Persistent Radical Anions: Efficient Catalysts for Iodine-Mediated Reversible-Deactivation Radical Polymerization Driven by NIR LED Light

Abstract

Developing new catalysts with obvious advantages than existing ones is charming but very challenging for near infrared (NIR)photocontrolled reversible-deactivation radical polymerization (RDRP). Herein, a high-efficiency NIR-photocontrolled bromine-iodine transformation RDRP (BIT-RDRP) system was developed by employing persistent radical anions (PRAs) as the catalysts. Specifically, some inherent electron deficient species, such as 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA), can be reduced to PRAs in the presence of common reducing agents (e.g., sodium ascorbate (SA)). Subsequently, the electron-donating PRAs activate the carbon-halogen bonds of dormant species with the help of NIR light and facilitate the formation of carbon-centered radicals (CCRs) to initiate polymerizations. With the assistance of this catalytic system, a monomer conversion of more than 97.0% was achieved within 180−240 min and the polymerization process was still controllable. In addition, several other types of PRA catalysts have also been developed for confirming the catalytic mechanism. All PRAs exhibit highly catalytic ability in the BIT-RDRP system, which opens up a direction for the further development of NIR-photocontrolled RDRP.

Near‐Infrared Light‐Induced Reversible Deactivation Radical Polymerization: Expanding Frontiers in Photopolymerization

“…Additionally, excellent temporal control and oxygen tolerance were also demonstrated in this RCMP system. In another recent study conducted by the same research group, [54] the authors identified certain electron-deficient species, such as 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA; Figure 8, #17), as highly efficient catalysts for mediating RCMP in the presence of common reducing agents, like sodium ascorbate, under NIR irradiation. According to the proposed mechanism, NTCDA is initially reduced by sodium ascorbate, leading to the generation of NTCDA anionic radical (NTCDA•−), which subsequently initiates the cleavage of the C─I bond within the complex (P n -I-NTCDA•−), thereby producing Pn• for mediating RCMP (Table 2, #22).…”

Zinc Phthalocyanine Covalent Polymers as Recyclable Catalysts for NIR-Photocontrolled RAFT Polymerization in Water

“…Reversible-deactivation radical polymerization (RDRP), through which polymers with low dispersity, a defined degree of polymerization, and excellent spatiotemporal reaction control can be obtained, has received much attention in recent years. − Although photocontrolled RDRP has been extensively studied in the visible light range (λ = 400–700 nm), there are only a few cases mediated by near-infrared (NIR) light (λ = 700–2500 nm), mainly due to the lower energy of NIR light, which makes it difficult to drive photochemical reactions . Many NIR photosensitizers have been developed for phototherapeutic and photoantibacterial applications; − however, their application in photocontrolled RDRP is still relatively rare.…”