Orthogonal\nAtom Transfer Radical Polymerization and\nReversible Addition–Fragmentation Chain Transfer Polymerization\nfor Controlled Polymer Architectures

Here, we report an orthogonal atom transfer radical polymerization\n(ATRP) and reversible addition–fragmentation chain transfer\n(RAFT) polymerization approach by selecting a suitable RAFT agent.\nReverse ATRP of poly(ethylene glycol) methyl ether methacrylate using\nethyl 2-bromoisobutyrate was performed in the presence of 2-(<i>n</i>-butyltrithiocarbonate)propionic acid (BTPA). Size exclusion\nchromatography and UV–vis spectroscopy confirmed that BTPA\nremained inert under reverse ATRP conditions. The effect of the structure\nof the RAFT agent on the orthogonal ATRP–RAFT polymerization\nwas then investigated in detail, demonstrating the importance of the\nleaving R-group of the RAFT agent. This approach was then used to\ncopolymerize and homopolymerize a RAFT chain transfer monomer (CTM),\n2-(2-(<i>n</i>-butyltrithiocarbonate)propionate)ethyl methacrylate,\nunder ATRP conditions with the trithiocarbonate group on the CTM unit\nbeing unreacted. RAFT solution polymerization and RAFT dispersion\npolymerization were then performed to synthesize graft and bottlebrush\ncopolymers. Upon RAFT dispersion polymerization, graft copolymer assemblies\nwere also obtained, and the effect of the distribution of solvophobic\nside chains on graft copolymer assemblies was investigated. This approach\nnot only provides a facile route for the rational synthesis of well-defined\npolymers with controlled architectures but also offers new mechanistic\ninsights into ATRP and RAFT polymerization.