Vinylic polymerization by homogeneous chromium(III) catalysts

A new class of homogeneous chromium(III)-based catalysts of the type [Cp*CrMeCl](2)/MAO with different kinds of Cp ligands has been synthesized. The influence of the electronic nature and the sterical demand of the catalysts were explored with regard to the vinylic polymerization of norbornene. The catalyst activity could be increased by intensifying the electron-donating character of the Cp ligand, whereas the sterical demand of the Cp ligand affects the crystallinity of the obtained polynorbornene. In order to improve their processability, copolymers of norbornene with ethene were made using the [Cp*CrMeCl](2)/MAO catalyst, which led to copolymers with a high alpha-olefin content. Furthermore, highly linear, ultra-high molecular weight polyethylene was obtained using the new class of chromium(III)-based catalysts.