Study of molecular size in ethylene‐propene copolymerization with zirconocene and hafnocene catalysts

Ethylene‐propene copolymerization was carried out with Cp2MCl2 (Cp = cyclopentadienyl), rac‐Et(Ind)2MCl2, rac‐Me2Si(Ind)2MCl2 (Et = ethylene, Me2Si = dimethylsilyl, Ind = indenyl, M = Zr or Hf)/methylaluminoxane. In the case of using ansa‐hafnocenes, the minimum molecular size (extended chain length) of ethylene‐propene copolymer was obtained at about 50 mol‐% of propene content in the copolymer. The polymerization activity decreased with increase of propene feed ratio in non‐bridged non‐specific metallocenes. Higher polymerization activities were observed for the copolymerization compared to ethylene and propene homo‐polymerization with ansa‐isospecific metallocenes. The factor of molecular size lowering was studied by the chain propagation and chain transfer reaction.