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The performance profile of a supported metallocene catalyst in slurry-phase ethylene polymerisation can be significantly enhanced by tuning the chemical composition of the support. By employing catalyst supports derived from zinc-containing layered double hydroxides (LDHs), the slurry phase ethylene polymerisation productivity of (EBI)ZrCl2 (EBI = rac-ethylenebis(indenyl)) can be quadrupled relative to a magnesium-containing support. Productivity increases approximately linearly with zinc content of the LDH before reaching a plateau; our experiments suggest the productivity of this catalyst system is related to the overall Lewis acidity of the support surface. We have found that iron-containing LDH supports with a similar overall Lewis acidity also result in productivity enhancements, demonstrating the general nature of this phenomena.

We report the synthesis and characterisation of eight constrained geometry complexes, with variation of the amido fragment, ansa-bridge, permethylindenyl group, metal centre and initiator groups from the parent complex Me2SB(tBuN,I*)TiCl2. These complexes have been shown to be highly active for slurry-phase ethylene polymerisation when supported on solid polymethylaluminoxane (sMAO), with activities up to 7048 kgPE/molTi/h/bar. Ethylene/1-hexene and ethylene/styrene copolymerisations have shown these complexes to be good incorporators of comonomers into the polymer chain.

Five new group 4 ansa-bridged permethylindenyl complexes with either a dimethylsilane bridge or a tetramethyldisilane bridge have been synthesised and fully characterised. These complexes were supported on a hydrocarbon insoluble polymethylaluminoxane (sMAO) and their slurry-phase ethylene polymerisation performance was investigated. The highest activity was achieved using S B M e 2 (CpMe,I*)Zr(CH2SiMe3)2 (8042 kgPE molZr–1 h–1 bar–1 at 60 °C) but a decrease in activity was observed with an increase in the length of the bridge. DSC analysis of the polymers revealed the production of HDPE with minimal branching and defects, while SEM showed the production of polymer particles with commercially desirable uniform, ‘popcorn’, morphology. GPC analysis showed the production of polyethylenes with Mw S B M e 2 (Cp,I*)Zr(CH2SiMe3)2 was immobilised on MAO modified layered double hydroxide (LDHMAO). The slurry-phase polymerisation activity of S B M e 2 (Cp,I*)Zr(CH2SiMe3)2 on this support system was similar to the sMAO support; however, the polymer morphology was much less uniform.

A family of well-defined cyclopentadienyl and indenyl group 4 complexes has been prepared. The complexes Cp2ZrCl(O-2,6-Me-C6H3) (1), Cp2Zr(O-2,6-Me-C6H3)2 (2), Cp2ZrMe(O-2,6-Me-C6H3) (3), (Ind)2ZrCl(O-2,6-Me-C6H3) (4), (Ind)2ZrMe(O-2,6-Me-C6H3) (5), (Ind)2ZrMe(OtBu) (6), and rac-(EBI)ZrCl(O-2,6-Me-C6H3) (7) were investigated as catalysts for the polymerization of L- and rac-lactide. (Ind)2ZrMe(OtBu) was shown to be the fastest catalyst. At 100 °C, the rates of polymerization (kobs) for L- and rac-lactide were very similar (0.317 and 0.293 h−1 respectively). However, at 80 °C it was found that polymerization of L-LA (kobs = 0.217 h−1) was twice as fast as rac-LA (kobs = 0.120 h−1).