Graft copolymerization of tertiary butyl acrylate onto chitosan initiated by ceric ammonium nitrate in an acidic medium

Abstract

This study introduces a novel approach to enhance chitosan’s functional properties through grafting with tertiary butyl acrylate (chitosan-g-TBA) via free radical polymerization. The process utilized ceric ammonium nitrate as a redox initiator in an acidic medium, with optimal conditions identified as 2 g chitosan, 3.5 g tertiary butyl acrylate, 0.15 g ceric ammonium nitrate, and a reaction time of 240 min at 70 °C. The study’s significance lies in achieving a grafting efficiency of 98.9% and a grafting percentage of 131.9%, surpassing previously reported values for similar systems, while maintaining a low homopolymer content of 0.7%. Successful grafting and substantial structural modifications were confirmed through FTIR, TGA, GPC, SEM, and XRD analyses. FTIR spectra revealed the incorporation of ester functional groups, while TGA demonstrated improved thermal stability, with chitosan-g-TBA retaining 25.13% mass at 700 °C compared to 19.52% for unmodified chitosan. SEM imaging showed increased surface roughness and porosity, and XRD analysis indicated reduced crystallinity, further confirming successful grafting. Moreover, water swelling behavior decreased from 513.4% in unmodified chitosan to 245.6% in chitosan-g-TBA, highlighting its potential for applications requiring reduced hydrophilicity and enhanced thermal resistance. These results suggest that chitosan-g-TBA is a promising material for biomedical, environmental, and industrial applications, offering improved thermal stability and tailored hydrophilic-hydrophobic balance. This research provides a comprehensive understanding of optimizing graft copolymerization parameters and their impact on material properties.