Mechanistic Perspectives on Stereocontrol in Lewis Acid-Mediated Radical Polymerization

Noble, Benjamin B.; Coote, Michelle L.

doi:10.1016/bs.apoc.2015.07.002

Cited by 11 publications

(11 citation statements)

References 222 publications

(212 reference statements)

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“…As a result, a 4-methylbenzophenone radical (BP • ) is generated, which we predict efficiently adds to a monomer with a exergonicity of −29.1 kcal/mol. BP • behaves similarly to an electron-rich styrene-like radical that reacts efficiently with an electron-poor monomer such as (meth)acrylate. , Biphenyl, 4-methyl benzophenone, and bis(4-methyl benzophenone) species were experimentally observed, indicating the generation of a phenyl radical and 4-methyl benzophenone radical . The final product of the photochemical process following ET 2 is an amine species with a regained lone pair (DMPT) that can react with BPO via inner-sphere electron transfer (ET 3 ), generating two additional initiating radicals: a benzoyloxy radical (BzR • ) and alpha-aminoalkyl radical (AAR • ).…”

Section: Resultsmentioning

confidence: 99%

High-Efficiency Radical Photopolymerization Enhanced by Autonomous Dark Cure

et al. 2020

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Radical photopolymerization (RPP) has grown into a multibillion-dollar technology for reduced energy consumption and waste with increased productivity. However, radical-mediated polymerization ceases almost immediately following discontinuation of irradiation because of rapid termination of reactive centers. This restricts the wider use of RPP in applications that involve light attenuation or irregular surfaces because uniform polymerization is not guaranteed for these challenging exposure conditions and the resultant undercuring leads to compromised material properties and harmful leachable monomers. Herein, we developed a unique radical dark-curing photoinitiator (DCPI) that continues its polymerization beyond the cessation of irradiation. The DCPI achieved a remarkable 25–60% additional conversion over a 1 h period, when light was shuttered at 20% conversion, compared to the 1–3% additional conversion achieved by a Norrish type II control photoinitiator. We elucidated the origin of the high photon efficiency using computational studies and experiments, which suggest that the DCPI may be the most-photon-efficient photoinitiator to date. We also demonstrated that the mechanical properties of dark-cured polymer are similar to and even exceed those of the corresponding polymer obtained by extended photocuring. In particular, the initial 0.1 MPa storage modulus continuously developed to 4.3 MPa without further irradiation, while also exhibiting ∼30% less shrinkage stress than the full exposure control. With its superior photo- and dark-polymerization efficiency, the DCPI enhances the performance of many existing RPP processes while extending RPP to heretofore unattainable applications. The DCPI accomplishes such a performance through an inherent automatic rectification of initially undercured regions and defies the RPP paradigm that light dosage directly correlates to conversion.

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Section: Resultsmentioning

confidence: 99%

High-Efficiency Radical Photopolymerization Enhanced by Autonomous Dark Cure

et al. 2020

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“…The strength of Lewis acid−base interactions depends on the identity of the Lewis acid and base donors and is highly variable, ranging in strength from that of weak hydrogen bonding (4 kJ mol −1 ) to significantly stronger than some covalent bonds (>100 kJ mol −1 ). 22 In fact, the Lewis acid−base interaction in eutectic electrolytes was not expected to be strong enough to foster a Lewis chemical reaction (covalent bond). It would be preferable that it only changes the coordination environment, resulting in a lowmelting-point eutectic electrolyte.…”

Section: Concepts and Formation Mechanisms Of Eutectic Electrolytesmentioning

confidence: 99%

“…However, due to the vital role of the specific effect between hydrogen atoms and more electronegative atoms, it is essential to discuss it separately. The strength of Lewis acid–base interactions depends on the identity of the Lewis acid and base donors and is highly variable, ranging in strength from that of weak hydrogen bonding (4 kJ mol –1 ) to significantly stronger than some covalent bonds (>100 kJ mol –1 ) . In fact, the Lewis acid–base interaction in eutectic electrolytes was not expected to be strong enough to foster a Lewis chemical reaction (covalent bond).…”

Section: Concepts and Formation Mechanisms Of Eutectic Electrolytesmentioning

confidence: 99%

Eutectic Electrolytes as a Promising Platform for Next-Generation Electrochemical Energy Storage

2020

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Conspectus The rising global energy demand and environmental challenges have spurred intensive interest in renewable energy and advanced electrochemical energy storage (EES), including redox flow batteries (RFBs), metal-based rechargeable batteries, and supercapacitors. While many researchers focus on the design of new chemistry and structures for high-capacity and stable electrode materials, the electrolyte also plays a significant role in enabling the successful function of these new electrode materials and chemistries. Discovery of new electrolytes is urgently needed to keep up with the rapid growth of EES. Benefiting from the strong intermolecular interaction between different components, eutectic electrolytes possess various specific functionalities that conventional electrolytes do not have, such as highly concentrated systems, non-flammability, high degrees of structural flexibility, and good thermal and chemical stability, thereby leading researchers to consider them as a new class of ionic fluids for EES applications. In this Account, we aim to provide a mechanistic understanding of this energy chemistry and an overview of recent progress in the development of eutectic electrolytes for next-generation EES. First, we describe different mechanisms that guide the formation of eutectic electrolytes and discuss the structure–property relations, electron transfer and ion transport mechanisms, and interfacial chemistry in eutectic electrolytes. Generally, three main intermolecular interactions, namely hydrogen-bond interactions, Lewis acid–base interactions, and van der Waals interactions, control the formation of eutectic electrolytes and determine their unique characters in terms of electrochemical, thermal, ion transport, and interfacial properties. These versatile intermolecular interactions can be further modified by tailoring the functional moieties of organic molecules and/or selecting suitable compositions of mixtures. The solvent-free eutectic electrolyte can maximize the molar ratio of redox-active materials, thus increasing the energy density of RFBs. We discuss the relationships between eutectic parameters (viscosity, polarity, ionic conductivity, surface tension, and coordination environment) and the molar ratio, stability, utilization, and electrochemical reversibility of redox-active materials, RFB power, and energy density. We then introduce the application of both metal- and organic-based eutectic electrolytes in the RFB field, along with the relevant perspective for future study in this field. The highly concentrated eutectic electrolytes show attractive features at electrolyte/electrode interfaces to expand the electrochemical window and meanwhile inhibit metal dendrite formation in metal-based rechargeable batteries, supercapacitors, and hybrids of these. The remaining challenges and potential research directions in these areas are also discussed. Eutectic electrolytes offer enormous opportunities and open appealing prospects as redox reaction and charge transport media for EES...

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“…In radical polymerization, the planar (sp 2 hybridized) carbon radical of the polymer terminus is prochiral, and its stereochemistry is revealed during subsequent monomer addition. The prochiral polymer terminus has two configurational arrangements: pro- meso and pro- racemo , which are defined by the relative orientation of the terminal and penultimate side chains with respect to the polymer C–C backbone . This process is unpredictable and difficult to control.…”

Section: Sumi For Stereochemistry Regulation In Free Radical Polymeri...mentioning

confidence: 99%

“…For many years since its discovery, free radical chemistry was regarded as unpredictable and prone to forming complex reaction products, and thus controlling chemoselectivity via radical reactions was challenging. However, beginning in the 1980s and driven by pioneering contributions from many organic chemists, − new methods to generate carbon radicals and mechanistic studies of their reactivity led to a new understanding that radical reactions are actually reasonably predictable and highly selective, if provided with sensible reagents and reaction conditions. ,, …”

Section: Introductionmentioning

confidence: 99%

Single Unit Monomer Insertion: A Versatile Platform for Molecular Engineering through Radical Addition Reactions and Polymerization

2019

Macromolecules

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Single unit monomer insertion (SUMI) is an emerging technology for precise polymer synthesis through a radical addition reaction mechanism with monomer additions occurring one at a time. It possesses the capability of highly efficient and economical chemical conversion for carbon−carbon bond formation. Originating from reversible deactivation radical polymerization (RDRP), SUMI retains the virtues of mild reaction conditions and remarkable tolerance toward functionalities. Additionally, SUMI can provide a versatile platform for the engineering of stereochemistry as well as mechanistic and kinetic studies of radical addition reactions and RDRP. Herein, the history and development of SUMI are reviewed, and the advances since its advent in organic transformation and sequence-defined polymer synthesis are highlighted. Current challenges are discussed, and a perspective on future opportunities for this promising synthetic technology is also presented.

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Mechanistic Perspectives on Stereocontrol in Lewis Acid-Mediated Radical Polymerization

Cited by 11 publications

References 222 publications

High-Efficiency Radical Photopolymerization Enhanced by Autonomous Dark Cure

High-Efficiency Radical Photopolymerization Enhanced by Autonomous Dark Cure

Eutectic Electrolytes as a Promising Platform for Next-Generation Electrochemical Energy Storage

Single Unit Monomer Insertion: A Versatile Platform for Molecular Engineering through Radical Addition Reactions and Polymerization

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