Organocatalytic atom transfer radical polymerization with light and pH dual-gated regulation

To improve the control and precision in polymer synthesis, the development of polymerization with logical control by multiple stimuli has attracted considerable attention in recent years. Herein, we describe the introduction of a dual regulation by light and pH to organocatalytic atom transfer radical polymerization (O-ATRP), which features mild pH conditions, visible light irradiation, transition metal-free products, and excellent on/off control by both pH and light. 1,1-Binaphthol (BINOL) was successfully identified as a class of pH-responsive photoredox catalysts for O-ATRP, and show readily tunable photophysical properties and highly reversible chromic shift of maximum absorption (up to 60 nm) by very mild pH-mediation (pH 5/7). Moreover, the unique pH-responsive feature of BINOL also inspires the discovery of simple phenols like naphthol and pyrenol that could also drive the radical polymerization under light and afford higher catalytic efficiency and better control upon basic mediation. Given the widespread presence of phenols in natural compounds, we anticipate this work could also draw greater attention to their potential pH-responsive photophysical properties or other roles in catalysis or life systems. Stimuli-responsive catalysts offer routes to on-off controlled polymerizations. Here, the authors report a pH-responsive organo-photoredox catalyst which enables dual regulation by light and pH for the atom transfer radical polymerization of methyl methacrylate under mild conditions.