Gillies Graeme, Lin Wei, Borkovec Michal
Laboratory of Colloid and Surface Chemistry, Department of Inorganic, Analytical, and Applied Chemistry, University of Geneva, Sciences II, 30 Quai Ernest Ansermet, 1211 Geneva 4, Switzerland.
J Phys Chem B. 2007 Jul 26;111(29):8626-33. doi: 10.1021/jp069009z. Epub 2007 Apr 28.
Charging behavior and colloidal stability of amidine latex particles are studied in the presence of poly(sodium styrene sulfonate) (PSS) and KCl. Detailed measurements of electrophoretic mobility, adsorbed layer thickness, and aggregation (or coagulation) rate constant on varying the polymer dose, molecular mass of the polymer, and ionic strength are reported. Polyelectrolyte adsorption leads to the characteristic charge reversal (or overcharging) of the colloidal particles at the isoelectric point (IEP). In accordance with classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, uncharged particles tend to aggregate because of van der Waals attraction, whereas charged particles are stabilized by electrical double layer repulsion. Attractive patch-charge interactions originating from the laterally inhomogeneous structure of the adsorbed polymer substantially decrease the suspension stability or even accelerate the aggregation rate beyond diffusion control. These electrostatic non-DLVO forces become progressively important with increasing molecular mass of the polymer and the ionic strength of the solution. At higher polymer dose of typically 10 times the IEP, one observes the formation of a saturated layer of the adsorbed polymer with a thickness of several nanometers. Its thickness increases with increasing molecular mass, whereby the layer becomes increasingly porous. This layer does not seem to be involved in the suspension stabilization, since at such high polymer doses the double layer repulsion has attained sufficient strength to stabilize the suspension.
在聚（苯乙烯磺酸钠）（PSS）和KCl存在的情况下，研究了脒乳胶颗粒的充电行为和胶体稳定性。报告了在改变聚合物剂量、聚合物分子量和离子强度时，对电泳迁移率、吸附层厚度和聚集（或凝聚）速率常数的详细测量结果。聚电解质吸附导致胶体颗粒在等电点（IEP）处出现特征性的电荷反转（或过充电）。根据经典的德亚金-朗道-韦弗-奥弗贝克（DLVO）理论，不带电的颗粒由于范德华引力而倾向于聚集，而带电颗粒则通过双电层排斥作用而稳定。源自吸附聚合物横向不均匀结构的吸引性补丁电荷相互作用显著降低了悬浮液的稳定性，甚至使聚集速率加快到超过扩散控制。随着聚合物分子量和溶液离子强度的增加，这些静电非DLVO力变得越来越重要。在通常为IEP 10倍的较高聚合物剂量下，可以观察到形成了一层厚度为几纳米的吸附聚合物饱和层。其厚度随着分子量的增加而增加，从而使该层变得越来越多孔。该层似乎与悬浮液的稳定无关，因为在如此高的聚合物剂量下，双电层排斥力已经达到足够的强度来稳定悬浮液。
