The first well‐controlled aqueous atom‐transfer radical polymerization (ATRP) conducted in the open air is reported. This air‐tolerant ATRP was enabled by the continuous conversion of oxygen to ...carbon dioxide catalyzed by glucose oxidase (GOx), in the presence of glucose and sodium pyruvate as sequential sacrificial substrates. Controlled polymerization using initiators for continuous activator regeneration (ICAR) ATRP of oligo(ethylene oxide) methyl ether methacrylate (OEOMA, Mn=500) yielded polymers with low dispersity (1.09≤Đ≤1.29) and molecular weights (MWs) close to theoretical values in the presence of pyruvate. Without added pyruvates, lower MWs were observed due to generation of new chains by H2O2 formed by reaction of O2 with GOx. Successful chain extension of POEOMA500 macroinitiator with OEOMA300 (Đ≤1.3) and Bovine Serum Albumin bioconjugates (Đ≤1.22) confirmed a well‐controlled polymerization. The reactions in the open air in larger scale (25 mL) were also successful.
Oxygen‐tolerant: Well‐controlled aqueous atom‐transfer radical polymerization (ATRP) conducted in the open air was made possible by continuous conversion of oxygen to carbon dioxide catalyzed by glucose oxidase (GOx), in the presence of glucose and sodium pyruvate as sequential sacrificial substrates. Without pyruvate lower molecular weights were observed due to the generation of new chains by H2O2 formed by reaction of O2 with GOx.
Polymer brush coatings are frequently prepared by radical polymerization, a notoriously oxygen sensitive process. Glucose oxidase (GOx) can inexpensively enable radical polymerization in solution by ...enzymatically consuming oxygen as it oxidizes glucose. Here, we report the growth of polymeric brushes using GOx-assisted atom transfer radical polymerization (ATRP) from a surface while open to air. Specifically, we grew a set of biomedically relevant polymer brushes, including poly(oligo(ethylene glycol) methacrylate) (POEGMA), poly(2-dimethylaminoethyl methacrylate) (PDMAEMA), poly(sulfobetaine methacrylate) (PSBMA), and poly(2-(methylsulfinyl)ethyl acrylate (PMSEA). For each of these polymers, we monitored GOx-assisted and GOx-free ATRP reaction kinetics in real time using quartz crystal microbalance (QCM) and verified findings with localized surface plasmon resonance (LSPR). We modeled brush growth kinetics considering bimolecular termination. This model fit our data well (r 2 > 0.987 for all samples) and shows the addition of GOx increased effective kinetic chain lengths, propagation rates, and reproducibility. We tested the antifouling properties of the polymer brush coatings against human blood plasma and were surprised to find that coatings prepared with GOx repelled more plasma proteins in all cases than their GOx-free counterparts.
Atom transfer radical polymerization (ATRP) can be carried out in a flask completely open to air using a biocatalytic system composed of glucose oxidase (GOx) and horseradish peroxidase (HRP) with an ...active copper catalyst complex. Nanomolar concentrations of the enzymes and ppm amounts of Cu provided excellent control over the polymerization of oligo(ethylene oxide) methyl ether methacrylate (OEOMA500), generating polymers with high molecular weight (Mn>70 000) and low dispersities (1.13≤Đ≤1.27) in less than an hour. The continuous oxygen supply was necessary for the generation of radicals and polymer chain growth as demonstrated by temporal control and by inducing hypoxic conditions. In addition, the enzymatic cascade polymerization triggered by oxygen was used for a protein and DNA functionalized with initiators to form protein‐b‐POEOMA and DNA‐b‐POEOMA bioconjugates, respectively.
Oxygen keeps polymerization alive: An oxygen‐dependent atom transfer radical polymerization was accomplished through the biocatalytic mediation of radicals by a glucose oxidase/horseradish peroxidase system “orchestrated” by a Cu/tris(2‐pyridylmethyl)amine (TPMA) catalyst (see picture; ACAC=acetylacetonate). This system provides polymers with high molecular weights and low dispersities, and is compatible with biologically relevant environments.
In atom transfer radical polymerization (ATRP), radicals (R•) can react with CuI/L catalysts forming organometallic complexes, R–CuII/L (L = N-based ligand). R–CuII/L favors additional catalyzed ...radical termination (CRT) pathways, which should be understood and harnessed to tune the polymerization outcome. Therefore, the preparation of precise polymer architectures by ATRP depends on the stability and on the role of R–CuII/L intermediates. Herein, spectroscopic and electrochemical techniques were used to quantify the thermodynamic and kinetic parameters of the interactions between radicals and Cu catalysts. The effects of radical structure, catalyst structure and solvent nature were investigated. The stability of R–CuII/L depends on the radical-stabilizing group in the following order: cyano > ester > phenyl. Primary radicals form the most stable R–CuII/L species. Overall, the stability of R–CuII/L does not significantly depend on the electronic properties of the ligand, contrary to the ATRP activity. Under typical ATRP conditions, the R–CuII/L build-up and the CRT contribution may be suppressed by using more ATRP-active catalysts or solvents that promote a higher ATRP activity.
The interaction of low-energy light with matter that leads to the production of high-energy light is known as photon upconversion. This phenomenon is of importance because of its potential ...applications in optoelectronics, energy harvesting, and the biomedical arena. Herein, we report a pillared-paddlewheel metal–organic framework (MOF), constructed from a tetrakis(4-carboxyphenyl)porphyrin sensitizer and a dipyridyl thiazolothiazole annihilator, designed for efficient triplet–triplet annihilation upconversion (TTA-UC). Single-crystal X-ray diffraction studies reveal that the Zn-metalated sensitizers are coordinated to Zn2 nodes in a paddlewheel fashion, forming 2D sheets, to which are linked annihilators, such that each sensitizer is connected to five of them. The precise arrangements of sensitizers with respect to annihilators, and the high annihilator-to-sensitizer ratio, facilitate Dexter energy transfer. This level of organization in an extended structure leads to a high TTA-UC efficiency of 1.95% (theoretical maximum = 50%) at an excitation power density of 25 mW cm–2.
A new procedure for ultrasonication-induced atom transfer radical polymerization (sono-ATRP) in aqueous media was developed. Polymerizations of oligo(ethylene oxide) methyl ether methacrylate ...(OEOMA) and 2-hydroxyethyl acrylate (HEA) in water were successfully carried out in the presence of ppm amounts of CuBr2 catalyst and tris(2-pyridylmethyl)amine ligand when exposed to ultrasonication (40 kHz, 110 W) at room temperature. Aqueous sono-ATRP enabled polymerization of water-soluble monomers with excellent control over the molecular weight, dispersity, and high retention of chain-end functionality. Temporal control over the polymer chain growth was demonstrated by switching the ultrasound on/off due to the regeneration of activators by hydroxyl radicals formed by ultrasonication. The synthesis of a well-defined block copolymer and DNA–polymer biohybrid was also successful using this process.
A facile and efficient two‐step synthesis of p‐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 of n‐butyl acrylate using only 10–25 part per million loadings of CuII(TPMANR2)Br+ exhibited excellent control.
Evolution of activity: A facile and high‐yield synthesis of para‐substituted tris(2‐pyridylmethyl)amine‐based ligands is presented. Copper complexes with these ligands exhibit very high activity in atom transfer radical polymerization.
The rational design of wholly synthetic receptors that bind active substrates with ultrahigh affinities is a challenging goal, especially in water. Here, we report the synthesis of a tricyclic ...octacationic cyclophane, which exhibits complementary stereoelectronic binding toward a widely used fluorescent dye, perylene diimide, with picomolar affinity in water. The ultrahigh binding affinity is sustained by a large and rigid hydrophobic binding surface, which provides a highly favorable enthalpy and a slightly positive entropy of complexation. The receptor–substrate complex shows significant improvement in optical properties, including red-shifted absorption and emission, turn-on fluorescence, and efficient energy transfer. An unusual single-excitation, dual-emission, imaging study of living cells was performed by taking advantage of a large pseudo-Stokes shift, produced by the efficient energy transfer.
Efficient heterogeneous photosensitizing materials require both large accessible surface areas and excitons of suitable energies and with well‐defined spin structures. Confinement of the ...tetracationic cyclophane (ExBox4+) within a nonporous anionic polystyrene sulfonate (PSS) matrix leads to a surface area increase of up to 225 m2 g−1 in ExBox•PSS. Efficient intersystem crossing is achieved by combining the spin‐orbit coupling associated to Br heavy atoms in 1,3,5,8‐tetrabromopyrene (TBP), and the photoinduced electron transfer in a TBP⊂ExBox4+ supramolecular dyad. The TBP⊂ExBox4+ complex displays a charge transfer band at 450 nm and an exciplex emission at 520 nm, indicating the formation of new mixed‐electronic states. The lowest triplet state (T1, 1.89 eV) is localized on the TBP and is close in energy with the charge separated state (CT, 2.14 eV). The homogeneous and heterogeneous photocatalytic activities of the TBP⊂ExBox4+, for the elimination of a sulfur mustard simulant, has proved to be significantly more efficient than TBP and ExBox+4, confirming the importance of the newly formed excited‐state manifold in TBP⊂ExBox4+ for the population of the low‐lying T1 state. The high stability, facile preparation, and high performance of the TBP⊂ExBox•PSS nanocomposites augur well for the future development of new supramolecular heterogeneous photosensitizers using host–guest chemistry.
A supramolecular photosensitizer with efficient intersystem crossing is achieved by combining the spin‐orbit coupling associated with heavy atoms and the photoinduced electron transfer in a donor–acceptor host–guest dyad. Incorporation of these supramolecular cationic photosensitizers with anionic polymer matrices generates porous nanocomposites with remarkable photocatalytic performances against sulfur mustard simulant.
A rapid blue-light-induced atom transfer radical polymerization (ATRP) was conducted in a biologically friendly environment. Well-controlled polymerization of oligo(ethylene oxide) methyl ether ...methacrylate (OEOMA) was successfully performed in aqueous media (1X PBS) under irradiation by blue LED strips. With 10.0 mW/cm2 intensity output at 450 nm, >90% conversion was achieved in 2 h in the presence of a system comprising glucose, glucose oxidase, and sodium pyruvate. Poly(OEOMA) was synthesized with predetermined M n and low dispersities using low ppm of Cu catalysts. Importantly, secondary structures of proteins, as analyzed by circular dichroism (CD), were preserved under blue-light irradiation due to its lower energy output. The aqueous blue-light ATRP technique was applied to biological systems by synthesizing well-defined protein–polymer and DNA–polymer hybrids by the “grafting-from” method.
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