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1. Electrochemically Mediated Atom Transfer Radical Polymerization Driven by Alternating Current

   https://doi.org/10.1002/anie.202406484  

   De_Bon, Francesco; Fantin, Marco; Pereira, Vanessa A; Lourenço_Bernardino, Teresa J; Serra, Armenio C; Matyjaszewski, Krzysztof; Coelho, Jorge_F J (July 2024, Angewandte Chemie International Edition)

   Abstract Alternating current (AC) and pulsed electrolysis are gaining traction in electro(organic) synthesis due to their advantageous characteristics. We employed AC electrolysis in electrochemically mediated Atom Transfer Radical Polymerization (eATRP) to facilitate the regeneration of the activator Cu^Icomplex on Cu⁰electrodes. Additionally, Cu⁰served as a slow supplemental activator and reducing agent (SARA ATRP), enabling the activation of alkyl halides and the regeneration of the Cu^Iactivator through a comproportionation reaction. We harnessed the distinct properties of Cu⁰dual regeneration, both chemical and electrochemical, by employing sinusoidal, triangular, and square‐wave AC electrolysis alongside some of the most active ATRP catalysts available. Compared to linear waveform (DC electrolysis) or SARA ATRP (without electrolysis), pulsed and AC electrolysis facilitated slightly faster and more controlled polymerizations of acrylates. The same AC electrolysis conditions could successfully polymerize eleven different monomers across different mediums, from water to bulk. Moreover, it proved effective across a spectrum of catalyst activity, from low‐activity Cu/2,2‐bipyridine to highly active Cu complexes with substituted tripodal amine ligands. Chain extension experiments confirmed the high chain‐end fidelity of the produced polymers, yielding functional and high molecular‐weight block copolymers. SEM analysis indicated the robustness of the Cu⁰electrodes, sustaining at least 15 consecutive polymerizations. 

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2. Mechanism of supplemental activator and reducing agent atom transfer radical polymerization mediated by inorganic sulfites: experimental measurements and kinetic simulations

   https://doi.org/10.1039/c7py01319a  

   Krys, Pawel; Fantin, Marco; Mendonça, Patrícia V.; Abreu, Carlos M.; Guliashvili, Tamaz; Rosa, Jaquelino; Santos, Lino O.; Serra, Arménio C.; Matyjaszewski, Krzysztof; Coelho, Jorge F. (January 2017, Polymer Chemistry)

   The mechanism of atom transfer radical polymerization (ATRP) mediated by sodium dithionite (Na 2 S 2 O 4 ), with Cu II Br 2 /Me 6 TREN as catalyst (Me 6 TREN: tris[2-(dimethylamino)ethyl]amine) in ethanol/water mixtures, was investigated experimentally and by kinetic simulations. A kinetic model was proposed and the rate coefficients of the relevant reactions were measured. The kinetic model was validated by the agreement between experimental and simulated results. The results indicated that the polymerization followed the SARA ATRP mechanism, with a SO 2 ˙ − radical anion derived from Na 2 S 2 O 4 , acting as both supplemental activator (SA) of alkyl halides and reducing agent (RA) for Cu II /L to regenerate the main activator Cu I /L. This is similar to the reversible-deactivation radical polymerization (RDRP) procedure conducted in the presence of Cu 0 . The electron transfer from SO 2 ˙ − , to either Cu II Br 2 /Me 6 TREN or R–Br initiator, appears to follow an outer sphere electron transfer (OSET) process. The developed kinetic model was used to study the influence of targeted degree of polymerization, concentration of Cu II Br 2 /Me 6 TREN and solubility of Na 2 S 2 O 4 on the level of polymerization control. The presence of small amounts of water in the polymerization mixtures slightly increased the reactivity of the Cu I /L complex, but markedly increased the reactivity of sulfites. 

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3. Better Together: Photoredox/Copper Dual Catalysis in Atom Transfer Radical Polymerization

   https://doi.org/10.1002/anie.202415785  

   Sobieski, Julian; Gorczyński, Adam; Jazani, Arman Moini; Yilmaz, Gorkem; Matyjaszewski, Krzysztof (January 2025, Angewandte Chemie International Edition)

   Abstract Photomediated Atom Transfer Radical Polymerization (photoATRP) is an activator regeneration method, which allows for the controlled synthesis of well‐defined polymers via light irradiation. Traditional photoATRP is often limited by the need for high‐energy ultraviolet or violet light. These could negatively affect the control and selectivity of the polymerization, promote side reactions, and may not be applicable to biologically relevant systems. This drawback can be circumvented by an introduction of the catalytic amount of photocatalysts, which absorb visible and/or NIR light and, therefore, controlled, regenerative ATRP can be performed with the dual‐catalytic cycle. Herein, a critical summary of recent developments in the field of dual‐catalysis concerning Cu‐catalyzed ATRP is provided. Contributions of involved species are examined mechanistically, followed by challenges and future directions towards the next generation of advanced functional macromolecular materials. 

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4. Reversible Deactivation Radical Polymerization: State-of-the-Art in 2017

   https://doi.org/10.1021/bk-2018-1284.ch001  

   Shanmugam, Sivaprakash; Matyjaszewski, Krzysztof (August 2018, ACS symposium series)

   This chapter highlights the current advancements in reversible-deactivation radical polymerization (RDRP) with a specific focus on atom transfer radical polymerization (ATRP). The chapter begins with highlighting the termination pathways for acrylates radicals that were recently explored via RDRP techniques. This led to a better understanding of the catalytic radical termination (CRT) in ATRP for acrylate radicals. The designed new ligands for ATRP also enabled the suppression of CRT and increased chain end functionality. In addition, further mechanistic understandings of SARA-ATRP with Cu0 activation and comproportionation were studied using model reactions with different ligands and alkyl halide initiators. Another focus of RDRP in recent years has been on systems that are regulated by external stimuli such as light, electricity, mechanical forces and chemical redox reactions. Recent advancements made in RDRP in the field of complex polymeric architectures, organic-inorganic hybrid materials and bioconjugates have also been summarized. 

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5. Open-air green-light-driven ATRP enabled by dual photoredox/copper catalysis

   https://doi.org/10.1039/D2SC04210J  

   Szczepaniak, Grzegorz; Jeong, Jaepil; Kapil, Kriti; Dadashi-Silab, Sajjad; Yerneni, Saigopalakrishna S.; Ratajczyk, Paulina; Lathwal, Sushil; Schild, Dirk J.; Das, Subha R.; Matyjaszewski, Krzysztof (October 2022, Chemical Science)

   Photoinduced atom transfer radical polymerization (photo-ATRP) has risen to the forefront of modern polymer chemistry as a powerful tool giving access to well-defined materials with complex architecture. However, most photo-ATRP systems can only generate radicals under biocidal UV light and are oxygen-sensitive, hindering their practical use in the synthesis of polymer biohybrids. Herein, inspired by the photoinduced electron transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization, we demonstrate a dual photoredox/copper catalysis that allows open-air ATRP under green light irradiation. Eosin Y was used as an organic photoredox catalyst (PC) in combination with a copper complex (X–Cu II /L). The role of PC was to trigger and drive the polymerization, while X–Cu II /L acted as a deactivator, providing a well-controlled polymerization. The excited PC was oxidatively quenched by X–Cu II /L, generating Cu I /L activator and PC˙ + . The ATRP ligand (L) used in excess then reduced the PC˙ + , closing the photocatalytic cycle. The continuous reduction of X–Cu II /L back to Cu I /L by excited PC provided high oxygen tolerance. As a result, a well-controlled and rapid ATRP could proceed even in an open vessel despite continuous oxygen diffusion. This method allowed the synthesis of polymers with narrow molecular weight distributions and controlled molecular weights using Cu catalyst and PC at ppm levels in both aqueous and organic media. A detailed comparison of photo-ATRP with PET-RAFT polymerization revealed the superiority of dual photoredox/copper catalysis under biologically relevant conditions. The kinetic studies and fluorescence measurements indicated that in the absence of the X–Cu II /L complex, green light irradiation caused faster photobleaching of eosin Y, leading to inhibition of PET-RAFT polymerization. Importantly, PET-RAFT polymerizations showed significantly higher dispersity values (1.14 ≤ Đ ≤ 4.01) in contrast to photo-ATRP (1.15 ≤ Đ ≤ 1.22) under identical conditions. 

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