Preparation and properties of polystyrene model colloids: II. Effect of surface charge density on coagulation behavior

• Published in: Journal of colloid and interface science 1987, Vol.115 (2), p.463-471
• Main Authors: Tsaur, Sheng-Liang, Fitch, Robert M
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Surface properties
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/0021-9797(87)90063-4

The influence of surface charge density on the stability of model polymer colloids was studied through the coagulation kinetics of monodisperse polystyrene latexes in which particle size and surface charge density were independent variables. The time dependence of light scattering intensity was used to measure the stability ratios of the colloids as a function of electrolyte concentration. These were used to calculate the Stern potential and the Hamaker constant by means of the method suggested by Reerink and Overbeek. The calculated Stern potential increases systematically with increasing surface charge density at constant latex particle size. The difference between this Stern potential and the surface potential calculated from the Gouy Chapman equation was found to depend on the surface charge density of the particles. A high surface charge density produces a larger potential drop through the Stern layer. The calculated value of the Hamaker “constant” increased regularly with increasing surface charge density. Variation of the calculated Hamaker constant was attributed to interactions other than the van der Waals attractive force and the electrostatic repulsive force involved in the colloidal system.