Perfectly Isotactic Polypropylene upon In Situ Activation of Ultrarigid meso Hafnocenes.

ABSTRACT: For more than 40 years, the synthesis of C₂ -symmetric indenyl-based racemic metallocenes for the isoselective polymerization of propylene relied on a tedious separation of the produced rac and meso isomers. Status quo, latter are considered wasteful as they produce atactic polypropylene (aPP) rather than isotactic polypropylene (iPP) if activated with methylaluminoxane (MAO). Unexpectedly, the in situ activation of meso hafnocene I yielded perfectly isotactic polypropylene. We verified an isomerization of the meso compound to the corresponding racemic one upon triisobutylaluminum (TIBA) addition via nuclear magnetic resonance (NMR) spectroscopy and established an easy and convenient polymerization protocol, enabling productivities comparable to pure rac-I if applied to pure mes

SUBMITTER: Stieglitz L 

PROVIDER: S-EPMC9828379 | biostudies-literature | 2022 Nov

REPOSITORIES: biostudies-literature