Kinetics of photopolymerization of acrylamide initiated by copper (II)-bis(amino acid) chelates in aqueous solution. II.

Abstract

The kinetics of photopolymerization reactions of acrylamide initiated by copper (II)-bis(amino acid) chelates with amino acids glutamic acid, serine, or valine were studied at 30°C. The extent of monomer conversion increases with increased initiator concentration and falls off after reaching a maximum. Analysis of the results shows that for lower concentrations of the initiator, the rate of monomer disappearance is proportional to light absorption fraction fε^1/2[monomer] and the square root of the intensity. At higher concentrations of the initiator, the rate of monomer disappearance is proportional to Fε/[initiator]^1/2; the monomer exponent is 1.5 and the intensity exponent 0.5. Mutual termination of the radicals is proposed at lower concentrations of the initiator; at higher concentrations of the initiator termination of the initiator radical by the copper (II) complex along with mutual termination occurs. The initiator radical species is identified from flash photolysis studies of these complexes as the Cu(I)-coordinated radical. The effect of pH on the monomer conversion is explained. The data indicate a free-radical mechanism of polymerization and a reaction scheme is proposed for the polymerization reactions.