Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8505, Japan.
Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan.
Adv Mater. 2023 Jun;35(23):e2301124. doi: 10.1002/adma.202301124. Epub 2023 Apr 20.
Elastomers are indispensable materials due to their flexible, stretchable, and elastic nature. However, the polymer network structure constituting an elastomer is generally inhomogeneous, limiting the performance of the material. Here, a highly stretchable elastomer with unprecedented strain-stiffening capability is developed based on a highly homogeneous network structure enabled by a module assembly strategy. The elastomer is synthesized by efficient end-linking of a star-shaped aliphatic polyester precursor with a narrow molecular-weight distribution. The resulting product shows high strength (≈26 MPa) and remarkable stretchability (stretch ratio at break ≈1900%), as well as good fatigue resistance and notch insensitivity. Moreover, it shows extraordinary strain-stiffening capability (>2000-fold increase in the apparent stiffness) that exceeds the performance of any existing soft material. These unique properties are due to strain-induced ordering of the polymer chains in a uniformly stretched network, as revealed by in situ X-ray scattering analyses. The utility of this great strain-stiffening capability is demonstrated by realizing a simple variable stiffness actuator for soft robotics.
弹性体因其灵活、可拉伸和弹性的特性而不可或缺。然而，构成弹性体的聚合物网络结构通常是不均匀的，限制了材料的性能。在这里，通过模块组装策略实现了高度均匀的网络结构，从而开发出了具有前所未有的应变硬化能力的高拉伸弹性体。该弹性体是通过高效的端接具有窄分子量分布的星形脂肪族聚酯前体合成的。所得产物表现出高强度（≈26 MPa）和显著的拉伸性（断裂拉伸比≈1900%），以及良好的耐疲劳性和无缺口敏感性。此外，它表现出非凡的应变硬化能力（表观刚度增加超过 2000 倍），超过了任何现有软材料的性能。这些独特的性能归因于在均匀拉伸的网络中聚合物链的应变诱导有序，这是通过原位 X 射线散射分析揭示的。通过实现用于软机器人的简单可变刚度致动器，展示了这种高应变硬化能力的实用性。
