Fracture of Polymer Networks Containing Topological Defects,Macromolecules

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Fracture of Polymer Networks Containing Topological Defects
Macromolecules ( IF 5.1 ) Pub Date : 2020-08-24 , DOI: 10.1021/acs.macromol.0c01038
Akash Arora ₁ , Tzyy-Shyang Lin ₁ , Haley K. Beech ₁ , Hidenobu Mochigase _{1,

2} , Rui Wang ₁ , Bradley D. Olsen ₁

Affiliation

The failure properties of a polymer network, including toughness, ultimate strain, and ultimate stress, are some of the most critical properties for network performance. The polymer networks often contain various topological defects, such as primary loops and dangling ends, which have a noticeable effect on these properties. This work focuses on understanding the effect of these defects on the fracture strength of a material by expanding the classical Lake–Thomas theory to account for such defects under the assumption that each defect is unaffected by the presence of other defects in its environment. A Flory–Stockmayer gel point criterion is combined with the improved theory to identify the incipience of fracture. The predictions demonstrate that although the presence of defects weakens the material by reducing the tearing energy, the overall network elongation depends strongly on the primary loop fraction. Specifically, a transition from a low ultimate-strain to a significantly high ultimate-strain behavior is predicted. The addition of a kinetic theory for bond scission predicts that the sharpness of this transition is a strong function of the strain rate. To experimentally test these predictions, a series of poly(ethylene glycol) (PEG) gels with previously characterized primary loop fractions were synthesized. Remarkably, the measured tearing energies agree quite well with the theoretical predictions and also suggest the onset of the low to high extensibility transition.

中文翻译：

包含拓扑缺陷的聚合物网络的断裂

聚合物网络的失效特性，包括韧性，极限应变和极限应力，是网络性能最关键的特性。聚合物网络通常包含各种拓扑缺陷，例如主回路和悬空末端，这些缺陷对这些性能有明显影响。这项工作着重于通过扩展经典的Lake–Thomas理论来解释这些缺陷对材料的断裂强度的影响，并假设每种缺陷不受环境中其他缺陷的影响，从而解释了此类缺陷。Flory–Stockmayer凝胶点判据与改进的理论相结合，可以确定断裂的开始。这些预测表明，尽管缺陷的存在会通过降低撕裂能量来削弱材料，整个网络的伸长率在很大程度上取决于主回路分数。具体地，预测了从低极限应变到明显高的极限应变行为的过渡。对于键断裂的动力学理论的增加预示了这种转变的清晰度是应变速率的强函数。为了实验上测试这些预测，合成了一系列具有先前表征的一级回路级分的聚（乙二醇）（PEG）凝胶。值得注意的是，测得的撕裂能量与理论预测非常吻合，也暗示了从低到高延伸性转变的开始。对于键断裂的动力学理论的增加预示了这种转变的清晰度是应变速率的强函数。为了实验上测试这些预测，合成了一系列具有先前表征的一级回路级分的聚（乙二醇）（PEG）凝胶。值得注意的是，测得的撕裂能量与理论预测非常吻合，也暗示了从低到高延伸性转变的开始。对于键断裂的动力学理论的增加预示了这种转变的清晰度是应变速率的强函数。为了实验上测试这些预测，合成了一系列具有先前表征的一级回路级分的聚（乙二醇）（PEG）凝胶。值得注意的是，测得的撕裂能量与理论预测非常吻合，也暗示了从低到高延伸性转变的开始。

更新日期：2020-09-09

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