Mechanistic features and radical intermediates in atom transfer radical polymerization

Abstract

Fundamental mechanistic features of copper mediated atom transfer radical polymerization (ATRP) are presented together with a discussion on radical intermediates involved in atom transfer process. Rate constants of racemization of optically active methyl 2-bromopropionate, of halogen exchange, of trapping with TEMPO and with methyl methacrylate are very similar, confirming free radical intermediates. Rate constant of reaction of propionate radical with methyl methacrylate under model ATRP conditions at 22 °C (k= 5.6 10 4 mol -1 L s -1 ) is nearly identical to that measured by time resolved EPR (k= 6.0 10 4 mol -1 L s -1 ).