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

Abstract

AbstractThe 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 (KMnO4) 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, Na2SO4 and Na2C2O4) depress the rate considerably but the manganous salt (MnSO4) 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.