Aqueous polymerization of acrylamide initiated by permanganate/oxalic acid redox system

Abstract

Abstract The polymerization of acrylamide initiated by permanganate/oxalic acid redox pair has been studied in aqueous media at 35 ± 0.2°C in nitrogen atmosphere. The rate of polymerization is independent of activator (oxalic acid) concentration (0.75·10 −3 to 7.5·10 −3 mole/l.) except at very high (above 7.5·10 −3 mole/l.) or very low (below 0.75·10 −3 mole/l.) concentrations of the activator. The rate varies linearly at low monomer concentration. The catalyst exponent decreases from nearly unity to 0.65 with the increase in the concentration of catalyst (KMnO 4 ) probably due to participation of primary radicals in the termination of the growing chain. The initial rate increases with increase in the polymerization temperature. The overall energy of activation has been found to be 11.97 Kcal/mole within the temperature range 25‐50°C. Organic solvents (water miscible only) and salts (KCI, Na 2 SO 4 ) depress the initial rate but small amounts of manganous salts (MnSO 4 ) can increase the initial rate to a considerable extent. High concentration of salts (Na 2 SO 4 , KCl, and MnSO 4 ) causes termination of the growing chain. A complexing agent, NaF, decreases the initial rate but the limiting conversion is increased. Introduction of new catalyst at intermediate stages of polymerization increases both the rate and the limiting conversion.