采用分子动力学方法,对接枝在两相对平板上的有限尺寸聚电解质刷在良溶剂中的行为进行了研究.溶剂被视为隐性处理.通过改变板间距,考察了两刷的形态变化和相互作用机制.通过模拟发现,静电相互作用和体积排斥作用之间的相互竞争决定了聚电解质刷的动态行为.多价抗衡离子与接枝在不同板上的聚电解质链之间的桥接作用对刷高和压强有着重要影响.此外,相对于无限大的平板刷,有限尺寸聚电解质刷的自由度更大,导致其末端单体密度分布、刷高、桥接系数和压强随板间距的变化与无限尺寸体系不同.有限尺寸聚电解质平板刷体系与实验中的真实体系更相似,所得结论将对以后的实验研究具有一定的指导意义.
Using molecular dynamics (MD) method,the behavior of finite sized planar polyelectrolyte brushes grafted on two apposing substrates in good solvent is studied.The solvent is treated implicitly.By varying the plate spacing,the change of the morphology and the interaction mechanism of two brushes are investigated.Simulation results indicate that the dynamic behavior of polyelectrolyte brushes is decided by the competition between electrostatic interaction and volume repulsion interaction.Furthermore,the bridge effect between multivalent counterions and polyelectrolyte chains grafted on different substrates plays an important role in brush thickness and the pressure.In addition,compared to the infinite sized planar brush,the finite sized polyelectrolyte brush has a larger degree of freedom,which causes that the density profiles of end monomers,the brush thickness,the bridge coefficient and the pressure are different from the infinite sized system when plate spacing is changed.The finite sized planar polyelectrolyte brush system is close to the real system in the experiment,and the result will be instructive in some extent for the experiment study in future.