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Keywords:

  • D/A metallocenes;
  • long chain branching;
  • monomodal/multimodal molecular weight distributions;
  • polyethylene;
  • polymerization catalysts;
  • polypropylene;
  • short chain branches;
  • ultrahigh molecular weight polyolefins

Abstract

D/A metallocenes constitute a novel unique class of catalysts, in that they are able to express structural information within the elementary steps of the catalytic cycle out of bridged as well as out of unbridged states due to the coexistence of donor (D) and acceptor (A) atoms in complex sandwich structures. Highly polarized transannular bridging interactions as well as Lewis basic and Lewis acidic functionalities in unbridged states are the prerequisites which define a modular highly flexible catalyst system with outstanding options to tailor materials and processes.