Photopolymerization of Acrylamide Sensitized by Acidopentaamminecobalt(III) Complexes

Abstract

In the photopolymerization of acrylamide sensitized by acidopentaamminecobalt(M) complexes [CoL(NH3)6] X2 in aqueous solutions, their sensitizing abilities are dependent on the nature of the acid-ligands (L) greatly. Neither the chloro- nor the bromo-complex can initiate the photopolymerization without ultraviolet irradiation. But the complexes containing such acidligand as N3-, NCS- or NO2- can sensitize the Polymerization even under irradiation with visible light(470nm).In the latter cases, the polymerization rates (Rp) are dependent on the light intensities (I0)and on the concentrations of the complexes (c) and the monomer([M])variously. For the azido-complex Rp=, for the thiocyanato-complex and for the nitro-complex R . The initiation effciencies, that is, the ratio of the number of radicals initiating the polymerization to the total number of radicals produced from the complex, are only 0.15 and 0.06 for the azido-and nitro-complexes, respectively.From these results it is concluded that the polymerization sensitized by the azido-complex is slightly retarded by the complex itself and that in the case of the thiocyanato-and the nitro- complexes the radidals formed by the interaction between the ligand-radical and the monomer initiate the polymerization and the primary radical termination by nitro-radicals takes place predominantly in the case of the nitro-complex.