Copolymerization of Ethylene with Norbornene Catalyzed by Cationic Rare-Earth Metal Half-Sandwich Complexes

Ethylene-co-norbornene Copolymerization Using a Dual Catalyst System in the Presence of a Chain Transfer Agent

Ethylene-co-norbornene copolymers were synthesized by a dual catalyst system at three concentrations of norbornene in the feed and variable amounts of ZnEt₂, as a possible chain transfer agent. The dual catalyst system consists of two ansa-metallocenes, isopropyliden(η5-cyclopentadienyl)(η⁵-indenyl)zirconium dichloride (1) and isopropyliden(η⁵-3-methylcyclopentadienyl)(η⁵-fluorenyl)zirconium dichloride (2), activated with dimethylanilinium tetrakis(pentafluorophenyl)borate, in presence of TIBA. Values of norbornene content, molecular mass, glass transition temperature, and reactivity ratios r11 and r21 of copolymers prepared in the presence of 1+2 are intermediate between those of reference copolymers. The study of tensile and elastic properties of ethylene-co-norbornene copolymers (poly(E-co-N)s) gave evidence that copolymers were obtained in part through transfer of polymer chains between different transition metal sites. Mechanical properties are clearly different from those expected from a blend of the parent samples and reveal that copolymers obtained in the presence of 1+2 and ZnEt₂ consist of a reactor blend of segmented chains produced by exchange from 2 to 1 and 1 to 2 acting as the ideal compatibilizer of chains produced by the chain transfer from 1 to 1, and from 2 to 2.

Bis-(salicylaldehyde-benzhydrylimino)nickel complexes with different electron groups: crystal structure and their catalytic properties toward (co)polymerization of norbornene and 1-hexene

Eight bis-(salicylaldehyde-benzhydrylimino)nickel complexes with different electron groups (Ni1–Ni8), Ni{(3-R₁)(5-R₂)C₆H₂(O)CHNCH(C₆H₅)₂}₂, (R₁ = H, R₂ = H, Ni1; R₁ = H, R₂ = CH₃, Ni2; R₁ = H, R₂ = OCH₃, Ni3; R₁ = H, R₂ = Br, Ni4; R₁ = CH₃, R₂ = H, Ni5; R₁ = OCH₃, R₂ = H, Ni6; R₁ = Br, R₂ = Br, Ni7; R₁ = Cl, R₂ = Cl, Ni8), were synthesized and their crystal structures were characterized using single crystal X-ray diffraction. The results revealed that Ni1–Ni6 belong to the monoclinic system (space group P2(1)/n), Ni7 belongs to the monoclinic system (space group C2/c) and Ni8 belongs to the triclinic system (space group P1̄). All nickel complexes exhibited high activities (0.46–2.07 × 10⁶ g_polymer mol_Ni⁻¹ h⁻¹) toward norbornene homopolymerization, and a strong electron-withdrawing group on the salicylaldimino aromatic ring can enhance the catalytic activity and favor polymerization. Ni1 and Ni2 exhibited high activities (0.55–2.40 × 10⁵ g_polymer mol_Ni⁻¹ h⁻¹) toward copolymerization of norbornene and 1-hexene in the presence of B(C₆F₅)₃. The 1-hexene content in the copolymers could be controlled up to 7.98–12.50% by varying the comonomer feed ratio of 1-hexene from 10 to 50%. It is observed that when the 5-position of the salicylaldimino aromatic ring has a substituent (–CH₃), the 1-hexene insertion rate is lower than that without a substituent. In addition, the polymers showed high molecular weights (1.5–2.4 × 10⁵ g mol⁻¹) and narrow molecular weight distributions (1.62–1.89). The obtained polymers were also verified to be amorphous copolymers and had high thermal stability, good solubility and optical transparency.

Ni(ii) complexes were successfully synthesized and characterized, and were highly active toward (co)polymerization of norbornene, and the 1-hexene content could be controlled.

Homo- and Copolymerizations of Ethylene and Norbornene Using Bis(β-ketoamino) Titanium Catalysts Containing Pyrazolone Rings

A series of bis(β-ketoamino) titanium complexes containing pyrazolone rings (1⁻3) have been synthesized, characterized, and used as precursors for homo- and copolymerization of ethylene and norbornene. The titanium complexes activated with methylaluminoxane (MAO) exhibited good activities for homopolymerization of ethylene (E) to produce linear polyethylenes (PEs). Ethylene⁻norbornene copolymers (E⁻N) were also prepared by these catalysts with moderate activities, and influences of ligand substituents and norbornene addition on copolymer microstructure were studied in detail. Microstructure analysis of the E⁻N copolymers by 13C NMR and differential scanning calorimetry (DSC) techniques showed that alternating (ENEN) and isolated (ENEE) norbornene predominately appeared in the copolymer chain, and the NN dyad and NNN triad sequences were also present in the copolymers obtained by the less bulky catalyst 1.

Synthesis of bis-(benzocyclohexan-ketoimino) Ni(ii) with different electron groups and their catalytic copolymerization of norbornene and polar norbornene

Several N,O-chelating type bidentate ligand nickel complexes were synthesized, characterized and applied to catalyze copolymerization of norbornene and polar norbornene.

Catalytic synthesis of polyethylene-block-polynorbornene copolymers using a living polymerization nickel catalyst

Well-defined polyethylene-block-polynorbornene copolymers were synthesized using an amine–imine nickel catalyst.

Synthesis, characterization, and catalytic behaviours of beta-carbonylenamine-derived [O- NS]TiCl3 complexes in ethylene homo- and copolymerization

A series of [O(-)NS]TiCl(3) complexes 5a-l derived from beta-carbonylenamine were synthesized and characterized. In the presence of modified methylaluminoxane (MMAO), complexes 1, 5a-i and 5l are highly active for ethylene polymerization and copolymerization of ethylene with 1-hexene, CPE and NBE. Up to 5.12 x 10(6) g mol(-1) h(-1) atm(-1) of activity for the copolymerization of ethylene with 1-hexene is achieved with a 28.9 mol% incorporation ratio.