The Thermolysis Behaviours of the First Generation Dendritic Polyamidoamine

Dendritic polyamidoamine (PAMAM) is one of the first synthesized and commercialized dendrimers, and because of its peculiar properties it is widely used in many fields. In this paper, the first generation polyamidoamine dendrimer (G1.0 PAMAM) with primary amine terminal groups was synthesized by the Michael addition reaction of ethylenediamine and acrylic acid ester in the divergent approach. The first grade mass molecule ions [M+H+]+, m/z 518 in mass spectra indicated that the molecular weight of G1.0 PAMAM was 517 g.mol-1, which was in accordance with the theoretical molecular weight. The characteristic structure of the products was corroborated by FTIR spectra. Moreover, thermal behaviours of G1.0 PAMAM were investigated by DSC and TG-DTG techniques. It was suggested that G1.0 PAMAM had a two-stage thermal weight loss curve between 150؛C and 450؛C, the intersection temperature 282.32؛C divided the weight loss curve into two stages, the normalized heat was -485.48 J.g-1, and the heat flow values at the intersection temperature of two stages reached a maximum. The weight loss ratio to the total weight ratio was 55.71% at the first temperature stage between 150؛C to 282.32؛C, and at the same stage the integral heat area to the total heat ratio was about 53.93%. Standard MS and the second order MS spectra of G1.0 PAMAM showed that the decomposed structure at the low temperature stage would be the fragment ion, m/z 289. A possible formation mechanism of the fragment ion was also proposed as that the primary amine terminal of G1.0 PAMAM was decomposed from terminal tetra-amino structure to bi-amino structure.