Core-Shell Nanogels With Raspberry Architecture and Amine Loading in the Core via Precipitation Polymerization: A Mechanistic Study

Nanogels (NGs) are synthesized by precipitation polymerization of dendritic polyglycerol (dPG), N-isopropylacrylamide (NIPAM), and N-isopropyl methacrylamide (NIPMAM). The stabilization and agglomeration of subunits during the NG growth result in raspberry-like structures, as shown by transmission electron microscopy, atomic force microscopy, and small-angle X-ray scattering measurements. Positive charges are introduced into dPG-NIPAM-NIPMAM NGs by (1) the copolymerization of dimethylaminoethyl methacrylate (DMAEMA) and (2) the copolymerization of glycidyl methacrylate (GMA), followed by its functionalization with ethylenediamine (ED) through the epoxy group. Homogeneous structures are obtained by the copolymerization in batch of DMAEMA with the other monomers, whereas core-shell NGs are reached by semibatch copolymerization of GMA. After amination, the charges are restricted to the core of the NGs.