Carbon dot driven near infrared light induced miniemulsion atom transfer radical polymerization

Photoinduced polymerization methods are increasingly valued for their mild operating conditions, precise spatiotemporal control, and operational simplicity. Beyond homogeneous systems, adapting photopolymerization to emulsions offers a greener and more practical approach. Nevertheless, the poor penetration of short-wavelength light sources commonly adopted in previous studies, combined with the opacity inherent to heterogeneous systems, led to inefficient light energy utilization. This work presents an efficient near-infrared (NIR) light induced miniemulsion atom transfer radical polymerization (mini-ATRP), by utilizing phosphorus and nitrogen codoped carbon dots (PN-CDs) as the photocatalyst. Owing to the absorption in the NIR region, PN-CDs can generate electrons upon excitation with an 808 nm laser, thereby initiating a mini-ATRP through electron transfer with a Cu(II)/surfactant ion-pair at the interface of oil/water droplets. This NIR induced mini-ATRP system successfully produced polymers with low dispersity (Đ < 1.25) and high monomer conversion (∼86%) within 2 hours. Excellent temporal control of the polymerization and the chain fidelity of polymers were illustrated by a light-switching experiment and chain extension, respectively. This research establishes new pathways for robust emulsion photopolymerization techniques, providing enhanced control, efficiency, and a more sustainable process.