Reinvestigation of the Mechanism of the Free Radical Polymerization Photoinitiation Process by Camphorquinone–Coinitiator Systems: New Results

Pyszka, Ilona; Kucybała, Zdzisław; Pączkowski, Jerzy

doi:10.1002/macp.200400218

Cited by 28 publications

(26 citation statements)

References 18 publications

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“…Conversely, the replacement of ITX by EAB (entry c) and CQ (entry d) prevents the formation of 1 . In accordance with this result, the electron‐transfer between BPh 4 − and the excited state of these two electron donors was found to be non‐thermodynamically favorable (Δ G et, EAB =0.44 eV, Δ G et, CQ =0.07 eV) …”

Section: Resultssupporting

confidence: 74%

Mixture of Azolium Tetraphenylborate with Isopropylthioxanthone: A New Class of N‐Heterocyclic Carbene (NHC) Photogenerator for Polyurethane, Polyester, and ROMP Polymers Synthesis

Trinh

Malval

Morlet‐Savary

et al. 2019

Chemistry A European J

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In the search of smarter routes to control the conditions of N‐heterocyclic carbene (NHCs) formation, a two‐component air‐stable NHC photogenerating system is reported. It relies on the irradiation at 365 nm of a mixture of 2‐isopropylthioxanthone (ITX) with 1,3‐bis(mesityl)imidazoli(ni)um tetraphenylborate. The photoinduced liberation of NHC is evidenced by reaction with a mesitoyl radical to form an NHC‐radical adduct detectable by electron spin resonance spectroscopy. The NHC yield can be determined by 1H NMR spectroscopy through the formation of a soluble and stable NHC–carbodiimide adduct. To deprotonate the azolium salt and liberate the NHC, a mechanism is proposed in which the role of base is played by ITX radical anion formed in situ by a primary photoinduced electron‐transfer reaction between electronically excited ITX (oxidant) and BPh4− (reductant). An NHC yield as high as 70 % is achieved upon starting with a stoichiometric ratio of ITX and azolium salt. Three different photoNHC‐mediated polymerizations are described: synthesis of polyurethane and polyester by organocatalyzed step‐growth polymerization and ring‐opening copolymerization, respectively, and generation of polynorbornene by ring‐opening metathesis polymerization using an NHC‐coordinated Ru catalyst formed in situ.

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Section: Resultssupporting

confidence: 74%

Mixture of Azolium Tetraphenylborate with Isopropylthioxanthone: A New Class of N‐Heterocyclic Carbene (NHC) Photogenerator for Polyurethane, Polyester, and ROMP Polymers Synthesis

Trinh

Malval

Morlet‐Savary

et al. 2019

Chemistry A European J

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“…The ability to spatially localize the irradiation and alter the photo flux over a very wide range offers both physical and chemical approaches to control polymer network development including the evolution of properties and the final properties achieved. Visible light activation over the range of 400 to 500 nm, primarily based on camphorquinone and tertiary amine photoinitiation [1–3], remains the convention used in dentistry to avoid the potential for biological damage to both patients and practitioners. The shorter UV wavelengths compared with visible light also limit the light penetration depth, particularly in highly scattering materials such as composites [4–5].…”

Section: Introductionmentioning

confidence: 99%

Dimethacrylate network formation and polymer property evolution as determined by the selection of monomers and curing conditions

2012

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Objectives This overview is intended to highlight connections between monomer structure and the development of highly crosslinked photopolymer networks including the conversion dependent properties of shrinkage, modulus and stress. Methods A review is provided that combines the polymer science and dental materials literature along with examples of relevant experimental results, which include measurements of reaction kinetics, photorheology as well as polymerization shrinkage and stress. Results While new monomers are continually under development for dental materials applications, mixtures of dimethacrylate monomers persist as the most common form of dental resins used on composite restorative materials. Monomer viscosity and reaction potential is derived from molecular structure and by employing real-time near-infrared spectroscopic techniques, the development of macromolecular networks is linked to the evolution of polymerization shrinkage (measured by linometer), modulus (measured by photorheometer), and stress (measured by tensometer). Relationships between the respective polymer properties are examined. Significance Through a better understanding of the polymer network formation and property development processes using conventional dimethacrylate monomer formulations, the rational design of improved materials is facilitated with the ultimate goal of achieving dental polymers that deliver enhanced clinical outcomes.

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“…56,60,61 Within the concentrations used for this study d[CQ]/dt was observed to be independent of [EDMAB] 0 , as observed when the amine reductant is used in excess. R p0 for EBADMA also remained roughly constant with increase in [EDMAB] 0 .…”

Section: Resultsmentioning

confidence: 54%

Coupled UV–Vis/FT–NIR Spectroscopy for Kinetic Analysis of Multiple Reaction Steps in Polymerizations

et al. 2015

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We couple UV−vis and FT−NIR spectroscopy for the real-time monitoring of polymerization reactions, allowing the simultaneous tracking of the rates of light absorption and initiator/monomer consumption, from which dynamic and previously difficult-to-measure parameters are calculated: quantum yields of initiator consumption, initiation and polymerization, photosensitivity, and residual content of leachable chromophore. Estimating these parameters from one set of experiments is not possible with any other probing technique. We demonstrate the potential of this technique using the free radical initiating system including camphorquinone as photoreducible chromophore and amines as reductants for the visible-light-triggered bulk polymerization of methacrylate monomers, important for dental and biomaterials. Photoinitiation by camphorquinone/amine pairs in two dimethacrylates serves to show the importance of obtaining quantum yields in the polymerizing medium instead of using inert solvents. Additionally, the often-intricate interactions between initiation reactions and the developing macromolecular architectures can be elucidated. For instance, we present the quantification of fluctuations in quantum yields as a function of polymerization. This robust analytical tool with up to millisecond resolution opens opportunities in gaining mechanistic insights from the myriad of macromolecular syntheses available to date.

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Reinvestigation of the Mechanism of the Free Radical Polymerization Photoinitiation Process by Camphorquinone–Coinitiator Systems: New Results

Cited by 28 publications

References 18 publications

Mixture of Azolium Tetraphenylborate with Isopropylthioxanthone: A New Class of N‐Heterocyclic Carbene (NHC) Photogenerator for Polyurethane, Polyester, and ROMP Polymers Synthesis

Mixture of Azolium Tetraphenylborate with Isopropylthioxanthone: A New Class of N‐Heterocyclic Carbene (NHC) Photogenerator for Polyurethane, Polyester, and ROMP Polymers Synthesis

Dimethacrylate network formation and polymer property evolution as determined by the selection of monomers and curing conditions

Coupled UV–Vis/FT–NIR Spectroscopy for Kinetic Analysis of Multiple Reaction Steps in Polymerizations

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