Search Results (27)

As far as history tells, people have set efforts both to improve the conditions and to change the visual outfit of the skin, nails, and hair. The first information on nail cosmetics is found in ancient China and Egypt, where various nature-derived compositions were used for changing the colour of the nails. Nowadays more mechanically and chemically durable systems for nail polishes are elaborated. This review focuses on the latest achievements in the field of UV-curable nail polishes. Herein, the polymerization mechanisms of various systems (acrylates, as well as epoxides and thiols) occurring in nail polishes are described. Besides plausible side reactions of the polymerization process are characterized. Thus, the main drawbacks for forming a uniform, perfect layer are illuminated. For effective curing, the choice of photoinitiators may be crucial; thus, various types of photoinitiators as well as their main advantages and disadvantages are characterized. Ensuring effective adhesion between the substrate (human nail) and the polymer film is one of the challenges for the nail polish industry—thus the plausible interactions between the adhesion promoters and the keratin are described. Regarding the film-forming agents, a comprehensive overview of the composition of the traditional UV-curing nail polishes is provided, but the main emphasis is devoted to alternative, nature-derived film-forming agents that could introduce renewable resources into nail cosmetics. Additionally, this review gives short insight into the latest innovations in UV-curing nail cosmetics, like (1) nail polishes with improved pealability, (2) covalently polymer-bonded dyes and photoinitiators, thus reducing the release of the low-molecular compounds or their degradation products, and (3) UV-curing nail polishes as delivery systems for nail treatment medicine. Full article

In this work, photoinitiation systems based on dibenzo[a,c]phenazine sensitivity to visible light were designed for their potential application in dentistry. Modification of the structure of dibenzo[a,c]phenazine consisted of introducing electron-donating and electron-withdrawing substituents and heavy atoms into position 11. The synthesized compounds are able to absorb radiation emitted by dental lamps during photoinitiation of the polymerization process. In the presence of acrylates, dibenzo[a,c]phenazines show excellent photoinitiating abilities in systems containing an electron donor or a hydrogen-atom donor as a second component. The developed systems initiate the polymerization process comparable to a commercial photoinitiator, i.e., camphorquinone. Moreover, the performed studies showed a significant shortening of the polymerization time and a reduction in the amount of light absorber. This indicates that polymeric materials are obtained at a similar rate despite a significant reduction in the concentration of the newly developed two-component photoinitiating systems. Full article

Dyes based on quinoline and quinoxaline skeletons were designed for application as visible light photoinitiators. The obtained compounds absorb electromagnetic radiation on the border between ultraviolet and visible light, which allows the use of dental lamps as light sources during the initiation of the photopolymerization reaction. Their another desirable feature is the ability to create a long-lived excited state, which enables the chain reaction to proceed through the mechanism of intermolecular electron transfer. In two-component photoinitiating systems, in the presence of an electron donor or a hydrogen atom donor, the synthesized compounds show excellent abilities to photoinitiate the polymerization of acrylates. In control tests, the efficiency of photopolymerization using modified quinoline and quinoxaline derivatives is comparable to that obtained using a typical, commercial photoinitiator for dentistry, camphorquinone. Moreover, the use of the tested compounds requires a small amount of photoinitiator (only 0.04% by weight) to initiate the reaction. The research also showed a significant acceleration of the photopolymerization process and shortening of the reaction time. In practice, this means that the new two-component initiating systems can be used in much lower concentrations without slowing down the speed of obtaining polymer materials. It is worth emphasizing that these two features of the new initiating system allow for cost reduction by reducing financial outlays on both materials (photoinitiators) and electricity. Full article

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(M_UB) 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 M_UB 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. Full article

Photopolymerization offers a unique opportunity to convert liquid monomers to polymers using light as the activation source. Recently, major efforts have been devoted to developing visible light photo-initiating systems, and the search for new dyes that can be incorporated into photocurable resins and polymerize a resin within a few seconds is still ongoing. With the aim of exploring a maximum of structures to reach this goal, quinoxaline has been identified to be a promising scaffold for the design of UV-centered and visible light photo-initiating systems. In this review, an overview of the different quinoxaline-based dyes will be given. In order to evidence the interest in these structures, comparisons with reference systems will be given. Full article

Light-activated polymerization is one of the most important and powerful strategies for fabrication of various types of advanced polymer materials. Because of many advantages, such as economy, efficiency, energy saving and being environmentally friendly, etc., photopolymerization is commonly used in different fields of science and technology. Generally, the initiation of polymerization reactions requires not only light energy but also the presence of a suitable photoinitiator (PI) in the photocurable composition. In recent years, dye-based photoinitiating systems have revolutionized and conquered the global market of innovative PIs. Since then, numerous photoinitiators for radical polymerization containing different organic dyes as light absorbers have been proposed. However, despite the large number of initiators designed, this topic is still relevant today. The interest towards dye-based photoinitiating systems continues to gain in importance, which is related to the need for new initiators capable of effectively initiating chain reactions under mild conditions. In this paper we present the most important information about photoinitiated radical polymerization. We describe the main directions for the application of this technique in various areas. Attention is mainly focused on the review of high-performance radical photoinitiators containing different sensitizers. Moreover, we present our latest achievements in the field of modern dye-based photoinitiating systems for the radical polymerization of acrylates. Full article

Modern dentistry places great demands on the dental composites used for filling tooth cavities or treating cavitated tooth decay. The aim of the work was to modify the properties of composites by changing the initiators and co-initiators. This was achieved by using initiators based on a quinoxaline skeleton and co-initiators that are derivatives of acetic acid, which is an advantage of these photoinitiating systems due to the elimination of aromatic amines from the photocurable composition. The composites also differed in dental fillers. The effect of the compounds on the exothermicity of the photopolymerization process, the surface morphology of the obtained materials and the maximum compressive strength were determined. The photoinitiating capacity of the two-component systems was tested by the microcalorimetric method using the multifunctional monomer TMPTA, typical for dental filler compositions. The new photoinitiating systems show particularly good efficiency of free radical polymerization initiation, which occurs by the photoinduced intermolecular electron transfer (PET) mechanism. The comparison of the tested systems with camphorquinone, a photoinitiator traditionally used in dentistry, made it possible to observe a decrease in temperature during photopolymerization without a significant decrease in the polymerization rate or increase in photocuring time, as well as a better homogeneity of the surface of the obtained polymeric materials. This indicates that dye–acetic acid derivative systems may be useful in dental applications. Full article

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. Full article

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. Full article

Herein we report on the preparation of a bioactive glass (BAG)-based photocurable resin for the additive manufacturing of BAG scaffolds with high filler loadings. The preparation of glass/ceramics resins for stereolithography with high filler loading is always a challenge, especially for fillers with a high refractive index variance. Various photocurable resin compositions with and without bioactive glass fillers have been investigated to see the influence of bioactive glass on physical properties of the resin and resulting green body. The effect of concentration of monomers, reactive diluent, light absorber (Sudan orange G dye), photoinitiator (PI), non-reactive diluent, and fillers (BAG) on rheology and photocuring behavior of the resin and tomography of the resulting 3D structures have been investigated. The BAG contents affect the rheology of resin and influence the rate of the polymerization reaction. The resin compositions with 55–60% BAG, 10% PEG-200 (diluent), 1% of PI and 0.015% of the dye were found to be suitable compositions for the stereolithographic fabrication. A higher percentage of PI caused over-curing, while a higher amount of dye decreased the cure depth of the resin. The micro-computed tomography (µ-CT) and scanning electron microscopic (SEM) images of the resulting green bodies display a relatively dense glass scaffold without any visible cracks and good interlayer connection and surface finishing. These properties play an important role in the mechanical behavior of 3D scaffolds. This study will be helpful to prepare high density glass/ceramic slurries and optimize their printing properties. Full article

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 (λ_max = 350–410 nm; ε_max = 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. Full article

The popularity of using the photopolymerization reactions in various areas of science and technique is constantly gaining importance. Light-induced photopolymerization is the basic process for the production of various polymeric materials. The key role in the polymerization reaction is the photoinitiator. The huge demand for radical and cationic initiators results from the dynamic development of the medical sector, and the optoelectronic, paints, coatings, varnishes and adhesives industries. For this reason, we dealt with the subject of designing new, highly-efficient radical photoinitiators. This paper describes novel photoinitiating systems operating in UV-Vis light for radical polymerization of acrylates. The proposed photoinitiators are composed of squaraine (SQ) as a light absorber and various diphenyliodonium (Iod) salts as co-initiators. The kinetic parameters of radical polymerization of trimethylolpropane triacrylate (TMPTA), such as the degree of double bonds conversion (C_%), the rate of photopolymerization (R_p), as well as the photoinitiation index (I_p) were calculated. It was found that 2-aminobenzothiazole derivatives in the presence of iodonium salts effectively initiated the polymerization of TMPTA. The rates of polymerization were at about 2 × 10⁻² s⁻¹ and the degree of conversion of acrylate groups from 10% to 36% were observed. The values of the photoinitiating indexes for the most optimal initiator concentration, i.e., 5 × 10⁻³ M were in the range from 1 × 10⁻³ s⁻² even to above 9 × 10⁻³ s⁻². The photoinitiating efficiency of new radical initiators depends on the concentration and chemical structure of used photoinitiator. The role of squaraine-based photoinitiating systems as effective dyeing photoinitiators for radical polymerization is highlighted in this article. Full article

As a metal-free polymeric semiconductor with an absorption in the visible range, carbon nitride has numerous advantages for photo-based applications spanning hydrogen evolution, CO₂ reduction, ion transport, organic synthesis and organic dye degradation. The combination of g-C₃N₄ and polymer networks grants mutual benefit for both platforms, as networks are upgraded with photoactivity or formed by photoinitiation, and g-C₃N₄ is integrated into novel applications. In the present contribution, some of the recently published projects regarding g-C₃N₄ and polymeric materials will be highlighted. In the first study, organodispersible g-C₃N₄ were incorporated into a highly commercialized porous resin called poly(styrene-co-divinylbenzene) through suspension photopolymerization, and performances of resulting beads were investigated as recyclable photocatalysts. In the other study, g-C₃N₄ nanosheets were embedded in porous hydrogel networks, and so-formed hydrogels with photoactivity were transformed either into a ‘hydrophobic hydrogel’ or pore-patched materials via secondary network introduction, where both processes were accomplished via visible light. Since g-C₃N₄ is an organic semiconductor exhibiting sufficient charge separation under visible light illumination, a novel method for the oxidative photopolymerization of EDOT was successfully accomplished. As a result of the absence of dissolved anions during polymerization, so-formed neutral PEDOT is a highly viscous liquid that can be processed and post-doped easily, and grants facile coating processes. Full article

In this article, five new organic dyes based on the naphthalimide scaffold (Napht-1–Napht-5) were synthesized and tested as high-performance photoinitiators for both the Free Radical Photopolymerization (FRP) of acrylates and the Cationic Polymerization (CP) of epoxides using blue Light-Emitting Diodes (LEDs) as a safe irradiation source (LED @405 nm and 455). In fact, very good photopolymerization profiles (high final conversions and high polymerization rates) were obtained once these photoinitiators were combined with an Iodonium salt (Iod) or Iod/amine NPG and NVK). Remarkably, these dyes were able to generate interpenetrating polymer networks (IPN) by polymerization of a blend of monomers. These experiments were carried out to improve the polymerization profiles as well as the mechanical properties of the obtained materials. Due to their high photoinitiation abilities, these compounds were used in some applications such as photocomposite synthesis, direct laser write, and 3D printing experiments. To determine the chemical mechanisms, the photochemical/photophysical properties of these compounds were studied using different characterization techniques such as UV–visible absorption spectroscopy, steady-state photolysis, Fluorescence quenching, time-resolved fluorescence spectroscopy, FTIR spectroscopy, and cyclic voltammetry Full article

Versatile substituted electron-deficient trichloromethylarenes can easily be synthesized and combined with a Safranine O/triarylalkylborate salt to form a highly efficient three-component photo-initiation system that starts free radical polymerization to finally form holographic gratings with a single-pulsed laser. The mechanism of this photo-initiation most likely relies on an electron transfer from the borate salt into the semi-occupied HOMO of the excited dye molecule Safranine O, which after fragmentation generates an initiating alkyl radical and longer-lived dye radical species. This dye radical is most probably oxidized by the newly introduced trichloromethylarene derivative as an electron acceptor. The two generated radicals from one absorbed photon initiate the photopolymerization and form index gratings in a suitable holographic recording material. This process is purely photonic and does not require further non-photonic post treatments. Full article