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1. p ‐Substituted Tris(2‐pyridylmethyl)amines as Ligands for Highly Active ATRP Catalysts: Facile Synthesis and Characterization

   https://doi.org/10.1002/ange.202004724  

   Enciso, Alan E. ; Lorandi, Francesca ; Mehmood, Arshad ; Fantin, Marco ; Szczepaniak, Grzegorz ; Janesko, Benjamin G. ; Matyjaszewski, Krzysztof ( June 2020 , Angewandte Chemie)

   A facile and efficient two‐step synthesis ofp‐substituted tris(2‐pyridylmethyl)amine (TPMA) ligands to form Cu complexes with the highest activity to date in atom transfer radical polymerization (ATRP) is presented. In the divergent synthesis,p‐Cl substituents in tris(4‐chloro‐2‐pyridylmethyl)amine (TPMA^3Cl) were replaced in one step and high yield by electron‐donating cyclic amines (pyrrolidine (TPMA^PYR), piperidine (TPMA^PIP), and morpholine (TPMA^MOR)) by nucleophilic aromatic substitution. The [Cu^II(TPMA^NR2)Br]⁺complexes exhibited larger energy gaps between frontier molecular orbitals and >0.2 V more negative reduction potentials than [Cu^II(TPMA)Br]⁺, indicating >3 orders of magnitude higher ATRP activity. [Cu^I(TPMA^PYR)]⁺exhibited the highest reported activity for Br‐capped acrylate chain ends in DMF, and moderate activity toward C−F bonds at room temperature. ATRP ofn‐butyl acrylate using only 10–25 part per million loadings of [Cu^II(TPMA^NR2)Br]⁺exhibited excellent control.

    

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2. Two-compartment kinetic Monte Carlo modelling of electrochemically mediated ATRP

   https://doi.org/10.1039/C8RE00156A  

   D'hooge, Dagmar R. ; Fantin, Marco ; Magenau, Andrew J. ; Konkolewicz, Dominik ; Matyjaszewski, Krzysztof ( November 2018 , Reaction Chemistry & Engineering)

   For electrochemically mediated atom transfer radical polymerization (eATRP), novel mechanistic insights are formulated based on a two-compartment kinetic Monte Carlo model in which catalyst concentration gradients between a large “bulk” compartment away from the electrode and a very small compartment around the electrode are accounted for to reflect the concept of the Nernst diffusion layer. The mass transport of deactivator catalyst to the electrode and its electrochemical reduction at the electrode are treated separately to enable the model to explicitly distinguish between limitations of mass transport and limitations due to intrinsic chemical reactivity. The model is applied to eATRP of methyl acrylate at 298 K with Cu II Br 2 /Me 6 TREN (Me 6 TREN: tris((2-dimethylamino)ethyl)amine) and eATRP of n -butyl acrylate at 317 K with Cu II Br 2 /TPMA (TPMA: tris(2-pyridylmethyl)amine). Diffusional limitations on termination need to be accounted for to properly reflect the eATRP kinetics and the microstructural properties of the obtained polymers. In most cases, an eATRP with mixed chemical and mass transport control is obtained. 

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3. Visible Light‐ATRP Driven by Tris(2‐Pyridylmethyl)Amine (TPMA) Impurities in the Open Air

   https://doi.org/10.1002/marc.202200855  

   Jazani, Arman Moini ; Schild, Dirk J. ; Sobieski, Julian ; Hu, Xiaolei ; Matyjaszewski, Krzysztof ( December 2022 , Macromolecular Rapid Communications)

   Atom transfer radical polymerization (ATRP) of oligo(ethylene oxide) monomethyl ether methacrylate (OEOMA₅₀₀) in water is enabled using CuBr₂with tris(2‐pyridylmethyl)amine (TPMA) as a ligand under blue or green‐light irradiation without requiring any additional reagent, such as a photo‐reductant, or the need for prior deoxygenation. Polymers with low dispersity (Đ = 1.18–1.25) are synthesized at high conversion (>95%) using TPMA from three different suppliers, while no polymerization occurred with TPMA is synthesized and purified in the laboratory. Based on spectroscopic studies, it is proposed that TPMA impurities (i.e., imine and nitrone dipyridine), which absorb blue and green light, can act as photosensitive co‐catalyst(s) in a light region where neither pure TPMA nor [(TPMA)CuBr]⁺absorbs light.

    

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4. Catalytic effect of DMSO in metal‐catalyzed radical polymerization mediated by disproportionation facilitates living and immortal radical polymerizations

   https://doi.org/10.1002/pol.20220632  

   Maurya, Devendra S. ; Adamson, Jasper ; Bensabeh, Nabil ; Lligadas, Gerard ; Percec, Virgil ( February 2023 , Journal of Polymer Science)

   DMSO, an interesting solvent for copper‐catalyzed living radical polymerization (LRP) mediated by disproportionation, does not exhibit the greatest disproportionation of Cu(I)X into Cu(0) and Cu(II)X₂. Under suitable conditions, DMSO provides 100% conversion and absence of termination, facilitating the development of complex‐architecture methodologies by living and immortal polymerizations. The mechanism yielding this level of precision is being investigated. Here we compare Cu(0)‐wire‐catalyzed LRP of methyl acrylate mediated by disproportionating ligands tris(2‐dimethylaminoethyl)amine, Me₆‐TREN, tris(2‐aminoethyl)amine, TREN, and Me₆‐TREN/TREN = 1/1 in presence of eight disproportionating solvents, some more efficient than DMSO in disproportionation. Unexpectedly, we observed that all solvents increased the rate of polymerization when monomer concentration decreased. This reversed trend from that of conventional LRPs demonstrates catalytic effect for disproportionating solvents. Above a certain concentration, the classic concentration‐rate dependence was observed. The external order of reaction of the apparent rate constant of propagation,k_p^appon solvent concentration demonstrated the highest order of reaction for the least disproportionating DMSO. Of all solvents investigated, DMSO has the highest ability to stabilize Cu(0) nanoparticles and therefore, yields the highest activity of Cu(0) nanoparticles rather than their greatest concentration. The implications of the catalytic effect of solvent in this and other reactions were discussed.

    

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5. A green solvent-to-polymer upgrading approach to water-soluble LCST poly( N -substituted lactamide acrylate)s

   https://doi.org/10.1039/D2GC02780A  

   Palà, Marc ; El Khannaji, Hafssa ; Garay-Sarmiento, Manuela ; Ronda, Juan Carlos ; Cádiz, Virginia ; Galià, Marina ; Percec, Virgil ; Rodriguez-Emmenegger, César ; Lligadas, Gerard ( October 2022 , Green Chemistry)

   We report a green solvent-to-polymer upgrading transformation of chemicals of the lactic acid portfolio into water-soluble lower critical solution temperature (LCST)-type acrylic polymers. Aqueous Cu(0)-mediated living radical polymerization (SET-LRP) was utilized for the rapid synthesis of N -substituted lactamide-type homo and random acrylic copolymers under mild conditions. A particularly unique aspect of this work is that the water-soluble monomers and the SET-LRP initiator used to produce the corresponding polymers were synthesized from biorenewable and non-toxic solvents, namely natural ethyl lactate and BASF's Agnique® AMD 3L ( N , N -dimethyl lactamide, DML). The pre-disproportionation of Cu( i )Br in the presence of tris[2-(dimethylamino)ethyl]amine (Me 6 TREN) in water generated nascent Cu(0) and Cu( ii ) complexes that facilitated the fast polymerization of N -tetrahydrofurfuryl lactamide and N , N -dimethyl lactamide acrylate monomers (THFLA and DMLA, respectively) up to near-quantitative conversion with excellent control over molecular weight (5000 < M n < 83 000) and dispersity (1.05 < Đ < 1.16). Interestingly, poly(THFLA) showed a degree of polymerization and concentration dependent LCST behavior, which can be fine-tuned ( T cp = 12–62 °C) through random copolymerization with the more hydrophilic DMLA monomer. Finally, covalent cross-linking of these polymers resulted in a new family of thermo-responsive hydrogels with excellent biocompatibility and tunable swelling and LCST transition. These illustrate the versatility of these neoteric green polymers in the preparation of smart and biocompatible soft materials. 

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