Molecular dynamics simulations of polyelectrolyte adsorption
Molecular dynamics simulations of polyelectrolyte adsorption
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DOI：
10.1021/la063079f
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发表时间：
2007-02-27
期刊：
影响因子：
3.9
通讯作者：
Dobrynin, Andrey V.
中科院分区：
文献类型：
--
作者：
Carrillo, Jan-Michael Y.;Dobrynin, Andrey V.
我们已经进行了分子动力学模拟，从稀溶液中的相反电荷的表面上的吸附。在我们的模拟中，聚电解质被建模为具有明确抗衡离子的带电Lennard-Jones粒子链。我们已经研究了表面电荷密度，表面电荷分布，溶剂质量的聚合物主链，聚合物和基板之间的短程相互作用的强度对聚合物表面覆盖度的影响，和吸附层的厚度。聚合物表面覆盖率单调增加，增加表面电荷密度几乎所有的研究系统，除了系统的亲水性聚电解质吸附在亲水性表面。在这种情况下，聚合物表面覆盖在高表面电荷密度下饱和。这是由于吸附的聚合物链之间的额外单体-单体排斥，这在致密的聚合物层中变得重要。这些相互作用也排除了在高表面电荷密度下亲水性聚电解质的表面过充电。吸附层的厚度表现出单调依赖于表面电荷密度的疏水性聚电解质的疏水性和亲水性表面的系统。在亲水性表面的情况下，厚度是表面电荷密度的递减函数，而对于疏水性基底，厚度随着表面电荷密度而增加。在亲水性表面上的亲水性聚电解质的吸附层的厚度观察到质的不同行为。在这种情况下，厚度首先随着表面电荷密度的增加而减小，然后开始增加。
We have performed molecular dynamics simulations of polyelectrolyte adsorption at oppositely charged surfaces from dilute polyelectrolyte solutions. In our simulations, polyelectrolytes were modeled by chains of charged Lennard-Jones particles with explicit counterions. We have studied the effects of the surface charge density, surface charge distribution, solvent quality for the polymer backbone, strength of the short-range interactions between polymers and substrates on the polymer surface coverage, and the thickness of the adsorbed layer. The polymer surface coverage monotonically increases with increasing surface charge density for almost all studied systems except for the system of hydrophilic polyelectrolytes adsorbing at hydrophilic surfaces. In this case the polymer surface coverage saturates at high surface charge densities. This is due to additional monomer-monomer repulsion between adsorbed polymer chains, which becomes important in dense polymeric layers. These interactions also preclude surface overcharging by hydrophilic polyelectrolytes at high surface charge densities. The thickness of the adsorbed layer shows monotonic dependence on the surface charge density for the systems of hydrophobic polyelectrolytes for both hydrophobic and hydrophilic surfaces. Thickness is a decreasing function of the surface charge density in the case of hydrophilic surfaces while it increases with the surface charge density for hydrophobic substrates. Qualitatively different behavior is observed for the thickness of the adsorbed layer of hydrophilic polyelectrolytes at hydrophilic surfaces. In this case, thickness first decreases with increasing surface charge density, then it begins to increase.