Permanganate‐malic acid redox pair as the initiating system in the homogeneous polymerization of acrylamide

The homogeneous polymerization of acrylamide initiated by the new redox system permanganate‐malic acid was investigated in aqueous media under nitrogen at 35±0,2°C. Over a wide range of concentration (2,5 to 30 mmol dm−3) of the activator (malic acid), (4), the polymerization rate remains unaffected. Addition of sulfuric acid (0,1 to 5 mmol dm−3) increases the rate but decreases the maximum conversion. The value 0,53 of the catalyst exponent confirms a bimolecular termination mechanism. The variation of the rate at a low monomer concentration is linear. The initial rate and the conversion increase with increasing temperature. The activation energy is found to be 82,20 kJ/mol (19,74 kcal/mol) in the temperature range of 25 to 50°C. Neutral salts, water miscible organic solvents, and ethylenediaminetetraacetic acid all suppress both the limiting conversion and the rate of polymerization. The addition of more catalyst at intermediate stages as well as the addition of MnSO4 raise the initial rate and the conversion. Sodium fluoride enhances the rate but lowers the limiting conversion.