Langevin dynamics of semiflexible polyelectrolytes: Rod-toroid-globule-coil structures and counterion distribution
Langevin dynamics of semiflexible polyelectrolytes: Rod-toroid-globule-coil structures and counterion distribution
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DOI：
10.1063/1.1940054
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发表时间：
2005-08-15
影响因子：
4.4
通讯作者：
Muthukumar, M
中科院分区：
文献类型：
--
作者：
Ou, ZY;Muthukumar, M
我们通过监测链的刚性、链长、反离子价态和静电相互作用的强度，研究了均匀带电的半柔性聚电解质链上反离子凝聚的性质和伴随的构型。反离子凝聚遵循吸附过程，聚合物有效电荷随链刚性增大而增大。研究了通过回转半径、有效停留长度和水动力半径计算出的大小和形状。在合适的链刚性、链长、静电相互作用强度和反离子价态的组合下，稳定的线圈状、球形、折叠链、环形和棒状构型是可能的。对于高强度的静电相互作用，在多价反离子存在下，足够坚硬的聚电解质形成环状，而柔性聚电解质形成无序球状。监测了圆环形核和长大的动力学特征。发现几种亚稳态结构阻碍了环状结构的形成。通用途径包括沿着链轮廓的某个地方的一个初级环的成核，随后是一个生长过程，其中链的其余部分在初级环的顶部连续折叠。环面平均半径与链长的关系大致呈线性关系，这与已有的标度理论不一致。(C)2005年美国物理研究所。
We have investigated the nature of counterion condensation on uniformly charged semiflexible polyelectrolyte chains and the concomitant configurations by monitoring the role of chain stiffness, chain length, counterion valency, and the strength of electrostatic interaction. The counterion condensation is seen to follow the adsorption process and the effective polymer charge increases with chain stiffness. Size and shape, as calculated through the radius of gyration, effective persistence length, and hydrodynamic radius, are studied. Stable coil-like, globular, folded-chain, toroidal, and rodlike configurations are possible at suitable combinations of values of chain stiffness, chain length, electrostatic interaction strength, and the valency of counterion. For high strengths of electrostatic interactions, sufficiently stiff polyelectrolytes form toroids in the presence of multivalent counterions, whereas flexible polyelectrolytes form disordered globules. The kinetic features of the nucleation and growth of toroids are monitored. Several metastable structures are found to frustrate the formation of toroids. The generic pathway involves the nucleation of one primary loop somewhere along the chain contour, followed by a growth process where the rest of the chain is folded continuously on top of the primary loop. The dependence of the average radii of toroids on the chain length is found to be roughly linear, in disagreement with existing scaling arguments. (c) 2005 American Institute of Physics.