, 11498.
[4] Fujiyabu T., Sakumichi N., Katashima T., Liu C., Mayumi K., Chung U. I., Sakai T.* Sci. Adv. 2022, 8, eabk0010.
[5] Hashimoto K., Enoki T., Liu C., Li X., Sakai T., Mayumi K.* Macromolecules 2024, 57, 1461.
[6] Mayumi K.* Polym. J. 2024, 57, 449.
[7] Geonzon, L. C., Chan, J., Kou, H., Hou, L. X., Oda, T., Tuvikene, R., Matsukawa, S., Mayumi, K.*, Chem. Mater., 37, 6991 (2025).
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