Tupitsyna Alla I, Darinskii Anatoly A, Emri Igor, Allen Michael P
Institute of Problems of Mechanical Engineering, Russian Academy of Sciences, St. Petersburg, Russia.
Institute of Macromolecular Compounds, Russian Academy of Sciences, St. Petersburg, Russia.
Soft Matter. 2007 Dec 11;4(1):108-121. doi: 10.1039/b711649g.
A polymer brush with chains consisting of anisotropic monomers, in a liquid consisting of free spherical particles, is studied by the molecular dynamics method. It is shown that, at some value of the concentration of spheres, a liquid-crystal or oriented-domain transition occurs in the brush. A densely-grafted brush and a sparsely-grafted brush are studied; for this system, the transition point seems not to depend strongly upon the grafting density. In the case of the densely-grafted brush, a liquid-crystal transition proceeds via an intermediate microphase segregated state. One microphase, located near the grafting surface, is characterized by high density and high degree of ordering of monomers. This part of the brush contains only a small concentration of spheres. On the periphery of the brush, a disordered microphase with low monomer density is located. This part of the brush is enriched with spherical particles. The two microphases are separated by a well-defined boundary. On increasing the sphere concentration, the boundary between microphases shifts towards the periphery, and eventually the ordered microphase extends through the whole brush volume. The monomers of the densely-grafted brush in their ordered state form different structures, namely, a smectic structure at relatively low values of sphere concentration, and a structure of orientationally ordered domains at the higher sphere densities.
采用分子动力学方法研究了一种由各向异性单体构成链状结构的聚合物刷，该聚合物刷处于由自由球形颗粒组成的液体中。结果表明，在球体浓度的某个值时，聚合物刷中会发生液晶或取向域转变。研究了接枝密度高的刷子和接枝密度低的刷子；对于该体系，转变点似乎不太强烈地依赖于接枝密度。在接枝密度高的刷子的情况下，液晶转变通过中间的微相分离状态进行。靠近接枝表面的一个微相，其特征是单体密度高且有序度高。刷子的这一部分仅含有少量的球体。在刷子的外围，存在一个单体密度低的无序微相。刷子的这一部分富含球形颗粒。两个微相由一个清晰的边界隔开。随着球体浓度的增加，微相之间的边界向周边移动，最终有序微相延伸至整个刷子体积。接枝密度高的刷子中处于有序状态的单体形成不同的结构，即在球体浓度相对较低时形成近晶结构，在球体密度较高时形成取向有序域结构。
