Kinetic Study of Graft Polymerization of Acrylic Acid and Ethyl Methacrylate onto Starch by Ceric Ammonium Nitrate

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Graft polymerization of acrylic acid (AA) and ethyl methacrylate (EMA) onto starch (St) were carried out in aqueous solution using ceric ammonium nitrate (CAN) as redox system under N2 atmosphere. The effect of pH, reaction time, temperature, concentrations of CAN, St, and monomers on the graft yield was investigated. Monomer reactivity was in the following order: AA>EMA.The kinetics of the graft polymerization of AA and EMA onto starch in same system with CAN was studied by acid-base and boromometric titration, respectively. The rate expressions for graft polymerization are Rg=k[AA]0.92[CAN]0.56[St]0.46 and R/g=k/[EMA]0.92[CAN]0.53[St]0.48 and a suitable mechanism is suggested. The graft copolymers were investigated by FT-IR spectroscopy. The overall activation energy of graft polymerization of AA onto starch was found to be 36.25 kJ.mol-1 within the temperature range 20-40°C, and for graft polymerization of EMA onto starch is found to be 11.88 kJmol-1 within the temperature range 25-45°C.