Clustering of binary colloidal suspensions: Experiment

Abstract

The stability of binary colloidal suspensions is examined and compared to that of particle—polymer systems. In particle—polymer systems, it is known that the addition of free polymers within a concentration range of polymers to a stabilized dispersion leads to flocculation. Similar to particle—polymer systems, we have observed that in binary colloidal suspensions, particles of the first kind can be induced to flocculate by the presence of particles of the second kind, within a certain range of concentration of the second kind of particles. Moreover, we have observed the growth of clusters of particles 1 at a later time in the initially restabilized regime. This slow growth of clusters in the initially restabilized suspensions is associated with the slowing of particle movement due to higher particle 2 concentrations. The aging phenomenon (growth of clusters) that occurs at high particle 2 concentrations clearly indicates that the seemingly restabilized suspension at high particle 2 concentrations is not due to thermodynamics, but to slow kinetics associated with slow particle movements at high densities. A similar aging phenomenon was observed with a particle—polymer (α-Al 2O 3/PAA) system in the seeming restabilization regime at high polymer concentrations.