Long-chain polymers make dominant trefoil knots that could influence their crystallization behaviors. We performed dynamic Monte Carlo simulations of polymer crystallization to investigate the constraint effects of one or two trefoil knots on the initiation of crystallization by comparing their parallel results to zero knot, encompassing single chains in the dilute solutions, melt chains in the quiescent bulk phase, and melt chains in the stretching process. The results demonstrated that single chains hold relatively loose knots owing to the volume exclusion of knot monomers, and the constraint effects enhance the thermodynamic stability of crystal nuclei inside the knots to accelerate intramolecular crystal nucleation. In contrast, melt chains hold relatively tight knots owing to polymer interpenetration that screens off the volume exclusion of knot monomers, and the constraint effects retard their dominant intramolecular crystal nucleation due to both shortened segments inside and outside the knots. Meanwhile, the knots show much smaller effects on the dominantly intermolecular crystal nucleation in strain-induced polymer crystallization. In conclusion, the constraint effects of polymer knots mainly influence intramolecular rather than intermolecular crystal nucleation. Our observations shed light on the effects of polymer knots on crystallization behaviors.

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三叶结对聚合物结晶引发的影响

长链聚合物形成主要的三叶结，这可能会影响其结晶行为。我们对聚合物结晶进行了动态蒙特卡罗模拟，通过将其平行结果与零结进行比较，研究一两个三叶结对结晶引发的约束影响，包括稀溶液中的单链、静态本体相中的熔体链、和拉伸过程中的熔链。结果表明，由于结单体的体积排斥，单链具有相对松散的结，约束效应增强了结内晶核的热力学稳定性，加速了分子内晶体成核。相比之下，熔体链由于聚合物互穿而保持相对紧密的结，从而屏蔽了结单体的体积排斥，并且由于结内部和外部的链段缩短，约束效应阻碍了其主要的分子内晶体成核。同时，结对应变诱导聚合物结晶中主要的分子间晶核的影响要小得多。综上所述，聚合物结的约束作用主要影响分子内晶体成核，而不是分子间晶体成核。我们的观察揭示了聚合物结对结晶行为的影响。