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1. Fully oxygen-tolerant atom transfer radical polymerization triggered by sodium pyruvate

   https://doi.org/10.1039/d0sc03179h  

   Szczepaniak, Grzegorz; Łagodzińska, Matylda; Dadashi-Silab, Sajjad; Gorczyński, Adam; Matyjaszewski, Krzysztof (August 2020, Chemical Science)

   null (Ed.)

   ATRP (atom transfer radical polymerization) is one of the most robust reversible deactivation radical polymerization (RDRP) systems. However, the limited oxygen tolerance of conventional ATRP impedes its practical use in an ambient atmosphere. In this work, we developed a fully oxygen-tolerant PICAR (photoinduced initiators for continuous activator regeneration) ATRP process occurring in both water and organic solvents in an open reaction vessel. Continuous regeneration of the oxidized form of the copper catalyst with sodium pyruvate through UV excitation allowed the chemical removal of oxygen from the reaction mixture while maintaining a well-controlled polymerization of N -isopropylacrylamide (NIPAM) or methyl acrylate (MA) monomers. The polymerizations of NIPAM were conducted with 250 ppm (with respect to the monomer) or lower concentrations of CuBr 2 and a tris[2-(dimethylamino)ethyl]amine ligand. The polymers were synthesized to nearly quantitative monomer conversions (>99%), high molecular weights ( M n > 270 000), and low dispersities (1.16 < Đ < 1.44) in less than 30 min under biologically relevant conditions. The reported method provided a well-controlled ATRP ( Đ = 1.16) of MA in dimethyl sulfoxide despite oxygen diffusion from the atmosphere into the reaction system. 

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2. 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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3. Under pressure: electrochemically-mediated atom transfer radical polymerization of vinyl chloride

   https://doi.org/10.1039/d0py00995d  

   De Bon, Francesco; Ribeiro, Diana C.; Abreu, Carlos M.; Rebelo, Rafael A.; Isse, Abdirisak A.; Serra, Arménio C.; Gennaro, Armando; Matyjaszewski, Krzysztof; Coelho, Jorge F. (November 2020, Polymer Chemistry)

   null (Ed.)

   The stringent control over the polymerization of less activated monomers remains one major challenge for Reversible Deactivation Radical Polymerizations (RDRP), including Atom Transfer Radical Polymerization (ATRP). Electrochemically mediated ATRP ( e ATRP) of a gaseous monomer, vinyl chloride (VC), was successfully achieved for the first time using a stainless-steel 304 (SS304) electrochemical reactor equipped with a simplified electrochemical setup. Controlled polymerizations were confirmed by the good agreement between theoretical and measured molecular weights, as well as the relatively narrow molecular weight distributions. Preservation of chain-end fidelity was verified by chain extension experiments, yielding poly(vinyl chloride) (PVC) homopolymers, block and statistical copolymers. The possibility of synthesizing PVC by e ATRP is a promising alternative to afford cleaner (co)polymers, with low catalyst concentration. The metal body of the reactor was also successfully used as a cathode. The setup proposed in this contribution opens an avenue for the polymerization of other gaseous monomers. 

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4. A Degradable Difunctional Initiator for ATRP That Responds to Hydrogen Peroxide

   https://doi.org/10.3390/polym14091733  

   Hill, Lawrence; Sims, Hunter; Nguyen, Ngoc; Collins, Christopher; Palmer, Jeffery; Wasson, Fiona (May 2022, Polymers)

   Mid-chain degradable polymers can be prepared by atom transfer radical polymerization from difunctional initiators that include triggers for the desired stimuli. While many difunctional initiators can respond to reducing conditions, procedures to prepare difunctional initiators that respond to oxidizing conditions are significantly less available in the literature. Here, a difunctional initiator incorporating an oxidizable boronic ester trigger was synthesized over four steps using simple and scalable procedures. Methyl methacrylate was polymerized by atom transfer radical polymerization using this initiator, and the polymerization kinetics were consistent with a controlled polymerization. The polymer synthesized using the difunctional initiator was found to decrease in molecular weight by 58% in the presence of hydrogen peroxide, while a control experiment using poly(methyl methacrylate) without a degradable linkage showed a much smaller decrease in molecular weight of only 9%. These observed molecular weight decreases were consistent with cleavage of the difunctional initiator via a quinone methide shift and hydrolysis of the methyl ester pendent groups in both polymers, and both polymers increased in polydispersity after oxidative degradation. 

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5. Aerobic mechanochemical reversible-deactivation radical polymerization

   https://doi.org/10.1038/s41467-024-50562-z  

   Feng, Haoyang; Chen, Zhe; Li, Lei; Shao, Xiaoyang; Fan, Wenru; Wang, Chen; Song, Lin; Matyjaszewski, Krzysztof; Pan, Xiangcheng; Wang, Zhenhua (December 2024, Nature Communications)

   Abstract Polymer materials suffer mechano-oxidative deterioration or degradation in the presence of molecular oxygen and mechanical forces. In contrast, aerobic biological activities combined with mechanical stimulus promote tissue regeneration and repair in various organs. A synthetic approach in which molecular oxygen and mechanical energy synergistically initiate polymerization will afford similar robustness in polymeric materials. Herein, aerobic mechanochemical reversible-deactivation radical polymerization was developed by the design of an organic mechano-labile initiator which converts oxygen into activators in response to ball milling, enabling the reaction to proceed in the air with low-energy input, operative simplicity, and the avoidance of potentially harmful organic solvents. In addition, this approach not only complements the existing methods to access well-defined polymers but also has been successfully employed for the controlled polymerization of (meth)acrylates, styrenic monomers and solid acrylamides as well as the synthesis of polymer/perovskite hybrids without solvent at room temperature which are inaccessible by other means. 

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