Department of Inorganic and Analytical Chemistry, University of Geneva, Sciences II, 30 Quai Ernest-Ansermet, 1205 Geneva, Switzerland.
Soft Matter. 2017 May 14;13(18):3284-3295. doi: 10.1039/c7sm00314e. Epub 2017 Apr 12.
Interaction forces between silica particles were measured in aqueous solutions of the sodium salt of poly(styrene sulphonate) (PSS) and NaCl using the colloidal probe technique based on an atomic force microscope (AFM). The observed forces can be rationalized through a superposition of damped oscillatory forces and double layer forces quantitatively. The double layer forces are modeled using Poisson-Boltzmann (PB) theory for a mixture of a monovalent symmetric electrolyte and a highly asymmetric electrolyte, whereby the multivalent coions represent the polyelectrolyte chains. The effective charge of the polyelectrolyte is found to be smaller than the bare number of charged groups residing on one polyelectrolyte molecule. This effect can be explained by counterion condensation. The interplay between depletion and double layer forces can be further used to predict the phase of the depletion force oscillations. However, this picture holds only at not too elevated concentrations of the polyelectrolyte and salt. At higher salt concentrations, attractive van der Waals forces become important, while at higher polyelectrolyte concentrations, the macromolecules adsorb onto the like-charged silica interface.
使用基于原子力显微镜 (AFM) 的胶体探针技术，在聚（苯乙烯磺酸钠）（PSS）的钠盐和 NaCl 的水溶液中测量了二氧化硅颗粒之间的相互作用力。通过定量的叠加衰减振荡力和双层力，可以对观察到的力进行合理化解释。使用泊松-玻尔兹曼 (PB) 理论对一价对称电解质和高不对称电解质的混合物进行双层力建模，其中多价共离子代表聚电解质链。发现聚电解质的有效电荷小于驻留在一个聚电解质分子上的带电基团的裸数。这种效应可以通过抗衡离子凝聚来解释。耗散力和双层力之间的相互作用可以进一步用于预测耗散力振荡的相。然而，这种情况仅在聚电解质和盐的浓度不是太高的情况下成立。在较高的盐浓度下，吸引力范德华力变得重要，而在较高的聚电解质浓度下，大分子吸附在带相同电荷的二氧化硅界面上。
