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

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.