Universal Visible-Light Photoiniferter Polymerization

Abstract

Currently, there is no versatile method for the synthesis of high molecular weight (MW) polymers by controlled radical polymerization from a broad range of monomers using a single agent. Herein, we report a universal photoiniferter reversible addition-fragmentation chain transfer (RAFT) polymerization formulation using a suitable pyrazole-based chain transfer agent (CTA) combined with blue light irradiation. Well-controlled polymerization was observed for methyl methacrylate (MMA), methyl acrylate (MA), N,N-dimethylacrylamide (DMA), and N-vinylpyrrolidone (NVP). High polymerization rates were achieved, attributed to the high molar absorption coefficient of the pyrazole-based CTA and its rapid rate of photolysis. Poly(methyl acrylate) (PMA) and poly(N,N-dimethylacrylamide) (PDMA) syntheses yielded low-dispersity ultrahigh MW chains (>10⁶ g mol⁻¹, Р< 1.3). High end-group fidelity enabled the preparation of well-defined high MW diblock copolymers comprising both more activated and less activated monomers, including PDMA-b-PNVP and PMA-b-PNVP. Such syntheses demonstrated that visible light-mediated photoiniferter RAFT polymerization conducted using pyrazole-based CTAs was both highly efficient and versatile.