An official website of the United States government
Abstract Traditional mechanochemically controlled reversible‐deactivation radical polymerization (RDRP) utilizes ultrasound or ball milling to regenerate activators, which induce side reactions because of the high‐energy and high‐frequency stimuli. Here, we propose a facile approach for tribochemically controlled atom transfer radical polymerization (tribo‐ATRP) that relies on contact‐electro‐catalysis (CEC) between titanium oxide (TiO2) particles and CuBr2/tris(2‐pyridylmethylamine (TPMA), without any high‐energy input. Under the friction induced by stirring, the TiO2particles are electrified, continuously reducing CuBr2/TPMA into CuBr/TPMA, thereby conversing alkyl halides into active radicals to start ATRP. In addition, the effect of friction on the reaction was elucidated by theoretical simulation. The results indicated that increasing the frequency could reduce the energy barrier for the electron transfer from TiO2particles to CuBr2/TPMA. In this study, the design of tribo‐ATRP was successfully achieved, enabling CEC (ca. 10 Hz) access to a variety of polymers with predetermined molecular weights, low dispersity, and high chain‐end fidelity.
more »
« less
Visible Light‐ATRP Driven by Tris(2‐Pyridylmethyl)Amine (TPMA) Impurities in the Open Air
Abstract 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.
more »
« less
- PAR ID:
- 10386240
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Macromolecular Rapid Communications
- Volume:
- 44
- Issue:
- 16
- ISSN:
- 1022-1336
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Photoinduced initiators for continuous activator regeneration atom transfer radical polymerization (PICAR ATRP) using sodium pyruvate and blue light (λmax = 456 nm) is reported. Water‐soluble oligo(ethylene oxide) methyl ether methacrylate (OEOMA500) was polymerized under biologically relevant conditions. Polymerizations were conducted with 1000 ppm (with respect to the monomer) concentrations of CuBr2, tris(2‐pyridylmethyl)amine, and 1000 ppm or less FeCl3as a cocatalyst in water. Well‐defined polymers with up to 90% monomer conversion, high molecular weights (Mn > 190,000), and low dispersity (1.14 < Ð < 1.19) were synthesized in less than 60 min. The polymerization rate and dispersity were tuned by varying the concentration of sodium pyruvate (SP), iron, and supporting halide, as well as light intensity. The Cu/Fe dual catalysis provided oxygen tolerance enabling rapid, well‐controlled, aqueous PICAR ATRP of OEOMA500without deoxygenation.more » « less
-
Abstract The photoATRP of methyl acrylate (MA) is investigated using riboflavin (RF) and CuBr2/Me6TREN as a dual catalyst system under green LED irradiation (λ ≈ 525 nm). Both RF and CuBr2/Me6TREN enhanced oxygen tolerance, enabling effective ATRP in the presence of residual oxygen. High molar mass polymers (up toMn ≈ 129 000 g·mol−1) with low dispersity (Đ≤ 1.16) are prepared, and chain‐end fidelity is confirmed through successful chain extension. The molecular masses of the obtained polymer increased linearly with conversion and showed high initiation efficiency. Mechanistic studies by laser flash photolysis reveal that the predominant activator generation mechanism is reductive quenching of RF by Me6TREN (83%, under [CuBr2]/[Me6TREN] = 1/3 condition), supported by polymerization kinetics and thermodynamic calculations.more » « less
-
Abstract 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 (TPMA3Cl) were replaced in one step and high yield by electron‐donating cyclic amines (pyrrolidine (TPMAPYR), piperidine (TPMAPIP), and morpholine (TPMAMOR)) by nucleophilic aromatic substitution. The [CuII(TPMANR2)Br]+complexes exhibited larger energy gaps between frontier molecular orbitals and >0.2 V more negative reduction potentials than [CuII(TPMA)Br]+, indicating >3 orders of magnitude higher ATRP activity. [CuI(TPMAPYR)]+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 [CuII(TPMANR2)Br]+exhibited excellent control.more » « less
-
Abstract Hyperbranched polymethacrylates were synthesized by green‐light‐induced atom transfer radical polymerization (ATRP) under biologically relevant conditions in the open air. Sodium 2‐bromoacrylate (SBA) was prepared in situ from commercially available 2‐bromoacrylic acid and used as a water‐soluble inibramer to induce branching during the copolymerization of methacrylate monomers. As a result, well‐defined branched polymethacrylates were obtained in less than 30 min with predetermined molecular weights (36 000<Mn<170 000), tunable degree of branching, and low dispersity values (1.14≤Đ≤1.33). Moreover, the use of SBA inibramer enabled the synthesis of bioconjugates with a well‐controlled branched architecture.more » « less
