Schwenke Konrad, Isa Lucio, Cheung David L, Del Gado Emanuela
Department of Civil, Environmental and Geomatic Engineering and ‡Laboratory for Interfaces, Soft Matter and Assembly, Department of Materials, ETH Zürich , 8093 Zurich, Switzerland.
Langmuir. 2014 Oct 28;30(42):12578-86. doi: 10.1021/la503379z. Epub 2014 Oct 16.
We investigate conformations and effective interactions of polymer-coated nanoparticles adsorbed at a model liquid-liquid interface via molecular dynamics simulations. The polymer shells strongly deform at the interface, with the shape governed by a balance between maximizing the decrease in interfacial area between the two solvent components, minimizing unfavorable contact between polymer and solvent, and maximizing the conformational entropy of the polymers. Using potential of mean force calculations, we compute the effective interaction between the nanoparticles at the liquid-liquid interface. We find that it differs quantitatively from the bulk and is significantly affected by the length of the polymer chains and by the solvent quality. Under good solvent conditions, the effective interactions are always repulsive and soft for long chains. The repulsion range decreases as the solvent quality decreases. In particular, under poor solvent conditions, short chains may fail to induce steric repulsion, leading to a net attraction between the nanoparticles, whereas with long-enough chains the effective interaction potential may feature an additional repulsive shoulder at intermediate distances.
我们通过分子动力学模拟研究了吸附在模型液-液界面的聚合物包覆纳米颗粒的构象和有效相互作用。聚合物壳层在界面处强烈变形，其形状由两种溶剂组分之间界面面积减小最大化、聚合物与溶剂之间不利接触最小化以及聚合物构象熵最大化之间的平衡所决定。利用平均力势计算，我们计算了液-液界面处纳米颗粒之间的有效相互作用。我们发现它在数量上与本体不同，并且受到聚合物链长度和溶剂质量的显著影响。在良溶剂条件下，对于长链，有效相互作用总是排斥性的且较弱。随着溶剂质量降低，排斥范围减小。特别是，在不良溶剂条件下，短链可能无法诱导空间排斥，导致纳米颗粒之间产生净吸引力，而对于足够长的链，有效相互作用势在中间距离处可能具有额外的排斥峰。
