Solid-state polymerization of EDTA and ethylenediamine as one-step approach to monodisperse hyperbranched polyamides

Abstract

Hyperbranched polyamides (HBPAs), a special class of polymers with extended use in colloidal systems, is synthesized by an innovative method taking advantage of the ordered aggregation of positive and negative molecular ions in solid-state. This novel and facile procedure introduces a one-step approach to convert ethylenediaminetetraacetic acid (EDTA) and ethylenediamine (EDA) in macromolecules with ordered framework. EDTA and EDA are converted in negative and positive molecular ions through acid–base reaction. Then, Coulomb interaction among the charged molecules are used to drive the aggregation of the ions during the precipitation induced by casting process. The solid material composed by the molecular ions are subjected to thermal treatment to promote amide formation reaction in solid-state. The synthesis condition is evaluated to understand the macromolecule growth. Solid-state reaction products are chemically characterized by FTIR and ¹H and ¹³C NMR. Molecular weight is determined by gel permeation chromatography (GPC) and the particles diameter in solution and charges are measured by dynamic light scattering (DLS) and zeta potential, respectively, at different pH values. The results attested the synthesis of hyperbranched polyamides with features similar to polyamide dendrimers. Surprisingly, the method enables the synthesis of macromolecules with very low dispersity index (DPI), that in some cases can be as low as 1.1.