Porphyrins and Their Metal Complexes in Radical Polymerization of Vinyl Monomers

Recently, controlled radical polymerization has become one of the most important methods for producing synthetic vinyl polymers. At the moment several techniques enabling such polymerizations exist, of which ATRP (atom transfer radical polymerization) and RATRP (reverse atom transfer radical polymerization) are the most commonly used ones. [1] The significant advantages of these polymerization techniques include the ability to polymerize polymers with controlled density and chain length, and narrow molecular weight distribution (MWD) in a controlled manner. A wide range of compounds as alkoxyamines, dithioesters, trithiocarbonates, xanthates and others were proposed as propagation regulators. Metalloorganic compounds of general formula MtnYL, where Mt transition metal (Cu, Fe, Ru, Re, Ni and others); Y – halogen anion (mainly chlorine or bromine); L – organic ligand (mostly 2,2’-bipyridine, 4,4’-bi-(5-nonyl)-2,2’-pyridine, triphenylphosphine) are of great interests also. The use of metal complexes of porphyrins in controlled radical polymerization could be very promising.[2-6] Thus, catalytic chain transfer to the monomer and catalytic inhibition were discovered in the polymerization of methacrylates carried out in the presence of cobalt porphyrins.[2-5] It was found by B.B. Wayland and M. Fryd that cobalt complex of tetramesitylporphyrin initiates polymerization of acrylates leading to the formation of homopolymers and block copolymers.[7-9] However, only few metal porphyrins, which are well-soluble in organic media, mainly, cobalt, rhodium, aluminum complexes, allowing the radical polymerization of vinyl monomers under controlled mode, have been studied by now.[7-11] The goal of this work was the study of radical polymerization of vinyl monomers (by the example of methyl methacrylate (MMA) and styrene) initiated by azo-bis-isobutironitrile (AIBN) or benzoyl peroxide (BP) in the presence of various porphyrins and their metal complexes.