Photoinitiation Ability Research Articles

Oxime esters: Potential alternatives to phosphine oxides, for overcoming oxygen inhibition in material jetting applications

Material jetting technology is emerging as a prominent technique within the additive manufacturing domain for printing multi-material objects. Despite its various advantages, including high printing resolution, oxygen inhibition remains the main issue for UV-curable materials. Oxime esters are interesting photoinitiators for this application due to their ability to undergo a photocleavage reaction followed by decarboxylation, limiting the diffusion of oxygen. A series of four commercially available oxime esters were studied as Type I photoinitiators, with the photoinitiating ability and photochemical properties of two of them never having been investigated before. Initially, their UV–visible absorption properties were studied, revealing significant absorption up to 420nm. Photopolymerization kinetic studies indicate that the oxime esters can outperformed benchmark photoinitiators such as phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO) by reaching around 80% of double bond conversion in 12µm layer under air (for O-16) against 60% for BAPO under the same conditions. Finally, the oxime esters were tested in 3D-inkjet printing applications, displaying highly promising results with tack-free surfaces.

Triphenylamine based oxime ester photoinitiator for LED-induced free radical photopolymerization and 3D printing

With the development of light-emitting diode (LED), it is increasingly important to design and prepare photoinitiators that can be used for LED excitation. We designed and synthesized four new LED oxime ester photoinitiators (TOXEs) based on the triphenylamine group. Among them, the maximum absorption wavelengths of TOXE-3 and TOXE-4 are red-shifted to 402 nm and 397 nm, and have high molar absorption coefficients (ε) of 24315 M-1cm−1 and 29915 M-1cm−1, respectively, which are higher than that of ethenone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl] ethanone 1-(O-acetyloxime) (OXE02, 342 nm, 21836 M-1cm−1), indicating that it can be used in LED polymerization. Investigating the photopolymerization properties of the TOXEs/α, ω-diacryloyl poly(ethylene glycol) (PEGDA) system, under LED@365 nm irradiation, the double bond conversion rate (DC) of TOXE-1 and TOXE-2 were 83 % and 92 %, which were higher than OXE02 (80 %). Under LED@405 nm irradiation, the DC of TOXE-3 and TOXE-4 are 80 % and 78 % respectively, which is higher than that of OXE02 (52 %). To improve the photoinitiation ability of TOXEs, a two-component photoinitiation system using bis(4-tert-butylphenyl) iodonium (Iod) as an additive was tested. The DC of TOXEs has been improved under different light sources. Under LED@480 nm irradiation, the final DC of TOXE-4/Iod/PEGDA is 83 %. In addition, TOXE-3 and TOXE-4 can be applied to the laser cladding deposition (LCD) 3D printers. At the same time, we conduct research and verification on the polymerization mechanism of TOXEs through steady-state photolysis and electron spin resonance spin trapping experiments (ESR-ST). In addition, cytotoxicity assay and thermal stability testing showed that TOXEs exhibited excellent biocompatibility and thermal stability.

Charge transfer complexes (CTCs) with iodonium salts: Efficient initiators for single/two-photon polymerization

Charge transfer complexes (CTCs), as a new type of photoinitiator system, exhibit excellent initiating abilities and are widely used in free radical polymerization. The reason is that it has safe photo or photo/thermal or dual initiator properties, which cannot be achieved by classical initiators. Thus, five novel iodonium salts (acceptors) and two amines (donors) capable of initiating thermal and photochemical polymerizations were investigated. The formations of the CTCs were assessed through their UV–visible (UV–vis) absorption spectra. The theoretical model study also attempted to show the relationship among the structure, reactivity, and efficiency of CTCs. Further explanation of the cause of this mechanism was provided by 1H NMR. The UV–vis photoinitiation ability of radical photopolymerization was also studied by real-time Fourier transform infrared spectroscopy and photo-DSC under LED@395–425 nm. The application of the newly developed initiating system in laser direct writing experiments at two-photon polymerization (780 nm) shows excellent spatial resolution performance. Such characteristic demonstrates that potential versatility can be applied in single/two-photon polymerization to manufacture high-precision materials.

3D Printed Ion-Responsive Personalized Transdermal Patch.

Microneedle patches are easy-to-use medical devices for transdermal administration. However, the insufficient insertion of microneedles due to the gap between planar patches and contoured skin affects drug delivery. Herein, we formulate a prepolymer for high-fidelity three-dimensional (3D) printed personalized transdermal patches. With the excellent photoinitiation ability of 2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine (Tz), a high-fidelity and precise microneedle patch is successfully fabricated. Upon irradiation of the white illuminator, the doped gold nanoparticles (AuNPs) in the patch release heat and promisingly induce sweat production. With the introduction of Na+, the dominant component of sweat, the curvature of the produced transdermal patch is observed due to the ion-induced network rearrangement. The alkanethiol-stabilized AuNP with an end group of a carboxyl group causes controlled drug release behavior. Furthermore, the irradiation-induced photothermal heating of AuNP can facilitate the sustainability of drug release thanks to the substantially increased particle size of AuNP. These findings demonstrate that the developed prepolymer is a promising candidate for the production of transdermal patches fitting the curvature of the body surface.

Synthesis of One‐Component Type II Visible‐Light‐Absorbing Chalcones Containing Fused Aromatic Rings and Investigation of Free Radical Photopolymerization Properties

AbstractThis paper presents four one‐component Type II visible‐light‐absorbing chalcones (CY10‐13) that containing various fused aromatic rings as its π‐conjugated moiety, that is a 2‐naphthalene moiety for CY10, 1‐naphthalene for CY11, benzofuran for CY12, and benzothiophene for CY13. The absorption region changes significantly when introducing various fused aromatic rings. However, they all exhibit good absorption properties ranging from 300 to 450 nm that can be well‐matched under ultraviolet (UV), 365 and 405 nm light irradiations. Furthermore, the structure–reactivity relationship is also studied through thermal, photochemical, electrochemical, and computation properties. Finally, all the chalcones demonstrate photoinitiating ability without additive additional hydrogen donor in their systems. Both of the CY11 and CY12 based photoinitiating formulations initiate sufficiently upon UV and light‐emitting diode (LED)@405 nm light exposures. Furthermore, triphenylamine‐substituted chalcone analogous (CY8) is added for comparison. Although CY10‐13 compounds have lower light harvesting regions than CY8, some of those new chalcones exhibit better photoreactivity. Thus, a chalcone containing fuses aromatic ring featuring straightforward synthesis as well as versatile absorption region and photoinitiating performance, has great potential in photopolymerization applications.

Study on the photoinitiation mechanism of carbazole-based oxime esters (OXEs) as novel photoinitiators for free radical photopolymerization under near UV/visible-light irradiation exposure and the application of 3D printing

In this work, twenty-two oxime esters bearing different functional groups and based on carbazole as the chromophore were designed and synthesized as Type I photoinitiators. Interestingly, all structures mentioned in this work have never been reported before (even for their synthesis). These oxime esters were found to have good light absorption properties in the UV–visible range, and especially at 405 nm which is a reference wavelength in photopolymerization. Noticeably, several structures showed better photoinitiation abilities than the benchmark photoinitiator i.e. diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), evidencing the interest of these structures. In order to investigate the photoinitiation mechanism of the two series of oxime esters differing by the position of the photocleavable groups, electronic absorption spectra were determined by molecular modeling and density functional theory calculations. Photopolymerization abilities of the different oxime esters and release of CO2 during the polymerization experiments were determined by Real-Time Fourier Transformed Infrared (RT-FTIR). Active free radicals were characterized by mean of Electron Spin Resonance Spin Trapping (ESR-ST) experiments. On the basis of these different complementary experiments, chemical mechanisms occurring during photopolymerization could be proposed. Experimental results showed that the decarboxylation reaction occurring subsequent to the photocleavage of oxime esters had a beneficial effect on the photoinitiation ability. Finally, 3D printed objects were successfully obtained by using oxime esters exhibiting the best photoinitiating abilities.

A New Strategy of Chemical Photo Grafting Metal Organic Framework to Construct NH2-UiO-66/BiOBr/PVDF Photocatalytic Membrane for Synergistic Separation and Self-Cleaning Dyes.

Photocatalytic membranes are typical multifunctional membranes that have emerged in recent years. The lack of active functional groups on the surface of membranes made of inert materials such as polyvinylidene fluoride(PVDF) makes it difficult to have a stable binding interaction with photocatalysts directly. Therefore, in this study, we developed a simple method to prepare NH2-UiO-66/BiOBr/PVDF(MUB) membranes for efficient dye treatment by grafting benzophenolic acid-functionalized NH2-UiO-66 onto the surface of membranes with photocatalytic properties under visible light irradiation using benzophenolic acid with photoinitiating ability as an anchor. The structural characteristics, photocatalytic properties, antifouling properties, and reusability of the composite membranes were investigated in subsequent experiments using a series of experiments and characterizations. The results showed that the benzophenone acid grafting method was stable and the nanoparticles were not easily dislodged. The MUB composite membrane achieved a higher dye degradation efficiency (99.2%) than the pristine PVDF membrane at 62.9% within a reaction time of 180 min. In addition, the composite membranes exhibited higher permeate fluxes for both pure and mixed dyes and also demonstrated outstanding water flux recovery (>96%) after the light self-cleaning cycle operation. This combination proved to improve the performance of the membranes instead of reducing them, increasing their durability and reusability, and helping to broaden the application areas of membrane filtration technology.

Photoinitiating Ability of Pyrene–Chalcone‐Based Oxime Esters with Different Substituents

AbstractWith the rapid development of new irradiation setups as well as the ongoing interest in 3D printing, photopolymerization is extensively studied during the last decades. In photopolymerization, a photoinitiator and/or photosensitizer play(s) a crucial role in the photoinitiation step as this component absorbs light, thus creating the initiating species. In this study, a series of 17 chalcone‐based oxime esters (OXEs) featuring the pyrene chromophore are designed, synthesized, and studied for their photoinitiation properties upon irradiation with visible light. Precisely, their photoinitiation abilities are examined during the free radical photopolymerization of acrylates under the irradiation of light‐emitting diode (LED) at 405 nm. In the series of oxime esters, five of them demonstrate excellent photoinitiation abilities. Their thermal initiation abilities are also examined. To improve their photoinitiation abilities, these type I photoinitiators are also tested as type II photoinitiators in two‐component photoinitiating systems using bis‐(4‐tert‐butylphenyl)iodonium or ethyl 4‐(dimethylamino)benzoate as additives. In this process, the OXE‐B/iodonium system shows the best photopolymerization. To develop the use of these chalcone‐based oxime esters, the best OXE is used as a monocomponent photoinitiating system in 2D laser writing at 405 nm. The design of composites using glass fibers or carbon fiber as fillers is also examined.

Photoinitiation Mechanisms of Novel Phenothiazine‐Based Oxime and Oxime Esters Acting as Visible Light Sensitive Type I and Multicomponent Photoinitiators

AbstractIn this work, three new photoinitiators, based on the phenothiazine scaffold as a chromophore and potentially bearing the oxime ester functionality as an initiating group are designed and synthesized for the free radical polymerization of acrylates, the cationic polymerization of epoxides, and the formation of interpenetrated polymer networks upon irradiation with a light emitting diode emitting at 405 nm. These phenothiazine‐based oxime and oxime esters revealed impressive photoinitiation ability manifested by excellent polymerization rates and high final reactive function conversions. Significantly, they can be used as both; one‐component (Type I) and two‐component photoinitiating systems. Photoinitiation mechanisms through which reactive species are produced are investigated by means of different complementary techniques including real‐time Fourier transform infrared spectroscopy, UV–visible absorption spectroscopy, electron spin resonance spectroscopy, fluorescence (steady state and time resolved), cyclic voltammetry, and molecular modeling calculations. Thermal initiation behavior of the different oxime esters is also studied by using differential scanning calorimetry, highlighting their dual thermal/photochemical initiation ability. Finally, 3D printed objects are successfully fabricated by conducting both direct laser writing and 3D printing experiments.

The Blue‐LED‐Sensitive Naphthoquinone‐Imidazolyl Derivatives as Type II Photoinitiators of Free Radical Photopolymerization

AbstractIn this work, new naphthoquinone‐based photoinitiators are synthesized and applied for the first time in free radical photopolymerization. In the presence of acrylate monomers, these PIs display excellent photoinitiation capabilities under blue‐light LED@405 nm irradiation in a two‐component photoinitiating system in which the additive is a common iodonium salt (bis‐(4‐tert‐butylphenyl)iodonium hexafluorophosphate ‐ Iod) or a tertiary amine (ethyl 4‐dimethylaminobenzoate ‐ EDB). In controlled tests, the polymerization performance of dye4/Iod is equal to or better than that of common commercial Type II photoinitiators (2‐isopropylthioxanthone and benzophenone). Meanwhile, only a trace amount of photoinitiator is required (as low as 0.05%) to initiate the photopolymerization. It is worth noting that some of these compounds can also be used in one‐component photoinitiating system (monocomponent Type II behavior) and exhibit high photoinitiation ability. A series of complementary characterization analyses of two new naphthoquinone dyes (i.e. dye 1 and dye 4) with very similar chemical structures are carried out to investigate the relevant photochemical mechanism. Finally, 3D printing experiments are carried out by a simple and convenient Direct Laser Write (DLW) technique.

A cyclopolymerizable, doubly Irgacure 2959 functionalized quaternary ammonium salt photoinitiator and its water-soluble copolymer with diallyldimethylammonium chloride

A novel cyclopolymerizable allyl–acrylate quaternary ammonium salt PI based on I2959 and its cyclocopolymer with DADMAC are synthesized and their water solubility, photoinitiation ability, migration stability and thermal stability is evaluated.

Photoinitiation abilities of indeno- and indoloquinoxaline derivatives and mechanical properties of dental fillings based on multifunctional acrylic monomers and glass ionomer

Photopolymerization is a rapidly expanding technology with a wide variety of applications, from imaging to biomedical uses. Here, we present enhanced photosensitization of polymerization by photoredox pairs based on indene- and indoloquinoxaline dyes and thiophenoxyacetic acid for dental applications. The photoinitiating ability of the two-component systems was tested using several multifunctional monomers of various structures typical for dental fillings. The new photoinitiating systems show excellent efficiency in initiating free radical polymerization which occurs by photoinduced intermolecular electron transfer (PET) mechanism. Modification of the dye structure by extending the chain of conjugated π bonds, the arrangement of aromatic rings and the type of heteroatom, allowed to change the spectroscopic properties of the tested compounds and use them as absorbers of light emitted by dental lamps. The improved mechanical properties of the cured polymers, i.e., lowering the temperature during photopolymerization and an increase in polymer hardness were observed for the proposed photoinitiating systems compared to the camphorquinone – photoinitiator traditionally used in dentistry. This indicates that the dye – thiophenoxyacetic acid systems may be useful as photoinitiators in dental applications. The undoubted advantage of these photoinitiating systems is the elimination of the toxic aromatic amines traditionally used as co-initiators from the dental composition. It was possible thanks to the use of thiophenoxyacetic acid. Its application does not reduce the polymerization rate and does not extend the photocuring time.

Photoinitiation Mechanism and Ability of Thioxanthone‐Based Versatile Visible Photoinitiators

AbstractThe development of visible photoinitiating systems is attracting increasing attention due to their great applications in various fields. Three thioxanthone (TX) derivatives differing by their substituent groups are investigated as photoinitiators (PIs) for visible photopolymerization. They can be used as one‐component PIs to initiate free radical polymerization. Furthermore, a two‐component system with an iodonium can initiate cationic polymerization and hybrid polymerization and could make interpenetrating polymer networks synthesis. The high efficiency of these systems is found as being worthwhile for photocomposites preparations. Moreover, the mechanism of these TX derivatives is clarified using computational quantum chemistry, fluorescence quenching, steady‐state photolysis, cyclic voltammetry, and electron spin resonance spin‐trapping techniques.

Indigo carmine: A base and neutral electrolyte-mediated photoinitiator for 3D printing in high fidelity

Volumetric additive manufacturing with light is an advanced technology in diverse conventional fields. However, with the raising awareness of environmental concerns and the growing interest in biomedical applications, the safety and water solubility of the existing photoinitiators are challenged. Herein, we developed a photoinitiating system based on a blue food colorant, i.e., indigo carmine. The indigo carmine-based photoinitiating system induced a rapid photochemical reaction and photobleaching under blue and green LEDs in the alkaline medium. The unprecedented photoinitiation ability of the indigo carmine-based photoinitiating system in terms of rate of photopolymerization and the final monomer conversion was achieved under the irradiation of low-intensity light sources. Subsequently, a sophisticated 3D printing in high fidelity was carried out and a 2D seashell was designed and printed with the function of 2D–3D reversible switching. These findings demonstrated that the indigo carmine-based photoinitiating system could resolve the safety and water solubility challenges and be involved in the 3D printing of biomedical materials.

Visible-Light-Sensitive Polymerizable and Polymeric Triazine-Based Photoinitiators with Enhanced Migration Stability

Photopolymerization has attracted great interest because of its mild reaction conditions, spatiotemporal controllability, cost efficiency, and fast speed. However, with the raising environmental awareness and the increasing attention to life and health, the leachability of photoinitiators has become a growing concern. In this research, a methacrylate functionalized triazine-based polymerizable visible light photoinitiator, 2-(((4-(2-(4,6-bis(trichloromethyl)-1,3,5-triazin-2-yl)vinyl)phenoxy)carbonyl)amino)ethyl methacrylate (CT) and its reversible addition–fragmentation chain transfer (RAFT) polymerized CT (pCT) were designed as the polymerizable and polymeric photoinitiators, respectively. The photoinitiation abilities of the investigated triazine derivatives were evaluated under violet LEDs. Due to the steric effect, pCT showed slightly reduced photoinitiation ability under both LED at 400 nm and 410 nm irradiation. Nevertheless, photopolymers initiated using CT and pCT showed excellent migration stability compared to those prepared by 2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine (MT) and 4-(2-(4,6-bis(trichloromethyl)-1,3,5-triazin-2-yl)vinyl)phenol (PT). Specifically, CT and pCT-based polymers prepared under the irradiation of LED at 400 nm exhibited only 1/3-fold and 1/14-fold of photoinitiators leachability, while 1/2-fold and 1/6-fold of photoinitiator leachability were obtained compared to the MT-based photocured polymers when using LED at 410 nm. The excellent migration stability of pCT reveals potential applications in the biomedical and food packaging fields.

5,12‐Dialkyl‐5,12‐dihydroindolo[3,2‐a]carbazole‐Based Oxime‐Esters for LED Photoinitiating Systems and Application on 3D Printing

AbstractIn order to expand the application of oxime‐esters (OXEs) and to introduce a one‐component photoinitiating system of high performance in visible light photopolymerization, a series of 5,12‐dialkyl‐5,12‐dihydroindolo[3,2‐a]carbazole‐based oxime‐esters with visible light absorption abilities is designed and synthesized. Notably, when irradiated with light‐emitting diodes at 405 nm, the proposed structures can undergo a direct cleavage of the NO bond followed by decarboxylation, generating free radicals capable to efficiently initiate free radical photopolymerizations (FRP). Furthermore, the new OXEs showed good thermal initiation abilities and can be used as dual photo and thermal initiators. An interesting structure/reactivity/efficiency relationship can be obtained by comparing the reactivity of the different radicals generated upon photoexcitation at identical chromophore but also by comparing the photoinitiating ability of the hexyl derivatives (1)–(10) with that of methyl derivatives (1′)–(10′) characterized by a lower solubility than the previous series in resins. Chemical mechanisms are studied through different techniques including real‐time Fourier transform infrared spectroscopy, UVvisible absorption spectroscopy, fluorescence (time‐resolved or steady‐state) as well as molecular modeling calculations. To finish, OXEs are incorporated in new photosensitive 3D printing resins, furnishing 3D objects with a remarkable spatial resolution.

Zeolite‐Reinforced Interpenetrating Polymer Network Initiated by Chalcone Based Photoinitiating System and Their Application in 3D/4D Printing

AbstractWith the rapid development of photopolymerization, the search for new near‐UV/visible light sensitive photoinitiating system (PIS) is one of the most interesting topics in polymerization area. In this work, a new PIS (chalcone dye/amine/iodonium salt) could efficiently and simultaneously initiate the free radical photopolymerization of polyethylene glycol diacrylate (PEGDA) and the cationic photopolymerization (CP) of 3,4‐epoxycyclohexylmethyl‐3,4‐epoxycyclohexanecarboxylate (EPOX) upon LED@405 nm irradiation to obtain interpenetrating polymer network (IPN). Furthermore, this PIS was employed in the photopolymerization of LTA‐5A zeolite filled interpenetrating polymer network composites (IPN, PEGDA/EPOX). Compared to the pure IPN, the depth of cure (DOC) for IPN with 50 wt% LTA‐5A remarkably increased by ca. 90%, which was the first time reported that DOC could increase with the increase of the filler content. 3D patterns with good resolution were manufactured through direct laser write technique, and those with high filler contents showed good water swelling property. Under hydrothermal stimuli, IPN composite with 50 wt% LTA‐5A exhibited a good 4D printing behavior. Therefore, not only this chalcone dye has a good photoinitiation ability for photopolymerization, but also the resulting IPN composites prepared with the photoinitiating system containing this dye have potential applications for 3D/4D printing and composites preparation.

Effect of Decarboxylation on the Photoinitiation Behavior of Nitrocarbazole-Based Oxime Esters

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).

Silyl Glyoximides: Toward a New Class of Visible Light Photoinitiators

AbstractMany academic and industrial works are carried out for the search of new classes of visible light photoinitiators. In the last decade, new Type I photoinitiator generating silyl, germyl, or stannyl radicals is elegantly reported; the chemical mechanisms being often associated with the cleavage of the C(═O)Si, C(═O)Ge, or C(═O)Sn bonds. In this context, silyl glyoxylates are also reported as dual Type I and Type II photoinitiators. Silyl glyoximides are proposed here as new near‐UV and blue light sensitive photoinitiators. The synthesis of such compounds as well as their light absorption properties is discussed. Their photochemical properties are studied through steady state photolysis experiments and molecular modeling data (i.e., through the calculations of the frontier orbitals, CC bond dissociation energies and triplet state energy levels). To finish, their photoinitiating ability upon near‐UV or blue light emitting diode light is examined in a benchmark methacrylate monomer blend (BisGMA/TEGDMA). Markedly, a Type I photoinitiator behavior is highlighted but better initiating properties are found in multicomponent systems in combination with iodonium salt and amine.

New BODIPY Dyes Based on Benzoxazole as Photosensitizers in Radical Polymerization of Acrylate Monomers.

A series of 2-phenacylbenzoxazole difluoroboranes named BODIPY dyes (1–8) was designed and applied as photosensitizers (PS) for radical photopolymerization of acrylate monomer. The light absorption within the ultraviolet-visible (UV–Vis) range (λmax = 350–410 nm; εmax = 23,000–42,500 M−1cm−1), that is strongly influenced by the substituents on the C3 and C4 atoms of phenyl ring, matched the emission of the Omnicure S2000 light within 320–500 nm. The photosensitizer possess fluorescence quantum yield from about 0.005 to 0.99. The 2-phenacylbenzoxazole difluoroboranes, together with borate salt (Bor), iodonium salt (Iod) or pyridinium salt (Pyr) acting as co-initiators, can generate active radicals upon the irradiation with a High Pressure Mercury Lamp which initiates a high-performance UV–Vis light-induced radical polymerization at 320–500 nm. The polymers obtained are characterized by strong photoluminescence. It was found that the type of radical generator (co-initiator) has a significant effect on the kinetic of radical polymerization of acrylate monomer. Moreover, the chemical structure of the BODIPY dyes does not influence the photoinitiating ability of the photoinitiator. The concentration of the photoinitiating system affects the photoinitiating performance. These 2-phenacylbenzoxazole difluoroborane-based photoinitiating systems have promising applications in UV–Vis-light induced polymerization.