四臂星型聚电解质刷在外加三价盐离子和电场下的塌缩

本文采用Langevin动力学模拟的方法，研究存在三价盐离子时，接枝在带相反电荷的极板上的部分带电的四个臂星型链呈现出的塌缩现象. 结果表明，在电场作用下，接枝星型链的平均带电分数和盐浓度在带电单体和三价盐离子的竞争性吸附中起关键作用. 对于接枝在带相反电荷的极板上的带电分数较高的星型链，刷子会塌缩到接枝极板上，并会产生极板表面电荷的过度补偿现象. 当带电分数较低时，如果星型链所带电荷数与三价盐离子电荷数相同，即使在很低的盐浓度下，极板对三价盐离子的吸引能力也高于对星型链中的带电单体的吸引. 结果表明，星型链在带电分数较低的情况下，三价盐离子的加入不会导致接枝电极表面电荷的过度补偿. 此外，本文还研究了三价盐离子对电场作用下星型刷的拉伸的影响.

Collapse of Four-Arm Stars Polyelectrolyte Brushes Under An Electric Field in the Presence of Trivalent Salt Coions

Langevin dynamics simulations were conducted to study the collapse of grafted partially charged 4-arm star chains onto the oppositely charged grafting electrode in the presence of trivalent salt coions. Simulation re-sults reveal that the average charge fraction of the grafted star chains and the salt concentration play crit-ical roles in the competitive adsorp-tion of charged monomers and triva-lent salt coions onto the oppositely charged electrode. For grafted star chains with relatively high charge fraction, charged monomers are the dominant species collapsing on the oppositely charged electrode with the emergence of charge reversal on the grafting electrode. At a low charge fraction such that the total amount of charges on a grafted star molecule is comparable to that of a trivalent salt coion, trivalent salt coions absorb more strongly onto the electrode than grafted stars even at very low salt concentration. It is found that at relatively low charge fraction of star chains, the addition of trivalent salt coions does not lead to charge overcompensation of the surface charges on the grafting electrode. The stretching of star brushes under an electric field in the presence of trivalent salt coions was also briefly investigated.