A novel method of controlled grafting modification of chitosan via RAFT polymerization using chitosan-RAFT agent

The controlled grafting modification of chitosan has first been achieved by RAFT polymerization using chitosan-RAFT agent. The chitosan was first modified with S-1-dodecyl-S′-(α,α′-dimethyl-α′′-acetic acid)trithiocarbonate (DDACT) to serve as RAFT agent, and then the controlled grafting polymerization of acrylic acid were performed. The resultant copolymers were characterized by 1H nuclear magnetic resonance (1H NMR), Fourier transform infrared spectrometer (FT-IR), X-ray powder diffractometer (XRD), high performance particle sizer (HPPS), and transmission electron microscopy (TEM). The results indicate that the graft copolymers were successfully synthesized and that the grafting polymerization was a first-order reaction with respect to monomer concentration. The size distribution of chitosan-g-PAA in ethanol is very narrow, which may be associated with the grafting density and the “well-defined” PAAs onto chitosan from RAFT polymerization. TEM shows chitosan-g-PAA in dilute ethanol dispersions is roughly 80 nm in size with some aggregation. This work provides a new method to prepare chitosan grafting copolymers with controlled molecular weights and “well-defined” structures.