Additional retardation in RAFT polymerization: Detection of terminated intermediate radicals

Abstract

The reversible addition-fragmentation chain transfer (RAFT) polymerization of N-acryloylmorpholine (NAM) is performed using three dithioesters (DT) as chain transfer agents (CTA) that incorporate a morpholine (morpholine-DT), a biotin (biotin-DT), or a sugar (sugar-DT) moiety in the R group. PolyNAM chains of controlled characteristics are synthesized. Anunexpected behavior is observed with morpholine-DT, described as an 'additional retardation', which is especially visible when low molar masses are targeted (M̄n < 5000 g ̇ mol -1). In that particular case, further investigations using MALDI-TOF mass spectrometry show the presence of terminated intermediate radicals (IRs), which corroborates the assumption based on a specific protection of IR according to the nature of the α-chain-end. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA,.