Polymer particles : electrophoresis

Electrophoresis of particles dispersed in a liquid medium is an experimental method used to investigate some important features of the interfaces between the different phases. These interfaces are, more often than not, characterized by a charge distribution between the different phases, to make the overall charge equal to zero. Thus a solid dispersed in a liquid may have a negative charge usually located at the interface, whereas the surrounding liquid may contain the positive charges necessary for making the total charge equal to zero, in the form of an excess of positive ions. These are distributed as an "ion cloud" around the solid. Electrophoresis gives an indication of the distribution of electrical charges at the interfaces studied, and this in turn is important not only for an understanding of the behavior of dispersions of, for example, solids in liquids with regard to their stability against aggregate formation, but may also form a basis for obtaining a model of what occurs on such dispersions when other components such as surfactants are added. In recent years, research in the field of electrophoresis of polymer particles has been predominantly devoted to dispersions in aqueous media. Questions still remain about how to understand the way electrophoresis is influenced by changes in salt concentration and pH in the liquid phase. In addition, considerable attention has been paid to questions about how polymers dissolved in the liquid medium and adsorbed on the particles concerned influence electrophoresis. Because an understanding of the results obtained on the second point depends, in several respects, on what has been learned with regard to the first question, we will start in the section "The Influence of Changes in the Electrolyte Concentration in the Surrounding Liquid Medium on the Electrophoresis of Polymer Particles" by discussing the influence of changes in pH and electrolyte concentration on the electrophoresis of polymer particles, and return to the second point in "Influence of Adsorbed Polymer Layers on the Electrophoresis of Latex Particles.