Stringing Large Rings

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Science  08 Aug 2008:
Vol. 321, Issue 5890, pp. 747
DOI: 10.1126/science.321.5890.747a

Polymerization reactions that yield products with large cyclic side chains tend to be rare and often exhibit high product polydispersity (a measure of the spread in the length of chains created). However, large cyclic side chains can act as sites for trapping small molecules, which make the polymers useful as absorbents or stationary supports in chromatography, Ochiai et al. report that a bis-methacrylate monomer, in which a central cyclohexane linkage and terminal urethane groups act as structure-directing agents, can be used to form polymers with 19-atom cyclic side chains; the macrocycles close during the chain-propagation process. Low polydispersity was observed for RAFT synthesis (reversible addition-fragmentation chain-transfer polymerization, a form of living chain polymerization) in dioxane solvent with cumyl dithiobenzoate as a RAFT agent. The controlled nature of the polymerization should allow further modifications through the formation of block copolymers. — PDS

J. Am. Chem. Soc. 130, 10.1021/ja801491m (2008).

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