Carbon Dioxide and Nitrogen-Modulated Shape Transformation of Chitosan-Based Composite Nanogels

Chitosan/poly[N-(3-(dimethylamino)propyl)methacrylamide]/poly(acrylic acid) (CS/PDMAPMA/PAA) composite nanogels (CPACNGs) were fabricated in the solution of chitosan by surfactant-free emulsion polymerization. N-(3-(Dimethylamino)propyl)methacrylamide (DMAPMA) and acrylic acid (AA) were initiated by 2,2'-azobis-2-methyl-propanimidamide to graft from the backbone of chitosan. Nanogels were formed by noncovalent forces, including of hydrogen bonds, hydrophobic, and electrostatic interaction. Nanogels were characterized by transmission electron microscopy, scanning electron microscope dynamic light scattering, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer spectra, and ¹H NMR. Spherical nanoparticles were observed in the latex system. Nanogels exhibited an excellent CO₂ responsivity and CO₂/N₂ reversible response and switchability and had a faster response rate. The morphological shape transformation of nanogels was modulated by bubbling with CO₂ and N₂. The responsive mechanism was explored by determining the pH and electrical conductivity. In addition, nanogels were successfully emulsified by bubbling with CO₂, and then a phase transition was achieved by bubbling with N₂ in the organic solvent/water mixture.