Functional Polyolefins

Popcorn Polyethylene Waxes

Solid polymethylaluminoxane (sMAO) supported ansa-bridged permethylindenyl zirconocenes ^Me₂SB(Cp^R,I*)ZrX₂ ({(η⁵-C₉Me₆)Me₂Si(η⁵-C₅H₃R)}ZrX₂; R = H, Me, and nBu; X = Cl, Br, Me, and CH₂Ph) have been investigated as catalysts for the slurry-phase polymerization of ethylene in the presence of H₂. The catalysts demonstrated remarkable stability to H2 both in a high-throughput screening system and in a 2 L batch reactor, with an almost constant ethylene uptake maintained throughout the polymerization runs. The catalysts demonstrated very high ethylene polymerization activities, almost 3 times higher than sMAO-(Cp^nBu)₂ZrCl₂ (industrial standard zirconocene catalyst) under the same conditions. The presence of small quantities of H₂ (<1%) led to significant decreases in polymer molecular weights to produce commercially desirable polyethylene waxes (M_n < 10 kg mol^–1) in a batch reactor.

Unsymmetrical permethylindenyl bent metallocene complexes have been synthesised and reacted with inorganic solid supports to afford catalysts for the slurry phase polymerisation of ethylene. Those supported on solid polymethylaluminoxane were both highly active catalysts and afforded polymers with a desirable, low aggregation, “popcorn” morphology.

Recent publications:

• Metallocene polyethylene wax synthesis, J.V. Lamb, J.-C. Buffet, Z. R. Turner, T. Khamnaen, and D. O′Hare, Macromolecules, (2020),  53, 5847–5856.
• Popcorn-shaped polyethylene synthesised using highly active supported permethylindenyl metallocene catalyst systems, J.-C. Buffet, Z. R. Turner and D. O’Hare, Chem. Commun. (2018), 54, 10970-10973
• Efficient synthesis of thermoplastic elastomeric amorphous ultra-high molecular weight atactic polypropylene (UHMWaPP) C. G. Collins-Rice, J. C. Buffet, Z. R. Turner, D. O’Hare, Polymer Chemistry, 2022, 13, 5597-5603 DOI: 10.1039/d2py00708h

• Supported permethylindenyl titanium catalysts for the synthesis of disentangled ultra-high molecular weight polyethylene (disUHMWPE) C. G. Collins-Rice, J. C. Buffet, Z. R. Turner, D. O’Hare, Chemical Communications, 2021, 57, 8600-8603 DOI: 10.1039/d1cc03418a