Group 12 and 13 metal-alkenyl promoted generation of long-chain branching in metallocene-based polyethylene

Orlando Santoro (1) , Lorenzo Piola (1) , Karl Mc Cabe (2) , Olivier Lhost (3) , Katty den Dauw (3) , Alvaro Fernandez (4) , Alexandre Welle (3) , Laurent Maron (2) , Jean-François Carpentier (1) , Evgueni Kirillov (1)

1 ISCR - Institut des Sciences Chimiques de Rennes
2 LPCNO - Laboratoire de physique et chimie des nano-objets
3 [TRTF] - Total Research and Technology Feluy
4 Universidad de Guadalajara

In situ synthesis of topologically modified linear polyethylenes (PEs) using single-site polymerization catalysis is a challenging task that enables the production of advanced materials with tailored properties. We describe here our investigations aimed at an efficient generation of long-chain branches (LCB) in linear PEs using discrete B-, Al- and Zn-alkenyl co-reagents in combination with homogeneous rac-{EBTHI}ZrCl2 (1)/ or (nBuCp)ZrCl2 (2)/MAO catalytic systems. As corroborated by extensive rheological studies and 13C NMR spectroscopy, Al-and Zn-based reagents promote LCB formation via a two-step mechanism involving both vinylic group insertion and M → Zr transmetallation steps. In striking contrast, the B-alkenyl species was found to form hydrolytically stable B-centred cross-linked PE structures. The Mg-based reagent appeared to be reluctant towards Mg → Zr transmetallation reaction, providing only the products of vinylic group insertion, which after hydrolysis afforded short-chain branched (SCB) PEs. The experimental observations were rationalized by DFT computations.

Domains: Chemical Sciences

Orlando Santoro, Lorenzo Piola, Karl Mc Cabe, Olivier Lhost, Katty den Dauw, et al.. Group 12 and 13 metal-alkenyl promoted generation of long-chain branching in metallocene-based polyethylene. European Polymer Journal, 2022, 173, pp.111257. ⟨10.1016/j.eurpolymj.2022.111257⟩. ⟨hal-04013388⟩