A Trinuclear Pd-Diimine Catalyst for "Core-First" Synthesis of Three-Arm Star Polyethylenes via Ethylene "Living" Polymerization

The synthesis of a novel trinuclear Pd-diimine catalyst that further enabled the first 'core-first' synthesis of three-arm star polyethylenes through ethylene trifunctional 'living' polymerization was reported. The synthesis was carried out in one step by reacting an acetonitrile Pd-diimine complex with a triacrylate monomer 'trimethylolpropane triacrylate'. Synthesis was based on the characteristic reaction with acrylate functionality, where the acrylate double bond was inserted into the Pd-Me bond through 2,1-insertion followed by rearrangement, which produced a stable 6-membered chelate structure. It was observed that well-defined narrow-distributed three arm star polyethylenes of controllable arm lengths can be obtained by purifying the as-produced polymers. It was also found that the arms of these star polymers contained a backbone of linear topology with short branching structures.