Colloidal diffusion-limited aggregation

In contrast, the three- or two-dimensional morphologies of colloidal aggregates via Brownian particle trajectories show a fractal-like structure. One of the most prominent features of the surface deposits formed by the diffusion-limited aggregation mechanism is the formation of isolated treelike clusters (9). In our experiments, the surface morphology of the silica-coated polyethylene composite prepared by... 

The basic theoretical approach for the analysis of diffusion controlled reactions is due to Smoluchowski [9] who developed it for the analysis of diffusion limited aggregation of colloidal particles. We discuss the generalization of this approach to the case of rodlike molecules here. The computational method best suited for the simulation of the polymerization of rodlike molecules is Brownian dynamics. We discuss in this review both multiparticle Brownian dynamics and pairwise Brownian dynamics the latter is a hybrid method combining Smoluchowski s [9] theory and Brownian... 

Stoll S, Pefferkorn E. Modes of spontaneous and provoked cluster fragmentation. I. During diffusion-limited aggregation. J Colloid Interface Sci 1992 152 247-256. 

Figure 4.19 Postulated structures (A) stable hematite colloids in absence of organics, (B) reaction limited aggregation (RLAJ, (C) diffusion limited aggregation (DLAJ, (D) SPO aggregates with organics, (E) OPS colloids stabilised with organics, (F) OPS colloids stabilised with NOM, (G) OPS colloids stabilised with organics and destabilised with calcium.

In nature, ordered colloidal systems are unusual for two reasons. First, large scale lattices require monodispersity of the individual particle units within the lattice. Second, both diffusion limited aggregation and reaction limited aggregation in solution produce fractal structures rather... 

Hence, purely physical model of irreversible diffusion-limited aggregation cluster-cluster can be used successfully for chemical processes description (including a quantitative one) in the considered case — radical polymerization. Let us note, that in paper [75] the Eq. (70) of Chapter 1 was used for gold colloidal particles aggregation, i.e., purely physical process, description. 

Ferretti, R., Zhang, J. and Buffle, J. (1998). Flocculation of hematite with polyacrylic acid fractal structures in the reaction and diffusion-limited aggregation regimes. J. Colloid Interface ScL, 208, 509-517. 

Phys. Rev. Lett. 51(13), 1119-1122 (1983). doi 10.1103/PhysRevLett.51.1119 P. Meakin, The effects of rotational diffusion on the fractal dimensionality of stiuctures formed by cluster-cluster aggregation. J. Chem. Phys. 81(10), 4637-4639 (1984a). doi 10.1063/L447398 P. Meakin, Diffusion-limited aggregation in three dimensions results from a new eluster-eluster aggregation model. J. Colloid Interface Sci. 102(2), 491-504 (1984b). doi 10.1016/0021-9797 (84)90252-2... 

Self-similar behavior has also been observed in computer simulation of aggregation processes. Thus aggregates of colloidal particles in diffusion-limited aggregation processes have been found to display self-similar behavior (Meakin, 1983). 

Figure 8. Transmission electron micrographs of typical clusters of gold, silica, and polystyrene colloids, prepared by both diffusion-limited and reaction-limited cluster aggregation and by computer simulation. There is a striking similarity in the structure of the clusters of different colloids in each regime.

---