Physiochemical Characterization of the Graft Copolymerization of Acrylamide and Acrylonitrile onto Sodium Alginate by Ceric-Ion/Allyl Alcohol Redox Pair

Abstract Sodium alginate was chemically modified via graft copolymerization with acrylamide and acrylonitrile via a ceric ion allyl alcohol redox system in aqueous media. The synthesized graft copolymers were characterized via viscometry, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). FTIR confirmed the successful incorporation of acrylamide (3294 cm⁻ ¹ and 3064 cm⁻ ¹) and acrylonitrile functional groups (at 2383 cm⁻ ¹ for the repeat unit) into the sodium alginate backbone. SEM micrographs revealed distinct morphological changes, with sodium alginate-g-polyacrylamide showing a uniform distribution, whereas sodium alginate-g-polyacrylonitrile exhibited random surface deposition. Thermal stability studies indicated that the graft copolymers demonstrated improved overall resistance to decomposition compared with that of pristine sodium alginate, although the ungrafted polymer remained more stable at low weight loss (≤ 50%). These findings suggest that grafting enhances the structural and thermal properties of sodium alginate and significantly broadens its potential application in flocculant, dye and paint thickeners, and other eco-friendly polymer-based industries.