ESR study of hydroxyl alkoxyamine (HMPAP) in DMF and tert ‐butylbenzene

Hydroxyl alkoxyamine (HMPAP) in DMF and in tert ‐butylbenzene with oxygen as a scavenger was studied with electron spin resonance spectroscopy. From kinetics studies performed at 120°C, it was found that the rate constant of CO bond homolysis was smaller in DMF than in tert ‐butylbenzene. The difference in the behavior could be related to the formation of an activated six‐membered intermediate formed through intramolecular H‐bonding in tert ‐butylbenzene and the disruption of H‐bonding in the polar solvent DMF. This led to alteration of the equilibrium constant between the alkoxyamine and the corresponding nitroxide and C‐centered radical in DMF and decreased initiating efficiency for the controlled/living radical polymerization using HMPAP as initiator. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4116–4120, 2006