Shape and Diffusion of Circular Polyelectrolytes in Salt-Free Dilute Solutions and Comparison with Linear Polyelectrolytes
Shape and Diffusion of Circular Polyelectrolytes in Salt-Free Dilute Solutions and Comparison with Linear Polyelectrolytes
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无盐稀溶液中环状聚电解质的形状和扩散以及与线性聚电解质的比较
DOI：
10.1021/acs.macromol.7b00189
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发表时间：
2017
期刊：
影响因子：
5.5
通讯作者：
Chen Jizhong
中科院分区：
文献类型：
--
作者：
Liu Lijun;Chen Wenduo;Chen Jizhong
采用介观流体动力学模拟方法，研究了圆形聚电解质在无盐稀溶液中的形状和扩散行为.一个全面的比较线性和环状聚电解质的拓扑约束的构象和动力学性质的影响，也获得了深刻的理解。随着IB的增加，抗衡离子由于它们在主链上的凝聚而变得越来越重要。在smallB处，圆形螺旋的形状从扁长螺旋变为扁圆环，然后在中间1B处变为扁长螺旋，最后在大1B处变为致密螺旋;相比之下，线性螺旋的形状从扁长螺旋变为杆，然后变为扁长螺旋，最后变为致密螺旋。通过打开/关闭流体动力学相互作用（HI），模拟澄清了复杂的耦合效应的流体动力学和静电相互作用的聚电解质的扩散。随着lB的增加，有氢离子的扩散系数迅速减小，然后逐渐增大，而无氢离子的扩散系数则呈现出几乎单调减小的行为，并最终趋于平稳。线性和圆形的聚电解质具有相同的链长，但有显着的，定量的，但不是定性的差异，在存在的HI的扩散系数之间的发现，但只有轻微的差异，在没有HI的扩散系数。通过利用链的大小和凝聚抗衡离子的数量的变化，我们表明，聚电解质的扩散仍然可以定性地理解的Zimm和Rouse模型的框架内。
The shape and diffusion of circular polyelectrolytes in salt-free dilute solutions are investigated over a large range of the Bjerrum lengthlBby mesoscale hydrodynamic simulations, wherelBcharacterizes the strength of electrostatic interactions (EIs). A comprehensive comparison of linear and circular polyelectrolytes is also made to gain a deep understanding of the effects of topological constraints on the conformational and dynamical properties. AslBincreases, counterions become increasingly important due to their condensations on the polyelectrolyte backbone. The shape of a circular polyelectrolyte changes from a prolate coil to an oblate ring at smalllB, then to a prolate coil at intermediatelB, and finally to a dense coil at largelB; in contrast, the shape of a linear polyelectrolyte changes from a prolate coil to a rod, then to a prolate coil, and finally to a dense coil. By switching on/off hydrodynamic interactions (HIs), the simulations clarify the complex coupling effects of hydrodynamic and electrostatic interactions on the diffusion of polyelectrolytes. With increasinglB, the diffusion coefficient with HIs decreases rapidly and then increases gradually, but the diffusion coefficient without HIs displays an almost monotonically decreasing behavior and eventually approaches a plateau. The significant, quantitative but not qualitative difference in diffusion coefficient in the presence of HIs is found between linear and circular polyelectrolytes with an identical chain length, but there are only slight differences between their diffusion coefficients in the absence of HIs. By exploitation of the changes in chain size and the number of condensed counterions, we show that the diffusion of polyelectrolytes can be still qualitatively understood within the framework of Zimm and Rouse models.