Mesoscopic dynamics of inhomogeneous polymers based on variable cell shape dynamic self-consistent field theory.
Mesoscopic dynamics of inhomogeneous polymers based on variable cell shape dynamic self-consistent field theory.
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DOI：
10.1063/1.2839306
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发表时间：
2008-03
期刊：
影响因子：
--
通讯作者：
Xuan Li;P. Tang;Hong-dong Zhang;F. Qiu;Yuliang Yang
中科院分区：
文献类型：
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作者：
Xuan Li;P. Tang;Hong-dong Zhang;F. Qiu;Yuliang Yang
本文将变胞形法与动态自洽场理论相结合，扩展到三嵌段共聚物熔体在剪切作用下的结构和动力学研究。由于剪切作用，计算单元的形状是可变的，不再是正交的。采用伪谱法求解链传播子在非正交坐标系上的扩散方程，利用变胞形法可以方便地设计剪切周期条件。利用这一策略，研究了拓扑复杂聚合物体系（如线性和星形三嵌段共聚物）的剪切诱导形态演化；线性ABC三嵌段共聚物的形貌比星形三嵌段共聚物更具有剪切敏感性。特别是，一旦得到链传播子，就可以推导出细观弹性应力和空间应力分布，从而计算出剪切作用下的动态力学性能。通过模拟振荡剪切测量中任意给定形貌对应的动态存储模量G‘，我们探索了形貌与存储模量G’之间的关系，并扩展到研究线性和星形三嵌段共聚物的相分离动力学以及有序-无序转变（ODT）机制。结果表明，虽然AB对称二嵌段共聚物和AB前体偶联ABA三嵌段共聚物的微观结构基本相似，但通过研究ODT可以很容易地区分链结构。此外，存储模量G‘和损耗模量G’可以在振荡剪切测量的扫频中同时确定，并研究了模量与相分离模式和链拓扑的关系。模拟结果与实验结果在定性上是一致的。
In this paper, we combine variable cell shape method with dynamic self-consistent field theory and extend to study structure and dynamics under shear for triblock copolymer melts. Due to shear, the calculation cell shape is variable and no longer orthogonal. Pseudospectral method is employed to solve the diffusion equation for chain propagator on the nonorthogonal coordinate and the shear periodical condition can be easily designed in terms of the variable cell shape method. By using this strategy, the shear induced morphology evolution is investigated for topologically complex polymeric systems such as linear and star triblock copolymers; the morphology of linear ABC triblock copolymers is more shear sensitive than that of star triblocks. In particular, once the chain propagator is obtained, the microscopic elastic stress and spatial stress distribution can be derived and thus the dynamic mechanical property can be calculated under shear. By imitating the dynamic storage modulus G' corresponding to any given morphology in the oscillatory shear measurements, we explore the relationship between the morphology and the storage modulus G' and extend to study the mechanism of phase separation dynamics as well as order-disorder transition (ODT) for linear and star triblock copolymers. The results show that the chain architecture can be easily distinguished by investigating the ODT, though the systems such as AB symmetric diblock and ABA triblock copolymers by coupling AB precursors almost exhibit similar microstructures. In addition, the storage modulus G' and loss modulus G" can be simultaneously determined in frequency sweeps of oscillatory shear measurements and the dependence of the moduli on phase separated patterns and the chain topology is investigated. The simulation findings are in qualitatively agreement with the experimental results.