Impact of Methylaluminoxane Oxidation on Ethylene Polymerization Using Ni Catalysts

Abstract

The effect of oxidation of methylaluminoxane (MAO) on ethylene polymerization was investigated to see the effect of aging and the possibility of using monomer gas that is not purified enough. In the polymerization using phenoxyimine-ligated titanium catalyst, almost no changes in polymerization behavior were observed until 35% of O 2 was added to MAO at enough Al/Ti ratio. However, Brookhart-type nickel-diimine catalysts activated with oxidized MAO gave polyethylenes with improved molecular weight and linearity. NMR, UV−vis, and electron paramagnetic resonance studies combined with theoretical prediction revealed that the electronic property on nickel was consistent, regardless of MAO modification. The effect on the polymerization behavior can thus be explained by the change of steric effect of counteranions derived from MAO via modification with oxygen.

Research Progress of Iron Catalysts with N,N,N‐tridentate Ligands for Ethylene Polymerization

“…In addition, the cocatalyst also plays a role in removing residual AlMe 3 from the solution. [65][66][67] Bryliakov studied the mechanism of chain transfer and chain end formation in the presence of MMAO and explained the "multisite-like" nature of the catalyst (Figure 7). [68] In the early and middle stages of polymerization, (iBu) 2 AlMe was prone to chain transfer to aluminum, forming low molecular weight of PE.…”

“…At the same time, it takes the electron‐rich group to become the equilibrium anion, and is in a dynamic equilibrium with the metal cation. In addition, the cocatalyst also plays a role in removing residual AlMe 3 from the solution [65–67] …”

Aggregation-induced emission of a bis(imino)acenaphthene zinc complex with tetraphenylethene units

“…The consideration of dispersion correction has previously reproduced the UV-vis spectra of a series of BIAN Ni complexes. 41,42 For Zn-2, the S 0 → S 1 transition is solely attributed to the transition (oscillator strength ( f ) = 0.35) from the HOMO to the LUMO (Table S2, ESI †), leading to the appearance of a photoabsorption band on the ILCT from the TPE units to the BIAN unit. Pd-2 showed a similar absorption band for the S 0 → S 1 transition with a lower oscillator strength (Table S3, ESI, † ( f ) = 0.13).…”

Facile access to diverse polyethylenesvianeutral salicylaldiminato nickel catalysts

“…[1][2][3][4] Since Brookhart et al discovered nickel(II) and palladium(II) catalysts supported by α-diimine ligands, 5,6 late transition metal catalysts have received tremendous attention over the past 30 years and have been proved to be very versatile in accessing diverse polyolefins. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] In contrast to extensive studies on cationic α-diimine nickel (II) catalysts with the activation of co-catalysts, another milestone in catalyst studies, neutral salicylaldiminato nickel(II) catalysts, discovered by Johnson et al 27 and Grubbs et al, 28,29 have better tolerance toward polar media but have attracted much less attention in terms of the production of diverse polyolefins. Unlike the α-diimine nickel(II) catalysts, the active center of this type of catalyst is electrically neutral, and thus it allows ethylene polymerization without the help of Lewisacidic co-catalysts.…”

“…1–4 Since Brookhart et al discovered nickel( ii ) and palladium( ii ) catalysts supported by α-diimine ligands, 5,6 late transition metal catalysts have received tremendous attention over the past 30 years and have been proved to be very versatile in accessing diverse polyolefins. 7–26…”