Additional Retardation in RAFT Polymerization: Detection of Terminated Intermediate Radicals

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. An unexpected behavior is observed with morpholine‐DT, described as an ‘additional retardation’, which is especially visible when low molar masses are targeted ( $\overline M _{\rm n} $  < 5 000 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.