Exploring ferrocene-directed photo-Fenton initiation of RAFT polymerization

Abstract

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.