狭缝中单个polymer链的普适性质：标度与MD模拟
Universal properties of a single polymer chain in slit: Scaling versus MD simulations
摘要：
我们重新审视了经典的问题，聚合物限制在一个狭缝在其静态和动态方面。我们确认了许多众所周知的缩放预测，并通过使用柔性聚合物链的粗粒度珠弹簧模型进行全面的分子动力学模拟来分析其有效性范围。的平均端到端的距离，平均回转半径和它们的分布，密度分布，施加在狭缝壁上的力，和局部键的取向特性的正常和平行的组件中得到的狭缝宽度$D$ = $4 ÷10$（在珠半径的单位）和链长$N=50 ÷300$。我们证明了一个广泛的静态链性质在正常方向上可以描述{ \em定量}的解析模型无关的表达式与计算机实验完全一致。特别是，所观察到的约束诱导键取向的配置文件，显示密切匹配的理论预测。禁闭的各向异性被认为是最显着地表现在聚合物链的动态行为。我们研究平移扩散和横向弛豫的特征时间之间的关系。它表明，横向和正常的弛豫时间的标度预测与我们的观察是很好的协议。一个新的功能是观察到的耦合的正常和横向模式有两个截然不同的弛豫时间。我们表明，接枝对横向弛豫的影响相当于链长加倍。
英文摘要：
We revisit the classical problem of a polymer confined in a slit in both of its static and dynamic aspects. We confirm a number of well known scaling predictions and analyse their range of validity by means of comprehensive Molecular Dynamics simulations using a coarse-grained bead-spring model of a flexible polymer chain. The normal and parallel components of the average end-to-end distance, mean radius of gyration and their distributions, the density profile, the force exerted on the slit walls, and the local bond orientation characteristics are obtained in slits of width $D$ = $4 ÷10$ (in units of the bead radius) and for chain lengths $N=50 ÷300$. We demonstrate that a wide range of static chain properties in normal direction can be described {\em quantitatively} by analytic model - independent expressions in perfect agreement with computer experiment. In particular, the observed profile of confinement-induced bond orientation, is shown to closely match theory predictions. The anisotropy of confinement is found to be manifested most dramatically in the dynamic behavior of the polymer chain. We examine the relation between characteristic times for translational diffusion and lateral relaxation. It is demonstrated that the scaling predictions for lateral and normal relaxation times are in good agreement with our observations. A novel feature is the observed coupling of normal and lateral modes with two vastly different relaxation times. We show that the impact of grafting on lateral relaxation is equivalent to doubling the chain length.
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