Metallocene-Containing Homopolymers and Heterobimetallic Block Copolymers via Photoinduced RAFT Polymerization

Abstract

We report the synthesis of cationic cobaltocenium and neutral ferrocene containing homopolymers mediated by photoinduced reversible addition-fragmentation chain transfer (RAFT) polymerization with a photocatalyst fac-[Ir(ppy)3]. The homopolymers were further used as macromolecular chain transfer agents to synthesize diblock copolymers via chain extension. Controlled/“living” feature of photoinduced RAFT polymerization was confirmed by kinetic studies even without prior deoxygenation. A light switch between ON and OFF provided a spatiotemporal control of polymerization.

Visible‐light induced RAFT polymerization of styrenic monomers with aromatic aldehydes as organophotoredox catalysts

“…The external activation methods to RDRPs include photochemical, thermochemical, electrochemical and mechanical forces, and so on. Among them, as a more environmentally friendly external methods, visible light is the most ideal stimulus due to its low energy consumption, high performance and safe operation, it also could reversibly trigger the growth of polymer chains by simply switching the light “on” or “off.” So far, a lot of photoinduced RDRPs have been developed including atom transfer radical polymerization (ATRP), reversible addition‐fragmentation chain transfer polymerization (RAFT), ring‐opening metathesis polymerization (ROMP), iodine mediated polymerization (IMP), and cobalt mediated radical polymerization (CMRP) …”

Visible light‐induced RAFT polymerization of methacrylates with benzaldehyde derivatives as organophotoredox catalysts

“…In 2010, Kwak and Matyjaszewski demonstrated the controlled polymerization of MMA using a copper catalyst and dithiocarbamate initiator under UV irradiation. Up to now, the metal‐based photocatalysts have been intensively investigated in both photoinduced ATRP and photoinduced RAFT . A significant breakthrough of visible light‐induced polymerizations based on fac ‐[Ir(ppy) 3 ] photoredox catalyst was first reported by Fors and Hawker .…”

“…Light excited Ir III* species is able to reduce an alkyl bromide initiator to give an active alkyl radical (added to monomers to initiate chain growing) and Ir IV –Br complex through a photoinduced electron transfer process. Since then, a large number of well‐controlled photo‐catalyzed LRPs based on fac ‐[Ir(ppy) 3 ] have been reported …”

“…Up to now, the metal-based photocatalysts have been intensively investigated in both photoinduced ATRP and photoinduced RAFT. [21][22][23][24][25][26] A significant breakthrough of visible light-induced polymerizations based on fac-[Ir(ppy) 3 ] photoredox catalyst was first reported by Fors and Hawker. 27 Light excited Ir III * species is able to reduce an alkyl bromide initiator to give an active alkyl radical (added to monomers to initiate chain growing) and Ir IV -Br complex through a photoinduced electron transfer process.…”

New ROMP Synthesis of Ferrocenyl Dendronized Polymers

“…Polyferrocenylsilanes (PFS), developed by Manners' group and prepared by ring‐opening polymerization (ROP), are by far the most widely developed and well‐studied type of the former category. Metallopolymers of the latter category have been synthesized by various living and controlled polymerization methods including atom transfer radical polymerization (ATRP), reversible addition fragmentation chain transfer polymerization (RAFT), and ring‐opening metathesis polymerization (ROMP) . Fc‐containing dendrimers occupy a special place with specific properties such as the near‐identity of redox potential of iron sandwich systems located at their tether termini .…”