Bimodal colloidal mixtures: From fast to slow aggregation regions

The characteristics of the initial stability in bimodal colloidal mixtures with different sizes but similar surface chemistries are given in the graphical abstract. In the fast aggregation region, the homo- aggregation dominates the initial stability, while the hybrid aggregation (homo- and hetero-aggregation) becomes the main characteristics in the slow aggregation region. [Display omitted] ►We model the aggregation kinetics of bimodal colloidal mixtures with different sizes but similar surface chemistries. ► Under fast aggregation conditions, the homoaggregation of least stable component dominates the initial stability. ► With the electrolyte ionic strength decreasing (toward the slow aggregation), the hybrid aggregation including the homo- and hetero-aggregation gradually dominates the initial stability. A Brownian dynamics simulation has been used to investigate the aggregation kinetics of bimodal colloidal mixtures with similar surface chemistries but different sizes, driven by the DLVO interaction potential. The time evolution of structural formation is examined by the mean number of neighbors under fast and slow aggregation regions. It was found that the electrolyte ionic strength affects the kinetic pattern of colloidal aggregation. Under the high electrolyte ionic strength conditions (fast aggregation), the selective aggregation of the least stable single component can take place in the early stage, while the other component is enriched in this least stable component in the later stage. With the ionic strength decreasing (towards the slow aggregation), the hybrid aggregation (selective aggregation and heteroaggregation) gradually dominates the aggregation kinetics. Also in the early stage, this evolves to the heteroaggregation of different components under lower ionic strength conditions. The volume fraction has no obvious influence on this kinetic pattern in the early stage.