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A comparative analysis of SET‐LRP of MA in solvents mediating different degrees of disproportionation of Cu(I)Br

2008; Wiley; Volume: 46; Issue: 20 Linguagem: Inglês

10.1002/pola.22998

1099-0518

Gerard Lligadas, Virgil Percec,

Lanthanide and Transition Metal Complexes

Abstract Cu(I)Br/Me 6 ‐TREN species are unstable and disproportionate into metallic Cu(0) and Cu(II)Br 2 /Me 6 ‐TREN in DMSO, whereas in toluene are stable and do not undergo disproportionation, at least at 25 °C. To estimate the role of the disproportionating solvent in single electron‐transfer living radical polymerization (SET‐LRP) a comparative analysis of Cu(0)/Me 6 ‐TREN‐catalyzed polymerization of MA initiated with methyl 2‐bromopropionate at 25 °C was performed in DMSO and toluene. A combination of kinetic experiments and chain end analysis by 500‐MHz 1 H NMR spectroscopy was used to demonstrate that disproportionation represents the crucial requirement for a successful SET‐LRP of MA at 25 °C. In DMSO a perfect SET‐LRP occurs and yields close to 100% conversion in 45 min. A first order polymerization in growing species up to 100% conversion and a PMA with perfectly functional chain ends are obtained. However, in toluene within 17 h only about 60% conversion is obtained, the polymerization does not show first order in growing species and therefore is not a living polymerization. Moreover, at 60% conversion the resulting PMA has only 80% active chain ends. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6880–6895, 2008