受限于平行板中高分子刷/磁性纳米粒子体系的构象性质研究

STATISTICAL PROPERTIES OF POLYMER BRUSHES/MAGNETIC NANO-PARTICLES CONFINED IN PARALLEL PLANES

采用蒙特卡洛模拟方法研究了在外磁场作用下磁性纳米粒子/高分子刷组成的共混体系的统计构象性质.共混体系受限于两平行板之间,高分子刷一端随机嫁接在平行板上,另一端自由生长,高分子刷与高分子刷之间以及磁性纳米粒子与磁性纳米粒子之间存在相互排斥作用,而高分子刷和磁性纳米粒子之间存在相互吸引作用,所施加的磁场方向与两平行板垂直.研究发现高分子刷的平均高度与外加磁场的强度密切相关,同时也与高分子刷的嫁接密度、高分子刷长度和磁性纳米粒子的浓度有关.外加磁场影响磁性纳米粒子的排布,而磁性纳米粒子的排布又会影响高分子刷的空间分布.随着磁场强度的增加,由于磁性纳米粒子的磁矩方向会渐渐地朝向磁场方向而呈现磁性纳米粒子沿外磁场方向排列,所以高分子刷的平均高度会相应的升高.同时,高分子刷的链长和嫁接密度也会影响磁性纳米粒子在体系中的各种性质,如磁性纳米粒子的分布,磁化率和径向关联函数等.模拟结果与实验的结果较为吻合.

The statistical properties of systems composed of polymer brushes and magnetic nanoparticles placed in a magnetic field are studied by means of Monte Carlo simulation.The direction of the magnetic field is perpendicular to the substrate plane.Polymer brushes and magnetic nanoparticles are attractive to each other.The average heights of polymer brushes depend not only on the strength of applied magnetic field,but also on the brush grafting density,chain length and magnetic nanoparticle concentration.The applied magnetic field influences the arrangement of magnetic nanoparticles,and in turn the permutation of magnetic nanoparticles affects the spatial distribution of brush monomers.When the strength of the magnetic field increases,the average height of polymer brushes increases accordingly,because orientations of the magnetic moments of nanoparticles must be along the magnetic field direction.At the same time,the chain length,the grafting density of polymer brushes and the nanoparticle concentration also have an effect on the properties of the magnetic nanoparticles,such as the magnetic nanoparticles distribution,magnetic susceptibility and pair correlation functions.Our results are in agreement with the experimental ones,and this investigation can provide some insights into statistical properties of magnetic nanoparticle-loaded brushes induced by external magnetic field.