Pastorino C, Binder K, Kreer T, Müller M
Institut für Physik WA331, Johannes Gutenberg-Universität, Mainz, Germany.
J Chem Phys. 2006 Feb 14;124(6):64902. doi: 10.1063/1.2162883.
Molecular-dynamics simulations of a short-chain polymer melt between two brush-covered surfaces under shear have been performed. The end-grafted polymers which constitute the brush have the same chemical properties as the free chains in the melt and provide a soft deformable substrate. Polymer chains are described by a coarse-grained bead-spring model, which includes excluded volume and backbone connectivity of the chains. The grafting density of the brush layer offers a way of controlling the behavior of the surface without altering the molecular interactions. We perform equilibrium and nonequilibrium molecular-dynamics simulations at constant temperature and volume using the dissipative particle dynamics thermostat. The equilibrium density profiles and the behavior under shear are studied as well as the interdigitation of the melt into the brush, the orientation on different length scales (bond vectors, radius of gyration, and end-to-end vector) of free and grafted chains, and velocity profiles. The obtained boundary conditions and slip length show a rich behavior as a function of grafting density and shear velocity.
我们对处于剪切作用下的两个刷状覆盖表面之间的短链聚合物熔体进行了分子动力学模拟。构成刷状结构的末端接枝聚合物与熔体中的自由链具有相同的化学性质，并提供了一个柔软可变形的基底。聚合物链由粗粒化的珠簧模型描述，该模型包括链的排除体积和主链连通性。刷层的接枝密度提供了一种在不改变分子相互作用的情况下控制表面行为的方法。我们使用耗散粒子动力学恒温器在恒温恒容条件下进行平衡和非平衡分子动力学模拟。研究了平衡密度分布和剪切作用下的行为，以及熔体向刷状结构的相互贯穿、自由链和接枝链在不同长度尺度（键向量、回转半径和端到端向量）上的取向，还有速度分布。所得到的边界条件和滑移长度表现出随接枝密度和剪切速度变化的丰富行为。
