Palladium-Catalyzed Synthesis of Hyperbranched Polar Functionalized Polyethylene with High Density Hydrophilic Groups
Beihang Ding, Shengyu Dai
Abstract
The chain-walking polymerization (CWP) strategy is a promising concept for the convenient synthesis of hyperbranched polar functionalized polyethylene with unique properties. In this study, we synthesized and described a series of o -aryl monosubstituted dibenzosuberyl iminopyridine ligands containing benzocycloalkyl or naphthyl moieties as well as the corresponding Pd(II) complexes, in a highly efficient manner. The Pd(II) complexes catalyzed efficient ethylene chain walking polymerization to produce hyperbranched polyethylenes (HBPEs) with high molecular weights ( M n values up to 71.4 kg/mol). Notably, copolymerization of ethylene and methyl acrylate, catalyzed by iminopyridine Pd(II) complexes, resulted in successful polar functionalized HBPEs with high density hydrophilic groups (21.4 mol %) at the end of branching. The polar functionalized HBPEs resulting from the process are saponified or reduced to yield more hydrophilic polymers that can solubilize water-insoluble drug molecules.