Structural influences in nitroxide mediated controlled radical polymerisation
This work describes the synthesis and application in controlled radical polymerisation of several novel pyrrolidine-N-oxyl, PROXYL, based nitroxide and alkoxyamines species bearing a variety of substituents adjacent to the nitroxide functionality. Through variation of the nitroxide electronic structure a variation in rate of styrene polymerisation was observed and one nitroxide demonstrated the ability to mediate polymerisation of w-butyl acrylate. In an attempt to rationalise this behaviour examination was carried out on model species studying the influence of nitroxide structure on thermal dissociation of alkoxyamine carbon to oxygen bond and the propensity of alkoxyamines towards hydrogen transfer disproportionation. It is suggested that the reduced propensity for this hydrogen transfer disproportionation in addition to the rate of the alkoxyamine homolysis is a key factor in determining the activity of nitroxide in mediated controlled radical polymerisation. The results of this study are placed within the context of the current state of knowledge in nitroxide mediated controlled radical polymerisation.