ON THE DEVELOPMENT OF CHITOSAN-GRAFT-POLY(N-ISOPROPYLACRYLAMIDE) BY RAFT POLYMERIZATION TECHNIQUE

The present paper aimed the synthesis of a functional biopolymer based on chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAAm) using the "grafting from" technique via reversible addition-fragmentation chain transfer (RAFT) polymerization. Two different chain transfer agents, both compatible with the acrylic monomer were used. All intermediary products obtained from each step of chemical synthesis were quantified by ATR-FT-IR, H-1-NMR and elemental analysis. Thermal properties confirmed that, with the chemical modification, chitosan structures became more complex and more thermally stable. The grafting efficiency was quantified as 40% and the final copolymer had double functionality, free amino groups and PNIPAAm segments on the side chains. Thanks to this, water solubility, pH and temperature sensitivity were achieved. The particle size of the aqueous solutions increased from 500 nm to 3.5 mu m, with the increase of temperature from 25 to 50 degrees C. The lower critical solution temperature (LCST) of the solution was determined as 38-42 degrees C. CS-g-PNIPAAm could be used as a polymeric carrier within a pharmaceutical formulation for topical applications.