Two-dimensional aggregation of polystyrene latex particles

Salt-induced aggregation of polystyrene latex confined to two dimensions on an air-water interface has been studied. Fractal dimensions of the aggregates are determined (i) from relation between the radius of gyration and cluster masses and (ii) by the box method. They both increase with aggregation time. While the fractal dimensions are insensitive to electrolyte concentration, the aggregation rate does depend on it. Our results for aggregation kinetics are in good agreement with the dynamic scaling law nₘ(t){~}m^-2f(m/tᶻ), for z=1, for dilute latex dispersions [nₘ(t) is the number of clusters of size m at time t]. A nonlinear behavior in time, however, is observed for more concentrated latex dispersions. We find bell-shaped cluster-size distributions.