Palladium-Catalyzed Synthesis of Hyperbranched Polar Functionalized Polyethylene with High Density Hydrophilic Groups

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.

Direct synthesis of poly(α-olefin) thermoplastic elastomers via controlled chain straightening using bulky α-diimine palladium complexes

“…Late-transition-metal catalysts, such as α-diimine nickel( ii ) or palladium( ii ) catalysts (Scheme 1b), exhibit a unique chain-walking process. 30–47 This process involves β-hydride elimination followed by reinsertion with opposite regiochemistry into the olefin hydride (Scheme 1c). Based on this unique process, late-transition-metal catalyzed ethylene homopolymerization has been widely used for the preparation of TPEs.…”