Abstract
AbstractRadical‐induced oxidation of reversible addition‐fragmentation chain transfer (RAFT) agents is investigated with respect to the effect of molecular structure on oxidation rate. The radicals are generated by homolysis of either azobisisobutyronitrile or alkoxyamine and transformed in situ immediately into peroxy radicals through transfer to molecular oxygen. It is found that the oxidation rate depends on the structure of Z‐ and R‐group of thiocarbonylthio compounds. For dithioesters with identical Z‐phenyl substituent, the oxidation rate decreases in the order of cyanoisopropyl (C(Me)2CN) > cumyl (C(Me)2Ph) > phenylethyl (CH(Me)Ph) > 2‐methoxy‐1‐methyl‐2‐oxoethyl (CH(Me) C(O)OCH3) > benzyl (CH2Ph). For dithioesters with identical R‐group, the oxidation rate decreases in the order of Z = phenyl− ∼ benzyl− > RS− (trithiocarbonates) > RO− (xanthates). The stability of the RAFT agents toward oxidation correlates well with the chain transfer abilities as those previously reported by Rizzardo and coworkers. The priority of the oxidation reaction over the RAFT process, and the subsequent influence on RAFT polymerization are also investigated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
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