The monomer friction coefficient ζ is known to vary with monomer structure, solvent, and concentration; its variation with chain conformation is less well known and appreciated. We explore the decrease of the friction coefficient in the extensional flow of polymer liquids, during which chains become partially stretched and aligned. To induce stretching and alignment similar to the extensional flow without a nonequilibrium flow simulation, we apply equal and opposite forces to the chain ends. We measure the friction coefficient by observing the diffusion of chains along the direction of pull. Our results for friction coefficient versus stretching qualitatively support recent arguments from rheology that friction reduction is necessary to account for smaller than predicted stress overshoots in the startup of the flow.

中文翻译：

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链张力降低了模拟聚合物熔体中的单体摩擦

已知单体摩擦系数 ζ 随单体结构、溶剂和浓度而变化；它与链构象的变化鲜为人知和受到重视。我们探索了聚合物液体拉伸流动中摩擦系数的降低，在此期间链变得部分拉伸和对齐。为了在没有非平衡流动模拟的情况下引起类似于拉伸流动的拉伸和对齐，我们对链端施加相等和相反的力。我们通过观察链沿拉力方向的扩散来测量摩擦系数。我们关于摩擦系数与拉伸的结果定性地支持了流变学的最新论点，即摩擦减少是必要的，以解决流动开始时小于预测的应力超调。