Department of Mathematics and Statistics, University of Strathclyde, Glasgow G1 1XH, Scotland, United Kingdom.
Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, 119991 Moscow, Russia.
Phys Rev E. 2018 Apr;97(4-1):042706. doi: 10.1103/PhysRevE.97.042706.
A molecular field theory and coarse-grained computer simulations with dissipative particle dynamics have been used to study the spontaneous orientational ordering of anisotropic nanoparticles in the lamellar and hexagonal phases of diblock copolymers and the effect of nanoparticles on the phase behavior of these systems. Both the molecular theory and computer simulations indicate that strongly anisotropic nanoparticles are ordered orientationally mainly in the boundary region between the domains and the nematic order parameter possesses opposite signs in adjacent domains. The orientational order is induced by the boundary and by the interaction between nanoparticles and the monomer units in different domains. In simulations, sufficiently long and strongly selective nanoparticles are ordered also inside the domains. The nematic order parameter and local concentration profiles of nanoparticles have been calculated numerically using the model of a nanoparticle with two interaction centers and also determined using the results of computer simulations. A number of phase diagrams have been obtained which illustrate the effect of nanoparticle selectivity and molar fraction of the stability ranges of various phases. Different morphologies have been identified by analyzing the static structure factor and a phase diagram has been constructed in coordinates' nanoparticle concentration-copolymer composition. Orientational ordering of even a small fraction of nanoparticles may result in a significant increase of the dielectric anisotropy of a polymer nanocomposite, which is important for various applications.
已经使用分子场理论和耗散粒子动力学的粗粒化计算机模拟来研究各向异性纳米粒子在两嵌段共聚物的层状相和六方相中的自发取向有序以及纳米粒子对这些体系相行为的影响。分子理论和计算机模拟都表明，强各向异性纳米粒子主要在畴之间的边界区域中具有定向有序，并且相邻畴中的向列序参量具有相反的符号。取向有序是由边界和纳米粒子与不同畴中的单体单元之间的相互作用引起的。在模拟中，足够长且具有强选择性的纳米粒子也在畴内有序。使用具有两个相互作用中心的纳米粒子模型，通过数值计算和计算机模拟结果，计算出了纳米粒子的向列序参量和局部浓度分布。已经获得了一些相图，这些相图说明了纳米粒子选择性和各种相的稳定范围的摩尔分数的影响。通过分析静态结构因子来识别不同的形态，并在纳米粒子浓度-共聚物组成的坐标中构建了相图。即使纳米粒子的一小部分具有取向有序性，也可能导致聚合物纳米复合材料的介电各向异性显著增加，这对于各种应用非常重要。
