School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA.
J Chem Phys. 2009 Dec 7;131(21):214904. doi: 10.1063/1.3266511.
Symmetric diblock copolymer/nanoparticle (NP) systems under planar elongational flow have been modeled and simulated using coarse-grained nonequilibrium molecular dynamics. The aim of our present study is to understand how the dispersion of NPs in a block copolymer system is influenced by elongational flow and how the presence of NPs changes the rheology and flow-induced morphology transition in block copolymers. We consider two different kinds of spherical NPs categorized with respect to their interaction potential with the polymeric blocks: (1) selective NPs that show a preference toward one of the blocks of a model diblock copolymer and (2) nonselective NPs that show equal attraction toward both blocks. For unrestricted simulation times during elongational flow, spatially and temporally periodic boundary conditions devised by Kraynik and Reinelt [Int. J. Multiphase Flow 18, 1045 (1992)] have been implemented. Our results show that the concentration peak of both selective NPs at the center of the preferred domain and nonselective NPs at the domain interface becomes broader with increasing elongation rate, suggesting that elongational flow can be used as another parameter to control nanocomposite self-assembly. In addition, our results reveal that the onset of flow-induced transition from lamellar to disordered morphology is greatly influenced by particle-particle and particle-polymer interactions.
对称二嵌段共聚物/纳米粒子（NP）体系在平面拉伸流中的模型和模拟采用粗粒非平衡分子动力学进行。我们目前的研究目的是了解 NP 在嵌段共聚物体系中的分散如何受到拉伸流的影响，以及 NP 的存在如何改变嵌段共聚物的流变学和流动诱导的形态转变。我们考虑了两种不同种类的球形 NP，根据它们与聚合物嵌段的相互作用势能进行分类：（1）选择性 NP，它们对模型二嵌段共聚物的一个嵌段表现出偏好；（2）非选择性 NP，它们对两个嵌段都表现出相等的吸引力。对于拉伸流过程中的无限制模拟时间，我们采用了 Kraynik 和 Reinelt [Int. J. Multiphase Flow 18, 1045 (1992)] 设计的空间和时间周期性边界条件。我们的结果表明，随着拉伸速率的增加，选择性 NP 在优先域中心和非选择性 NP 在域界面的浓度峰值变得更宽，这表明拉伸流可以作为另一个参数来控制纳米复合材料的自组装。此外，我们的结果表明，颗粒-颗粒和颗粒-聚合物相互作用极大地影响了流动诱导从层状到无序形态的转变的开始。
