Preparation and Characterization of Hyperbranched Poly(amino-ester) with Poly(ethylene glycol)

Hyperbranched poly(amino-ester)s with the surface containing acrylate bonds, backbone containing poly(ethylene glycol) (PEG), and interior containing tertiary amines have been synthesized via an one-step route associated with the Michael addition polymerization of trifunctional amine, 1-amino-2-(ethylamino)ethane (B'B₂-type monomer), and a double molar diacrylate, poly(ethylene glycol) diacrylate (A₂-type monomer). The hyperbranched poly(amino-ester) was modified with imidazole by Michael addition reaction of acrylate in hyperbranched poly(amino-ester)s and amine in imidazole. The polymerization kinetics of hyperbranched poly(amino-ester) was studied by ¹H-NMR. The chemical structures of these hyperbranched polymers were confirmed by ¹H-NMR, GPC and FT-IR. Results showed that the molecular weight of the hyperbranched poly(amino-ester) modified with imidazole was 1.42×10³, and the polydispersity index(PDI) was 1.05. The water solubility and pH responsiveness of the hyperbranched polymers were investigated by Zeta potential analyzer. Results demonstrated that the hyperbranched polymers showed excellent water solubility due to the presence of PEG backbone. Additionally, the hyperbranched poly(amino-ester) modified with imidazole has numerous tertiary amines which make the polymer carry more charges than the hyperbranched poly(amino-ester), therefore offering it with more sensitive pH responsiveness.