Exploring ferrocene-directed photo-Fenton initiation of RAFT polymerization

The iron-based Fenton chemistry has been used as the radical initiator in reversible addition-fragmentation chain-transfer (RAFT) polymerization. However, its practical application in polymeric materials science has been restricted due to the unmodified nature of inorganic iron and its non-functional properties. To address this, we introduce a strategy termed ferrocene-directed photo-Fenton RAFT polymerization, abbreviated as Fc-PF-RAFT, which combines visible light-controlled ferrocene-based Fenton chemistry as the initiator with the upgradation of RAFT polymerization, enabling the exploration of polymers with unique properties and structures. For demonstration, we employed ferrocenyl compounds Fc1-Fc3 in the Fc-PF-RAFT polymerization of N,N-dimethylacrylamide (DMA) in an open aqueous system. The ferrocene-directed photo-Fenton reaction facilitated the generation of dual radicals Fc-COO˙ and ˙OH, initiating well-controlled RAFT polymers with distinct end-group functionalization types: Fc-, OH-, and carboxylic acid group derived from the RAFT agent. By adjusting the role of Fc-ended functionalization in polymer evolution, we fine-tuned self-assembled morphologies, ranging from simple spherical micelles to crosslinked clusters. Notably, the selenium (Se)-containing Fc3-end group polymer underwent self-assembly driven by Se⋯N noncovalent interactions, along with phenyl and cyclopentadienyl π-π interactions, leading to the formation of hierarchical structures. As Fc3-ended functionalization increased, the driving force for self-assembly transitioned from noncovalent interactions to crystallization, as evidenced by the growth from a polymeric DMA-based corona to an Fc3-based core. This study demonstrates the impact of incorporating ferrocene into the Fenton reaction for radical generation, thereby enhancing the versatility and effectiveness of RAFT polymerization. The resulting Fc-PF-RAFT technique provides a transformative platform for the creation of advanced materials with tailored properties and structures.