Oxygen-Tolerant Ab Initio Emulsion ATRP Driven by Red or Near-Infrared Light

Emulsion polymerization technique is widely used as a practical and greener approach to polymer synthesis. However, previous reversible deactivation radical polymerization (RDRP) in heterogeneous systems has mostly focused on microemulsion and miniemulsion, requiring a large amount of surfactant and/or vigorous homogenization. To expand the scope and enhance the practicality of RDRP in emulsion, we demonstrate a highly efficient and O₂-tolerant ab initio emulsion atom transfer radical polymerization (ATRP), driven by red or near-infrared (NIR) light. This was facilitated using a water-soluble photocatalyst, methylene blue (MB⁺), a hydrophilic initiator, and an interfacial ion-pair catalyst. Excitation of MB⁺ under red/NIR light irradiation enabled efficient photoreduction of the ATRP deactivator and subsequent initiation in the aqueous phase, thereby mediating polymerization via a classic emulsion mechanism. The ab initio emulsion ATRP provided successful synthesis of polymers with controlled molar masses ranging from 10,000 to 600 000 g/mol and low dispersity (1.09 ≤ Đ ≤ 1.29), excellent chain-end fidelity, and facile temporal control.