Abstract Revealing the structure formation kinetics is a long-term challenging issue in the development of tough hydrogels, although they are significant for understanding structure-property relationship and toughening mechanism. Here, we report a series of tough and stiff poly(methacrylamide-co-methacrylic acid) hydrogels, with a focus on the structure-property relationship and structure formation kinetics. These hydrogels in a glassy state possess moderate water content and excellent mechanical properties with Young's modulus up to 200 MPa. The microstructure of the gels changes from uniform to bicontinuous and then to colloidal network as the fraction of methacrylamide, fam, increases, accounting for the ductile-brittle transition of the mechanical performances. Sequential gelation and vitrification take place in the systems with relatively low fam to form transparent gels with a homogeneous matrix, whereas colloidal jamming and coarsening occur in the systems with high fam to form opaque gels with a colloidal network structure. The structure and properties of the glassy gels are determined by the hydrogen bond complexation and the microphase separation that are strengthened by the increase in fam. Based on these findings, the mechanical properties of hydrogels with high fam can be improved by suppressing the microphase separation during the gel synthesis. Understanding the structure-property relationship and regulation strategy of both microstructure and macroscopic performance of these glassy hydrogels should be inspirative for designing other tough materials with diverse applications as structural elements in biomedical and engineering fields.

中文翻译：

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以氢键配合物作为交联的玻璃水凝胶的动力学见解

摘要 揭示结构形成动力学是韧性水凝胶开发中长期具有挑战性的问题，尽管它们对于理解结构-性能关系和增韧机制具有重要意义。在这里，我们报告了一系列坚韧而坚硬的聚（甲基丙烯酰胺-共聚-甲基丙烯酸）水凝胶，重点是结构-性能关系和结构形成动力学。这些处于玻璃态的水凝胶具有适中的含水量和优异的机械性能，杨氏模量高达 200 MPa。随着甲基丙烯酰胺、fam 含量的增加，凝胶的微观结构从均匀变为双连续，然后变为胶体网络，这是机械性能发生韧脆转变的原因。在 fam 相对较低的系统中发生顺序凝胶化和玻璃化，形成具有均匀基质的透明凝胶，而在 fam 高的系统中发生胶体堵塞和粗化，形成具有胶体网络结构的不透明凝胶。玻璃状凝胶的结构和性质是由氢键络合和微相分离决定的，随着 fam 的增加而增强。基于这些发现，可以通过抑制凝胶合成过程中的微相分离来改善高 fam 水凝胶的机械性能。