立方聚电解质刷形貌的模拟研究

Simulation of the morphologies of cubic polyelectrolyte brush

采用分子动力学模拟方法,研究了溶剂性质和带电分数对接枝在立方体表面的聚电解质刷形貌的影响。对于控制溶剂性质的能量参数εLJ存在一个临界点,当能量参数εLJ低于临界点所对应的数值,整个刷保持膨胀的一种状态;相反,聚电解质刷会发生侧向相分离,形成pinned patches结构。该临界点随带电分数的改变而改变。聚电解质刷所呈现出的不同形貌是由于溶剂性质与静电作用相互竞争的结果。此外,链的聚合度和接枝密度的改变会导致pinned patches数量发生变化。

Using molecular dynamics simulation, the effects of the solvent quality and the charge fraction on the conformations of cubic polyelectrolyte brushes are studied. The energy parameter εLJ of controlling the solvent quality has a critical value. Below the critical value, the effect of electrostatic interactions dominates and polyelectrolyte brush extents to form a swelling state. Above the critical value, the polyelectrolyte brush displays lateral microphase segregation and forms the pinned patches conformation. The critical value of εLJ changes with the charge fraction. These different morphologies of the brush appear as a result of interplay between solvent quality and electrostatic interactions. Furthermore, the number of pinned patches varies with the degree of the polymerization or the grafting density.