Orthogonal Atom Transfer Radical Polymerization and Reversible Addition-Fragmentation Chain Transfer Polymerization for Controlled Polymer Architectures

Here, we report an orthogonal atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization approach by selecting a suitable RAFT agent. Reverse ATRP of poly(ethylene glycol) methyl ether methacrylate using ethyl 2-bromoisobutyrate was performed in the presence of 2-(n-butyltrithiocarbonate)propionic acid (BTPA). Size exclusion chromatography and UV-vis spectroscopy confirmed that BTPA remained inert under reverse ATRP conditions. The effect of the structure of the RAFT agent on the orthogonal ATRP-RAFT polymerization was then investigated in detail, demonstrating the importance of the leaving R-group of the RAFT agent. This approach was then used to copolymerize and homopolymerize a RAFT chain transfer monomer (CTM), 2-(2-(n-butyltrithiocarbonate)propionate)ethyl methacrylate, under ATRP conditions with the trithiocarbonate group on the CTM unit being unreacted. RAFT solution polymerization and RAFT dispersion polymerization were then performed to synthesize graft and bottlebrush copolymers. Upon RAFT dispersion polymerization, graft copolymer assemblies were also obtained, and the effect of the distribution of solvophobic side chains on graft copolymer assemblies was investigated. This approach not only provides a facile route for the rational synthesis of well-defined polymers with controlled architectures but also offers new mechanistic insights into ATRP and RAFT polymerization.