On the Modification of Chitosan Through Grafting

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Abstract
The feasibility of grafting poly(methyl acrylate) and poly[1-(methoxycarbonyl) ethylene] onto chitosan, poly-β(1←-4)-2-amino-2-deoxy-d-glucose, was investigated. The grafting reaction was carried out in aqueous solution by using ferrous ammonium sulfate (FAS) in combination with H2O2 as redox initiator. The effects of such reaction variables as chitosan, monomer and initiator concentrations, reaction time, and reaction temperature were determined. Through this study the grafting reaction could be optimized. The grafting yield reached its maximum value of 332% when 0.3 g chitosan was copolymerized with 3 mL monomer at 70°C for 120 minutes with [FAS] = 6 × 10−5 M, [H2O2] = 6 × 10−3 M, and 8 mL water. The grafted chitosan was found to be insoluble in solvents for chitosan and solvents for poly(methyl acrylate), but did show swelling in dilute acetic acid, methanol, acetone, and in an ethanol/2% acetic acid 1:1 mixture. The thermal stability of chitosan and grafted chitosan were studied by dynamic thermogravimetric analysis. The results show that the graft copolymer is thermally more stable than pure chitosan. The overall activation energy for graft copolymerization was estimated to be 32.8 kcal/mol.