Hydrogen‐transfer reaction in nitroxide mediated polymerization of methyl methacrylate: 2,2‐Diphenyl‐3‐phenylimino‐2,3‐dihydroindol‐1‐yloxyl nitroxide (DPAIO) vs. TEMPO

Abstract

Abstract In a recent article, we have showed that the nitroxide mediated polymerization of methyl methacrylate was possible up to 80% conversion for reasonable masses M n = 60,000 g mol −1 when 2,2‐diphenyl‐3‐phenylimino‐2,3‐dihydroindol‐1‐yloxyl nitroxide (DPAIO) was used as control agent. We have claimed that the success of this experiment relied on the absence of H‐transfer reaction both in the alkoxyamine and between alkyl and nitroxyl radical. In this article, the decomposition of 4‐nitrophenyl 2‐(2,2,6,6‐tetramethylpiperidine‐1‐yloxy)‐2‐methylpropionate ( 1a ) and 4‐nitrophenyl 2‐(2,2‐diphenyl‐3‐phenylimino‐2,3‐dihydroindol‐1‐yloxy)‐2‐methylpropanoate ( 2a ) has been studied by 1 H NMR in the presence and in the absence (persistent radical effect condition) of scavenger (thiophenol PhSH). At temperature lower than the one used for polymerization, fast and quantitative H‐transfer reaction was observed for 1a whereas no H‐transfer reaction was observed for 2a . The scavenging technique proved for the first time that the H‐transfer was an intermolecular process for 1a . However, the slow side‐reaction of NOC bond homolysis, which did not impede the control of the polymerization but may exert a detrimental effect on the livingness, was observed and quantified for 2a . © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6828–6842, 2008