Polymerization of acrylamide and acrylic acid photoinitiated by diazidotetramminecobalt (III) azide

Abstract

The kinetics of polymerization of acrylamide and acrylic acid in aqueous solution photoinitiated by the complex, diazidotetramminecobalt(III) was systematically studied at 35°C and pH=3. Monochromatic radiation at γ=365, 405, and 435 mμ was employed. The kinetics of polymerization were followed by measurements of the rates of monomer disappearance (bromometrically) and complex disappearance (spectrophotometrically) and the chainlengths of the polymers formed (viscometrically). The dependences of the rate of polymerization on variables like light intensity, light absorption by the complex, wavelength, monomer concentration, and hydrogen ion concentration were studied. The rates of polymerization of acrylamide and acrylic acid were found to be propertional to the square of the monomer concentration and to the first power of light absorption fraction k_e and light intensity I. A kinetic scheme is proposed in the light of experimental results involving (1) a primary photochemical act of excitation of the complex, followed by the dark reaction of electron transfer within the complex producing the azide radical; (2) initiation of polymerization by the azide radical; (3) termination of the chain process by the complex molecule.