Fluid-mediated nuclearity control in heterogeneous polyolefin catalysis

The nuclearity of active sites in heterogeneous Ziegler-Natta catalysts fundamentally governs polyolefin microstructure, yet its dynamic regulation during polymerization remains challenging. Here, we report a liquid containing polymerization strategy that directs the formation of dinuclear titanium species through periodic wetting-drying of inert n-hexane on the catalytic particles. Operando spectroscopy reveals how this unique fluid environment promotes the formation of dinuclear centers, in contrast to the monomeric species dominant in conventional gas- or slurry-phase systems. These dinuclear sites substantially enhance comonomer incorporation efficiency, yielding polyethylene with more uniform short-chain branching (SCB) distribution. Diffusion-ordered NMR spectroscopy further confirms that the capillary condensation of inert n-hexane in catalyst pores during liquid containing polymerization can enrich 1‑octene concentration by over twofold compared to the bulk slurry environment, thereby effectively promoting the SCB content in the synthesized polyethylene. This work establishes reactor fluid dynamics as a powerful tool for in-situ active-site engineering, opening avenues for selective control of polymer microstructure without modifying catalyst composition. The nuclearity of active sites in heterogeneous Ziegler–Natta catalysts plays a key role in determining polyolefin microstructure yet remains difficult to control during polymerization. Here, the authors use a liquid-containing polymerization strategy to induce dinuclear titanium species via periodic wetting–drying of n-hexane, enabling polymer microstructure control without altering catalyst composition.