Photocatalysts in Polymerization Reactions

Zivic, Nicolas; Bouzrati-Zerelli, Mariem; Kermagoret, Anthony; Dumur, Frédéric; Fouassier, Jean‐Pierre; Gigmès, Didier; Lalevée, Jacques

doi:10.1002/cctc.201501389

Cited by 141 publications

(123 citation statements)

References 231 publications

(162 reference statements)

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“…Other strongly oxidizing photoredox catalysts were used for this study as well, including acridinium 4 and ruthenium or iridium complexes 5 and 6 . 12–17 …”

Section: Resultsmentioning

confidence: 99%

Mechanistic Insight into the Photocontrolled Cationic Polymerization of Vinyl Ethers

et al. 2017

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The mechanism of the recently reported photocontrolled cationic polymerization of vinyl ethers was investigated using a variety of catalysts and chain-transfer agents (CTAs) as well as diverse spectroscopic and electrochemical analytical techniques. Our study revealed a complex activation step characterized by one-electron oxidation of the CTA. This oxidation is followed by mesolytic cleavage of the resulting radical cation species, which leads to the generation of a reactive cation–this species initiates the polymerization of the vinyl ether monomer–and a dithiocarbamate radical that is likely in equilibrium with the corresponding thiuram disulfide dimer. Reversible addition–fragmentation type degenerative chain transfer contributes to the narrow dispersities and control over chain growth observed under these conditions. Finally, the deactivation step is contingent upon the oxidation of the reduced photocatalyst by the dithiocarbamate radical concomitant with the production of a dithiocarbamate anion that caps the polymer chain end. The fine-tuning of the electronic properties and redox potentials of the photocatalyst in both the excited and the ground states is necessary to obtain a photocontrolled system rather than simply a photoinitiated system. The elucidation of the elementary steps of this process will aid the design of new catalytic systems and their real-world applications.

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“…Other strongly oxidizing photoredox catalysts were used for this study as well, including acridinium 4 and ruthenium or iridium complexes 5 and 6 . 12–17 …”

Section: Resultsmentioning

confidence: 99%

Mechanistic Insight into the Photocontrolled Cationic Polymerization of Vinyl Ethers

et al. 2017

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“…11 Light mediated CRPs further introduce spatial and temporal control as an attractive interactive feature for the incorporation of added synthetic complexity. 12 However, the concerns of metal contamination and the sustainability of iridium or ruthenium metal PCs motivate the use of organic PCs. 14,13 …”

Section: Introductionmentioning

confidence: 99%

Organocatalyzed Atom Transfer Radical Polymerization Using N-Aryl Phenoxazines as Photoredox Catalysts

et al. 2016

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N-Aryl phenoxazines have been synthesized and introduced as strongly reducing metal-free photoredox catalysts in organocatalyzed atom transfer radical polymerization for the synthesis of well-defined polymers. Experiments confirmed quantum chemical predictions that, like their dihydrophenazine analogs, the photoexcited states of phenoxazine photoredox catalysts are strongly reducing and achieve superior performance when they possess charge transfer character. We compare phenoxazines to previously reported dihydrophenazines and phenothiazines as photoredox catalysts to gain insight into the performance of these catalysts and establish principles for catalyst design. A key finding reveals that maintenance of a planar conformation of the phenoxazine catalyst during the catalytic cycle encourages the synthesis of well-defined macromolecules. Using these principles, we realized a core substituted phenoxazine as a visible light photoredox catalyst that performed superior to UV-absorbing phenoxazines as well as previously reported organic photocatalysts in organocatalyzed atom transfer radical polymerization. Using this catalyst and irradiating with white LEDs resulted in the production of polymers with targeted molecular weights through achieving quantitative initiator efficiencies, which possess dispersities ranging from 1.13 to 1.31.

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“…This is asevere limitation if one wants to access larger objects,a nd it stems from the use of UV light from mainly Hg lamps to trigger the radical reactions.U Vr ays have severe drawbacks.T hey are highly energetic and harmful to the operators,n ecessitating special protection measures;f urthermore,t hey do not penetrate thick samples well because they are scattered by the large monomer droplets and/or polymer particles.T he penetration issue can be offset by running the polymerizations in at ubular vessel, but the diameter of the particles remains below 100 nm. [13] Oddly though, despite an early isolated report, [14] only very few works focus on visible-light photopolymerizations in dispersed media, [15] and almost none involving conventional emulsion polymerization. Because their wavelengths are longer, they are much less scattered by larger objects and thus penetrate better.And from atechnological point of view,the LEDs are very compact, long-lived and do not emit heat or ozone.They can therefore be easily included into chemical reactors.A s ac onsequence,v isible-light mediated radical reactions have grown exponentially over the last few years in both molecular [12] and polymer chemistry.…”

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confidence: 83%

Visible‐Light Emulsion Photopolymerization of Styrene

et al. 2017

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The photopolymerization of styrene in emulsion is achieved in ac onventional double-wall reactor equipped with aL ED ribbon coiled around the external glass wall. Styrene mixed to acridine orange is added to the water phase containing sodium dodecyl sulfate,awater-soluble N-heterocyclic carbene-borane and disulfide,a nd irradiated. Highly stable latexes are obtained, with particles up to ad iameter of 300 nm. The ability to reach such large particle sizes via ap hotochemical process in ad ispersed medium is due to the use of visible light:t he photons in the visible range are less scattered by larger objects and thus penetrate and initiate better the polymerizations.T hey are also greener and cheaper to produce via LEDs,a nd muchs afer than UVs.T he method presented does not require any specific glassware;i tw orks at lower temperature and delivers larger particles compared to thermal processes at similar solids contents and surfactant concentrations.

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Photocatalysts in Polymerization Reactions

Cited by 141 publications

References 231 publications

Mechanistic Insight into the Photocontrolled Cationic Polymerization of Vinyl Ethers

Mechanistic Insight into the Photocontrolled Cationic Polymerization of Vinyl Ethers

Organocatalyzed Atom Transfer Radical Polymerization Using N-Aryl Phenoxazines as Photoredox Catalysts

Visible‐Light Emulsion Photopolymerization of Styrene

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