Chain walking: A new strategy to control polymer topology

Ethylene pressure has been used to control the competition between isomeriz ation (chain walking) and monomer insertion processes for ethylene coordina tion polymerization catalyzed by a palladium-alpha-diimine catalyst. The to pology of the polyethylene varies from linear with moderate branching to "h yperbranched" structures. Although the overall branching number and the dis tribution of short-chain branching change very slightly, the architecture o r topology of the polyethylene changes from linear polyethylene with modera te branches at high ethylene pressures to a hyperbranched polyethylene at l ow pressures.