Dynamics of latex aggregation. Modes of cluster growth

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Abstract
The kinetics of aggregation of polystyrene latices occuring in the presence of an electrolyte or poly(4‐vinylpyridine) in aqueous media are examined. The aggregate size distribution was recorded at different times by counting the flocs containing a given number of elementary colloids. The moment of order zero ( the total number of clusters per unit volume of the suspension), as well as the second moment of the size distribution are computed. In the presence of an excess of electrolyte or an optimum amount of polymer, a dynamic scaling function of the form cg (t)=t−2 F[g/t] and a narrow time invariant polydispersity is found. Under slow flocculation conditions, a large time dependent polydispersity sets in. Large aggregates then react preferentially with equally large ones. This behavior is discussed in term of a sticking probability , using the formalism of the reaction limited cluster–cluster aggregation.