The protonation mechanisms of the poly(amidoamine) (PAMAM) andpoly(propyleneimine) (PPI)
dendrimers are clarified and related to their molecular structure. The overall proton binding
isotherms can be interpreted in terms of a site binding model, which involves a limited number
of parameters, and can be used to gain detailed insight in both macroscopic and microscopic
protonation mechanisms. The protonation of the PAMAM dendrimers is dominated by the
chemical environment of the amine sites, and the sites protonate almost independently leading
to protonation mechanism with a characteristic intermediate core-shell structure. In the case of
PPI, the protonation is dominated by the electrostatic nearest-neighbor repulsions between the
protonated sites, and leads to an intermediate »onion-like« structure where all the odd shells
are protonated
