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Nanocomposite materials are of great interest because of their superior properties. Besides the traditional synthesis methods that require high temperatures or toxic solvents, photopolymerization technology provides a simple, low-cost, and environmentally friendly route in preparing nanocomposites. In this research, the preparation of blue-light-sensitive triazine derivative-coated silica nanoparticles is presented. The resulting triazine-coated silica nanoparticles can play a dual role, i.e., acting as both photoinitiators to trigger photopolymerization reactions under the irradiation of LED@410 nm and fillers to endow the produced photopolymer nanocomposite materials with enhanced properties. Specifically, the triazine-coated silica nanoparticles can successfully induce free radical polymerization of trimethylolpropane triacrylate efficiently under the irradiation of LED@410 nm and demonstrate comparable photoinitiation ability to the triazine derivative-based photoinitiator. The effects of different loading amounts of triazine-coated silica nanoparticles toward the photopolymerization kinetics are also evaluated. By coating with the triazine derivative, the nanoparticles show good dispersion in the polymer matrix and significantly reduce the shrinkage of the samples during the photopolymerization. Moreover, the photocured nanocomposites exhibit enhanced migration stability and mechanical properties when an optimal amount of triazine-coated silica nanoparticles is added in the formulation.

International audience; Even though many organic dyes have been reported as photoinitiators for free radical polymerization in the literature, the design and development of novel photoinitiating systems based on organic dyes and adapted for visible light irradiation e.g. 405 nm LED and sunlight remains still challenging. Recently, major achievements in the development of high-performance photoinitiating systems based on organic dyes as light-harvesting compounds and their uses as photoinitiators for photopolymerization under visible-light irradiation have clearly emerged, giving rise to an abundant literature. In this review, an overview of the recently synthesized chromophores belonging to various families of organic dyes and used as photoinitiators of polymerization during the 2018-2021 period are systematically presented and classified into categories. Recent works have resulted in the development of new chromophores exhibiting remarkable visible light absorption properties and excellent photoinitiation abilities upon irradiation with LEDs and/or sunlight in free radical photopolymerization processes. These developments notably indicate that sunlight has the advantages of being a cheap, unlimited, broad emission spectrum, and energy-saving light source capable to be an efficient substitute to artificial light sources. The newly developed dyebased photoinitiating systems designed to initiate visible light-induced photopolymerization processes is likely to expand the scope of application of photopolymerization in modern sciences and technologies.

Silver nanoparticles (AgNPs) play a crucial role in biology and medical research as their extensive and efficient antibacterial activity and high electrical and thermal conductivity. However, the generation of them with a certain morphology under mild conditions (under air, solvent-free, room temperature, etc.,) is still a huge challenge. Herein, a simple one-step method is proposed to generate AgNPs in situ at room temperature under air by combining the photopolymerization process with the formation process of AgNPs within a few minutes. In detailed, 12 different dyes based on 2,5-diethylene-cyclopentan-1-one were first synthesized and used as high-performance type II photoinitiator. When using in conjunction of bis-(4-tert-butylphenyl) iodonium hexafluorophosphate (Iod) and ethyl 4-dimethylaminobenzoate (EDB), they can effectively boost the free radical photopolymerization (FRP) of polyethylene glycol diacrylate (PEG-DA) and the cationic photopolymerization (CP) of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (EPOX) upon irradiation with LED@405 nm. Furthermore, all the formulations containing/without AgNPs can be successfully used to perform the direct laser write experiment. However, even if all of the obtained 3D patterns exhibited reversible swelling performance and shape-memory effects caused by swelling and dehydration for the access to 4D printing, the presence of AgNPs will affect these properties.

It is highly desirable but challenging to develop humidity-responsive polymers with simultaneously improved mechanical properties and 3D printability, while still displaying fast, reversible and complex shape transformations. Herein, a facile and scalable supramolecular strategy of fabricating a new class of humidity-responsive polymers is proposed to address this issue. The multiple hydrogen-bond cross-linked network is used to provide high humidity sensitivity and shear-dependent rheological behavior. Further introduction of metal coordination bonds can not only improve mechanical strength and creep resistance, but also promote reversible humidity-driven actuation and generate viscoelastic hydrogel inks. This humidity-responsive polymer with these unique combined attributes enables the potential to fabricate diverse functional materials from artificial muscles, smart electronic and catalytic devices. Moreover, diverse arbitrary architectures with spatial thickness contrast exhibiting sophisticated biomimetic 4D printing process were manufactured by direct ink writing (DIW). This material and method not only provides a general route to tune versatile functionalities and intelligent responsiveness of polymeric actuators at the molecular level, but also provides new opportunities for building exceptional 4D printed products.

The design and development of versatile initiators for various types of polymerization reactions, i.e. thermal-/photo-crosslinked/controlled polymerizations, is highly interesting to fabricate high-performance polymer materials. Herein, we synthesized two N-aryl glycine-based initiators, N-(1-naphthyl)glycine (NNG) and N-(1-pyrenyl)glycine (NPYG), and investigated their ability to trigger thermal- or light-induced polymerizations. Relevant photochemical mechanisms to generate reactive species were studied by steady state photolysis, fluorescence, and electron paramagnetic resonance spin-trapping techniques. The synthesized N-aryl glycine-based initiators can act as monocomponent photoinitiators or be incorporated into multicomponent photoinitiating systems for free radical or cationic crosslinked photopolymerization under diverse blue LEDs. Moreover, NPYG was also capable of initiating reversible addition–fragmentation chain transfer polymerization under either thermal- or light-induced reaction.

Camellia oleifera Abel. is a cultivable plant with important economic value. It is very helpful for the scientific utilization, cultivation and preservation of germplasm resources through evaluating the genetic diversity. In this study, we estimated the genetic distances of 135 accessions of C. oleifera using ISSR and SCoT markers, respectively. The genetic dissimilarity coefficients of ISSR markers ranged from 0.56 to 1.00. And the accessions were divided into five groups. While the genetic dissimilarity coefficients of SCoT markers ranged from 0.62 to 1.00, the accessions were divided into four groups. The results demonstrated that C. oleifera germplasms perform a little genetic variation. This is the first report to evaluate the genetic diversity of different C. oleifera germplasms using the ISSR and SCoT molecular markers, and the results provide the useful foundation for plant breeding of C. oleifera.

Commercial or clinical tissue adhesives are currently limited due to their weak bonding strength on wet biological tissue surface, low biological compatibility, and slow adhesion formation. Although catechol-modified hyaluronic acid (HA) adhesives are developed, they suffer from limitations: insufficient adhesiveness and overfast degradation, attributed to low substitution of catechol groups. In this study, we demonstrate a simple and efficient strategy to prepare mussel-inspired HA hydrogel adhesives with improved degree of substitution of catechol groups. Because of the significantly increased grafting ratio of catechol groups, dopamine-conjugated dialdehyde-HA (DAHA) hydrogels exhibit excellent tissue adhesion performance (i.e., adhesive strength of 90.0 ± 6.7 kPa), which are significantly higher than those found in dopamine-conjugated HA hydrogels (∼10 kPa), photo-cross-linkable HA hydrogels (∼13 kPa), or commercially available fibrin glues (2-40 kPa). At the same time, their maximum adhesion energy is 384.6 ± 26.0 J m-2, which also is 40-400-fold, 2-40-fold, and ∼8-fold higher than those of the mussel-based adhesive, cyanoacrylate, and fibrin glues, respectively. Moreover, the hydrogels can gel rapidly within 60 s and have a tunable degradation suitable for tissue regeneration. Together with their cytocompatibility and good cell adhesion, they are promising materials as new biological adhesives.

Synthesis of high-value materials from natural resources via a simple chemical route is highly desirable due to the renewability and economy of biomass. Herein, we report the facile fabrication of ...

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.

International audience; In this article, a series of three-component photoinitiating systems (PISs) based on push-pull dyes are proposed. The systems are composed of the newly synthesized push-pull dyes and different co-initiators, namely an iodonium salt and a tertiary amine (ethyl dimethylaminobenzoate EDB). Photoinitiation abilities and photochemical properties of the different investigated photoinitiating systems were studied in detail. Notably, the mechanisms related to the polymerization efficiencies were determined using different techniques such as UV-visible absorption and fluorescence spectroscopy. Moreover, the photoinitiation abilities of the threecomponent systems for the sunlight-induced polymerization processes were also 2 examined, indicating that sunlight can act as an effective light source for photopolymerization. Finally, 3D patterns with a spatial resolution were successfully produced by the direct laser writing (DLW) approach, even with photosensitive resins containing silica fillers.

In this paper, seven new photoinitiators based on the benzophenone scaffold are specifically designed for photopolymerization under mild conditions upon light-emitting diode (LED) irradiation, i.e. four benzophenone-triphenylamine photoinitiators (denoted as BT1–BT4) and three benzophenone-carbazole photoinitiators (denoted as BC1–BC3). Noticeably, these structures have never been reported in the literature except for BT4, so these molecules have been specifically designed for photopolymerization applications. Remarkably, various combinations of chemical groups were investigated in this work to determine the effects of the substitution patterns on their photoinitiation abilities. The formation of benzophenone-triphenylamine and benzophenone-carbazole hybrid structures not only contributes to red-shift of the absorption maxima but also strongly enhances their molar extinction coefficients. The different compounds showed high photoinitiation abilities upon irradiation with an LED@405 nm, and the free radical photopolymerization of acrylates and the cationic polymerization of epoxides could be promoted with high final function conversions (e.g. 77% for the BT3/iodonium salt/amine system in free radical photopolymerization). Remarkably, these new PIs are also able to sensitize sulfonium salts upon irradiation @405 nm. Markedly, because of the benzophenone moiety, a monocomponent Type II PI behavior could be observed, e.g. these compounds could initiate the polymerization alone. Remarkably, benzophenone-triphenylamine compounds BT2, BT3 and BT4 exhibited better hydrogen abstraction abilities as Type II photoinitiators than the benchmark and commercial photoinitiator 2-isopropylthioxanthone in the absence of amines as well as in the presence of amines. Furthermore, the interaction between the photoinitiators and the different additives was investigated by steady state photolysis and fluorescence quenching experiments. The free radical generation in the BT3/amine system was confirmed by the electron spin resonance-spin trapping technique, and the chemical mechanisms related to the polymerization efficiency are discussed. In addition, the migration stability of BT3 was investigated, which was excellent due to its high molecular weight and its trifunctional character. Finally, the three-component photoinitiating system based on BT3 was successfully applied in 3D printing and the 3D patterns showed a good spatial resolution.

Five ketone derivatives (ketone-1~ketone-5) never synthesized in the literature and containing the same peripheral 1,3-bis(allyloxy)benzene substituting group but different central cyclohexanone cores were designed and proposed as high-performance photoinitiators for the free radical polymerization of acrylates under mild conditions. In combination with an amine and an iodonium salt (Iod), these ketones could initiate the photopolymerization of di(trimethylolpropane) tetraacrylate (TA), a tetrafunctional acrylates monomer, upon visible LED irradiation at room temperature in both thick films (1.4 mm) and thin films (25 μm) conditions. The distinct photopolymerization profiles of acrylates were studied by real time Fourier transform infrared spectroscopy, which indicated that the ketone-2/amine/Iod system could induce the highest final conversion of acrylates in thick films condition, while ketone-5/amine/Iod system could induce the highest final conversion of acrylates in thin films condition. Photoreactivity of ketone-2 and ketone-5 was systematically investigated by steady state photolysis and fluorescence quenching experiments in the presence of an amine and an iodonium salt, respectively. Moreover, eminent migration stability of ketones in photocured TA was observed. Finally, the ketone-2 and ketone-5-based three-component photoinitiating systems were applied for the laser writing experiments of TA, and macroscopically tridimensional patterns were fabricated with an excellent spatial resolution.

Four series of bis-chalcone compounds based on benzylpiperidinone, tetrahydrothiopyranone, pyridine or biphenyl central parts are designed and synthesized, enabling the development of ten bis-chalcones varying both by the central cores and by the substitution patterns (ortho, meta, para-positions) and the choice of the different groups attached to the peripheral substituents (alkoxy or allyloxy-substituted aromatic rings, thiophene, or ferrocene). In this series of ten bis-chalcones, eight of them were never synthesized before (i.e. only bis-chalcones 8 and 10 were already reported albeit never used as photoinitiators). These different dyes are proposed as new near-UV/visible light sensitive photoinitiators, in combination with an amine and an iodonium salt, to initiate the free radical photopolymerization (FRP) of PEG-diacrylate and the cationic photopolymerization (CP) of EPOX under LED@405 nm and LED@375 nm irradiation conditions. For the photopolymerization of acrylates carried out between thin films in laminate, all the bis-chalcones proposed in this work show higher photoinitiation abilities upon irradiation with a LED at 375 nm than at 405 nm, which is mainly due to their excellent light absorption properties in the near-UV region. Markedly, in contrast with the other two series of bis-chalcone compounds, pyridine-based bis-chalcones prove to be the most efficient photoinitiators, especially the bis-chalcones 5 and 9. Furthermore, all of them can also promote the cationic polymerization of epoxides upon LED irradiation at 375 nm, in the presence of an iodonium salt and an amine. More interestingly, some 3D patterns fabricated through the free radical polymerization of PEG-diacrylate demonstrate reversible swelling properties and shape-memory for access to 4D printing.

A series of Type I photoinitiators (PIs) based on a nitrocarbazole scaffold are developed and examined for the first time as photoinitiators for visible light photopolymerization. Three oxime esters (OXE-M, OXE-V, OXE-P) varying by the terminal groups (acetyl, acryloyl and benzoyl) attached via the oxime ester group are originally prepared. As a result of this, the three PIs exhibit excellent photoinitiation abilities in the presence of acrylate monomers upon LED@ 405 nm irradiation. Markedly, OXE-M exhibits a better performance than the benchmark Type I phosphine-oxide (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide TPO). Chemical mechanisms supporting the polymerization process with these PIs are investigated by steady state photolysis, molecular orbital calculations and real-time Fourier transformed infrared spectroscopy. After the cleavage of N─O bond and decarboxylation, free radicals are generated to initiate the free radical polymerization efficiently. Free radical photopolymerization of OXE-M is applied in direct laser write and 3D printing. Interestingly, OXE-M exhibits thermal initiation behaviors in monomers and can be used as dual photo and thermal initiators. The highly opaque feature of carbon fibers makes it difficult for light penetration, so dual photo/thermal curing are used here to prepare carbon fiber composites.

International audience; In this study, light-emitting diodes (LEDs) used as secure, low-cost and possessing long emission wavelengths irradiation sources were applied in photopolymerization. Seven novel anthracene derivatives (noted A1-A7) were proposed and evaluated in photosensitive systems. Three of them were never synthesized before (A1, A2 and A7) and the other derivatives were evaluated in other fields. Due to the in-silico design of molecular structure by molecular modeling, the proposed chalcone-anthracenes showed a broad absorption band in the visible region with favorable molar extinction coefficients. Photoinitiation abilities of the different photoinitiating systems were examined by the Real-Time Fourier Transformed Infrared Spectroscopy. The free radical polymerization of acrylates under LED@405 nm irradiation in laminate was evaluated and high final function conversions (FCs) were obtained in the presence of three-component photoinitiating systems based on chalcone-anthracenes/iodonium salt/amine. Meanwhile, the chalcone-anthracene derivatives exhibited high photoinitiation abilities in cationic photopolymerization of epoxides in combination with an iodonium salt under LED@405 nm irradiation. The final function conversions of epoxy using some anthracene/iodonium salt systems were even higher than the well-established dibutoxyanthracene (DBA)/iodonium salt benchmark system. In addition, due to the good light absorption properties, the cationic photopolymerization also was carried out in the presence of the chalcone-anthracene/iodonium salt systems under LED@470 nm or laser diode@447 nm irradiation (not possible to do with the reference DBA systems). Markedly, these derivatives were also able to sensitize sulfonium salts. The photochemical reactivity of anthracene derivatives was investigated through the steady state photolysis and fluorescence quenching experiments. Furthermore, the proposed interaction mechanisms of chalcone-anthracene derivatives and additives (iodonium salt and amine) were discussed using the free energy changes of electron transfer reactions. Interestingly, the cationic photopolymerization of A5/iodonium salt system was applied in 3D printing and the 3D patterns showed a good spatial resolution.

International audience; In this article, the free radical polymerization of acrylates was successfully achieved with a series of twelve push-pull chromophores comprising the N-ethyl carbazole-1-allylidene group as the electron-donating group. Using this strong donor, the resulting dyes, never synthesized before, could efficiently initiate the free radical photopolymerization of acrylates upon mild irradiation conditions e.g. using sunlight. These novel multi-component systems comprising the above mentioned push-pull dyes, a tertiary amine (ethyl dimethylaminobenzoate EDB) and an iodonium salt could act as efficient photoinitiating systems (PISs) in free radical polymerization (FRP), leading to the formation of 3D patterns with precise shapes under the direct laser write (DLW) approach. Among these new PISs, dyes 3, 6, 7 and 8 were selected due to their efficient photoinitiation performances for chemical mechanism studies including steady state photolysis, fluorescence quenching measurements, electron spin resonance (ESR) spin-trapping experiments and cyclic voltammetry. Markedly, their excellent photochemical reactivities prompted us to investigate the performance of these multi-component photoinitiating systems upon sunlight as an ecofriendly approach. As a result, this research proved that sunlight could be used as a potential light source that can advantageously replace LEDs when highly reactive push-pull dyes are used as photosensitizers for the free radical photopolymerization of acrylate resins. Finally, 3D patterns could be prepared with the new photocomposites, and silica fillers could be even incorporated within the photosensitive resins so that a gradient of resolution could be successfully demonstrated.

International audience; Herein, thirteen ketone derivatives composed of different cyclohexanone cores and peripheral moieties are designed, among which 10 ketones have never been synthesized before. These ketones are proposed as high‐performance photoinitiators for both free radical polymerizations and cationic polymerizations under soft conditions (visible LED@405 nm irradiation at room temperature). In combination with an amine and an iodonium salt (Iod), these ketones could be used in three−component photoinitiating systems to initiate the free radical polymerization of acrylates with distinct final conversions, among which the ketone−1/amine/Iod combination proved to be the most efficient one. Besides, the ketone−1/Iod two−component system also showed a remarkable photoinitiation ability for the cationic polymerization of epoxides. The photochemical sensitivity of ketone−1 in the presence of an amine and an iodonium salt was systematically investigated by steady state photolysis and excited state fluorescence quenching characterizations, respectively. Interestingly, macroscopic 3D patterns with excellent spatial resolution could be generated using the ketone−1/amine/Iod photoinitiating system for the free radical polymerization of acrylates. This high performance is also found useful to overcome the light penetration issue for the access to filled samples (silica) and the preparation of composites.

A series of eleven push&ndash, pull chromophores with specific structures have been designed for the free radical polymerization of acrylates, but also for the fabrication of photocomposites and 3D-printed structures. New photoinitiating systems comprising the different push&ndash, pull dyes showed excellent photochemical reactivities at 405 nm. Notably, polymerization reactions could be initiated with light-emitting diodes (LEDs) which constitute a unique opportunity to promote the free radical polymerization under mild conditions, i.e., low light intensity (e.g., sunlight) and under air. Photopolymerization is an active research field, and push&ndash, pull dyes have already been investigated for this purpose. Besides, it remains of crucial interest to investigate new reactive structures capable of efficiently initiating photopolymerization reactions. The plausible potential of these structures to act as efficient photoinitiators in vat photopolymerization (or 3D printing) and fabrication of photocomposites prompts us to select eleven new push&ndash, pull dyes to design multi-component photoinitiating systems activable with LEDs emitting at 405 nm. Precisely, a tertiary amine, i.e., ethyl dimethylaminobenzoate (EDB) used as an electron/hydrogen donor and an iodonium salt used as an electron acceptor were selected to behave as powerful co-initiators to construct three-component photoinitiating systems (PISs) with the different push&ndash, pull dyes. Among these new PISs, dye 8 and 9-based PISs could efficiently promote the free radical photopolymerization of acrylates upon exposure to a LED emitting at 405 nm also upon sunlight irradiation, highlighting their huge performance. Photoinitiating abilities could be explained on the basis of steady state photolysis experiments. Fluorescence measurements and electron spin resonance (ESR) spin-trapping experiments were also performed to obtain a deeper insight into the chemical mechanisms supporting the polymerization reaction and determine the way the initiating species, i.e., the radicals, are observed. Finally, two investigated dye-based PISs were applied to the fabrications of photocomposites. Three-dimensional patterns with excellent spatial resolutions were generated by the laser writing technique to identify the effects of photopolymerization of acrylates both in the absence and presence of fillers (silica). Interestingly, comparison between the 3D objects fabricated by the PISs/monomer systems and the PISs/monomer/filler photocomposites indicates that the newly designed photocomposites are suitable for practical applications.

Photopolymerization of acrylates under mild conditions is promising not only for academic research but also for industrial applications. However, it still remains a huge challenge to develop effective photoinitiators or photoinitiating systems for the free radical polymerization of acrylates under visible light-emitting diode (LED) irradiation. In this work, twelve novel ketone derivatives containing either tertiary amines or anthracenes as peripheral substituting groups (noted as Ami-1–Ami-6 and Anth-1–Anth-6) were elaborately synthesized and proposed for the polymerization of di(trimethylolpropane) tetraacrylate (TA), a tetrafunctional polyether acrylate, under both thin and thick film conditions under LED@405 nm irradiation. Remarkably, eight of the selected ketones (Ami-2, Ami-6, Anth-1–Anth-6) had never been synthesized before. In combination with an amine and/or an iodonium salt (Iod), these ketones could form distinct photoinitiating systems, among which the Ami-2/amine/Iod system could lead to the highest final conversion of acrylates under the thick film (∼1.4 mm) conditions while the Ami-6/amine/Iod system could induce the highest final conversion of acrylates under the thin film (∼25 μm) conditions. The photosensitivity of Ami-2 and Ami-6 was systematically investigated by steady state photolysis and fluorescence quenching experiments. Finally, the photocuring 3D printing technique was applied to TA, and both Ami-2- and Ami-6-based photoinitiating systems could be used to fabricate macroscopic 3D patterns with excellent spatial resolution.

International audience; Three monoamino-substituted anthraquinone derivatives (AAQs), that is, 1-aminoanthraquinone (AAQ), 1-(methylamino)anthraquinone (MAAQ), and 1-(benzamido)anthraquinone (BAAQ), incorporated with various additives [e.g., triethanolamine (TEAOH) and phenacyl bromide (PhC(═O)CH2Br)] are investigated for their roles as photoinitiating systems of free radical photopolymerization of (meth)acrylate monomers upon the exposure to UV to green LEDs. The AAQs-based photoinitiating systems, AAQ/TEAOH/PhC(═O)CH2Br and BAAQ/TEAOH/PhC(═O)CH2Br photoinitiators exhibit the highest efficiency for the free radical photopolymerization of DPGDA under the irradiation of blue LED and UV LED, respectively, which is consistent with the extent of overlap between their absorption spectra and the emission spectra of the LEDs. AAQ/TEAOH/PhC(═O)CH2Br photoinitiator can also initiate the free radical photopolymerization of different (meth)acrylate monomers, with an efficiency dependent on the chemical structures of these monomers.

International audience; In this study, a new generation of photoinitiator (PI) based on hybrid structures combining benzophenone and triphenylamine is proposed. Remarkably, these photoinitiators (noted monofunctional benzophenone‐triphenylamine (MBP‐TPA) and trifunctional benzophenone‐triphenylamine (TBP‐TPA)) are designed and developed for the photopolymerization under light‐emitting diodes (LEDs). Benzoyl substituents connected with triphenylamine moiety contribute to the excellent absorption properties which results in both high final conversions and polymerization rates in free radical photopolymerization (FRP). Remarkably, TBP‐TPA owning trifunctional benzophenone group exhibits a better Type II PI behavior than well‐known 2‐isopropylthioxanthone for photopolymerization under LED@365 and 405 nm irradiation. FRP and cationic photopolymerization of TBP‐TPA‐based systems are applied on 3D printing experiments, and good profiles of the 3D patterns are observed. The high molecular weight of TBP‐TPA associated with it trifunctional character can also be very interesting for a better migration stability of PIs that is a huge challenge. The development of this new generation of photoinitiators based on benzophenone hybrid structures is a real breakthrough. It reveals that the novel versatile photoinitiators based on benzophenone‐triphenylamine hybrid structures have great potentials for future industrial applications (e.g., 3D printing, composites, etc.).

Natural hydrogels are widely investigated for biomedical applications because of their structures similar to extracellular matrix of native tissues, possessing excellent biocompatibility and biodegradability. However, they are often susceptible to mechanical disruption. In this study, self-healing hyaluronic acid (HA) hydrogels are fabricated through a facile dynamic covalent Schiff base reaction. Dialdehyde-modified HA (AHA) precursor was synthesized, and then the AHA/cystamine dihydrochloride (AHA/Cys) hydrogels were formed by blending AHA and Cys at acidic pH levels. By varying Cys to AHA ratio, the hydrogel morphology, swelling and kinetics of gelation could be controlled. Gelation occurred fast, which was predominantly attributed to Schiff base reaction between the dialdehyde groups on AHA and amimo groups on Cys. The hydrogel exhibited improved mechanical properties with increase in Cys content. Furthermore, due to dynamic imine bonds, this hydrogel demonstrated excellent self-healing ability based on the stress after mechanical disruption. Also, it was found to be pH-responsive and injectable. Taken together, this kind of hyaluronic acid hydrogel can provide promising future for various biomedical applications in drug delivery, bioprinting, smart robots and tissue regeneration.

Nanodiamonds (NDs) are attracting increasing attention as drug delivery systems due to their outstanding mechanical and optical properties as well as excellent biocompatibility. However, the strong tendency to agglomerate limits their use in biological medium, especially when adsorbed hydrophobic compounds. Polymer coating is a convenient approach to enhance the colloidal stability and place therapeutic drugs. Here, we report an epoxy containing amphiphilic block copolymer poly(n-butyl methacrylate-co-polyglycidol methacrylate-block-poly(oligoethylene glycol methyl ether methacrylate)) (PBA-co-PGA-b-POEGMEMA) for coating NDs. The resultant polymer coating significantly reduced the particle size and enhanced the colloidal stability. The inner hydrophobic block was exploited to encapsulate hydrophobic anticancer drug-azonafide. The cytotoxicity of the azonafide-loaded NDs was evaluated by 2D and 3D models. Although azonafide encapsulation displayed higher IC50 than free azonafide in the 2D breast tumour cell culture model, the former showed accelerated cytotoxicity than free azonafide in the 3D breast multicellular tumour spheroids. The results indicate the amphiphilic polymer coated NDs could be a promising carrier for azonafide due to the facile synthesis protocol, the potential to reduce side effects and the enhanced toxicity.

International audience; One of the main challenges in the field of 3D printing/vat photopolymerization is the poor adaption of existing commercial photoinitiators (PIs) for the recently popular 3D printers with the irradiation wavelength at 405 nm. It is thus desirable to design and develop high-performance PIs which can work efficiently at this wavelength. In this work, different ketones were specifically designed by molecular mod-eling for good light absorption properties at 405 nm and the best theoretical structures showing intense violet/blue light absorption were synthesized for further investigation. The new proposed ketones were used in conjunction with different tertiary amines (e.g. ethyl dimethylaminobenzoate (EDB) or triethanol-amine (TEA)) and iodonium salt as photoinitiating systems (PISs) for the photopolymerization of trimethyl-olpropane triacrylate (TMPTA) and Ebecryl 40 (a tetrafunctional polyether acrylate) via an oxidation-reduction reaction mechanism. The results demonstrate that several ketone-based PISs can initiate free radical photopolymerization. The final conversions of Ebecryl 40 resin are higher than those of TMPTA, particularly in the presence of TEA. In addition, the light absorption properties and the photoinitiation mechanisms are also studied using UV-Visible absorption spectra, cyclic voltammetry, and fluorescence approaches. Moreover, the formation of the radicals is clearly determined by the electron spin resonance (ESR) spin-trapping experiments. Finally, the developed ketone-based three-component systems are applied to the generation of macroscopically stereoscopic letter patterns using the 3D printing technique. This research is expected to offer some fresh insights into photopolymerization reactions with three-component photoinitiating systems used in 3D printing. All this work shows that the in silico rational design of new photoinitiators by molecular modeling for specific wavelength (here 405 nm) and specific applications is a powerful tool for the development of high performance photosensitive resins.

Chitosan is a bioactive macromolecule with a wide variety of applications due to its excellent biological properties such as biodegradability, biocompatibility, and antibacterial activity, and so forth. This highlight focuses on the preparation of photoactive chitosans, the formation of photocrosslinkable chitosan hydrogels, and the related photopolymerization mechanisms. Moreover, the great potential applications of photocrosslinkable chitosan hydrogels for human tissues are also discussed. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1862–1871

The development of highly efficient and rapid photoinitiating systems for free radical photopolymerization under the irradiation of visible light has attracted increasing attention due to their widespread potential applications in, for example, 3D printing or dental polymers. Unfortunately, currently available visible-light-sensitive photoinitiators are not efficient enough for 3D printing applications suffering from low printing speeds. Here we describe a series of photoinitiating systems consisting of disubstituted aminoanthraquinone derivatives (i.e., 1-amino-4-hydroxyanthraquinone, 1,4-diaminoanthraquinone, and 1,5-diaminoanthraquinone) and various additives (e.g., tertiary amine and phenacyl bromide) toward the free radical photopolymerization of various acrylate monomers (such as commercial 3D resin) under the irradiation of blue to red LEDs. It is shown that the type and position of substituents of the aminoanthraquinone derivative can significantly affect its photoinitiation properties. The most e...

Despite their potential in various biomedical applications, photocrosslinkable hyaluronate hydrogels have often been limited by weak formation and unsatisfied mechanical strength which can be attributed to insufficient substitution of photoactive groups on the hyaluronate backbone and the oxygen inhibition effect. In this study, a new approach for the production of hyaluronic acid (MHA) with high acrylate group substitution (i.e. 2.27) is developed. It is based on the reaction of sodium hyaluronate and maleic anhydride in dimethyl sulfoxide, which has never been reported previously. Furthermore, the thiol-acrylate photopolymerization approach is employed to prepare maleiated hyaluronic acid/thiol-terminated poly(ethylene glycol) (MHA/TPEG) hydrogels which can overcome the oxygen inhibition effect. And the hydrogels possess porous structures, high swelling ratio, and tunable degradation rate. Specifically, the hydrogels could gel quickly within 15 s and demonstrate improved stiff (G′ = 4100 Pa). The in vitro cytotoxic evaluation demonstrates that the hydrogels are cytocompatible to L929 cells. As a result, the in-situ formable hydrogel scaffolds exhibit great potential for medical applications.

The investigation and clarification of the photoinitiation mechanism of novel systems are of importance for the design and development of compounds with high photoinitiation efficiency of photopolymerization. Some disubstituted aminoanthraquinone derivatives have been reported to exhibit interesting photochemical/photophysical properties and have the potential to act as high performance multicolor photoinitiators under the irradiation of various wavelengths of visible light from light-emitting diodes (LEDs). Herein, three disubstituted aminoanthraquinone derivatives, i.e., 1-amino-4-hydroxyanthraquinone, 1,4-diaminoanthraquinone, and 1,5-diaminoanthraquinone, with iodonium salt and N-vinylcarbazole as additives, have been investigated. Their photoinitiation mechanism was studied using fluorescence spectroscopy, laser flash photolysis, steady state photolysis, computational quantum chemistry, and electron spin resonance spin trapping techniques. Then, their photoinitiation ability for the cationic photopol...

N-Phenylglycine is normally used as a co-initiator and can be photodecomposed by different dyes under UV or visible light irradiation to generate radicals for the initiation of free radical photopo...

A ligand (A1) and four copper complexes (Cu1, Cu2, Cu3 and Cu4) were examined as photosensitizers in various photoinitiating systems (PISs). Interestingly, excellent photochemical reactivities were determined with the different compounds. Especially, notable photoinitiation abilities were determined upon exposure to LED@405 nm during the free radical polymerization of acrylates and the cationic polymerization of epoxides when combined with an iodonium salt and an amine. With regards to their remarkable reactivities, the different photoinitiating systems were applied to 3D printing experiments. By combining steady state photolysis and electron spin resonance spin trapping, the chemical mechanism supporting the polymerization processes could be fully detailed and proved. Among all PISs studied, the three-component PISs furnished the best monomer conversions during the free radical polymerization of trimethylolpropane triacrylate (TMPTA) and the cationic polymerization of (3,4-epoxycyclohexane)methyl 3,4-epoxycyclohexylcarboxylate (EPOX) monomers. The conversion process was monitored by real-time Fourier transform infrared spectroscopy (RT-FTIR). Three-component PISs based on A1, Cu1 and Cu2 showed better performances than those based on Cu3, Cu4 and the different two-component PIS (comprising only the iodonium salt or the amine) in FRP experiments. Based on the outstanding photoinitiation abilities of A1 and Cu1 with both TMPTA and EPOX, smooth and regular 3D patterns could be obtained by direct laser write experiments by generating interpenetrating polymer networks (IPN) with the blend of these two monomers.

The introduction of a strategy toward polymer/nanodiamond hybrids with high polymer grafting density and accessible polymer structural characterization is of critical importance for nanodiamonds' surface modification and bioagent attachment for their biomedical application. Here, we report a glycopolymer/nanodiamond hybrid drug delivery system, which was prepared by grafting amonafide-conjugated glycopolymers onto the surface of nanodiamonds via oxime ligation. Poly(1-O-methacryloyl-2,3:4,5-di-O-isopropylidene-β-d-fructopyranose)-b-poly(3-vinylbenzaldehyde-co-methyl methacrylate), featuring pendant aldehyde groups, is prepared via RAFT polymerization. The anticancer drug amonafide is conjugated to the polymer chains via imine chemistry, resulting in acid-degradable imine linkages. The obtained amonafide-conjugated glycopolymers are subsequently grafted onto the surface of aminooxy-functionalized nanodiamonds via oxime ligation. The molecular weight of the conjugated polymers is characterized by size-exclusion chromatography (SEC), while the successful conjugation and corresponding grafting density is assessed by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric aanalysis (TGA). Our results indicate that the mass percentage of amonafide in the polymer chains is around 17% and the surface density of polymer chains is 0.24 molecules/nm

Three-dimensional (3D) printing is a process of fabricating 3D objects by adding successive layers of materials (e.g. polymers) on top of each other. Among various 3D printing approaches, the photochemical approach is extremely attractive as objects can be produced via photopolymerisation reactions of monomers/oligomers, which possesses environmental, economical, and production benefits. In this approach, photoinitiators and monomers/oligomers are two of the most important components of photopolymers for 3D printing. Specifically, photoinitiators absorb the irradiation light of a 3D printer and initiate the photopolymerisation reactions of monomers/oligomers layer-by-layer to produce the designed 3D objects, while monomers/oligomers can determine the final properties of the printed products. In this review, commercial photoinitiators and monomers/oligomers applicable for 3D printing are presented. Moreover, the newly developed photoinitiators and monomers/oligomers (from 2015 to 2017) for 3D printing of polymer-based materials with various properties and the application in 3D bio-printing are also demonstrated.

Nanofibers based on natural polymers have recently been attracting research interest as promising materials for use as skin substitutes. Here, we prepared photocrosslinked nanofibrous scaffolds based on methacrylated chitosan (MACS) by photocrosslinking electrospun methacrylated chitosan/poly (vinyl alcohol) (PVA) mats and subsequently removing PVA from the nanofibers. We comprehensively investigated the solution properties of MACS/PVA precursors, the intermolecular action between MACS and PVA components, and the morphology of MACS/PVA nanofibers. Results indicated that the fiber diameter and morphology of the photocrosslinked methacrylated chitosan-based nanofibrous scaffolds were controlled by the MACS/PVA mass ratio and showed highly micro-porous structures with many fibrils. In vitro cytotoxicity evaluation and cell culture experiments confirmed that MACS-based mats with micro-pore structure were biocompatible with L929 cells and facilitated cellular migration into the 3D matrix, demonstrating their potential application as skin replacements for wound repair.

Light is one of the non-invasive stimuli which can be used in the spatiotemporal control of chemical reactions. Over the past decade, light has found wide applications in polymer science such as polymer synthesis, release of small molecules from polymers and polymeric photosensors etc. Reviews on light-regulated polymerisations have predominately focused on the free radical process. However, the marriage of light to non-radical polymerisations, e.g. ionic, ring-opening, metathesis, step-growth and supramolecular photopolymerisations, has also spurred tremendous research interest to develop materials. These kinds of non-radical photopolymerisations, compared to the free radical approach, are advantageous in overcoming oxygen inhibition, accessing novel polymer structures and fabricating degradable and dynamic polymers. The relevant light-regulation techniques involved in these polymerisations are usually based on photolinking reactions and photoactivation of latent species. These species produce initiators, catalysts or monomers upon light irradiation to manipulate polymer formation. These techniques have been successfully implemented to adapt conditional polymerisations under light, discover novel polymerisation methods and precisely control polymer structures. This review aims to highlight the recent progress in light-regulated non-radical polymerisations in the development of polymerisation techniques as well as the applications in materials science, emphasising the remaining challenges and promising perspective in the relevant fields.

A covalent organic polymer (COP) is prepared by crosslinking the photosensitizer 4,4',4'',4'''-(porphyrin-5,10,15,20-tetrayl)tetraaniline (TAPP) with 4,4'-(anthracene-9,10-diyl)dibenzoic acid (ADDA) via 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/4-dimethylaminopyridine coupling. The COP is further modified with a hydrophilic polymer, poly(poly(ethylene glycol) methyl ether methacrylate) by grafting-from reversible-addition-fragmentation chain transfer (RAFT) polymerization to enhance its solubility in various solvents. The modified COP can bind singlet oxygen through the formation of endoperoxide by ADDA upon the exposure to red light irradiation. Singlet oxygen can be then released via the photodynamic mechanism or the cycloreversion by endoperoxide when heated at 110 °C. These results open new possibilities for simultaneous generation of singlet oxygen by the photodynamic route and singlet oxygen carriers, demonstrating promise for treating hypoxic tumors.

International audience; A series of carbazole or triphenylamine based mono-chalcones, displaying either D–π-A or A–π-D–π-A architecture, have been designed and synthesized for intense absorption bands at around 405 nm with high molar extinction coefficients around 105 M−1 cm−1 corresponding to π–π* electronic transitions. Photosensitivity of the new photoinitiating systems composed of a chalcone and an iodonium salt (Iod) was investigated by UV-visible absorption and fluorescence spectroscopies, and their photoinitiation abilities were examined during the free radical polymerization of acrylates, whose polymerization kinetics were monitored by real-time Fourier Transform Infrared (RT-FTIR) spectroscopy upon irradiation with a LED@405 nm. In this work, a series of ten chalcones comprising a carbazole unit or a triphenylamine (TPA) group used as the electron donor for chalcones were specifically designed. Remarkably, nine of the proposed chalcones were never reported in the literature (never synthesized before). Only chalcone 7 was reported but only as a precursor for the design of pyrazolines for optical materials. As a result of this strategy, highly conjugated high-molecular-weight photoinitiators were obtained, displaying improved light absorption properties due to their extended polyaromaticity. These new photoinitiators offer new prospects for the design of novel and efficient photoinitiators. To evidence the interest of these new chalcones, 3D and 4D printing experiments were carried out with a polyethylene glycol (PEG)-diacrylate photosensitive resin comprising the best photoinitiating systems investigated. The shapes of 3D patterns can be reversibly modified by means of a thermal or hydrophilic response of PEG for a 4D activation.

The design of photoinitiating systems with excellent photochemical reactivities at 405nm LED is one of the obstacles to efficiently promote free radical polymerization in mild conditions (e.g., low light intensity, under air). Here, our actual search for new multicomponent photoinitiating systems at 405nm LED prompts us to develop new dyes based on push&ndash, pull structures. In the present paper, we chose two series of new dyes which possess indane-1,3-dione and 1H-cyclopenta naphthalene-1,3-dione groups as the electron-withdrawing groups, since they have the great potential to behave as sensitive and remarkable photoinitiators in vat photopolymerization/3D printing. When incorporated with a tertiary amine (ethyl dimethylaminobenzoate EDB, used as electron/hydrogen donor) and an iodonium salt (used as electron acceptor) as the three-component photoinitiating systems (PISs), and among a series of 21 dyes, 10 of them could efficiently promote the free radical photopolymerization of acrylates. Interestingly, steady state photolysis experiments revealed different behaviors of the dyes. Fluorescence experiments and free energy change calculations for redox processes were also carried out to investigate the relevant chemical mechanisms. Additionally, the formation of radicals from the investigated PISs was clearly observed by electron spin resonance (ESR) spin-trapping experiments. Finally, stereoscopic 3D patterns were successfully fabricated by the laser writing technique. In this work, the use of push&ndash, pull dyes based on the naphthalene scaffold as photoinitiators of polymerization is reported for the first time in a systematic study aiming at investigating the structure&ndash, performance relationship for irradiation carried out at 405 nm. By carefully selecting the electron donors used in the two series of push&ndash, pull dyes, novel and high-performance photoinitiating systems operating at 405 nm are thus proposed.

International audience; Six ketones (abbreviated as ketones 1-6) varying by the substitution pattern of the central cyclohexanones and the choice of the peripheral groups (thiophene or furane) were synthesized and proposed as unprecedented visible light sensitive photoinitiators, in combination with an amine and an iodonium salt, for the free radical polymerization of acrylates upon LED irradiation at 405 nm. For the photopolymerization of acrylates carried out as thin samples in laminate, all these ketones showed high photoinitiating abilities. Conversely, when tested as photoinitiators for thick samples, compared to the other 4 ketones, ketone 3 and ketone 5 both based onpiperidin-4-one as the central core and comprising furanes as peripheral groups proved to be the most efficient photoinitiators. Notably, the highest final polymerization conversion of Ebecryl 40, a tetrafunctional polyether acrylate, could be obtained using these two photoinitiators. The high photoreactivity of ketone 3 was highlighted by the steady state photolysis experiments. Meanwhile, ketone 3 could also promote the cationic polymerization of epoxides upon LED irradiation at 405 nm, in the presence of an iodonium salt. Interestingly, some 3D patterns could also be fabricated by free radical polymerization of Ebecryl 40 while using the ketone 3-based photoinitiating system.

International audience; A bifunctional benzophenone-carbazole-based photoinitiator BPC was designed from its molecular structure viewpoint. To get this, two benzoyl substituents were introduced as peripheral groups of carbazole so that a molecule in which two benzophenones were fused to one carbazole unit could be obtained in a one-step procedure. As a result of this combination, synergetic effects are thus attended. Interestingly, BPC could efficiently initiate the free radical photopolymerization (FRP) of acrylates without addition of any extra hydrogen donors demonstrating a monocomponent Type II behavior but also fast photoinitiation rates were obtained in the presence of an amine and/or an iodonium salt with a LED@365 nm. Meanwhile, BPC can also interact with the iodonium salt to generate cationic species for the cationic photopolymerization (CP) of epoxides. BPC was found as a versatile photoinitiator that can be used for both radical and cationic polymerizations. The best photoinitiating system (PIS) determined during the FRP tests was selected for 3D printing experiments. Steady state photolysis and fluorescence quenching experiments were carried out to verify the interaction between BPC and the different additives in the excited state. Electron spin resonance-spin trapping experiments successfully distinguished the free radicals generated by the different PISs and the proposed electron transfer mechanisms

Polydiacetylene (PDA) materials are appealing and gaining increasing research interest due to their outstanding chromatic transition and fluorescence enhancement effects upon exposure to various environmental stimuli. However, despite the photomask method, there are very few reports about the spatial controllable photopolymerization and subsequent 3D printing of PDA until now. Herein, for the first time, we reported the preparation of PDA photocomposite materials based on polyacrylate through the strategy of dual-wavelength polymerization and orthogonal chemistry. First, diacetylene (DA) monomers were homogeneously dispersed in acrylate resin. Then a violet light emitting diode (LED) (or laser diode) was used for the free radical polymerization of polyacrylate. Finally, UV irradiation was utilized to induce the 1,4-topopolymerization of PDA, which could show a successive blue to purple to red color transition in response to the gradient increment of temperature. Interestingly, instead of photomasks, we applied a 3D printing approach directly to this composite material and fabricated some macroscopic stereo patterns, which also illustrated thermochromic properties. This novel kind of functional photocomposite material would demonstrate a huge application prospect in many potential fields, including colorimetric sensing, information encryption, anticounterfeiting, and so on.

The design and development of photoinitiating systems applicable to UV or even visible light delivered from light-emitting diodes (LEDs) has been attracting increasing attention due to their great potential applications in various fields. Compared to the strategy of synthesizing novel compounds, the exploration of existing chemicals with interesting photochemical/photophysical properties for their usage as photoinitiators is more appealing and easily commercialized. Nevertheless, a number of compounds such as monoamino-substituted anthraquinone derivatives, which are intensively investigated for their photophysical and photochemical properties, have seldom been studied for their roles as photoinitiators under LED irradiation. Herein, three monoamino-substituted anthraquinone derivatives, that is, 1-aminoanthraquinone, 1-(methylamino)anthraquinone and 1-(benzamido)anthraquinone, are studied for their potential as photoinitiators. The photoinitiation mechanism of these monoamino-substituted anthraquinone derivatives, when combined with iodonium salt, is first clarified using computational quantum chemistry, fluorescence, steady-state photolysis, and electron spin resonance spin-trapping techniques. Then, their photoinitiation ability for the cationic photopolymerization of epoxide and divinyl ether monomers is also investigated.

Chalcones are well-known natural dyes, 18 different derivatives selected from the rational molecular design (i.e. through molecular orbital calculations) were synthesized. If used in conjunction with an amine (i.e. ethyl l, 4-(dimethylamino) benzoate, EDB) and an iodonium salt (bis(4-tert-butylphenyl) iodonium hexafluorophosphate, Iod) as photoinitiating systems (PISs), these dyes can initiate both the free radical polymerization of polyethylene glycol diacrylate (PEG-diacrylate) and the cationic polymerization of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (EPOX) via oxidation–reduction reaction mechanisms. Furthermore, among the 18 different suggested structures, except for dyes 9 and 10, which have been synthesized and used in other fields, the remaining 16 dyes have never been synthesized before. The photopolymerization efficiency of acrylates carried out under LED@405 nm are excellent both for thin films (the thickness is about 0.2 mm) and thick films (the thickness is about 2 mm). Furthermore, all of them can also boost the cationic polymerization of EPOX upon LED irradiation at 405 nm, in the presence of an iodonium salt and an amine. More interestingly, stereoscopic 3D patterns were successfully fabricated by the direct laser write (DLW) technique which demonstrated reversible swelling properties and reversible shape-memory effects induced via swelling and dehydration for the access to 4D printing.