Department of Chemical Engineering, Indian Institute of Technology, Kharagpur, West Bengal, India.
J Chem Phys. 2012 Sep 7;137(9):094907. doi: 10.1063/1.4749383.
Nanoparticles in polymer films have shown the tendency to migrate to the substrate due to an entropic-based attractive depletion interaction between the particles and the substrate. It is also known that polymer-grafted nanoparticles show better dispersion in a polymer matrix. Here, molecular dynamics simulations are employed to study the effect of grafting on the nanoparticle segregation to the substrate. The nanoparticles were modeled as spheres and the polymers as bead-spring chains. The polymers of the grafts and the matrix are identical in nature. For a purely repulsive system, the nanoparticle density near the surface was found to decrease as the length of grafted chains and the number of grafts increased and in the bulk, the nanoparticles are well-dispersed. Whereas, in case of attractive systems with interparticle interactions on the order of thermal energy, the nanoparticles segregated to the substrate even more strongly, essentially forming clusters on the wall and in the bulk. However, due to the presence of grafted chains on the nanoparticles, the clusters formed in the bulk are structurally anisotropic. The effect of grafts on nanoparticle segregation to the surface was found to be qualitatively similar to the purely repulsive case.
聚合物薄膜中的纳米粒子由于粒子与基底之间基于熵的吸引性耗尽相互作用，表现出向基底迁移的趋势。人们也知道，接枝聚合物的纳米粒子在聚合物基质中表现出更好的分散性。在这里，采用分子动力学模拟来研究接枝对纳米粒子与基底分离的影响。纳米粒子被建模为球体，聚合物被建模为串珠-弹簧链。接枝聚合物和基质聚合物在本质上是相同的。对于纯排斥体系，发现随着接枝链长度和接枝数的增加，表面附近的纳米粒子密度降低，而在体相，纳米粒子分散良好。然而，对于粒子间相互作用在热能量级的吸引体系，纳米粒子甚至更强烈地向基底分离，在壁上和体相基本上形成了团簇。然而，由于纳米粒子上存在接枝链，体相形成的团簇在结构上具有各向异性。接枝对纳米粒子向表面分离的影响与纯排斥情况定性相似。
