Riboflavin-Catalyzed Photoinduced Atom Transfer Radical Polymerization

Abstract

The photoATRP of methyl acrylate (MA) is investigated using riboflavin (RF) and CuBr₂/Me₆TREN as a dual catalyst system under green LED irradiation (λ ≈ 525 nm). Both RF and CuBr₂/Me₆TREN enhanced oxygen tolerance, enabling effective ATRP in the presence of residual oxygen. High molar mass polymers (up to M_n ≈ 129 000 g·mol⁻¹) with low dispersity (Đ ≤ 1.16) are prepared, and chain-end fidelity is confirmed through successful chain extension. The molecular masses of the obtained polymer increased linearly with conversion and showed high initiation efficiency. Mechanistic studies by laser flash photolysis reveal that the predominant activator generation mechanism is reductive quenching of RF by Me₆TREN (83%, under [CuBr₂]/[Me₆TREN] = 1/3 condition), supported by polymerization kinetics and thermodynamic calculations.