Metallocene‐Catalyzed Ethylene–Norbornene Copolymerization Employing Triisobutylaluminum/Borate Synergistic Cocatalyst Systems: High‐Efficiency Synthesis and Property Modulation

ABSTRACT This study develops a highly efficient, MAO‐free catalytic platform using a triisobutylaluminum/borate (TIBA/Borate) synergistic system to activate rac ‐ethylenebis(indenyl)zirconium dichloride ( rac ‐Et(Ind) 2 ZrCl 2 ) for ethylene‐norbornene (E‐NBE) copolymerization. Under low Al:Zr molar ratios, the binary systems achieved exceptional catalytic activities up to , yielding high‐molecular‐weight cyclic olefin copolymers () with a broad, tailorable window of 100°C–182.13°C. Microstructural and engineering evaluations demonstrate that the borate type serves as a critical process controller for both sequence distribution and melt processing behaviors. NMR analysis reveals that the Borate‐i system promotes adjacent N–N sequence insertions to ensure structural uniformity and eliminate crystalline domains. Conversely, the Borate‐ii system enhances melt strength and elasticity, making it highly compatible with high‐shear industrial extrusion. Furthermore, managing the Al:Zr ratio and reaction time provides a practical operational lever to control solution viscosity and mitigate reactor fouling. This work establishes a robust and cost‐effective synthesis framework for the industrial‐scale manufacturing of high‐performance COCs.