Transition metal catalyzed precise olefin polymerization for high performance materials

Abstract

In this work, half-titanocenes of the type Cp’TiCl₂(L), where L is anionic ancillary donor ligand, was studied in ethylene copolymerization in the presence of cocatalyst to investigate the efficient catalyst for ethylene copolymerization and to synthesize the new polymers. Half-titanocenes containing imidazolin-2-iminato ligand, Cp’TiCl₂[1,3-R₂(CH₂N)₂C=N], were used in the presence of MAO for ethylene/α-olefin copolymerization. The results suggested that CpTiCl₂[1,3-´Bu₂(CHN)₂C=N] exhibited remarkable catalytic activity, affording ultrahigh molecular weight copolymers with uniform molecular weight distributions. This complex also showed remarkable catalytic activity with efficient norbornene incorporation in ethylene/norbornene copolymerization. The resultant copolymer possessed high molecular weight with uniform molecular weight distribution. In the study of terpolymerization of ethylene, 1 -hexene and styrene, aryloxo-modified half-titanocenes, Cp’TiCl₂(O-2,6-´Pr₂C₆H₃), were used in the presence of cocatalyst. The results showed that Cp*TiCl₂(O-2,6-´Pr₂C₆H₃) and ´Bu(C₅H₄)TiCl₂(O-2,6-´Pr₂C₆H₃) provided high molecular weight polymers with unimodal distributions and efficient comonomer incorporation. To introduce vinyl group into polymer chain, terpolymerization of ethylene and styrene or 1-hexene with 3,3-divinylbiphenyl was conducted by using aryloxo-modified half-titanocenes. Efficient comonomer incorporations were achieved by this type of catalyst and the content of each comonomers could be varied by their concentration charged. Post-polymerization of styrene could also be obtained by initiating the vinyl group remained in the side chain by treatment with n-BuLi.