Physico-Chemical nanomaterials science
Synthesis and lower critical solution temperature behavior of chitosan and N-isopropylacrylamide graft copolymers
Babelyte M.1, Liudvinaviciute D.1, Navikaite-Snipaitiene V.1, Rosliuk D.1, Rutkaite R.1, Samaryk V.2
1 Department of Polymer Chemistry and Technology, Kaunas University of Technology, Radvilenu Rd. 19, Kaunas 50254, Lithuania.
E-mail: migle.babelyte@ktu.edu
2 Department of Organic Chemistry, Lviv Polytechnic National University, Stepana Bandery St. 14, Lviv, Ukraine.

Chitosan (CS) is nontoxic, biocompatible and biodegradable, pH-sensitive polymer with antimicrobial activity. Because of these properties, it is an interesting biopolymer which can be further modified via grafting reactions. One of the most attractive compounds which can be used for grafting of chitosan is N-isopropylacrylamide (NIPAAm). Poly(N-isopropylacrylamide) (PNIPAAm) is highly thermo-sensitive polymer and shows sharp solubility changes in water around a specific temperature which is known as lower critical solution temperature (LCST). Beyond 32 ºC PNIPAAm turns into precipitate which can be composed of nanosized particles. Therefore, the graft copolymers with CS in the backbone and NIPAAm in the side chains could have dual stimuli responsive behavior and may be interesting in terms of drug delivery system.
In this study, chitosan-graft-N-isopropylacrylamide (CS-g-NIPAAm) copolymers were synthesized by free-radical polymerization in aqueous solution using potassium persulfate (PPS) as an initiator. By changing the molar ratio of CS:NIPAAm from 1:0.25 to 1:10 the copolymers with different grafting ratio were prepared. The obtained CS-g-NIPAAm copolymers were characterized by FTIR, H-NMR spectroscopy and other techniques. Moreover, the LCST behavior of synthesized copolymers was assessed by cloud point, particle size and fluorescence spectroscopy analysis.

Acknowledgment. The financial support of the Research Council of Lithuania for the project No. S-LU-22-11 in the frame of Lithuanian–Ukrainian Cooperation Programme in the Fields of Research and Technologies is highly acknowledged.