Supernormal Valence State Transition Metal Dihydroxy Periodic Acid [ni (iv) Redox Studies, Caused By Free Radical Polymerization

This paper is focused on the research work of free radical polymerization initiated by diperiodatonickelate(IV) periodate complex (DPN). Many studies have been reported that the mechanism of the procedure, Ni(IV)棐~ Ni(II), was an one-step two-electron transfer process without free radical intermediate, and could not initiated polymerization of vinyl monomers such as acrylonitrile and acrylamide. However, our research work indicated that the redox system composed of Ni(IV) and different molecules could initiate not only the homopolymerization of vinyl monomer such as acrylonitrile and acrylamide but also graft copolymerization of high graft efficiency. So the mechanism of free radical polymerization was supposed, a two- step one-electron transfer process was indicated. With suitable reaction condition (such as temperature, [DPN], P1-I value, etc) and suitable reductive agents, the monomer can gain the free radical intermediate and free radical polymerization such occurs. The main contents of this paper are stated as follows: In the first part, the research progress of transitional metal complex of uncommon oxidation states were reviewed and the application of this system was prospected. Forty- three references were cited. In the second part, the methods of preparation and standardizing of diperiodatonickelate(IV) periodate complex were described and the main instruments and chemical agents were also referred to. In the third part, the homopolymerization of acrylonitrile and acrylamide initiated by DPN were discussed. The kinetic equation and the apparent activation energy were gained. The effects of different conditions on the polymerization rate or the polymer molecular weight were also studied. The initiation mechanism was proposed. In the fourth part, the graft copolymerization initiated by DPN were discussed. The effects of reaction temperature, initiator concentration, PH and ratio of monomers on copolymerization were investigated. The graft copolymer with high grafting efficiency was obtained. The possible initiation mechanism was proposed. In the fifth part, the application of other transitional metal complex of uncommon oxidation states, such an Cu(III) and Ag(III), was discussed.