Grzetic Douglas J, Wickham Robert A
Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
J Chem Phys. 2020 Mar 14;152(10):104903. doi: 10.1063/1.5142179.
We study the spinodal decomposition in a symmetric, binary homopolymer blend using our recently developed dynamical self-consistent field theory. By taking the extremal solution of a dynamical functional integral, the theory reduces the interacting, multi-chain dynamics to a Smoluchowski equation describing the statistical dynamics of a single, unentangled chain in a self-consistent, time-dependent, mean force-field. We numerically solve this equation by evaluating averages over a large ensemble of replica chains, each one of which obeys single-chain Langevin dynamics, subject to the mean field. Following a quench from the disordered state, an early time spinodal instability in the blend composition develops, before even one Rouse time elapses. The dominant, unstable, growing wavelength is on the order of the coil size. The blend then enters a late-time, t, scaling regime with a growing domain size that follows the expected Lifshitz-Slyozov-Wagner t power law, a characteristic of a diffusion-driven coarsening process. These results provide a satisfying test of this new method, which correctly captures both the early and late time physics in the blend. Our simulation spans five orders-of-magnitude in time as the domains coarsen to 20 times the coil size, while remaining faithful to the dynamics of the microscopic chain model.
我们使用最近开发的动力学自洽场理论研究对称二元均聚物共混物中的旋节线分解。通过求解动力学泛函积分的极值解，该理论将相互作用的多链动力学简化为一个斯莫卢霍夫斯基方程，该方程描述了在自洽、随时间变化的平均力场中单个非缠结链的统计动力学。我们通过对大量复制链的集合进行平均来数值求解这个方程，每个复制链都服从单链朗之万动力学，并受到平均场的作用。从无序状态淬火后，在甚至一个劳斯时间过去之前，共混物组成中就会出现早期的旋节线不稳定性。主导的、不稳定的、增长的波长约为线圈尺寸。然后，共混物进入后期的t标度区，其畴尺寸不断增大，遵循预期的利夫希茨 - 斯廖佐夫 - 瓦格纳t幂律，这是扩散驱动粗化过程的一个特征。这些结果对这种新方法进行了令人满意的检验，该方法正确地捕捉了共混物中早期和后期的物理现象。随着畴粗化到线圈尺寸的20倍，我们的模拟在时间上跨越了五个数量级，同时忠实于微观链模型的动力学。
