Cao Q Q, Zuo C C, Li L J
College of Mechanical Science and Engineering, Jilin University, 130022 Changchun, PR China.
Eur Phys J E Soft Matter. 2010 May;32(1):1-12. doi: 10.1140/epje/i2010-10585-3. Epub 2010 May 1.
We use molecular dynamics simulations to investigate centipede-like polymers with stiff charged side chains, end-grafted to a planar wall. The effect of the grafting density and the Bjerrum length on the conformational behaviour of the brush is examined in detail. In addition, we make a comparison of centipede-like polyelectrolyte (CPE) brushes with neutral centipede-like polymer (NCP) and linear polyelectrolyte (LPE) brushes. At weak electrostatic interaction, the main chains of the CPE chains adopt a strongly stretched conformation, and the monomer density profiles of side chains exhibit a clear oscillatory behaviour. With increasing Bjerrum length, the CPE brush undergoes a collapse transition. Compared to the CPE brushes, the counterion condensation effect is stronger for the LPE brushes, regardless of whether the electrostatic interaction is weak or strong and of whether the grafting density is low or high. Additionally, it is shown that the architecture of the grafted chains makes a weak contribution to the counterion condensation at strong electrostatic interaction. We also find that the electrostatic repulsion between charged side chains can enhance the stiffness of the main chains and thus limit the range of movement of the free-end monomers.
我们使用分子动力学模拟来研究末端接枝到平面壁上的具有刚性带电侧链的蜈蚣状聚合物。详细研究了接枝密度和 Bjerrum 长度对刷状聚合物构象行为的影响。此外，我们将蜈蚣状聚电解质（CPE）刷与中性蜈蚣状聚合物（NCP）刷和线性聚电解质（LPE）刷进行了比较。在弱静电相互作用下，CPE 链的主链呈现出强烈拉伸的构象，侧链的单体密度分布呈现出明显的振荡行为。随着 Bjerrum 长度的增加，CPE 刷经历塌缩转变。与 CPE 刷相比，无论静电相互作用是弱还是强，以及接枝密度是低还是高，LPE 刷的反离子凝聚效应都更强。此外，结果表明，在强静电相互作用下，接枝链的结构对反离子凝聚的贡献较弱。我们还发现，带电侧链之间的静电排斥可以增强主链的刚性，从而限制自由端单体的运动范围。
