Viscoelastic phase separation in shear flow.
Viscoelastic phase separation in shear flow.
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DOI：
10.1103/physreve.70.051503
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发表时间：
2003-09
期刊：
影响因子：
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通讯作者：
Tatsuhiro Imaeda;A. Furukawa;A. Onuki
中科院分区：
文献类型：
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作者：
Tatsuhiro Imaeda;A. Furukawa;A. Onuki
本文采用含时的Ginzburg-Landau模型数值研究了剪切作用下聚合物溶液的粘弹性相分离。在我们的模型中的总变量是聚合物的体积分数和构象张量。后者代表链变形和松弛缓慢的流变时间引起一个大的粘弹性应力。聚合物和溶剂服从双流体动力学，其中粘弹性应力不对称地作用在聚合物上，因此，应力和扩散动态地耦合。在共存曲线下方，随着淬冷深度的增加，界面出现，溶剂区起到润滑剂的作用。在这些情况下，组成的不均匀性导致更增强的粘弹性不均匀性，并且在固定的施加剪切速率下宏观应力降低。我们发现稳定的两相状态组成的富聚合物和富溶剂的区域，其中的特征域的大小是成反比的平均剪切应力为各种剪切速率。偏应力分量表现出很大的时间波动。在弱剪切作用下，正应力差可瞬时为负值。
We numerically investigate viscoelastic phase separation in polymer solutions under shear using a time-dependent Ginzburg-Landau model. The gross variables in our model are the polymer volume fraction and a conformation tensor. The latter represents chain deformations and relaxes slowly on the rheological time giving rise to a large viscoelastic stress. The polymer and the solvent obey two-fluid dynamics in which the viscoelastic stress acts asymmetrically on the polymer and, as a result, the stress and the diffusion are dynamically coupled. Below the coexistence curve, interfaces appear with increasing the quench depth and the solvent regions act as a lubricant. In these cases the composition heterogeneity causes more enhanced viscoelastic heterogeneity and the macroscopic stress is decreased at fixed applied shear rate. We find steady two-phase states composed of the polymer-rich and solvent-rich regions, where the characteristic domain size is inversely proportional to the average shear stress for various shear rates. The deviatoric stress components exhibit large temporal fluctuations. The normal stress difference can take negative values transiently at weak shear.