Mesoscale bicontinuous networks in self-healing hydrogels delay fatigue fracture
Mesoscale bicontinuous networks in self-healing hydrogels delay fatigue fracture
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DOI：
10.1073/pnas.2000189117
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发表时间：
2020-04-07
影响因子：
11.1
通讯作者：
Gong, Jian Ping
中科院分区：
文献类型：
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作者：
Li, Xueyu;Cui, Kunpeng;Gong, Jian Ping
承载负荷的生物组织，如肌肉，具有高度的抗疲劳性，但生物组织的精致层次结构如何有助于其优异的抗疲劳性尚不清楚。在这项工作中，我们研究了抗疲劳性能的软材料的分级结构，使用聚两性电解质水凝胶（PA凝胶）作为一个简单的模型系统。PA凝胶是坚韧和自密封的，由在1-nm尺度的可逆离子键，在10-nm尺度的交联聚合物网络，和在100-nm尺度的双连续硬/软相网络组成。我们发现，在10纳米尺度的聚合物网络确定的能量释放速率G（0）以上的裂纹增长的阈值，而在100纳米尺度的双连续相网络显着减速裂纹前进，直到过渡G（transan）远远高于G（0）。原位小角X射线散射分析表明，硬质相网络抑制了裂纹的扩展，表现为减速疲劳断裂，G（tran）对应于硬质相网络的断裂。
Load-bearing biological tissues, such as muscles, are highly fatigue-resistant, but how the exquisite hierarchical structures of biological tissues contribute to their excellent fatigue resistance is not well understood. In this work, we study antifatigue properties of soft materials with hierarchical structures using polyampholyte hydrogels (PA gels) as a simple model system. PA gels are tough and self-ealing, consisting of reversible ionic bonds at the 1-nm scale, a cross-linked polymer network at the 10-nm scale, and bicontinuous hard/soft phase networks at the 100-nm scale. We find that the polymer network at the 10-nm scale determines the threshold of energy release rate G(0) above which the crack grows, while the bicontinuous phase networks at the 100-nm scale significantly decelerate the crack advance until a transition G(tran) far above G(0). In situ small-angle X-ray scattering analysis reveals that the hard phase network suppresses the crack advance to show decelerated fatigue fracture, and G(tran) corresponds to the rupture of the hard phase network.