Investigation of the Formation Process of PNIPAM-Based Ionic Microgels

[Image: see text] The formation process of poly(N-isopropylacrylamide) (PNIPAM)-based ionic microgels was investigated in this work. Different from the traditional formation process of covalent bond cross-linked PNIPAM-based microgels, a disassembling and reassembling process for PNIPAM-based ionic microgels was observed. During the formation process, loose microgels were first formed in a short time, and then, these loose microgels disassembled into smaller nanogel pieces. Meanwhile, the nanogel pieces reassembled into microgels by electrostatic interaction. After reassembling, large amounts of nanogels could be seen clearly in the interior of PNIPAM-based ionic microgels. The thermo-sensitivity and composition of the final prepared microgels were characterized by dynamic light scattering, infrared spectroscopy, and X-ray photoelectron spectroscopy.