Long molecular dynamics simulations are performed for dilute solutions of ring poly(ethylene oxide) (PEO) molecules in matrices of linear PEO chains where we systematically vary the molecular length of the ring and host chains. Our focus is on the effect of linear chain size on microscopic structure, conformation, and dynamics of the guest ring molecules, and how these properties vary with the corresponding ones in the pure ring melts. Ring molecules are found to be significantly swollen in all ring–linear blends simulated. Ring swelling is more pronounced in matrices of very short linear chains (molecular weights less than about 1.5 kg/mol) due to excess, chain-end free-volume effects. In these very short linear hosts, all PEO rings simulated (molecular weights between 2 and 10 kg/mol) diffuse faster than in their own melts. However, as the size of the host linear chains increases above the entanglement molecular weight, the diffusivity of rings decreases considerably. Interestingly enough, for the shorter PEO rings simulated (molecular weight equal to 2 kg/mol), the diffusion coefficient in long, entangled matrices approaches a constant value independent of the molecular weight of the matrix, whereas that of longer rings (molecular weight equal to 5k and 10k g/mol) decreases continuously (at least for the linear matrix molecular weights examined here). Our simulation predictions for the diffusion coefficient of PEO rings in the linear PEO matrices compare remarkably well with the recent pulse-field gradient NMR measurements of Kruteva et al. [Macromolecules2017,50, 9482–9493]. A detailed topological analysis reveals that long ring molecules are heavily threaded by the host linear chains. Their segmental and diffusive dynamics is therefore governed by the rate with which threadings are created and released. Threadings, which are quantified in detail in our analysis, are also seen to cause strong fluctuations in the instantaneous conformation of the host linear chains, thus influencing their average dimensions. Our work provides strong evidence that ring–linear threadings is the key mechanism governing the size, the conformation, and the dynamic behavior of ring–linear polymer blends.

中文翻译：

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线性聚合物基体中聚合物环的尺寸和扩散性：穿线事件的关键作用

对线性PEO链矩阵中的环聚（环氧乙烷）（PEO）分子的稀溶液进行了长分子动力学模拟，我们系统地改变了环和主体链的分子长度。我们的重点是线性链大小对客体环分子的微观结构，构象和动力学的影响，以及这些性质如何随纯环熔体中的相应性质而变化。发现在所有模拟的环-线性混合物中，环分子均明显溶胀。由于过量的链端自由体积效应，在非常短的线性链（分子量小于约1.5kg / mol）的基质中，环溶胀更为明显。在这些非常短的线性主体中，所有模拟的PEO环（分子量在2至10 kg / mol之间）的扩散速度都快于其自身的熔体。然而，当主体线性链的大小增加到缠结分子量以上时，环的扩散率显着降低。有趣的是，对于较短的PEO环模拟（分子量等于2 kg / mol），在长的纠缠矩阵中，扩散系数接近恒定值，与基质的分子量无关，而较长的环（分子量等于降低至5k和10k g / mol）（至少对于此处考察的线性基质分子量而言）。我们对线性PEO矩阵中PEO环的扩散系数的模拟预测与最近的Kruteva等人的脉冲场梯度NMR测量结果相比有很好的对比。[ 有趣的是，对于较短的PEO环模拟（分子量等于2 kg / mol），在长的纠缠矩阵中，扩散系数接近恒定值，与基质的分子量无关，而较长的环（分子量等于降低至5k和10k g / mol）（至少对于此处考察的线性基质分子量而言）。我们对线性PEO矩阵中PEO环的扩散系数的模拟预测与最近的Kruteva等人的脉冲场梯度NMR测量结果相比有很好的对比。[ 有趣的是，对于较短的PEO环模拟（分子量等于2 kg / mol），在长的纠缠矩阵中，扩散系数接近恒定值，与基质的分子量无关，而较长的环（分子量等于降低至5k和10k g / mol）（至少对于此处考察的线性基质分子量而言）。我们对线性PEO矩阵中PEO环的扩散系数的模拟预测与最近的Kruteva等人的脉冲场梯度NMR测量结果相比有很好的对比。[ 而较长环的分子量（分子量分别为5k和10k g / mol）连续降低（至少对于此处考察的线性基质分子量而言）。我们对线性PEO矩阵中PEO环的扩散系数的模拟预测与最近的Kruteva等人的脉冲场梯度NMR测量结果相比有很好的对比。[ 而较长环的分子量（分子量分别为5k和10k g / mol）连续降低（至少对于此处考察的线性基质分子量而言）。我们对线性PEO矩阵中PEO环的扩散系数的模拟预测与最近的Kruteva等人的脉冲场梯度NMR测量结果相比有很好的对比。[大分子2017，50， 9482-9493]。详细的拓扑分析显示，长环分子被主体线性链紧密连接。因此，它们的分段和扩散动力学受线程创建和释放的速率控制。在我们的分析中详细量化的线程也被认为会导致宿主线性链的瞬时构型强烈波动，从而影响其平均尺寸。我们的工作提供了有力的证据，证明环线型螺纹是控制环线型聚合物共混物的大小，构象和动力学行为的关键机制。