Copolymerization of propylene with styrene and ethylene by a THF-containing half-sandwich scandium catalyst: efficient synthesis of polyolefins with a controllable styrene content

Abstract

The homopolymerization of propylene and its copolymerization with styrene and ethylene catalyzed by half-sandwich scandium complexes bearing different ligands were carried out. A significant influence of alkyl and THF ligands on the propylene polymerization activity has been observed. The THF-containing trimethylsilylmethyl complex (C₅Me₄SiMe₃)Sc(CH₂SiMe₃)₂(THF) (4) in combination with one equivalent of [Ph₃C][B(C₆F₅)₄], can serve as a high activity catalyst for the atactic polymerization of propylene. By using this high activity catalyst, the copolymerization of propylene with styrene has been achieved to afford multi-block propylene–styrene copolymers with syndiotactic styrene–styrene blocks. Moreover, a novel family of random propylene–ethylene–styrene terpolymers with a broad composition range, relatively high molecular weights and narrow molecular weight distributions was effectively obtained by the terpolymerization of propylene with ethylene and styrene in the presence of 4/[Ph₃C][B(C₆F₅)₄]. The incorporation of styrene units into atactic polypropylene or ethylene–propylene copolymers can be controlled in a wide range simply by changing the monomer feed ratios.