Synthesis and Analytical Characterization of Ester and Amine Terminated PAMAM Dendrimers

Abstract

PAMAM dendrimers containing ethylene diamine core and methyal acrylate as repeating unit were synthesized by divergent approach. Analytical characterization of PAMAM dendrimers amine terminated full generation 4.0G and ester terminated half generation 3.5G were performed using UV-Vis spectroscopy, FT-IR spectroscopy, differential scanning calorimetry, NMR spectroscopy and MASS spectroscopy. The half generation dendrimers have the methyl ester terminating groups, which have the characteristic IR peaks for carbonyl at 1730-1750 cm-1. For the full generation dendrimers, when the methyl ester groups were converted to amide groups, the corresponding carbonyl shifted to 1660 cm-1.The characteristic methyl ester peak, which appeared in all the 1H-NMR spectra of the ester terminating dendrimers, whereas it is absent in all the amine terminating dendrimers. The molecular weight was determined by ESI mass spectroscopy which further confirms the preparation of PAMAM dendrimers and provides information about the structural defects, polydispersity and purity.