Institut Charles Sadron, Université de Strasbourg, CNRS UPR22, 67034 Strasbourg, France.
Phys Rev Lett. 2011 Oct 21;107(17):178301. doi: 10.1103/PhysRevLett.107.178301. Epub 2011 Oct 17.
Contrary to common belief, hydrodynamic interactions in polymer melts are not screened beyond the monomer length and are important in transient regimes. We show that viscoelastic hydrodynamic interactions (VHIs) lead to anomalous dynamics of a tagged chain in an unentangled melt at t<t(N), the Rouse time. The center-of-mass (c.m.) mean-square displacement is enhanced by a large factor increasing with chain length. We develop a theory of VHI-controlled chain dynamics yielding a negative c.m. velocity autocorrelation function which agrees with our molecular dynamics simulations without any fitting parameter. It is also shown that Langevin friction strongly affects the short-t c.m. dynamics, also captured by our theory. The transient VHI effects thus provide the dominant contribution to the subdiffusive c.m. motion universally observed in simulations and experiments.
与普遍观点相反，聚合物熔体中的流体动力学相互作用并没有超出单体长度的屏蔽，并且在瞬态状态下很重要。我们表明，粘弹性流体动力学相互作用 (VHIs) 导致未缠结熔体中标记链在 t<t(N)，即罗瑟时间，的异常动力学。质心 (c.m.) 均方根位移被一个随着链长增加的大因子增强。我们开发了一种 VHIs 控制链动力学的理论，得到了一个负的 c.m. 速度自相关函数，该函数与我们的分子动力学模拟一致，没有任何拟合参数。还表明，兰格文摩擦强烈影响短时间 c.m. 动力学，这也被我们的理论所捕捉。因此，瞬态 VHIs 效应为普遍观察到的模拟和实验中亚扩散 c.m. 运动提供了主要贡献。
