Dispersion Stability of Mixed Microparticle Systems Studied by Their Morphological Observations and Interacting Surface Force Measurements

为了了解混合微粒分散体系的关键稳定性参数，通过使用原子力显微镜技术结合分散颗粒形态的原位观察来测量溶液中模型颗粒表面之间的相互作用力。在研究混合体系的吸附行为之前，通过电动势和表面力的测量研究了表面活性剂和表面活性剂在二氧化硅表面的吸附作用。在很宽的pH值范围内，阳离子吸附剂强烈地吸附在带负电荷的二氧化硅上。在高浓度的吸附剂下，二氧化硅将电荷从负变为正。水溶液中的表面活性剂改性的带正电的二氧化硅允许表面活性剂抗衡离子的强结合，这导致电荷符号从正到负。在乙醇中，相同的二氧化硅表面改性的表面活性剂的抗衡离子的存在下，没有显示出任何电荷反转。这些结果表明，当它们的表面用聚电解质改性以提供高表面电荷时，水中的混合颗粒通过静电力稳定。在乙醇中，表面活性剂离子可作为支持电解质调节静电力，在非对称表面的混合分散体系中，离子表面活性剂胶束与水共存时，表面力在较小的表面间距处表现为周期性的空间位阻力。空间位阻力可用于微粒分散体的混合物中的稳定化。

To understand the key stability parameters of mixed microparticle dispersion systems, the interaction forces between model particle surfaces in solution were measured by using a technique of atomic force microscopy in connection with the in-situ observation of dispersed particle morphology. Prior to study those of the mixed systems, the adsorption role of polyelectrolyte and surfactant in silica surfaces were studied by electrokinetic potential and surface force measurements. A cationic polyelectrolyte strongly adsorbs on negatively charged silica over a wide range of pH.At a high concentration of the polyelectrolyte the silica reversed the charge from negative to positive. The positively charged silica modified with the polyelectrolyte in water permits the strong binding of surfactant counterions, which led to the charge sign from positive to negative. In ethanol, the same silica surface modified with the polyelectrolyte does not show any charge reversal in the presence of the same surfactant counterions. These results suggested that the mixed particles in water are stabilized by electrostatic forces, when their surfaces are modified with polyelectrolytes to give a high surface charge. In ethanol, surfactant ions can be used as supporting electrolyte to adjust the electrostatic forces.In the mixed dispersion systems with asymmetrical surfaces in the co-presence of ionic surfactant micelles in water, the surface forces revealed a periodic, steric force at small surface separations in addition to an ordinary electrostatic force. The steric force may be utilized for the stabilization in the mixture of micro-particle dispersion.