1‐Bromopyrene as a Photoredox Catalyst for O‐<scp>ATRP</scp>: Exploring Low Loading Conditions

ABSTRACT Using low catalyst loadings while maintaining precise polymer property control is a critical challenge in the O‐ATRP field. Herein, we report a novel O‐ATRP system utilizing 1‐bromopyrene (Py‐Br) as a photoredox catalyst, enabling controlled polymerization of methyl methacrylate (MMA) at an ultra‐low loading of 10 ppm. When combined with ethyl α ‐bromophenylacetate (EBPA) as an initiator, this system produces polymers with a molecular weight distribution of 1.48 and an initiation efficiency of 66.7%. Mechanistic studies, including UV–Vis spectroscopy, fluorescence spectroscopy, cyclic voltammetry, and time‐resolved fluorescence measurements, elucidate the photophysical and photochemical properties of Py‐Br in O‐ATRP. Kinetic analyses reveal first‐order polymerization kinetics, while the linear increase of molecular weight with monomer conversion and low dispersity values indicate good control over the polymerization. The living nature of the system is further confirmed through successful chain extension experiments. This Py‐Br‐catalyzed O‐ATRP system explores the feasibility of conducting polymerization at lower catalyst concentrations, offering insights into approaches for reducing catalyst usage in polymer synthesis.