Abstract The rapid developments of tough hydrogels have broadened the applications of gel materials in biomedicine and engineering fields, which recalls the fundamental understanding of the fracture behaviors of these tough, soft materials. Herein, we study the fracture behaviors of a Fe3+ coordinated poly(acrylic acid-co-acrylamide) (P(AAc-co-AAm)) hydrogel through pure shear tests. We measure a material-specific length, called fractocohesive length Lf, defined by the ratio of fracture energy to fracture work (Lf = Г/Wf). We show that Lf scales several important lengths that characterize the fracture behaviors of the hydrogel, including the transition length of cut-sensitivity Lc measured by stretching samples of various initial crack lengths to rupture, the increment of the crack length needed to attain the steady state Lss measured from the resistance curve, and the size of large deformation zone Li measured by the polarized microscopic image. We further show that the fracture of P(AAc-co-AAm) hydrogel is viscoelastic, as demonstrated by tensile and rheological tests at different deformation rates. This work gives an insight into the fracture behaviors of P(AAc-co-AAm) hydrogel and provides a methodology that should be applicable in characterizing the fracture behaviors of other tough materials.

中文翻译：

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坚韧和坚硬的金属超分子水凝胶的断裂

摘要 坚韧水凝胶的快速发展拓宽了凝胶材料在生物医学和工程领域的应用，回顾了对这些坚韧、柔软材料的断裂行为的基本认识。在此，我们通过纯剪切试验研究了 Fe3+ 配位的聚（丙烯酸-共聚-丙烯酰胺）（P（AAc-co-AAm））水凝胶的断裂行为。我们测量特定于材料的长度，称为压裂内聚长度 Lf，由断裂能与断裂功的比值 (Lf = Г/Wf) 定义。我们表明，Lf 缩放了几个表征水凝胶断裂行为的重要长度，包括通过将各种初始裂纹长度的样品拉伸至断裂来测量的切割敏感性 Lc 的过渡长度，由电阻曲线测得的达到稳态 Lss 所需的裂纹长度的增量，以及由偏光显微图像测得的大变形区 Li 的大小。我们进一步表明，P(AAc-co-AAm) 水凝胶的断裂是粘弹性的，正如在不同变形率下的拉伸和流变测试所证明的那样。这项工作深入了解了 P(AAc-co-AAm) 水凝胶的断裂行为，并提供了一种适用于表征其他坚韧材料断裂行为的方法。