Grafted Copolymer Based on Chitosan and Poly(N-Isopropylacryl Amide) via Click Technique. I. Synthesis and Characterization

As chitosan’s solubility represents a drawback for further applications, the functionalization of chitosan became attractive by a variety of chemical methods. The present study deals with the chemical modification of chitosan by using click chemistry technique as versatile tool being easy to perform with high yields and no additional by products. The approach used herein was to attach a responsive moiety (e.g. NIPAAm, HEMA or DMAEMA) on the macromolecular chain of chitosan via an azide-alkyne coupled reaction. More specifically, the reaction occurred between azide-chitosan and alkyne terminated responsive polymer. The method includes the modification of chain transfer agent with alkyne terminated groups, polymerization of responsive monomer, azidation steps of chitosan and final click reaction between two end products. Structure of end products and intermediaries were confirmed by the FT-IR and H-NMR spectra. Thermal characterization was performed showing different thermal behavior with the chemical modification. As main outcome, chitosan-g-PNIPAAm was obtained, the structure being confirmed by the disappearance of azide group and the presence of triazole moiety within the final product. The new approach of advancing the reaction via alkyne terminated-PNIPAAm, synthesized by RAFT, seemed to be successful as verified by 1HNMR. Thermal properties revealed a better thermal stability for the new polymeric materials as the structure was more complex. Key-Words: Click chemistry, Chitosan, Phthaloylation, PNIPAAm, Alkyne terminated PNIPAAm, Triazole ring, Graft copolymer