Synthesis of block copolymersvia the combination of RAFT and a macromolecular azo coupling reaction

We report a novel modular strategy for the synthesis of block copolymers via the combination of a macromolecular azo coupling reaction and a reversible addition fragmentation chain transfer (RAFT) polymerization method. One block, with a terminus suitable for an azo coupling reaction, was obtained by RAFT polymerization using a synthesized chain transfer agent (CTA) with the designed functional group. The other block, with a diazonium salt terminus, was obtained by the diazotization of aniline-functionalized PEG, which was prepared by a nucleophilic substitution reaction between the synthesized tosylate ended mPEG and p-aminobenzoic acid. The macromolecular azo coupling reaction between the above two polymer blocks was carried out in a polar organic solvent such as DMF under extremely mild conditions. Block copolymers with well-defined structures can be efficiently prepared through this approach.