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zhangfangzhi

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[交流] 【讨论】RAFT 末端不带硫代羰基的死聚合物链有多少

RAFT后，末端不带硫代羰基的死聚合物链有多少，占总分子链多大比例？
Ezio Rizzardo说，
A key feature of RAFT polymerization is that the thiocarbonylthio
groups are retained in the polymeric product.

[ Last edited by zhangfangzhi on 2009-10-10 at 16:44 ]

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1楼 2009-10-10 15:22:46

已阅回复此楼关注TA 给TA发消息送TA红花 TA的回帖

zhangfangzhi

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In the absence of chain transfer (to solvent, initiator,
or monomer), the total number of chains formed will be
equal to (or less than) the moles of dithio compound
employed plus the moles of initiator-derived radicals
generated during the course of the polymerization. In
block synthesis, these additional initiator-derived chains
are a source of homopolymer impurity. The level of
impurities can be controlled by appropriate selection of
the reaction conditions.14 For maximum purity, it is
desirable to use as low a concentration of initiator as
practicable and to choose solvents and initiators which
give minimal chain transfer. As with conventional
radical polymerization, the rate of RAFT polymerization
is determined by the initiator concentration. In practice,
it is usually not difficult to achieve block copolymers
with no detectable homopolymer impurity (<5%) while
still achieving an acceptable rate of polymerization.