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Science 26 March 1999:
Vol. 283. no. 5410, pp. 2059 - 2062
DOI: 10.1126/science.283.5410.2059
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Reports

Chain Walking: A New Strategy to Control Polymer Topology

Zhibin Guan, * P. M. Cotts, E. F. McCord, S. J. McLain

Ethylene pressure has been used to control the competition between isomerization (chain walking) and monomer insertion processes for ethylene coordination polymerization catalyzed by a palladium-alpha -diimine catalyst. The topology of the polyethylene varies from linear with moderate branching to "hyperbranched" structures. Although the overall branching number and the distribution of short-chain branching change very slightly, the architecture or topology of the polyethylene changes from linear polyethylene with moderate branches at high ethylene pressures to a hyperbranched polyethylene at low pressures.

DuPont Central Research, Experimental Station, Wilmington, DE 19880, USA.
*   To whom correspondence should be addressed.

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