Using computer simulations, we have investigated the deformation and stress–strain behavior of a series of ideal gels without any defects, with a bimodal molecular weight distribution, subject to tensile strains. These networks were prepared with a spatially homogeneous distribution of short and long chains, where all chains are elastically active, without needing to consider possible effects of chain aggregation or entanglements on the physical properties. For all fractions of short chains, the first chains to rupture were the short chains that were initially oriented along the strain axis. The average orientation of the short chains slightly increased with decreasing fraction of short chains. This could be explained by the detailed structure of the network at different compositions. Analysis of the stress–strain relation for the short and long chains showed that the stress was not uniformly shared. Instead, the short chains are more strongly deformed whereas the long chains only make a negligible contribution at smaller strains. The mechanical properties of the bimodal networks at lower fractions of short chains also deviated from the behavior of equivalent unimodal networks with the corresponding average chain length, showing that bimodality alone is sufficient to increase both the maximum extensibility and toughness.

中文翻译：

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双峰网络的变形行为与失效

使用计算机模拟，我们研究了一系列理想凝胶的变形和应力-应变行为，这些凝胶无任何缺陷，具有双峰分子量分布，并受拉伸应变的影响。这些网络是按照短链和长链在空间上均匀分布的方式制备的，其中所有链都具有弹性，而无需考虑链聚集或缠结对物理性能的可能影响。对于短链的所有部分，首先断裂的短链是最初沿应变轴定向的短链。短链的平均取向随着短链分数的降低而略有增加。这可以通过网络在不同组成下的详细结构来解释。对短链和长链的应力-应变关系的分析表明，应力分布不均。相反，短链更强烈地变形，而长链仅在较小应变时贡献可忽略不计。双峰网络在较短链的较低分数下的机械性能也偏离了具有相应平均链长的等效单峰网络的行为，表明仅双峰就足以增加最大可扩展性和韧性。