Leaching- and fragmentation-free heterogenization of late transition metal complexes as a model system to prove the growth mechanism of polyethylene

Abstract

Adopting a leaching-and fragmentation-free protocol, Ni(II) a-diimine complexes were covalently anchored on nonporous silica without any conventional tedious process. The supported catalysts polymerized ethylene with activities > 10 6 g-PE mol-Ni À1 h À1 bar À1 (10 kg-PE g-cat À1 at 5.5 bar pressure) when activated with a small amount (Al/Ni $100) of common aluminium alkyls (ethylaluminium sesquichloride, methylaluminium dichloride, and diethylaluminium chloride) in the absence of any methylaluminoxane. The polymer growth pattern from uniform spheres to fibers was clearly traced by using this model supported system, which depends on the catalytic activity, metal loading, and effective selection of co-catalysts. The polymerization results were compared with conventional porous silica supports immobilized by the same complex that undergoes fragmentation leading to a poor PE morphology.

Easy one-pot method to control the morphology of polyethylene/carbon nanotube nanocomposites using metallocene catalysts

“…When no more absorption of ethylene into toluene was observed, the cocatalyst was injected into the reactor and then the polymerization was started. Polymerization was quenched by the addition of methanol containing HCl (5 vol.-%) and then the unreacted monomer was vented [20,21]. The polymer was washed with an excess amount of methanol and dried in vacuum at 50°C.…”

“…To make a worthy comparison all data were collected under similar conditions. Generally, polymerization activity is expressed as the amount (in g or kg) of PE synthesized per mol of metal under standard condition [1 h, 1.3 bar/1 atm]; ie, activity0kg-PE mol-M -1 h -1 bar -1 [17,20,21].…”

Mechanical Properties of Polyethylene‐Carbon Nanotube Composites Synthesized by In Situ Polymerization Using Metallocene Catalysts

“…Under ethylene-saturated situation, the cocatalyst was added to start the polymerization. At desired time, the polymerization was stopped by quenching with methanol-containing HCl (10 vol.%) [21,22]. Excess methanol was used to precipitate and wash the product (PE/MWCNT nanocomposites).…”

Recent progress in immobilization of late-transition-metal complexes with diimine ligands for olefin polymerization

“…The metal active center loading of the supported catalyst was 45.9 mg-Fe/gcatalyst, about four times higher than that obtained by Kaul et al [34] and Kim et al [35]. Kim and coworkers [37] used three methods to immobilize Ni-based α-diimine catalysts on nonporous SiO 2 covalently, without using any lengthy conventional processes. In the first method, a diimine ligand with an -OEt end-group reacted with -OH on the nonporous SiO 2 , eliminating one molecule of EtOH, and then the metal compound was introduced.…”