Polymerization-induced Self-assembly mediated by Vinyl-functionalized Macromolecular Chain Transfer Agents: A Straightforward Approach for Cross-linked Block Copolymer Nanoparticles with tunable Morphologies

Herein, block-type and random-type vinyl-functionalized macromolecular reversible addition-fragmentation chain transfer (macro-RAFT) agents were synthesized by RAFT solution polymerization and employed to mediate aqueous photoinitiated RAFT dispersion polymerization of hydroxylpropyl methacrylate (HPMA). When using the block-type macro-RAFT agent, cross-linked block copolymer nanoparticles with various morphologies could be prepared. Control experiments demonstrate that the vinyl group in the macro-RAFT agent has little impact on the polymerization process and the morphology of block copolymer nanoparticles. Morphologies of block copolymer nanoparticles could be controlled by changing the length of the stabilizer block, the [HPMA]/[macro-RAFT] ratio, and the HPMA concentration. When using the random-type macro-RAFT agent, cross-linked block copolymer nanoparticles were still obtained. Moreover, it was found that the random distribution of vinyl group in the macro-RAFT agent facilitated the formation of higher-order morphologies. Finally, the obtained cross-linked worms and vesicles were used as seeds for seeded RAFT polymerization of tert-butyl acrylate (tBA) or glycidyl methacrylate (GlyMA), which enables the further control over the surface morphology of block copolymer nanoparticles. We expect that this study will offer new opportunities for the rational preparation of cross-linked block copolymer nanoparticles with various morphologies.