Fig. 6

Time evolution of the average number of contacts between LCPA and either phosphate ions or silica precursors. The solid lines always refer to the random initial configuration while the dashed lines are related to the pre-aggregate initial configuration, see also Figs. 4 and 5 for reference. Contacts with phosphate ions are shown as green lines. a Dimers and b Octamers are used as silica precursors in separate simulations. The data was smoothed with a Savitzky–Golay filter [69]. The rapid decay in the average number of contacts between silica dimers and polyamines (a) reflects the rapid dissolution of the aggregate in the aqueous environment. The weaker decay in the average number of LCPA-phosphate contacts in a has most likely its origin in their mutual electrostatic interactions, which partly slows down the aggregate’s dissolution. In contrast, for the case of octamers (b), the average number of contacts between polyamine and silica remains nearly constant over the whole simulation time, illustrating the structural stability of the aggregates. However, the average number of contacts with the phosphate ions also decays as a function of the simulation time, but with a considerably slower rate