Monitoring aggregation of dilute suspensions in the intermediate regime using photon correlation spectroscopy

Abstract

A series of rapidly aggregating hydrophobic suspensions (polystyrene, AgI and TiO₂) has been monitored using photon correlation spectroscopy (PCS) employing a theory developed for polymer chains. Deviations from Smoluchowski kinetics are seen in the early stages of the aggregation, although in many cases a limiting value of ca. 6 × 10^–12 cm³ s^–1(close to the diffusion-limited values) is achieved for the coagulation of the larger aggregates. This value seems to justify the theoretical analysis used. Ludox, under reaction-limited conditions shows large deviations from Smoluchowski behaviour which were found to be consistent with a coagulation kernel of the form K_ij=K₀(ij)^0.5.