Structure of active centers, their stereospecificity distribution, and multiplicity in diene polymerization initiated by NdCl₃‐based catalytic systems

Abstract

Abstract On the basis of quantum‐chemical calculations, it was shown that among six types of active centers (ACs) that can form during the polymerization of butadiene with lanthanide‐based catalytic systems, five types (containing electron‐accepting chlorine atoms in the coordination sphere of a lanthanide) exhibit a π‐allyl binding of the terminal unit of a growing polymer chain to a lanthanide atom and function as cis ‐regulating. The sixth type of ACs is characterized by a σ‐alkyl structure and shows a trans ‐stereospecificity. This results was used to interpret the data on the microstructure of polybutadiene prepared using NdCl 3 · 3TBP‐Al(iso‐C 4 H 9 ) 3 , NdCl 3 · 3TBP–Mg(n‐C 4 H 9 )(iso‐C 8 H 17 ) catalytic systems and their combinations (TBP is tributyl phosphate). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 601–603, 2003