Exchange of Substituents between (Macro)Alkoxyamines and (Macro)RAFT Agents (ESARA): A Bridge between Nitroxide-Mediated and RAFT Controlled Radical Polymerization Techniques

Developing new tools to combine different polymerization techniques significantly extends the possibilities in terms of polymer design. Here, we report on a radical process abbreviated ESARA that creates a bridge between two controlled radical polymerization (CRP) techniques, nitroxide-mediated polymerization (NMP) and reversible addition-fragmentation chain transfer polymerization (RAFT). Proof of concept was first obtained with low molecular weight compounds. Alkoxyamine and thiocarbonylthio control agents were shown to exchange their respective substituents in selected experimental conditions, opening the way for the synthesis of new original control agents. The ESARA process was then implemented at the macromolecular level. Polystyryl macroalkoxyamines were converted to the corresponding polystyryl macroRAFT agents using thiocarbonylthio compounds. In addition, polystyryl macroRAFT agents were converted back to polystyryl macroalkoxyamine after reaction with an alkoxyamine. The bridge created between the two CRP techniques offers an access to a large number of well-defined polymer architectures such as block copolymers that would be difficult to obtain by only one technique.