Two six-membered non-metallocene titanium complexes based on diphenylamine ligands
[RN(CH
2
)
3
NR
]
TiMe
2
(
4a
: R = 2
6-Me
2
-C
6
H
3
;
4b
: R = 2
6-
i
Pr
2
-C
6
H
3
) were synthesized. The titanium complexes were applied for ethylene homo- and copolymerization with
α
-olefin and norbornene in the presence of modified methylaluminoxane (MMAO) as a cocatalyst by adjusting polymerization conditions such as temperature
ethylene pressure
and the dosage of MMAO. The polymerization results demonstrated that the electronic and steric effects of the substituents on the aniline ligands significantly influenced the catalytic activity. The isopropyl-substituted complex
4b
exhibited an ethylene homopolymerization activity of 1.68×10
6
g·mol
-1
·h
-1
under the conditions of Al/Ti = 800
temperature of 100 ℃
and 2 MPa ethylene pressure. Moreover
its activity in ethylene/1-decene copolymerization further increased to 4.08×10
6
g·moll
-1
·h
-1
. Both homo- and copolymerization activities of complex
4b
were higher than those of methyl-substituted complex
4a
. Additionally
this catalyst system maintained stable polymerization activity even at 145 ℃
demonstrating the excellent thermal stability of this diamine-based titanium catalyst. This study elucidated the mechanistic role of the electronic and steric effects of the substituents
providing valuable insights for the design and development of non-metallocene catalysts to achieve high catalyst activity
thermal
stability
and excellent copolymerization ability.
关键词
Keywords
references
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