Diene Polymerisation Mechanism with Lanthanide Catalytic Systems

Diene Polymerisation Mechanism with Lanthanide Catalytic Systems 

The distinctive feature of lanthanide and in particular Ziegler-Natta catalysts is that they allow one to synthesise polydienes with a high content of c/s-1,4-units. In most cases, lanthanides are used in the form of blends and concentrates. About 50% of lanthanides consumed worldwide are used for the production of catalysts for various chemical processes. Using lanthanide catalysts in the manufacture of synthetic rubbers can increase the number of these processes. A large number of studies have been devoted to polymerisation of dienes with lanthanide catalytic systems. Many of these studies are concerned with the problems related to the mechanism that controls the microstructure of polydienes. Although not all aspects of stereoregulation have been clarified, many problems have been solved and possible explanations offered for some of the others [1-4]. 

The objective of this chapter is to examine the basic research on diene (butadiene, isoprene, and piperylene) polymerisation with the LnHalj-nL-AlRj (Ln = lanthanide, Hal = halogen, ligand (L) = tributyl phosphate (TBP), AlRj = triisobutylaluminum and diisobutylaluminum hydride) catalytic system. The chapter will analyse the role of such factors as the electronic and geometric structure of bimetallic active centres, anti-syn and 7t-o-transitions of the terminal units of the growing polymer chains and the nature of the lanthanide, diene, and organoaluminum component in the mechanism of stereoregulation. 

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The objective of this part of work was to study the role of the structure of the diene (butadiene, isoprene and piperylene) in the mechanism of regio- and stereoselectivity in polymerisation with the lanthanide catalytic system NdCl3-3TBP-Al(2-C4H9)3. To this... 

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