Degradable and Chain Extendable Segmented Hyperbranched Copolymers by Wavelength-Selective Photoiniferter Polymerization Using a Trithiocarbonate-Derived Dimethacrylate

In this study, segmented hyperbranched copolymers with degradable and chain extendable cross-linker branch points were synthesized via green light-activated photoiniferter copolymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA) and a trithiocarbonate-derived dimethacrylate. A series of segmented hyperbranched copolymers with different degrees of branching were synthesized by changing the feed ratio of PEGMA to cross-linker to chain transfer agent. The segmented hyperbranched copolymers could be degraded into linear polymer chains by removing the trithocarbonate groups, which provides fundamental insights into the growth of primary chains during photoiniferter copolymerization. Switching to blue light irradiation allowed for the chain extension of poly(N,N-dimethylacrylamide) (PDMA) both at the branch points and at the chain ends. Finally, the formed segmented hyperbranched copolymers were explored as macromolecular chain transfer agents to prepare segmented hyperbranched block copolymer nanoparticles via polymerization-induced self-assembly. This study not only leads to new examples of degradable and chain extendable segmented hyperbranched polymers but also provides important insights into the formation of branched polymers via copolymerization of multivinyl monomers.