A coarse-grained model combining the acceptor–hydrogen–donor 3-body potential is first developed in this work to explore the fracture property and microscopic mechanisms of associative hydrogen-bonded polymers (AHBPs). Next, a triaxial deformation mode is performed to reveal that the fracture toughness of AHBPs initially improves and then is reduced as the number of active groups increases. By characterizing the stress decomposition, the strong hydrogen bond (HB) network improves the maximum stress but reduces the elongation. The destructive process of the HB network is described by quantifying the broken number and reduced energy of HBs. Interestingly, the strength of a single HB first decreases and then rises with strain. The initial decrease is mainly caused by the disruption of strong/moderate HBs, while the following rise is due to the further breakage of weak HBs and partial recovery of strong/moderate HBs. Meanwhile, the formed clusters of HBs due to the self-attraction act as the physical cross-links, whose evolution process is recorded by analyzing their number and size. Following it, the orientation degree and asphericity factor are calculated with strain to reflect the change in chain configuration, which is influenced by the HB network. Subsequently, the nucleation and growth process of voids is quantified. More than 90% of voids are nucleated in the polymer region, while others are in the HB region, which can be proved by the local elastic modulus and snapshots. The growth and coalescence rate of the voids can be suppressed by the strong HB network. Finally, the fracture toughness of AHBPs exhibits a continuous increase with improving strength of HBs due to the strong HB network. In summary, our work presents a clear and novel comprehension of the fracture property of AHBPs at the molecular scale.

中文翻译：

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通过分子动力学模拟研究氢键数量和强度对缔合氢键聚合物断裂性能和微观机制的影响


这项工作首先开发了一个结合了受体-氢-供体 3 体电位的粗晶模型，以探索缔合氢键聚合物 （AHBPs） 的断裂特性和微观机制。接下来，进行三轴变形模式，揭示 AHBPs 的断裂韧性最初提高，然后随着活性基团数量的增加而降低。通过表征应力分解，强氢键 （HB） 网络提高了最大应力，但降低了伸长率。HB 网络的破坏过程是通过量化 HB 的断裂数和减少的能量来描述的。有趣的是，单个 HB 的强度首先随着应变而降低，然后上升。最初的下降主要是由于强/中度 HBs 的破坏造成的，而随后的上升是由于弱 HBs 的进一步断裂和强/中度 HBs 的部分恢复。同时，由于自吸引而形成的 HBs 簇充当物理交联，通过分析它们的数量和大小来记录其进化过程。然后，用应变计算取向度和非球性因子，以反映受 HB 网络影响的链配置的变化。随后，量化空隙的成核和生长过程。超过 90% 的空隙在聚合物区域成核，而其他空隙在 HB 区域，这可以通过局部弹性模量和快照来证明。空隙的生长和聚结速率可以被强 HB 网络抑制。最后，由于HB网络较强，AHBPs的断裂韧性随着HBs强度的提高而不断提高。 总之，我们的工作在分子尺度上对 AHBP 的断裂特性提出了清晰而新颖的理解。