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

Abstract

Abstract The polymerization of methacrylic acid initiated by permanganate / oxalic acid redox pair has been studied in aqueous media at 30 ± 0.2°C in nitrogen atmosphere. The initial rate of polymerization has been found to be proportional to nearly the first power of the catalyst (KMnO 4 ) concentration ((0.8‐6.0)·10 −4 mole/l.) at low monomer concentration (5.89·10 −2 mole/l.) but the catalyst exponent varies from 1.2 to 0.2 at comparatively high monomer concentration (17.68·10 −2 mole/l.) and falls at comparatively higher concentrations of the activator ((COOH) 2 ) at constant concentration of catalyst (1.6·10 −4 mole/l.) and monomer (5.89·10 −2 mole/l.). The rate is proportional to the first power of the monomer concentration within the range (2.36–14.1)·10 −2 mole/l. and catalyst (2.8·10 −4 mole/l.). The initial rate increases with increase in polymerization temperature up to 45°C. The overall activation energy has been found to be 9.87 kcal/mole within the temperature range 30‐45°C. Organic solvents (water miscible only) and salts (KCl, Na 2 SO 4 and Na 2 C 2 O 4 ) depress the rate considerably but the manganous salt (MnSO 4 ) is found to increase the initial rate. A complexing agent, NaF, decreases the rate as well as the maximum conversion. Introduction of new catalyst at intermediate stages of polymerization increases the rate and the maximum conversion.