Living radical polymerization with reversible addition-fragmentation chain transfer (RAFT): direct ESR observation of intermediate radicals

Electron spin resonance (ESR) measurements were for performed by placing degassed solutions containing freshly distilled monomer, dimethyl 2,2′-azobis (isobutyrate) (AIBMe) initiator, RAFT agent, and benzene in the preheated cavity of the ESR spectrometer at 90°C. ESR spectra were obtained at 1 min intervals. Analysis of the obtained spectra indicate that ESR enables direct observations of the intermediate radicals that form during RAFT polymerizations.