Stretching-induced nucleation and crystallization of cyclic polyethylene (PE) were investigated by molecular dynamics (MD) simulation. The results show that nucleation and crystallization of cyclic PE are intimately related to the molecular weight of chains and strain rate. We found that there exists a critical molecular weight, below which increasing the molecular weight leads to the increase of crystallization rate and above which increasing the molecular weight leads to the slowdown of crystallization rate. This is caused by the fact that when the chain length is short, it is difficult to form a stable crystal nucleus because of its strong movement ability, while when the chain length is long, it hinders the conformational transformation and orderly arrangement of chain segments due to its reduced movement ability. The more the content of segments with longer conformational ordered segments and higher orientation in the system, the more conducive to the formation of more stable nuclei. Cyclic PE systems tend to form crystal nuclei through intramolecular nucleation with the increases of chain length. In addition, stretching will cause the chains to be disentangled and orderly arranged along the stretching direction to form crystal regions. The crystallization ability of the system will deteriorate with the acceleration of strain rate. This is because when the strain rate is low, it takes a long time to stretch to the same strain, and there is enough time to be stretched, resulting in more stretching of the chains and an increase in the probability of orderly arrangement of chain segments, so it is easier to orientation and crystallization. The opposite is true when the strain rate is high.

通过分子动力学（MD）模拟研究了环状聚乙烯（PE）的拉伸诱导成核和结晶。结果表明，环状PE的成核和结晶与链的分子量和应变速率密切相关。我们发现存在一个临界分子量，低​​于该临界值的分子量增加导致结晶速率增加，高于该临界值的分子量增加导致结晶速率减慢。这是因为当链长短时，由于其运动能力强，难以形成稳定的晶核，而当链长长时，则阻碍了链段的构象转变和有序排列。因其运动能力下降。体系中构象有序片段较长、取向度较高的片段含量越多，越有利于形成更稳定的原子核。随着链长的增加，环状PE体系倾向于通过分子内成核形成晶核。此外，拉伸会使链解开，沿着拉伸方向有序排列，形成晶区。体系的结晶能力会随着应变速率的加快而下降。这是因为当应变率较低时，拉伸到相同的应变需要很长时间，并且有足够的时间被拉伸，导致链的拉伸更多，链段有序排列的概率增加，因此更容易取向和结晶。