Poly(propylene imine) (PPI) dendrimers is composed of a surface layer of primary amine groups and a number of internal layers which contain tertiary amine groups.  Both the primary and tertiary amine groups are basic, capable of being protonated given the right pH conditions.  Knowledge of the precise nature and order of protonation of these various basic sites are very important for applications of these dendrimers.  In this research, 13C DEPT NMR-monitored titrations of the diaminobutane (DAB) core and the generation 1-3 PPI dendrimers have been performed, and from the NMR data, the protonation order and pKa values for each layer of amine groups have been obtained. Using NMR to monitor titrations lies in the fact that electronic changes at very specific sites in the structure can be observed; protonation of individual amine groups will have a marked effect on carbon nuclei nearby, while those further away will be relatively unaffected.

NMR titration on PPI dendrimers

244th National Meeting (2012)

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