Adolphe Merkle Institute, University of Fribourg , Rte de l'ancienne Papeterie 1, CH-1723 Marly, Switzerland.
Langmuir. 2013 Sep 10;29(36):11199-207. doi: 10.1021/la402104q. Epub 2013 Aug 27.
When studying tunable electrostatic repulsions in aqueous suspensions of charged colloids, irreversible colloid aggregation or gelation may occur at high salt concentrations. For many commonly used synthetic colloids, such as polystyrene and silica particles, the reason for coagulation is the presence of unbalanced, strongly attractive, and short-ranged van der Waals (VDW) forces. Here, we present an aqueous polystyrene model colloid that is sterically stabilized against VDW attractions. We show that the synthesis procedure, based on a neutral initiator couple and a nonionic surfactant, introduces surface charges that can be further increased by the addition of charged comonomer methacrylic acid. Thus, the interactions between the polystyrene spheres can be conveniently tuned from hard-sphere-like to charge-stabilized with long-ranged electrostatic repulsions described by a Yukawa-type pair potential. The particle size, grafting density, core-shell structure, and surface charge are characterized by light and neutron scattering. Using X-ray and neutron scattering in combination with an accurate analytic integral equation scheme for the colloidal static structure factor, we deduce effective particle charges for colloid volume fractions ≥0.1 and salt concentrations in the range of 1.5 to 50 mM.
在研究带电荷胶体在水悬浮液中的可调静电斥力时，在高盐浓度下可能会发生不可逆的胶体聚集或凝胶化。对于许多常用的合成胶体，如聚苯乙烯和二氧化硅颗粒，聚沉的原因是存在不平衡的、强烈吸引的、短程范德华（VDW）力。在这里，我们提出了一种水基聚苯乙烯模型胶体，它对 VDW 吸引力具有空间稳定作用。我们表明，基于中性引发剂对和非离子表面活性剂的合成程序引入了表面电荷，通过添加带电荷的共聚单体甲基丙烯酸可以进一步增加表面电荷。因此，聚苯乙烯球之间的相互作用可以方便地从硬球样调节为带有长程静电斥力的带电稳定，长程静电斥力由 Yukawa 型对势能描述。通过光和中子散射对粒径、接枝密度、核壳结构和表面电荷进行了表征。利用 X 射线和中子散射以及胶体静态结构因子的精确分析积分方程方案，我们推导出胶体体积分数≥0.1 和盐浓度在 1.5 至 50 mM 范围内的有效粒子电荷。
