(604e) Alternative Solvents for Efficient Visible-Light-Driven RAFT Polymerization Under an Open-to-Air Environment

This work demonstrates the effect of deep eutectic solvents (DESs) on the reversible addition-fragmentation chain-transfer (RAFT) polymerization driven by visible light. A DES composed of tetrabutylammonium chloride (TBACl) and ethylene glycol serves as a nonvolatile medium for a variety of monomers, including methyl methacrylate, methyl acrylate, dimethyl acrylamide, and styrene. Compared to organic solvents, the reaction in DESs exhibits an enhanced polymerization rate through the photoiniferter pathway in an open-to-air environment. In addition, the photo-stability of the chain transfer agent is improved in DESs to control the polymerization better. DES is also compatible with photoelectron/energy transfer (PET) RAFT polymerization, providing polymerization under natural sunlight. The rapid polymerization in DESs facilitates the synthesis of ultrahigh molecular weight (UHMW) poly(methyl methacrylate) (PMMA) (M_n ~ 10⁶ g/mol). The chain entanglement of UHMW PMMA leads to highly elastic polymer gels in DESs. In short, our work suggests that combining DESs and photoinduced RAFT polymerization enables a rapid synthesis of well-defined polymers.