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International audience; The free radical polymerization of acrylates photo-initiated by push–pull dye-based photoinitiating systems (PISs) is widely investigated in previous works. As a supplementary investigation on push–pull dyes, here in this article, 25 push–pull structures comprising electron acceptors derived from indane-1,3-dione and 1H-cyclopenta[b]naphthalene-1,3(2H)-dione (series 1) and 4-dimethoxyphenyl-1-allylidene moieties (series 2) and various electron donors are synthesized and examined as innovative structures for photoinitiation. Among the two series of dyes examined in this work and by monitoring the polymerization processes by RT-FTIR measurements, four dyes are determined as exhibiting excellent photoinitiation performances and these dyes are selected to perform further studies concerning the chemical mechanisms occurring inside the three-component PISs, for example, steady state photolysis, fluorescence quenching measurements, and cyclic voltammetry. Markedly, their reactivity is also proved by photoinitiation performance upon sunlight. These results prompt us to develop high performance push–pull dyes as photosensitizers and sunlight can be used as a mild and ecofriendly light source, which can advantageously replace LEDs for the free radical photopolymerization in the future. Finally, the formation of 3D patterns with an excellent gradient of resolution is successfully achieved by the direct laser write (DLW) with/without silica fillers.

International audience; A series of 50 oxime esters bearing various substituents were designed and synthesized as photoinitiators (48 of them were never synthesized before and only B1 and B10 were reported). Good light absorption properties in the visible range were observed for these oxime esters. Some structures exhibited better photoinitiation abilities than diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) upon exposure to a LED@405 nm. Interestingly, PIs with methyl substituent on the oxime ester group have better photoinitiation performance than the others. Substituent effects were investigated through molecular orbitals calculations, the detection of CO2, and the investigation of the generated free radicals. The results demonstrate that the substituents on the oxime ester group exert major effects on the photoinitiation ability via the decarboxylation reaction. In addition, a chemical mechanism was proposed. 3D printed objects were successfully obtained by using the most reactive oxime ester as photoinitiator, and their thermal initiation behaviors of several oxime esters were also studied (dual thermal/photochemical initiator behavior).

Two new monoterpene esters, illigerates H and I (1 and 2), and six known compounds actinodaphine (3), bulbocupnine (4), stephanine (5), hypserpanine B (6), betulinic acid (7) and gallic acid (8) were obtained from the root of Illigera paviflora Dunn. Their structures were elucidated by spectroscopic analysis. Anti-inflammatory and α-glucosidase inhibitory activity of some isolated compounds were assessed. Two monoterpenes 1 and 2 exhibited weak in vitro anti-inflammatory activity (IC50 64.5 ± 5.3 and 79.2 ± 7.5 μM) while compounds 3–6 showed inhibition of α-glucosidase with IC50 values ranged from 87.17 to 118.74 μM.

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Currently, increasing attention has been focused on light-emitting diodes (LEDs)-induced photopolymerization. The common LEDs (e.g., LED at 365 nm and LED at 405 nm) possess narrow emission bands. Due to their light absorption properties, most commercial photoinitiators are sensitive to UV light and cannot be optimally activated under visible LED irradiation. Although many photoinitiators have been designed for LED-induced free radical polymerization and cationic polymerization, there is still the issue of the mating between photoinitiators and LEDs. Therefore, the development of novel photoinitiators, which could be applied under LED irradiation, is significant. Many photoinitiating systems have been reported in the past decade. In this review, some recently developed photoinitiators used in LED-induced photopolymerization, mainly in the past 5 years, are summarized and categorized as Type Ⅰ photoinitiators, Type Ⅱ photoinitiators, and dye-based photoinitiating systems. In addition, their light absorption properties and photoinitiation efficiencies are discussed.

Self-healing natural hydrogels still suffer from some issues such as unfit stiffness, poor healing efficiency, and lack of biocompatibility and hydrolytic stability, although they have been used to treat spinal cord injury (SCI). Herein, we develop the injectable, self-healing hyaluronate hydrogels based on multiple dynamic covalent bonds. The hydrogels exhibit fast gelation and excellent self-healing capability as well as injectability, favoring in situ formation for the hydrogels in target sites and maintaining their structural stability. Furthermore, the hydrogels are compatible with neural stem cells and various tissues and possess proper stiffness similar to nervous tissue. Interestingly, the hydrogel can induce neural differentiation of neural stem cells. In vivo experiment further illustrates that the hydrogels promote angiogenesis and remyelination as well as neuron regeneration, leading to the significant locomotor recovery of the SCI model rats. This injectable self-healing hyaluronic acid-based hydrogel is a potential candidate for nerve repair.

Degradable hydrogel adhesives with multifunctional advantages are promising to be candidates as hemostatic agents, surgical sutures, and wound dressings. In this study, hydrogel adhesives are constructed by catechol-conjugated gelatin from natural resource, iron ions (Fe3+ ), and a synthetic polymer. Specifically, the latter is prepared by the radical ring-opening copolymerization of a cyclic ketene acetal monomer 5,6-benzo-2-methylene-1,3-dioxepane and N-(2-ethyl p-toluenesulfonate) maleimide. By the incorporation of ester bonds in the backbone and the combination with quaternary ammonium salt pendants in the polymer, it exhibits excellent degradability and antibacterial property. Remarkably, doping the synthetic polymer into the 3,4-dihydroxyphenylacetic acid-modified gelatin network forms a semi-interpenetrating polymer network which can effectively improve the rigidity, tissue adhesion, and antibacterial property of fabricated hydrogel adhesives. Moreover, non-covalent bonds from coordination interaction between catechol and Fe3+ contribute to the fast self-healing of the developed hydrogel adhesives. These hydrogel adhesives with the multiple merits including the degradability, enhanced tissue adhesion, superior self-healing, good cytocompatibility, and antibacterial property show the great potential to be used as tissue adhesives in biomedical fields. This article is protected by copyright. All rights reserved.

International audience; The development of visible-light 3D printing technology by using water-soluble initiatingsystems has attracted widespread attention due to their potential applications in the manufactureof hydrogels. Besides, at present, the preparation of water-soluble photoinitiators suitable forvisible light irradiation (such as LEDs) still remains a challenge. Therefore, this work is devotedto developing water-soluble photoinitiators (PI)/photoinitiating systems (PIS) upon irradiationwith a LED @ 405 nm. In detail, a new water-slightly-soluble chalcone derivative dye [(E)-3-(4-(dimethylamino) phenyl)-1-(4-(2-(2-(2-methoxyethoxy) ethoxy) ethoxy) phenyl) prop-2-en-1-one] wassynthesized here and used as a PI with a water-soluble coinitiator, i.e., triethanolamine (TEA) whichwas also used as an electron donor. When combined together, a charge transfer complex (CTC) formedimmediately which exhibited excellent initiating ability for the free radical photopolymerizationof poly(ethyleneglycol)diacrylate (PEG-DA). In light of the powerful CTC effect, the [dye-TEA]CTC could not only exhibit enhanced water solubility and mechanical properties but could also beeffectively applied for 3D printing. This CTC system is environmentally friendly and cost-savingwhich demonstrates a great potential to prepare hydrogels via photopolymerization.This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY)

International audience; 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.

The investigation on the preparation of thick samples or fillers contained composites through the photopolymerization approach is still in its infancy due to the relevant light penetration issue an...

Nanodiamonds (NDs) are emerging as a promising platform for theranostic particles because they unite a spectrum of important properties into a single agent, including facile synthesis, small size, ...

This work reports several 1,5-diaminoanthraquinone (1,5-DAAQ)-based visible-light-sensitive photoinitiating systems (PISs), which can efficiently initiate the free radical photopolymerization of (m...

Diamino-anthraquinone derivatives [1,4-bis(isopropylamino)anthraquinone (SB36), 1-amino-4-anilinoanthraquinone (SB68), and 1,4-bis(p-tolylamino)anthraquinone (SG3)] exhibit absorption maxima in red light wavelength range and demonstrate broad ground state light absorption from ultraviolet to infrared light. When combined with coinitiators (e.g. iodonium salt), SB36-based photoinitiating systems exhibit the highest photoinitiation efficiency among all the studied diamino-anthraquinone derivative-based combinations for both cationic and free radical photopolymerization upon exposure to a red LED bulb. And SB36-based systems even demonstrate higher photoinitiating ability for free radical photopolymerization than that of previously studied 1,4-bis(pentylamino)anthraquinone (i.e. oil blue N)-based systems. In contrast, SG3-based photoinitiating systems show the lowest photoinitiation efficiency especially for free radical photopolymerization. Interestingly, the SB36/iodonium salt/N-vinylcarbazole system is a capable multicolor photoinitiating system able to initiate both cationic and free radical photopolymerization under the irradiation of UV to red LED bulbs and IR lamp. The photochemical mechanism associated with the production of cations and radicals from the diamino-anthraquinone derivative-based photoinitiating systems are investigated using steady state photolysis, fluorescence, laser flash photolysis, and electron spin resonance spin-trapping techniques.

Sequence-defined and degradable polymers can mimic biopolymers, such as peptides and DNA, to undertake life-supporting functions in a chemical way. The design and development of well-structured oligomers/polymers is the most concern for the public, even to further uncover their degradation process illustrating the degraded products and their properties. However, seldom investigation has been reported on the aforementioned aspects. In this work, the alternating photo-reversible addition-fragmentation chain-transfer (photo-RAFT) single unit monomer insertion (SUMI) of different N-substituted maleimides and thermal radical ring-opening SUMI of a cyclic ketene acetal monomer (i.e., 5,6-benzo-2-methylene-1,3-dioxepane (BMDO)) is adopted, to produce two degradable pentamers owing to the conversion of the exo-methylene group of BMDO into ester bonds along the main chains of the prepared products. Moreover, the possible degraded approach of pentamers is studied by combining high-resolution mass spectrometry (HRMS) and liquid chromatography-mass spectrometry (LC-MS) for the first time. This work also sheds light on the precise structures and cytotoxicity of SUMI products and their degraded compounds, proposing a detailed and credible outlook for biomedical applications.

Even though numerous organic dyes which are used as photoinitiators/photocatalysts during photopolymerization have been systematically investigated and collected in previous reviews, further designs of these chromophores and the developments in high-performance photoinitiating systems have emerged in recent years, which play the crucial role in 3D printing/Vat polymerization. Here, in this mini-review, various families of organic dyes that are used as newly synthesized photoinitiators/photocatalysts which were reported in literature during 2021–2022 are specified by their photoinitiation mechanisms, which dominate their performance during photopolymerization, especially in 3D printing. Markedly, visible light-induced polymerization could be employed in circumstances not only upon the irradiation of artificial light sources, e.g., in LEDs, but also in sunlight irradiation. Furthermore, a short overview of the achievements of newly developed mechanisms, e.g., RAFT, photoinitiator-RAFT, and aqueous RAFT using organic chromophores as light-harvesting compounds to induce photopolymerization upon visible light irradiation are also thoroughly discussed. Finally, the reports on the semiconducting nanomaterials that have been used as photoinitiators/photocatalysts during photopolymerization are also introduced as perspectives that are able to expand the scope of 3D printing and materials science due to their various advantages such as high extinction coefficients, broad absorption spectra, and having multiple molecular binding points.