Conjugated phenothiazine oxime esters as free radical photoinitiators

Ma, Xiaoyu; Gu, Renquan; Yu, Liujian; Han, Weixiang; Li, Jie; Li, Xiuyan; Wang, Tao

doi:10.1039/c7py00797c

Cited by 69 publications

(58 citation statements)

References 42 publications

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“…In addition to the carbonyl group, oxime‐ester is another efficient group that generates active initiation species . In particular, oxime‐ester undergoes photocleavage of an N−O bond to generate an active free radicals .…”

Section: Methodsmentioning

confidence: 99%

“…Some commercially available oxime‐esters have been used in colour filter resists to cure pigmented thick films, which require a high curing speed and a low failure quote . Some recent work has proven that the N−O bond of the oxime‐esters can cleave under visible light irradiation of a light emitting diode (LED) when incorporated into suitable chromophores . The subsequent irreversible decarboxylation can suppress the back electron transfer and reduce the recombination of the generated radicals, leading to enhanced initiation performance.…”

Section: Methodsmentioning

confidence: 99%

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Cleavable Unimolecular Photoinitiators Based on Oxime‐Ester Chemistry for Two‐Photon Three‐Dimensional Printing

Qiu

Zhu

et al. 2019

ChemPhotoChem

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The development of efficient two-photon initiators (2PIs) is critical to promote two-photon three-dimensional (3D) printing for market applications. On the basis of the photocleavage concept, several unimolecular 2PIs that contain coumarin moieties (as two-photon absorption chromophores) and oximeester groups (as initiation functional groups) were synthesized. Under visible light irradiation, the investigated oxime-esters, sensitive to a broad wavelength range from 400 to 460 nm, undergo direct photocleavage followed by decarboxylation, forming active free radicals to effectively induce polymerization. Interestingly, the photoinitiators exhibit good photobleaching properties, which makes them applicable for photopolymerization of thick materials and dental restorative materials. In twophoton 3D printing tests with acrylate formulations, the oximeester derivatives were used to build complex 3D microstructures with submicrometer or even nanometer spatial resolution. The initiator comprised of a conjugated coumarin and an oxime ester attached at the 3-position exhibited a low threshold laser power required for polymerization and had a broad processing window similar to a highly efficient 2PI in the literature.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Cleavable Unimolecular Photoinitiators Based on Oxime‐Ester Chemistry for Two‐Photon Three‐Dimensional Printing

Qiu

Zhu

et al. 2019

ChemPhotoChem

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“…More interestingly, the similar CQ‐based PIS (CQ/iodonium salt (i.e.,[4‐[octyloxy]phenyl]phenyliodonium hexafluoroantimonate)/EDB) was reported for the polymerization of epoxide under blue light conditions for an additive manufacturing approach (i.e., solution mask liquid lithography) . Recently, an increasing number of novel PISs have been emerging and exhibited high efficiency for free‐radical and/or cationic photopolymerization under visible light . These novel PISs are mainly synthesized with designated chemical structures.…”

Section: Introductionmentioning

confidence: 99%

1,2‐Diketones as photoinitiators of both cationic and free‐radical photopolymerization under UV (392 nm) or Blue (455 nm) LEDs

Zhang

Wang

Lalevée

et al. 2020

Journal of Polymer Science

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The photoinitiation abilities of three 1,2‐diketones [i.e., acenaphthenequinone (ANPQ), aceanthrenequinone (AATQ), and 9,10‐phenanthrenequinone (PANQ)]‐based photoinitiating systems [PISs, with additives such as iodonium salt, N‐vinylcarbazole (NVK), tertiary amine, and phenacyl bromide (R‐Br)] for cationic photopolymerization and free‐radical photopolymerization under the irradiation of ultraviolet (UV; 392 nm) or blue (455 nm) light‐emitting diode (LED) bulb are investigated. All 1,2‐diketones studied exhibit ground state absorption that match with the emission spectra of UV (392 nm) or blue LED (455 nm) better than that of the well‐known blue‐light‐sensitive photoinitiator camphorquinone (CQ). In particular, AATQ/iodonium salt/NVK can show high photoinitiating ability (with epoxide conversion yield >70%) under the UV light irradiation due to the effect of NVK. In addition, 1,2‐diketone/iodonium salt (and optional NVK) systems are capable of initiating free‐radical photopolymerization of methacrylates, with conversions of 50–58%. Furthermore, some 1,2‐diketone/tertiary amine (and optional R‐Br) combinations are found to demonstrate high efficiency to initiate free‐radical photopolymerization, and 71% of methacrylate conversion can be achieved with PANQ/tertiary amine/R‐Br PIS. Some 1,2‐ketone‐based PISs can even exhibit higher efficiency than the CQ‐based systems. The photochemical mechanism of the radical generation from the 1,2‐diketone‐based PISs is investigated and found to be consistent with the related photopolymerization efficiency. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 792–802

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“…The followed photodecarboxylation can suppress recoupling of the generated free radicals and the released CO 2 might reduce oxygen inhibition . Wang et al., reported a series of phenothiazine‐substituted oxime esters as photocleavable PIs sensitive to 405 nm laser diodes . Our recent work has proven that when integrating the oxime‐ester moiety into a visible light sensitive coumarin skeleton, the N−O bond can be cleaved under 450 nm LED light irradiation or even under 980 nm near infrared laser excitation with assistance of upconversion nanoparticles .…”

Section: Introductionmentioning

confidence: 83%

“…[22] Wang et al, reported a series of phenothiazine-substituted oxime esters as photocleavable PIs sensitive to 405 nm laser diodes. [23,24] Our recent work has proven that when integrating the oxime-ester moiety into a visible light sensitive coumarin skeleton, the NÀ O bond can be cleaved under 450 nm LED light irradiation [25,26] or even under 980 nm near infrared laser excitation with assistance of upconversion nanoparticles. [27] It should be noted that these asymmetric oxime-esters can produce only one active initiation species after photolysis because the initiation ability of the generated primary iminyl radicals is limited.…”

Section: Introductionmentioning

confidence: 99%

Conjugated Bifunctional Carbazole‐Based Oxime Esters: Efficient and Versatile Photoinitiators for 3D Printing under One‐ and Two‐Photon Excitation

Qiu

Naumov

et al. 2020

ChemPhotoChem

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The rapid development of 3D printing using visible light as an irradiation source requires efficient visible light photoinitiators to realize a fast and reliable 3D printing process. Based on the photocleavage concept, a series of symmetric bifunctional photoinitiators comprising oxime‐ester moieties as latent initiation functionalities and conjugated carbazole as chromophores was synthesized. The impact of substitution position and the types of radicals on photophysical and photochemical behavior was investigated via experimental tests combined with quantum‐chemical calculations. The conjugated carbazole‐based oxime esters exhibit broad absorption bands from 250 to 400 nm and an interesting photobleaching property was observed during photolysis. Under 405 nm LED irradiation, the photoinitiation efficiency of the novel photoinitiators is comparable to that of the commercial visible light photoinitiator TPO. A vertical resolution of 50 μm was obtained when using oxime esters as photoinitiators in DLP 3D printing to fabricate delicate objects. The A‐π‐D‐π‐A core structures impart sufficient two‐photon cross sections (102–136 GM) to the oxime esters, enabling the construction of complex 3D microstructures of nanometer spatial resolution with two‐photon 3D printing technology. Notably, the threshold energy of the formulation containing 4d is lower than that of the commercial two‐photon resists IP−L. Also, the thermal stability of the PIs (>160 °C) is sufficient for daily storage.

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Conjugated phenothiazine oxime esters as free radical photoinitiators

Abstract: Three novel phenothiazine-substituted oxime esters (Ph-PTZ-OXE, TPA-PTZ-OXE and CZ-PTZ-OXE) applicable to visible laser diodes (405 nm and 455 nm) were successfully designed and synthesised.

Cited by 69 publications

References 42 publications

Cleavable Unimolecular Photoinitiators Based on Oxime‐Ester Chemistry for Two‐Photon Three‐Dimensional Printing

Cleavable Unimolecular Photoinitiators Based on Oxime‐Ester Chemistry for Two‐Photon Three‐Dimensional Printing

1,2‐Diketones as photoinitiators of both cationic and free‐radical photopolymerization under UV (392 nm) or Blue (455 nm) LEDs

Conjugated Bifunctional Carbazole‐Based Oxime Esters: Efficient and Versatile Photoinitiators for 3D Printing under One‐ and Two‐Photon Excitation

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