Comparison between NIR and UV-Sensitized Radical and Cationic Reactivity of Iodonium Salts Comprising Anions with Different Coordination Behavior

Shiraishi, Atsushi; Kimura, Hideki; Oprych, Dennis; Schmitz, Christian; Strehmel, Bernd

doi:10.2494/photopolymer.30.633

Cited by 22 publications

(24 citation statements)

References 21 publications

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“…Even if the absorption coefficients were extremely low at 785 nm (170 L•mol −1 •cm −1 ) and 940 nm (100 L•mol −1 •cm −1 ), the possibility to initiate the FRP of methacrylates in the NIR region was brilliantly demonstrated. Indeed, photopolymerization at these wavelengths is dominated by cyanines [145][146][147][148][149][150] but these compounds are expensive so that alternatives are actively researched. While polymerizing a resin composed of a mixture of three monomers (33.3 wt% of (hydroxypropyl)methacrylate (HPMA), 33.3 wt% of 1,4-butanediol dimethacrylate (1,4-BDMA) and 33.3 wt% of a urethane dimethacrylate monomer (UDMA), final monomer conversions of 92% upon irradiation at 785 nm and 60% upon irradiation at 940 nm could be obtained with the four component system Cbz_35/(t-Bu)Ph 2 I + /4-dppba/BlocBuilder®MA (0.1 wt%/ 3 wt%/2 wt%/2 wt%) where 4-dppba and BlockBuilder®MA stand for 4-(diphenylphosphino)benzoic acid and the acronym for a commercial alkoxyamine respectively.…”

Section: Carbazole-based Bopidysmentioning

confidence: 99%

Recent advances on carbazole-based photoinitiators of polymerization

Dumur

2020

European Polymer Journal

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Photoinitiators of polymerization that can be activated under visible light and low intensity are actively researched as these compounds constitute the next generation of photoinitiators that will replace the controverted UV-photoinitiators. Over the years, a family of compounds has been identified as being highly promising in light of its remarkable photoinitiating ability, photochemical stability, low cost and easiness to functionalize, namely carbazoles. In this review, an overview of the different carbazole-based photoinitiators reported to date is presented. Interestingly, carbazoles have mostly been used as electron donors in push-pull structures, as photosensitizers for iodonium salts, as ligands for ferrocenium salts or as chromophores for phenacyl onium salts. These different applications clearly demonstrate the versatility of this structure used as the elemental building block for the design of UV, near-UV or visible light photoinitiators.

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Section: Carbazole-based Bopidysmentioning

confidence: 99%

Recent advances on carbazole-based photoinitiators of polymerization

Dumur

2020

European Polymer Journal

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“…Im Allgemeinen stellte sich heraus, dass 2 d der beste Coinitiator für alle Systeme war, was durch den Vergleich der Polymerisationseffizienz zu Beginn und bei der endgültigen Umwandlung bestätigt wird. Es zeigt eine überraschend bessere Effektivität als das auf 2 b basierende System, das bisher als einer der effektivsten Iodonium‐Coinitiatoren angesehen wurde [44] . 1 d und 2 d funktionierten gut in Epoxiden ( M2 ), dem Vinylether M3 und dem Oxetan M4 a .…”

Section: Ergebnisse Und Diskussionunclassified

NIR‐sensibilisierte kationische und hybride radikalische/kationische Polymerisation und Vernetzung

Pang

Shiraishi²,

Keil

et al. 2020

Angewandte Chemie

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Die NIR-sensibilisierte kationischeP olymerisation verläuft effizient mit Epoxiden, einem Vinylether und Oxetan mit einem Heptacyanin als Sensibilisator und Iodoniumsalz als Coinitiator.D as Anion wurde von fluorierten Phosphaten (a: [PF 6 ] À , b:[PF 3 (C 2 F 5 ) 3 ] À , c:[PF 3 (n-C 4 F 9 ) 3 ] À ), Aluminaten (d: [Al(O-t-C 4 F 9 ) 4 ] À , e:[ Al(O(C 3 F 6 )CH 3 ) 4 ] À )u nd einem Methid [C(O-SO 2 CF 3 ) 3 ] À (f)a usgewählt. Der Vinylether zeigte die beste Effizienz in der kationischen Polymerisation, gefolgt von Oxetanen und Oxiranen. DFT-Rechnungen ermçglichten eine Abschätzung des elektrostatischen Potentials fürj edes Anion, wobei d eine bessere Reaktivitäta ls e und b bewirkte.D ie Bildung interpenetrierender Polymernetzwerke (IPNs) erfolgte unter Verwendung von Trimethylolpropantriacrylat und Epoxiden im Fall einer NIR-sensibilisierten Polymerisation erfolgreich mit d als Gegenion fürd as Initiatorsystem. Keine IPN-Bildung wurdeb ei UV-LED-Initiierung unter Verwendung der gleichen Monomere mit Thioxanthon/Iodoniumsalz beobachtet. Die Belichtung wurde mit neuen NIR-LEDs durchgeführt, die bei 805 oder 870 nm emittieren.

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“…[20][21][22] Both Lalevée 16,23,24 and Strehmel [25][26][27] and their coworkers have elegantly shown visible-to-NIR photocuring of acrylates and epoxies using Type II photosystems. For example, recent reports have shown that NIR polymerization chemistry can be either rapid (< 60 s) when using a high intensity (≥ 400 mW/cm 2 ) laser diode at 785 nm, 23 or reactive under low intensity (~30 mW/cm 2 ) LED light centered at ~790 nm, yet requiring longer exposure times (> 100 s) 25 . This apparent tradeoff between reaction rate and incident light intensity necessitates a closer examination of visible-to-NIR photosystems to advance state-of-the-art photocuring.…”

Section: Xanthenes and Cyanines Have Received Considerable Attention mentioning

confidence: 99%

Catalyst Halogenation Enables Rapid and Efficient Polymerizations with Visible to Near-Infrared Light

Stafford¹,

Ahn²,

Raulerson³

et al. 2020

Preprint

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Driving rapid polymerizations with visible to near-infrared (NIR) light will enable nascent technologies in the emerging fields of bio- and composite-printing. However, current photopolymerization strategies are limited by long reaction times, high light intensities, and/or large catalyst loadings. Improving efficiency remains elusive without a comprehensive, mechanistic evaluation of photocatalysis to better understand how composition relates to polymerization metrics. With this objective in mind, a series of methine- and aza-bridged boron dipyrromethene (BODIPY) derivatives were synthesized and systematically characterized to elucidate key structure-property relationships that facilitate efficient photopolymerization driven by visible to NIR light. For both BODIPY scaffolds, halogenation was shown as a general method to increase polymerization rate, quantitatively characterized using a custom real-time infrared spectroscopy setup. Furthermore, a combination of steady-state emission quenching experiments, electronic structure calculations, and ultrafast transient absorption revealed that efficient intersystem crossing to the lowest excited triplet state upon halogenation was a key mechanistic step to achieving rapid photopolymerization reactions. Unprecedented polymerization rates were achieved with extremely low light intensities (< 1 mW/cm<sup>2</sup>) and catalyst loadings (< 50 μM), exemplified by reaction completion within 60 seconds of irradiation using green, red, and NIR light-emitting diodes.

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Comparison between NIR and UV-Sensitized Radical and Cationic Reactivity of Iodonium Salts Comprising Anions with Different Coordination Behavior

Cited by 22 publications

References 21 publications

Recent advances on carbazole-based photoinitiators of polymerization

Recent advances on carbazole-based photoinitiators of polymerization

NIR‐sensibilisierte kationische und hybride radikalische/kationische Polymerisation und Vernetzung

Catalyst Halogenation Enables Rapid and Efficient Polymerizations with Visible to Near-Infrared Light

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