Metal-Free Atom Transfer Radical Polymerization

Treat, Nicolas J.; Sprafke, H. A.; Kramer, John W.; Clark, Paul G.; Barton, Bryan E.; Alaniz, Javier Read de; Fors, Brett P.; Hawker, Craig J.

doi:10.1021/ja510389m

Cited by 832 publications

(745 citation statements)

References 36 publications

(41 reference statements)

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“…Under these conditions, and in agreement with the literature, >99% conversion in a few hours can be achieved with dispersities as low as 1.06 (Table 3, Entry 1, Figure S32). 35,62,63 However, having a universal set of conditions and reagents that would allow for the controlled polymerization of acrylates, methacrylates and styrene would be advantageous as it enables greater accessibility of polymeric materials by non-experts. As such, we were initially interested to explore whether IPA could afford the controlled polymerization of MA (maintaining EBiB and Me6Tren).…”

Section: The Synthesis Of Well Controlled Poly(acrylates) Under Univementioning

confidence: 99%

“…31,32 The latter two approaches have demonstrated high end group fidelity even at near-quantitative conversions as exemplified by the in situ synthesis of multiblock copolymers. [33][34][35][36][37][38][39] Moreover, to the best of our knowledge, in situ chain extensions with copper mediated polymerization approaches have only been reported for relatively high kp monomers such as acrylates, as methacrylates are more susceptible to termination, chain transfer and side reactions. Importantly, all these techniques are capable of polymerizing specific families of monomers, however choosing the appropriate method depending on the targeted polymer can also be challenging.…”

Section: Introductionmentioning

confidence: 99%

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Universal Conditions for the Controlled Polymerization of Acrylates, Methacrylates, and Styrene via Cu(0)-RDRP

et al. 2017

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Usually atom transfer radical polymerization (ATRP) requires various parameters, such as the type of initiator, transition metal, ligand, solvent, temperature, deactivator, added salts and reducing agents, need to be optimised in order to achieve a high degree of control over molecular weight and dispersity. These components play a major role when switching monomers e.g. from acrylic to methacrylic and/or styrenic monomers during the synthesis of homo-and block copolymers as the stability and reactivity of the carbon centered propagating radical dramatically changes. This is a challenge for both "experts" and non-experts as choosing the appropriate conditions for successful polymerization can be time consuming and an arduous task. In this work we describe some universal conditions for the efficacious polymerization of acrylates, methacrylates and styrene (using an identical initiator, ligand, copper salt and solvent) based on commercially available reagents (PMDETA, IPA, Cu(0) wire). The versatility of these conditions is demonstrated by the near quantitative polymerization of these monomer families to yield well-defined materials over a range of molecular weights with low dispersities (~1.1-1.2). The control and high end group fidelity is further exemplified by in situ block copolymerization upon sequential monomer addition for the case of methacrylates and styrene furnishing higher molecular weight copolymers with minimal termination. The facile nature of these conditions, combined with readily available reagents will greatly expand the access and availability of tailored polymeric materials to all researchers.

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Section: The Synthesis Of Well Controlled Poly(acrylates) Under Univementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Universal Conditions for the Controlled Polymerization of Acrylates, Methacrylates, and Styrene via Cu(0)-RDRP

et al. 2017

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“…19 In this system, PTH acts as a photoreductant in a similar manner to Ir(ppy) 3 with a reduction potential (E 1/2 * = À2.1 V vs. SCE) significantly higher than Ir(ppy) 3 (E 1/2 * = À1.7 V vs. SCE). Based on our interest in metalfree ATRP, we envisioned that the same radical based processes enabled by PTH could also be used to access a variety of carboncentered radical intermediates that could be used for subsequent synthetic transformations, such as the reduction of carbon-halogen bonds.…”

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confidence: 96%

“…24 While the ground state oxidation potential of PTH (E ox 1/2 = 0.68 vs. SCE) 19 is only slightly lower than that of Ir(ppy) 3 (E ox 1/2 = 0.77 V vs. SCE), the photoluminescence maximum of PTH (l max = 445 nm, Fig. S3, ESI †) is significantly lower (Ir(ppy) 3 l max = 500 nm).…”

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A highly reducing metal-free photoredox catalyst: design and application in radical dehalogenations

et al. 2015

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Here we report the use of 10-phenylphenothiazine (PTH) as an inexpensive, highly reducing metal-free photocatalyst for the reduction of carbon-halogen bonds via the trapping of carbon-centered radical intermediates with a mild hydrogen atom donor. Dehalogenations were carried out on various substrates with excellent yields at room temperature in the presence of air.In recent years, photoredox chemistry has enabled the development of a wide variety of synthetic transformations. 1 These methods are based on photocatalysts which, upon absorption of light, enter either a highly reducing or oxidizing excited state capable of facilitating redox-based transformations. In particular, the reduction of activated carbon-halide (C-X) bonds has generated wide interest, largely because of the broad synthetic utility of resulting carbon-centered radical intermediates. [1][2][3][4][5][6][7][8][9][10] One example includes subsequent trapping of these intermediates with a mild H-atom source to achieve radical dehalogenations. 3,5,6,9 In this case, the power of using a photoredox approach is that it offers a more efficient and safer alternative to traditional dehalogenation protocols involving metal-halogen exchange, 11,12 stoichiometric tin hydride, 13 and various other highly toxic reagents. [14][15][16] However, despite the notable advantages of photoredox catalysis, 1 a number of major challenges still exist. This includes the use of catalysts based on rare-earth transition metals such as Ru and Ir, which have inherent limitations due to the cost of the catalyst itself (B$1 mg À1 for Ir(ppy) 3 ), 17 as well as the expense associated with the removal of trace metals from the desired products -critical for applications from pharmaceuticals to micro-electronics. In addition, although an assortment of activated carbon-halogen bonds have been accessed using these catalysts, 1 higher energy unactivated halides are a significantly more challenging task, with only unactivated iodides being explored to date. 5,18 To this end, a more affordable gold-based photocatalyst has been developed, 10 and although offering broader substrate scope, the disadvantages of metal-based systems remain. In addressing this, the use of an organic perylene diimide (PDI)-based photocatalyst was recently reported, and while providing a metal-free alternative, it requires elevated temperatures and has a scope limited to activated aryl-halides. 8 In this context, we envisioned the development of a highly reducing, inexpensive, metal-free photocatalyst that could offer access to a wide range of carbon-halogen substrates under markedly mild conditions (Fig. 1).Our groups previously employed 10-phenylphenothiazine (PTH) as a metal-free catalyst for photomediated atom transfer radical polymerizations (ATRP). 19 In this system, PTH acts as a photoreductant in a similar manner to Ir(ppy) 3 with a reduction potential (E 1/2 * = À2.1 V vs. SCE) significantly higher than Ir(ppy) 3 (E 1/2 * = À1.7 V vs. SCE). Based on our interest in metalfree ATRP, we envisioned that th...

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“…Number of strategies have been proposed to obtain metal-free ATRP polymers. Recently, phenothiazine derivatives [26][27][28], perylene [29], pyrene [30], diaryl dihydrophenazines [31] and phenoxazines [32] as photoactivators in conjunction with alkyl halides have been shown to realize photo-initiated CLRP of various monomers in the absence of Cu catalysts (Chart 1). Chart 1.…”

Section: Introductionmentioning

confidence: 99%

Photoinitiated Metal Free Living Radical and Cationic Polymerizations

Çiftçi

Yılmaz

Yaǧcı

2017

J. Photopol. Sci. Technol.

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Although conventional photoinitiated radical and cationic polymerizations are widely used in many industrial applications, they usually proceed in an uncontrolled manner. Recent developments in photomediated living/controlled radical and cationic polymerization made it possible to prepare various well-defined polymers with complex architecture under mild conditions. Various methods described for cationic and radical polymerization utilizes metal or Lewis acid catalysts. Several strategies eliminating the use of such additives in photoinduced controlled/living radical and cationic polymerizations have been developed. This article describes various photoinitiation systems acting in UV-vis range. Their mechanistic details are also evaluated and several specific examples involving combination both free radical and cationic routes are presented.

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Metal-Free Atom Transfer Radical Polymerization

Cited by 832 publications

References 36 publications

Universal Conditions for the Controlled Polymerization of Acrylates, Methacrylates, and Styrene via Cu(0)-RDRP

Universal Conditions for the Controlled Polymerization of Acrylates, Methacrylates, and Styrene via Cu(0)-RDRP

A highly reducing metal-free photoredox catalyst: design and application in radical dehalogenations

Photoinitiated Metal Free Living Radical and Cationic Polymerizations

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