Fracture Process of Double-Network Gels by Coarse-Grained Molecular Dynamics Simulation,Macromolecules

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Fracture Process of Double-Network Gels by Coarse-Grained Molecular Dynamics Simulation
Macromolecules ( IF 5.1 ) Pub Date : 2018-04-10 00:00:00 , DOI: 10.1021/acs.macromol.8b00124
Yuji Higuchi _{1,

2,

3} , Keisuke Saito ₁ , Takamasa Sakai _{2,

4} , Jian Ping Gong ₅ , Momoji Kubo ₁

Affiliation

Double-network (DN) gels consisting of highly and slightly cross-linked networks exhibit good mechanical properties, complicated deformation behavior, and fracture processes owing to the existence of a large number of influential parameters. To determine the effects of these factors at the molecular level to improve the mechanical properties further, we studied the fracture processes of DN gels using a coarse-grained molecular dynamics simulation. First, we propose a modeling method for DN gels consisting of highly (first) and slightly (second) cross-linked networks. Then, we stretch the DN gels and investigate the effects of the network ratio, chain length, and first- and second-network structures on the mechanical properties. During the stretching, the stress increases with the bond breaking in the first network. Then, the stress further increases with the simultaneous bond breaking in the first and second networks when they are entangled with one another. Finally, the bond breaking in the first network stops, and only the bond breaking in the second network occurs. The second network remains at a high strain, which prevents rupture of the gel. We find that (i) a low concentration of the first network is necessary for the gel to exhibit the properties of both the first and second networks, (ii) a tense first network increases the Young’s modulus, and (iii) the second network with a long chain length and separated cross-linking points increases the peak stress and ductility. We have therefore successfully elucidated the effects of the network structures on the mechanical properties of DN gels.

中文翻译：

粗粒化分子动力学模拟双网凝胶的断裂过程

由于存在大量影响参数，由高度交联的网络和轻微交联的网络组成的双网络（DN）凝胶具有良好的机械性能，复杂的变形行为和断裂过程。为了确定这些因素在分子水平上的影响，以进一步改善机械性能，我们使用粗粒度的分子动力学模拟研究了DN凝胶的断裂过程。首先，我们提出了由高度（第一）和轻微（第二）交联网络组成的DN凝胶的建模方法。然后，我们拉伸DN凝胶并研究网络比率，链长以及第一和第二网络结构对机械性能的影响。在拉伸过程中，应力随着第一网络中的键断裂而增加。然后，当第一和第二网络相互缠结时，应力会随着同时发生的键断裂而进一步增加。最终，第一个网络中的键断开停止，只有第二个网络中的键断开发生。第二网络保持高应变，防止凝胶破裂。我们发现（i）凝胶必须具有低浓度的第一网络以显示第一网络和第二网络的特性，（ii）紧张的第一网络会增加杨氏模量，以及（iii）第二网络具有较长的链长和分离的交联点会增加峰值应力和延展性。因此，我们已经成功地阐明了网络结构对DN凝胶力学性能的影响。

更新日期：2018-04-10

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