PROTONATION MECHANISM OF POLY(PROPYLENE IMINE) DENDRIMERS AND SOME ASSOCIATED OLIGO AMINES

The protonation behavior of poly(propylene imine) dendrimers and some related oligo amines has been measured using natural abundance N-15-NM R. The chemical shifts of the different shells of nitrogen nuclei as a function of pH have been directly interpreted as the degree of proton ation for that shell. The thus obtained protonation behavior is descri bed systematically using the Ising model which only requires values fo r the intrinsic protonation constants and for the pair interaction fre e energies between the different nitrogen nuclei. This subsequently le ads to a quantitative description of the titration curves of the indiv idual shells and to a rationalization of the microscopic and macroscop ic equilibrium constants for these molecules.