Rapid, Selective, and Reversible Nitroxide Radical Coupling (NRC) Reactions at Ambient Temperature

Kulis, Jakov; Bell, Craig A.; Micallef, Aaron S.; Jia, Zhongfan; Monteiro, Michael J.

doi:10.1021/ma9014565

Cited by 130 publications

(140 citation statements)

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“…[5] Our group attained ultrafast radical formation through single electron transfer (SET) to achieve a reaction with 'click'-type attributes at room temperature, which included near quantitative yields, selectivity in the presence of functional groups, rapid rates of alkoxyamine formation, and non-toxic byproducts. [6] Moreover, this reaction was reversible at high temperatures, and we demonstrated the further functionalization of end-groups through competitive exchange with other functional nitroxides. [6] Click reactions have become an important tool for the modification and coupling of small molecule [7] and macromolecular systems to create new advanced materials.…”

Section: Introductionmentioning

confidence: 76%

“…[6] Moreover, this reaction was reversible at high temperatures, and we demonstrated the further functionalization of end-groups through competitive exchange with other functional nitroxides. [6] Click reactions have become an important tool for the modification and coupling of small molecule [7] and macromolecular systems to create new advanced materials. [8,9] In the polymer field, the Cu I -catalyzed azide/alkyne cycloaddition (CuAAC) coupling reaction has been the dominant click reaction used to prepare complex architectures such as dendrimers, stars, miktoarm stars, and polymer grafts.…”

Section: Introductionmentioning

confidence: 76%

“…Single electron transfer-'living' radical polymerization (SET-LRP) was the first technique to utilize this approach, allowing the ultrafast production of well-controlled acrylate polymerizations at room temperature. [15] Similarly, we reported [6] the rapid (<7 min) formation of three-arm star polymers at room temperature using a tri-nitroxide core, linear polystyrene chains with halide chain-ends (PSTY-Br), and NRC methodology. We subsequently established that the SET-NRC reaction was much faster than previously thought, and highly effective as an ultrafast click-type reaction as demonstrated by the formation of two-arm PSTY in less than 1 min …”

Section: Introductionmentioning

confidence: 85%

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Ultrafast and Reversible Multiblock Formation by the SET-Nitroxide Radical Coupling Reaction

et al. 2010

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The single electron transfer-nitroxide radical coupling (SET-NRC) reaction has been used to produce multiblock polymers with high molecular weights in under 3 min at 50 • C by coupling a difunctional telechelic polystyrene (Br-PSTY-Br) with a dinitroxide. The well known combination of dimethyl sulfoxide as solvent and Me 6 TREN as ligand facilitated the in situ disproportionation of Cu I Br to the highly active nascent Cu 0 species. This SET reaction allowed polymeric radicals to be rapidly formed from their corresponding halide end-groups. Trapping of these carbon-centred radicals at close to diffusion controlled rates by dinitroxides resulted in high-molecular-weight multiblock polymers. Our results showed that the disproportionation of Cu I was critical in obtaining these ultrafast reactions, and confirmed that activation was primarily through Cu 0 . We took advantage of the reversibility of the NRC reaction at elevated temperatures to decouple the multiblock back to the original PSTY building block through capping the chain-ends with mono-functional nitroxides. These alkoxyamine end-groups were further exchanged with an alkyne mono-functional nitroxide (TEMPO-≡) and 'clicked' by a Cu I -catalyzed azide/alkyne cycloaddition (CuAAC) reaction with N 3 -PSTY-N 3 to reform the multiblocks. This final 'click' reaction, even after the consecutive decoupling and nitroxide-exchange reactions, still produced highmolecular-weight multiblocks efficiently. These SET-NRC reactions would have ideal applications in re-usable plastics and possibly as self-healing materials.

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Section: Introductionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 85%

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Ultrafast and Reversible Multiblock Formation by the SET-Nitroxide Radical Coupling Reaction

et al. 2010

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“…The current model might be controversial as the radical coupling is suggested to be reversible and further studies are needed for unveiling the mechanistic details of lignin polymerization. However, reversible radical couplings are known from polymer chemistry (Kulis et al 2009). …”

Section: Resultsmentioning

confidence: 99%

A possible explanation for the structural inhomogeneity of lignin in LCC networks

2017

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Lignin has a very complex structure, and this is partly due to the monomers being connected by many different types of covalent bonds. Furthermore, there are multiple covalent bonds between lignin and polysaccharides in wood, and it is known that the structure of lignin covalently bound to the hemicellulose xylan is different to lignin bound to the hemicellulose glucomannan. Here, synthetic lignin (DHP) is synthesized at different pH and it is shown that lignin made at lower pH has a structure more similar to the lignin bound to xylan, i.e., having higher relative content of b-O-4 ethers. It is hypothesized that xylan due to its carboxylic acids forms a locally lower pH and thus ''direct'' the lignin structure to have more b-O-4 ethers. The biological significance of these results is discussed.

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“…In addition, after the introduction of "click" chemistry, GPC has also become an essential instrument for the characterization of polymeric architectures as the presence of unreacted polymer blocks gives information on coupling efficiency. 27,161,212 In order to correctly quantify the amount of polymer species in GPC samples, log-normal distribution (LND) simulation is used in which a GPC trace of a polymer is fitted by a Gaussian function:…”

Section: Log-normal Distribution Simulationmentioning

confidence: 99%

New insights into copper-mediated polymerization and polymer topologies

Gavrilov¹

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Polymer science has developed new synthetic methods to create complex polymer architectures. The solution and bulk properties of these architectures are influenced by the structure and chemical composition of the original building blocks (e.g. monomers or reactive polymeric blocks). One of the greatest challenges to the field is characterization of these polymers with diverse structures and chemical compositions. Size exclusion chromatography (SEC) has been one of the most used characterization techniques to determine the molecular weight distribution (MWD) of polymers. The information obtained about the polymer from SEC is generally restricted to molecular weight averages and dispersity indexes. However, there is a wealth of valuable information that can be obtained from a deeper analysis of the SEC chromatograms. This information can provide insights into polymerization mechanisms, the amount of unreacted polymer in a coupling reaction, or even the amount of cyclic polymer formed during a ring-closure reaction.The thesis first develops the theory to analyse the SEC chromatograms and provides a methodology to fit the MWDs with a log-normal distribution (LND) model based on a Gaussian function. The LND model was then used to analyse polymers made by a variant of copper-mediated ‗living' radical polymerization (LRP) in water. This LRP technique is capable of producing hydrophilic polymers with both narrow MWDs and high chain-end functionality, but the chain-end halide groups were susceptible to hydrolysis upon purification attempts and, therefore, the polymers cannot be further used to create complex polymer architectures. To preserve high chain-end functionality, the terminal halide of the polymers was capped using in situ azidation at the end of aqueous coppermediated LRP. The azide chain-end fidelity of the purified polymer was tested in a coppercatalyzed azide-alkyne cycloaddition (CuAAC) ‗click' reaction. The LND model of MWDs of the resulting products gave an accurate determination of the end-group functionality and insight into the effectiveness of our new polymerization variant.In the final stage of this thesis, the LND model was used to quantify the sequential polymerization of cyclic macromers through successive CuAAC ‗click' reactions. The versatility of the LND model was further demonstrated by determining the multicyclic coil conformation as a function of the number of cyclic macromers in the polymer chain.iii Declaration by authorThis thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis.I have clearly stated the contribution of others to my thesis as a whole, including statistical assistance, survey design, data analysis, significant technical procedures, professional editorial advice, and any other original research work used or reported in my thesis. The content of my ...

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Rapid, Selective, and Reversible Nitroxide Radical Coupling (NRC) Reactions at Ambient Temperature

Cited by 130 publications

References 50 publications

Ultrafast and Reversible Multiblock Formation by the SET-Nitroxide Radical Coupling Reaction

Ultrafast and Reversible Multiblock Formation by the SET-Nitroxide Radical Coupling Reaction

A possible explanation for the structural inhomogeneity of lignin in LCC networks

New insights into copper-mediated polymerization and polymer topologies

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