From metal-catalyzed radical telomerization to MetalCatalyzed radical polymerization of vinyl chloride: Toward living radical polymerization of vinyl chloride

The metal-catalyzed radical polymerization of vinyl chloride (VC) in ortho-dichlorobenzene initiated with various activated halides, such as a,a-dihaloalkanes, alpha,alpha,alpha -trihaloalkanes, perfloroalkyl halides, benzyl halides, pseudohalides, allyl halides, sulfonyl halides, alpha -haloesters, alpha -halonitriles, and imidyl halides, in the presence of Cu(0)/2,2 ' -bipyridine, Fe(O)/o-phenantroline, TiCp2Cl2, and other metal catalysts is reported. The formation of the monoadduct between the initiator and VC was achieved with all catalysts. However, propagation was observed only for metals in their zero oxidation state because they were able to reinitiate from geminal dihalo or allylic chloride structures. Poly(vinyl chloride) with molecular weights larger then the theoretical limit allowed by chain transfer to VC were obtained even at 130 degreesC. In addition, the most elemental features of a living radical polymerization, such as a linear dependence of the molecular weight and a decrease of polydispersity with conversion, were observed for the most promising systems based on iodine-containing initiators and Cu(O), that is, I-CH2-Ph-CH2-I/Cu(0)/bpy (where bpy = 2,2 ' -bipyridyl), at 130 degreesC. However, because of the formation of inactive species via chain transfer to VC and other side reactions, the observed conversions were in most cases lower than 40%. A mechanistic interpretation of the chain transfer to monomer in the presence of Cu species is proposed. (C) 2001 John Wiley & Sons, Inc.