H ₂ O ₂ ‐Initiated Reversible Addition‐Fragmentation Chain Transfer Polymerization of Methyl Methacrylate Mediated by Peroxide‐Labile Dithiobenzoate in O ₂ ‐Rarefied <i>N,N</i> ‐Dimethylsulfoxide Under Aerobic Media

Abstract The effect of aerobic dioxygen (O 2 ) residues and hydrogen peroxide (H 2 O 2 ) on dithiobenzoate‐mediated reversible addition‐fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) was studied. 2‐cyano‐2‐propyl dithiobenzoate (CPDB) displayed excellent thermally oxidative stability against O 2 in O 2 ‐rarefied dimethylsulfoxide (DMSO) but was readily oxidized by H 2 O 2 . Azo‐initiated CPDB‐mediated RAFT polymerization of MMA in DMSO under different media led to multi‐component products, consisting of PMMA macro‐CTAs, MMA‐terminated oligomers and low‐MW byproducts, while nitrogen deoxygenating and headspace eliminating gave rise to a comparable CTA efficiency, higher than that headspace limiting. H 2 O 2 ‐initiated CPDB‐mediated headspace‐free RAFT polymerization of MMA smoothly proceeded in DMSO even at 50 °C, suggesting the co‐initiation by CPDB, and also formed predominant PMMA macro‐CTAs, negligible oligomers and some low‐MW byproducts. H 2 O 2 ‐initiated CPDB‐mediated headspace‐free RAFT polymerization of MMA at 70 °C displayed well‐controlled behaviors with 2–5 wt.% byproducts, and the high fidelity of the PMMA macro‐CTAs was confirmed by the chain extension via azo‐initiated RAFT polymerization and Cu I ‐catalyzed concurrent ATRP/RAFT polymerization.