A convenient way to synthesize comb-shaped chitosan-graft-poly (N-isopropylacrylamide) copolymer

Comb-shaped copolymers comprised of hydrophobic and hydrophilic blocks are self-assembled in aqueous solution, which results that they are suitable for delivery of hydrophobic drug molecules. Chitosan (CS) is an important biomaterial used widely in medical applications. Herein, a comb-shaped cationic copolymer composed of long biocompatible CS main chains and short PNIPAAm side chains was prepared via atom transfer radical polymerization (ATRP) by attaching an ATRP initiating group to N-phthaloyl chitosan. By subsequent removal of the protective groups on N-phthaloyl chitosan-graft-poly(N-isopropylacrylamide) (PHCS-g-PNIPAAm) copolymer with N2H4·H2O lead to the polymer pendant amino groups, this study attempted to synthesize a pH/temperature multi-responsive material. This chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAAm) copolymer is self-assembled in aqueous solution into stimuli-responsive core–shell micelles with hydrodynamic diameters of about 170 nm. Structural organization and solution behavior were then investigated utilizing 1H NMR spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS).