Photocontrolled RAFT Polymerization Catalyzed by Conjugated Polymers under Aerobic Aqueous Conditions

Photocontrolled polymerization offers a convenient way to direct the reaction progress and tailor the polymer structures. Nevertheless, conjugated polymers are yet to be utilized as the photocatalyst in associated reactions. Herein, we employed poly(boron dipyrromethene-alt-fluorene) (PBF), a conjugated polymer with better photostability than eosin Y, as the photo-catalyst for photo-RAFT polymerizations of acrylic monomers, and the polymers were obtained with moderately narrow molecular weight distributions. The reaction progress was effectively controlled by switching irradiation conditions, and the block copolymers were prepared from chain extension of a macro-initiator. As electron spin resonance (ESR) and optical spectra results suggested, the reductive quenching of PBF* by ascorbate was the key step leading to the reduction of a chain transfer agent (CTA), whereas the hydroxyl radical derived from superoxide was considered as a byproduct of deoxygenation.

Automated summary

Photocontrolled polymerization using PBF as a photocatalyst allows for effective control of reaction progress and preparation of polymers with narrow molecular weight distributions. The reaction can be controlled by switching irradiation conditions, and block copolymers can be prepared from chain extension of a macro-initiator. Antioxidants like ascorbate play a key role in the reduction of chain transfer agents during the process.