Mesoscale bicontinuous networks in self-healing hydrogels delay fatigue fracture.
basic_science · Level V
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- Record sourced from PubMed, PMID 32209673.
- Also identified by DOI 10.1073/pnas.2000189117 and PMC identifier 7149489.
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Abstract
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-healing, 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 <i>G</i><sub>0</sub> above which the crack grows, while the bicontinuous phase networks at the 100-nm scale significantly decelerate the crack advance until a transition <i>G</i><sub>tran</sub> far above <i>G</i><sub>0</sub> In situ small-angle X-ray scattering analysis reveals that the hard phase network suppresses the crack advance to show decelerated fatigue fracture, and <i>G</i><sub>tran</sub> corresponds to the rupture of the hard phase network.