Superkunststoff! Donor‐Acceptor‐Zirconocene mit einem Donor(P)‐substituierten Fluorenylliganden und einem Acceptor(B)‐substituierten Cyclopentadienylliganden (siehe Struktur) katalysieren die Ethylenpolymerisation mit hoher Aktivität und enormer Selektivität für das Kettenwachstum selbst bei hohen Temperaturen und machen so ultrahochmolekulare Polyethylene zugänglich (viskositätsgemittelte Molekulargewichte Mη>1×106 g mol−1).

No abstract

Within the last 2 decades a large number of metallocene/MAO copolymerization catalysts has been developed, targeting tailor-made high-quality ethylene−propylene elastomers. However, under the widely used EP(D)M solution polymerization process temperatures, conventional metallocene catalysts give only access to the lower 15% of the commercial molecular weight range, established with Ziegler−Natta catalysts, which extends to about 106 g/mol. The novel class of donor−acceptor metallocenes makes a quantum leap in enhancing in EP(D)M molecular weights by orders of magnitude. Thus, the full molecular weight range of tailor-made polyolefin elastomers up to ultra high molecular weights is now accessible. At lower temperatures the D−A metallocene catalyst systems approach 100% chain growth selectivity in living olefin homo- and copolymerizations.