Popcorn-shaped polyethylene synthesised using highly active supported permethylindenyl metallocene catalyst systems

Trends in Structure and Ethylene Polymerization Reactivity of Transition-Metal Permethylindenyl-phenoxy (PHENI*) Complexes

A family of ansa-permethylindenyl-phenoxy (PHENI*) transition-metal chloride complexes has been synthesized and characterized (1-7; {(η5-C9Me6)Me(R″)Si(2-R-4-R'-C6H2O)}MCl2; R,R' = Me, tBu, Cumyl (CMe2Ph); R″ = Me, nPr, Ph; M = Ti, Zr, Hf). The ancillary chloride ligands could readily be exchanged with halides, alkyls, alkoxides, aryloxides, or amides to form PHENI* complexes [L]TiX2 (8-17; X = Br, I, Me, CH2SiMe3, CH2Ph, NMe2, OEt, ODipp). The solid-state crystal structures of these PHENI* complexes indicate that one of two conformations may be preferred, parametrized by a characteristic torsion angle (TA'), in which the η5 system is either disposed away from the metal center or toward it. Compared to indenyl PHENICS complexes, the permethylindenyl (I*) ligand appears to favor a conformation in which the metal center is more accessible. When heterogenized on solid polymethylaluminoxane (sMAO), titanium PHENI* complexes exhibit exceptional catalytic activity toward the polymerization of ethylene. Substantially greater activities are reported than for comparable PHENICS catalysts, along with the formation of ultrahigh-molecular-weight polyethylenes (UHMWPE). Catalyst-cocatalyst ion pairing effects are observed in cationization experiments and found to be significant in homogeneous catalytic regimes; these effects are also related to the influence of the ancillary ligand leaving groups in slurry-phase polymerizations. Catalytic efficiency and polyethylene molecular weight are found to increase with pressure, and PHENI* catalysts can be categorized as being among the most active for the controlled synthesis of UHMWPE.

Efficient synthesis of thermoplastic elastomeric amorphous ultra-high molecular weight atactic polypropylene (UHMWaPP)

The synthesis of amorphous ultra-high molecular weight atactic polypropylene (UHMWaPP), with molecular weights (Mw) up to 2.0 MDa and narrow polydispersities is reported using remarkably efficient permethylindenyl-phenoxy (PHENI*) titanium complexes.

Synthesis of ultra-high molecular weight poly(ethylene)-co-(1-hexene) copolymers through high-throughput catalyst screening

A family of permethylindenyl titanium constrained geometry complexes, Me₂SB(^R′N,^3-RI*)TiX₂ ((3-R-η⁵-C₉Me₅)Me₂Si(^R′TiX₂)), supported on solid polymethylaluminoxane (sMAO) are investigated as slurry-phase catalysts for ethylene/H₂ homopolymerisation and ethylene/1-hexene copolymerisation by high-throughput catalyst screening. Me₂SB(^tBuN,I*)TiCl₂ supported on sMAO [sMAO-Me₂SB(^tBuN,I*)TiCl₂] is responsive to small quantities of H₂ (<1.6%), maintaining high polymerisation activities (up to 4900 kg_PE mol_Ti⁻¹ h⁻¹ bar⁻¹) and yielding polyethylenes with significantly decreased molecular weight (M_w) (from 2700 to 41 kDa with 1.6% H₂). In slurry-phase ethylene/1-hexene copolymerisation studies, a decrease in polymerisation activity and polymer molecular weights compared to ethylene homopolymerisation is observed. Compared to many solid supported system, these complexes all display high 1-hexene incorporation levels up to a maximum incorporation of 14.2 mol% for sMAO-Me₂SB(^iPrN,I*)TiCl₂). We observe a proportionate increase in 1-hexene incorporation with concentration, highlighting the ability of these catalysts to controllably tune the amount of 1-hexene incorporated into the polymer chain to produce linear low-density polyethylene (LLDPE) materials.

Permethylindenyl titanium CGCs supported on solid polymethylaluminoxane (sMAO) are investigated as slurry-phase catalysts by high-throughput catalyst screening (copolymerisation of ethylene/1-hexene with incorporation levels up to 14.2 mol%).

Polymethylaluminoxane organic frameworks (sMAOF) – highly active supports for slurry phase ethylene polymerisation

A series of modified solid polymethylaluminoxane (sMAO) catalyst supports have been developed for slurry phase ethylene polymerisation, using aryl di-ol modifier groups.

Constrained geometry scandium permethylindenyl complexes for the ring-opening polymerisation of l- and rac-lactide

The synthesis and characterisation of constrained geometry scandium permethylindenyl chloride, aryloxide and borohydride complexes ^Me₂SB(^tBuN,I*)Sc(Cl)(THF) (1), ^Me₂SB(^tBuN,I*)Sc(O-2,6-ⁱPr-C₆H₃)(THF) (2), ^Me₂SB(^tBuN,I*)Sc(O-2,4-^tBu-C₆H₃)(THF) (3) and ^Me₂SB(^tBuN,I*)Sc(BH₄)(THF) (4) are reported. The activity of complexes 1-4 as initiators for the ring-opening polymerisation (ROP) of l- and rac-lactide is presented. The ROP of l- and rac-lactide using complexes 2 and 3 show first-order dependence on monomer concentration, and produced isotactic polylactide (PLA) and moderately heterotactic PLA (P_r = 0.68-0.72), respectively. Good agreement between experimental and theoretical molecular weights of PLA (M_n) and relatively narrow dispersities (M_w/M_n < 1.20) were obtained. Complex 4 showed higher activity for ROP of l- and rac-lactide than 2 or 3, with second-order dependence on monomer concentrations. However, poorly controlled molecular weights and lower heteroselectivity (P_r = 0.61-0.67) were observed. The effect of temperature and catalyst concentration for the ROP of l-lactide using 2 and 3 was also studied.

Group 4 permethylindenyl complexes for slurry-phase polymerisation of ethylene

Supported group 4 permethylindenyl based catalysts displayed extremely high ethylene polymerisation activity affording popcorn shaped low molecular weights polyethylenes.

Group 4 permethylindenyl constrained geometry complexes for ethylene polymerisation catalysis

The synthesis and characterisation of six permethylindenyl constrained geometry complexes is reported. Slurry phase ethylene polymerisation studies demonstrate that activities increase with increasing electron donating character of the amido fragment.