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  1. 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.

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  2. 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.

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  3. Abstract

    This work develops the Polyolefin Active‐Ester Exchange (PACE) process to afford well‐defined polyolefin–polyvinyl block copolymers. α‐Diimine PdII‐catalyzed olefin polymerizations were investigated through in‐depth kinetic studies in comparison to an analog to establish the critical design that facilitates catalyst activation. Simple transformations lead to a diversity of functional groups forming polyolefin macroinitiators or macro‐mediators for various subsequent controlled polymerization techniques. Preparation of block copolymers with different architectures, molecular weights, and compositions was demonstrated with ring‐opening polymerization (ROP), nitroxide‐mediated polymerization (NMP), and photoiniferter reversible addition–fragmentation chain transfer (PI‐RAFT). The significant difference in the properties of polyolefin–polyacrylamide block copolymers was harnessed to carry out polymerization‐induced self‐assembly (PISA) and study the nanostructure behaviors.

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  4. Abstract

    Practical synthesis of polyolefin–polyvinyl block copolymers remains a challenge for transition‐metal catalyzed polymerizations. Common approaches functionalize polyolefins for post‐radical polymerization via insertion methods, yet sacrifice the livingness of the olefin polymerization. This work identifies an orthogonal radical/spin coupling technique which affords tandem living insertion and controlled radical polymerization. The broad tolerance of this coupling technique has been demonstrated for diverse radical/spin traps such as 2,2,5‐trimethyl‐4‐phenyl‐3‐azahexane‐3‐nitroxide (TIPNO), 1‐oxyl‐(2,2,6,6‐tetramethylpiperidine) ‐4‐yl‐α‐bromoisobutyrate (TEMPO‐Br), andN‐tert‐butyl‐α‐phenylnitrone (PBN). Subsequent controlled radical polymerization is demonstrated with nitroxide‐mediated polymerization (NMP) and atom transfer radical polymerization (ATRP), yielding polyolefin–polyvinyl di‐ and triblock copolymers (Đ<1.3) with acrylic, vinylic and styrenic segments. These findings highlight radical trapping as an approach to expand the scope of polyolefin‐functionalization techniques to access polyolefin macroinitiators.

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  5. Efficient transfer of halogen atoms is essential for controlling the growth of polymers in atom transfer radical polymerization (ATRP). The nature of halogens may influence the efficiency of the halogen atom transfer during the activation and deactivation processes. The effect of halogens can be associated with the C–X bond dissociation energy and the affinity of the halogens/halides to the transition metal catalyst. In this paper, we study the effect of halogens (Br vs. Cl) and reaction media in iron-catalyzed ATRP in the presence of halide anions as ligands. In Br-based initiating systems, polymerization of methacrylate monomers was well-controlled whereas Cl-based initiating systems provided limited control over the polymerization. The high affinity of the Cl atom to the iron catalyst renders it less efficient for fast deactivation of growing chains, resulting in polymers with molecular weights higher than predetermined by Δ[M]/[RX] o and with high dispersities. Conversely, Br can be exchanged with higher efficiency and hence provided good control over polymerization. Decreasing the polarity of the reaction medium improved the polymerization control. Polymerizations using ppm levels of the iron catalyst in acetonitrile (a more polar solvent) yielded polymers with larger dispersity values due to the slow rate of deactivation as opposed to the less polar solvent anisole, which afforded well-controlled polymers with dispersity <1.2. 
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