Metalloporphyrins living polymerization

Keywords Anionic polymerization. Living Polymerization, Immortal polymerization, Metalloporphyrin, Lewis acid... 

Additional well-defined side-chain liquid crystalline polymers should be synthesized by controlled polymerizations of mesogen-ic acrylates (anionic or free radical polymerizations), styrenes (anionic, cationic or free radical), vinyl pyridines (anionic), various heterocyclic monomers (anionic, cationic and metalloporphyrin-initiated), cyclobutenes (ROMP), and 7-oxanorbornenes and 7-oxanorbornadienes (ROMP). Ideally, the kinetics of these living polymerizations will be determined by measuring the individual rate constants for termination and... 

A key to achieving living polymerization is to develop well-behaved initiators, because the initiator affects both the relative rate of initiation to propagation and the potential for side reactions. - In this chapter, we focus on the precision synthesis of macromolecules with metalloporphyrins as initiators. Extensive initial studies by Inoue and Aida, - and more recent studies by Wayland et al.have shown that the metalloporphyrins which are applicable to controlled macromolecular synthesis include compounds of aluminum (1-4), zinc (5), manganese (6), cobalt (7) and rhodium (8). The first two nontransition metal metalloporphyrins are effective for anionic (nucleophilic) polymerization while... 

From propylene oxide these catalysts yield crystalline, isotactic polymers. Living polymerizations with metalloporphyrin derivatives are difficult to terminate and are therefore called by some immortal Catalysts like (C6H5)3-SbBr2-(C2H5)3N in combination with Lewis acids also yield crystalline poly(propylene oxide). Others, like pentavalent organoantimony halides, are useful in polymerizations of ethylene oxide. 

When compared to the abovementioned highly associated multinuclear coordination catalysts of very low initiation efficiency, metalloporphyrins with mononuclear Mt-X species have been reported to be excellent catatysts for the living polymerization of epoxides. The molar mass distribution of... 

Some monomers give the polymers with narrow molecular weight distribution even in the presence of a protic compound as a chain transfer agent. This is different from living polymerization, and a new concept of immortal polymerization has been presented . Living and immortal polymerizations initiated with metalloporphyrins can provide various types of block copolymers and end reactive polymers . ... 

In contrast to the above polymerizations via anionic and/or coordination anionic mechanisms, radical polymerization initiated with metalloporphyrins remains to be studied. The only example of controlled radical polymerization by metalloporphyrins has been reported by Wayland et al. where the living radical polymerization of acrylic esters initiated with cobalt porphyrins was demonstrated. In this section the radical polymerization of MMA initiated with tin porphyrin is discussed. 

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