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Science 5 May 2006:
Vol. 312. no. 5774, p. 653
DOI: 10.1126/science.312.5774.653b
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This Week in Science
In a "living" polymerization, each polymer chain grows at a steady rate from a single catalyst site. The successive removal and addition of different monomers to the reactor yields block copolymers with structurally distinct chain segments. Arriola et al. (p. 714; see the Perspective by Gibson) present an alternative strategy for building block copolymers in which diverse monomers are all present at once and a molecular shuttle transfers growing polymer chains back and forth between catalysts with differing selectivities. The shuttling technique tolerates high temperatures (to maintain polymer solubility) and is amenable to economically efficient continuous flow conditions. Screening of a wide range of catalyst and shuttle combinations revealed useful elastomeric copolymers in which polyethylene blocks alternate with high and low levels of a higher olefin, 1-octene, with a high degree of block intermixing.
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Science. ISSN 0036-8075 (print), 1095-9203 (online)
