Functionalized semi‐crystalline polyethylene with polar groups at branch end enabled by bulky cationic palladium catalysts

Abstract

AbstractTransition metal‐catalyzed copolymerization of ethylene with polar monomers is the most direct and efficient way to prepare polar functionalized polyethylene. Generally, the classical Brookhart type α‐diimine Pd(II) catalysts produced hyperbranched functionalized polyethylene with polar groups at the branch ends, which turns out to be amorphous polymer materials. In this contribution, we described the synthesis and characterization of three bulky diarylmethyl α‐diimine ligands and the corresponding Pd(II) complexes. Lightly branched (21–27/1000C) polyethylenes with high molecular weights (317.8–640.0 kg/mol) and high melting points (94–101°C) were prepared using these Pd(II) complexes at high activities (well above 105 g/mol.h). The resulting polyethylene materials exhibited high stress (23.8‐34.3 MPa) and high strain (559–839%) at break values with typical properties of thermoplastics. Polar functionalized semi‐crystalline polyethylenes with moderate incorporation ratios (0.35–2.99 mol%) and high melting points (84–109°C) were prepared using complexes Pd1‐3 in the copolymerization of ethylene with several polar comonomers (methyl acrylate and 10‐undecenoic acid and 10‐methyl undecanoate). The 1H and 13C NMR spectral analysis revealed that these polar functionalized polyethylenes have a low branching density (19–34/1000C) and are predominantly methyl‐branched, with polar groups located at the end of the branches. In addition, the 4‐methoxy group on the ligands in this work would facilitate the insertion of polar monomers in the copolymerization of ethylene with various polar monomers.