Diblock polyampholytes grafted onto spherical particles: Effect of stiffness, charge density, and grafting density
Diblock polyampholytes grafted onto spherical particles: Effect of stiffness, charge density, and grafting density
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DOI：
10.1021/la062481r
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发表时间：
2007-01-30
期刊：
影响因子：
3.9
通讯作者：
Linse, Per
中科院分区：
文献类型：
--
作者：
Akinchina, Anna;Linse, Per
在所谓的原始模型的框架内，使用Monte Carlo模拟研究由对称的二嵌段两性聚电解质端接枝到小的球形颗粒在水溶液中形成的球形刷的结构。除了电荷的符号不同外，两个块体的性质完全相同。三种不同的链柔性对应的灵活，半柔性，和刚性块被认为是在各种聚两性电解质的线性电荷密度和接枝密度。两个块之间的连接在所有条件下都是柔性的，并且接枝段是横向移动的。分析了不同类型和单链性质的径向和横向空间分布函数。刷子结构强烈地依赖于链的柔性。在柔性链的情况下，在颗粒的表面形成无序的纳米复合物，随着线性电荷密度的增加，复合物变得更加紧凑。对于刚性块体，内部块体径向定向。在低的线性带电密度下，外部嵌段是取向无序的，而在增加的静电相互作用下，聚两性电解质的两个嵌段是平行的并且彼此靠近，导致称为聚两性电解质星星的有序结构。随着接枝密度的增加，刷厚度响应不同的柔性和非柔性链，这取决于静电相互作用和排除体积效应之间的不同平衡。
The structure of spherical brushes formed by symmetric diblock polyampholytes end-grafted onto small spherical particles in aqueous solution is examined within the framework of the so-called primitive model using Monte Carlo simulations. The properties of the two blocks are identical except for the sign of their charges. Three different chain flexibilities corresponding to flexible, semiflexible, and stiff blocks are considered at various polyampholyte linear charge densities and grafting densities. The link between the two blocks is flexible at all conditions, and the grafted segments are laterally mobile. Radial and lateral spatial distribution functions of different types and single-chain properties are analyzed. The brush structure strongly depends on the chain flexibility. With flexible chains, a disordered polyelectrolyte complex is formed at the surface of the particle, the complex becoming more compact at increasing linear charge density. With stiff blocks, the inner blocks are radially oriented. At low linear charged density, the outer blocks are orientationally disordered, whereas at increasing electrostatic interaction the two blocks of a polyampholyte are parallel and close to each other, leading to an ordered structure referred to as a polyampholyte star. As the grafting density is increased, the brush thickness responds differently for flexible and nonflexible chains, depending on a different balance between electrostatic interactions and excluded volume effects.