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

Abstract

<em>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.</em><em>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</em><em> 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.</em>