Chemical and physical aggregation of small-functionality particles

The number of potentially relevant materials resulting from the aggregation of elementary units with a finite functionality continues to increase. The growth of branched clusters and networks may proceed through the formation of reversible (physical) or irreversible (chemical) bonds. The kinetics of bond formation is sensitive both to the intrinsic rate of the bonding process, controlled by the chemistry of the system, and to the encounter rate of clusters, controlled by cluster diffusion. In this Highlight we review a series of our recent numerical simulation studies designed to investigate the connections between chemical and physical aggregation and the crossover from a chemically controlled to diffusion-controlled regime. It is shown that in the chemically controlled limit, it is possible to formally correlate elapsed time during irreversible aggregation with equilibrium temperature in reversible aggregation. The diffusion-controlled regime sets in well-beyond percolation and the effect of diffusion can be described by introducing a single additional time scale, related to the average diffusion time. This concept can be readily generalized to interpret the experimental data.