Effects of acetic anhydride on the activation and polymerization rates in nitroxide-mediated polymerization of styrene

In order to assess the recent suggestion of Hawker et al.(1) that the C-ON bond of an alkoxyamine is weakened by acetic anhydride (Ac2O), the activati on (dissociation) rate constant k(act) of a polystyrene-nitroxide adduct wa s directly determined in the presence of Ac2O. The result showed that Ac2O has no effect on the activation rate, contrary to the suggestion. On the ot her hand, Ac2O was confirmed to accelerate the polymerization rate. The mec hanism of acceleration was discussed.