Gas‐Phase Synthesis of Hyperbranched UHMWPE by Enhancing Chain Walking and Minimizing Chain Transfer

A series of rigid‐flexible unsymmetrical bulky α‐diimine palladium catalysts was employed for the gas‐phase polymerization of ethylene, enabling the synthesis of hyperbranched ultrahigh molecular weight polyethylene (UHMWPE). Compared to conventional solution‐phase polymerization, the gas‐phase method significantly suppresses chain transfer while promoting chain walking, leading to a simultaneous increase in both molecular weight and branching density. Under optimized conditions, the resulting polyethylene exhibited high molecular weight (up to 2053 kg/mol) and branching densities as high as 107 branches per 1000 carbon atoms. Structural characterization confirmed the presence of long‐chain branches and branch‐on‐branch architectures, indicative of a hyperbranched topology. The unsymmetrical palladium catalysts produced polyethylene with higher molecular weight and branching density than the benchmark catalysts, by combining suppressed chain transfer with high chain‐walking ability. This work demonstrates the potential of gas‐phase polymerization as a solvent‐free, environmentally benign route to advanced polyolefin materials with tailored architectures.