A new approach to perform single-electron transfer living radical polymerization (SET-LRP) in water is described. The key step in this process is to allow full disproportionation of CuBr/Me6TREN (TREN = tris(dimethylamino)ethyl amine to Cu(0) powder and CuBr2 in water prior to addition of both monomer and initiator. This provides an extremely powerful tool for the synthesis of functional water-soluble polymers with controlled chain length and narrow molecular weight distributions (polydispersity index approximately 1.10), including poly(N-isopropylacrylamide), N,N-dimethylacrylamide, poly(ethylene glycol) acrylate, 2-hydroxyethyl acrylate (HEA), and an acrylamido glyco monomer. The polymerizations are performed at or below ambient temperature with quantitative conversions attained in minutes. Polymers have high chain end fidelity capable of undergoing chain extensions to full conversion or multiblock copolymerization via iterative monomer addition after full conversion. Activator generated by electron transfer atom transfer radical polymerization of N-isopropylacrylamide in water was also conducted as a comparison with the SET-LRP system. This shows that the addition sequence of l-ascorbic acid is crucial in determining the onset of disproportionation, or otherwise. Finally, this robust technique was applied to polymerizations under biologically relevant conditions (PBS buffer) and a complex ethanol/water mixture (tequila).

Photoinduced living radical polymerization of acrylates, in the absence of conventional photoinitiators or dye sensitizers, has been realized in "daylight'"and is enhanced upon irradiation with UV radiation (λ(max) ≈ 360 nm). In the presence of low concentrations of copper(II) bromide and an aliphatic tertiary amine ligand (Me6-Tren; Tren = tris(2-aminoethyl)amine), near-quantitative monomer conversion (>95%) is obtained within 80 min, yielding poly(acrylates) with dispersities as low as 1.05 and excellent end group fidelity (>99%). The versatility of the technique is demonstrated by polymerization of methyl acrylate to a range of chain lengths (DP(n) = 25-800) and a number of (meth)acrylate monomers, including macromonomer poly(ethylene glycol) methyl ether acrylate (PEGA480), tert-butyl acrylate, and methyl methacrylate, as well as styrene. Moreover, hydroxyl- and vic-diol-functional initiators are compatible with the polymerization conditions, forming α,ω-heterofunctional poly(acrylates) with unparalleled efficiency and control. The control retained during polymerization is confirmed by MALDI-ToF-MS and exemplified by in situ chain extension upon sequential monomer addition, furnishing higher molecular weight polymers with an observed reduction in dispersity (Đ = 1.03). Similarly, efficient one-pot diblock copolymerization by sequential addition of ethylene glycol methyl ether acrylate and PEGA480 to a poly(methyl acrylate) macroinitiator without prior workup or purification is also reported. Minimal polymerization in the absence of light confers temporal control and alludes to potential application at one of the frontiers of materials chemistry whereby precise spatiotemporal "on/off" control and resolution is desirable.

The synthesis of well-defined high molecular weight block copolymers by sequential in situ chain extensions via Cu(0)-mediated living radical polymerization is reported. Optimal conditions for iterative high molecular weight block formation were determined using model homopolymer quasiblock systems, including methyl acrylate (MA), ethyl acrylate (EA), and n-butyl acrylate (nBA; each block DP n ≈ 100). The PDI after each chain extension was below 1.2, with good agreement between theoretical and experimental molecular weights, while the conversion of monomer incorporation into each distinct block was 95−100% (up to 6 blocks). To demonstrate this approach for true block copolymer materials, well-defined block polymers containing MA, ethylene glycol methyl ether acrylate (EGMEA), and tert-butyl acrylate (tBA) were prepared in high purity: diblock P(MA-b-EGMEA) and triblock P(MA-b-tBA-b-MA). These were prepared in high yields, on multigram scales, and with purification only required at the final step. To the best of our knowledge, this is the first time that high molecular weight block copolymers have been reported using this novel technique. B lock copolymers display a wide range of interesting and useful properties due to the fact that the combination of monomers with different physicochemical properties, confined in block sequences, allows these systems to undergo selfassembly and phase separation into higher ordered structures. 1−8 The synthesis of AB or ABA amphiphilic block copolymers of high molecular weight is of particular interest for the formation of micelles, vesicles, and so on, in solution, and various morphologies in the solid state. 1−8 The morphology of these self-assembled constructs depends upon a well-controlled synthetic protocol allowing preordained molecular weights and volume fractions (ϕA/ϕB) to be obtained. 9−12 However, while there are many polymerization techniques that have been used to produce block copolymers, a number of drawbacks exist. For example, living anionic polymerization 13 is extremely labor intensive, and the number of functional monomers that can be polymerized using this technique is limited. The development of controlled radical polymerization (CRP) techniques, such as ATRP, 14,15 NMP, 16 and RAFT, 17 has expanded this monomer library but experimental and synthetic limitations remain. The most significant limitation is the loss of "livingness", or end group fidelity, as the polymerization proceeds due to unwanted side reactions. 18,19 This loss of "livingness" of the chain end, leads to a drift in PDI, which can be reflected in the structural polydispersity of resulting higher order polymers.Cu(0)-mediated living radical polymerization 20,21 has recently been demonstrated to yield polymers with extremely high livingness at quantitative conversions and extending into post-polymerization conditions. 22 The versatility of the approach has been demonstrated in a diverse range of polar solvents such as DMSO, 23 DMF, 24 ionic liquids, 25 water, 26,27 alcohols, 28 and even in bio...