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International audience; Photopolymerization is an active research field and recently, a great deal of efforts has been devoted to replace the energy-consuming UV irradiation setups by the popular and easily available energy-saving light-emitting diodes (LEDs). With aim at going a step further, sunlight can be used as an inexpensive and unlimited light source to perform polymerization processes. In this case, no energy is required anymore, and the use of photopolymerization for various outdoor applications becomes possible. Over the years, and with aim developing reliable photoinitiating systems, various dyes have been developed, enabling in the case of sunny days to efficiently promote polymerization processes. In this review, an overview on the different photoinitiating systems developed for polymerization processes done under sunlight or even daylight is provided. Polymerization efficiency is often compared to that obtained with artificial light sources, enabling to determine the efficacy of the photoinitiating systems under sunlight.

International audience; The surface modification of metal oxides by grafting an organic molecule allows the development of new specific properties on demand. In this work, we demonstrate the modification of the Yttria Tetragonal Zirconia Polycrystal (Y-TZP), which is a ceramic widely used in dental implantology, by polymer grafting of the surface in a three-steps protocol for tuning the wetting properties. The first step involved the preparation of zirconia pellet by sintering followed by their surface activation. In the second step, the organic initiator bearing a tertiary amine such as the N,N-dimethylamino group capable of initiating a radical photopolymerization reaction, was grafted onto the surface through a bisphosphonic acid functionality. In the last step, two monomers, namely methyl methacrylate and styrene, were photopolymerized on the zirconia surface by blue light irradiation.The chemical steps were monitored and characterized by X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE) and Atomic Force Microscopy (AFM). Wetting properties to different polar and nonpolar liquids and surface energies calculated with the Van Oss theory were found to vary systematically depending on the type of functionalization and grafting. This methodology is very promising for surface tuning of the dental ceramic.

We prepared a rhodamine-TEMPO chromophore-radical dyad (RB-TEMPO) to study the radical enhanced intersystem crossing (REISC). The visible light-harvesting chromophore rhodamine is connected with the TEMPO (a nitroxide radical) via a C–N bond. The UV-vis absorption spectrum indicates negligible electron interaction between the two units at the ground state. Interestingly, the fluorescence of the rhodamine moiety is strongly quenched in RB-TEMPO, and the fluorescence lifetime of the rhodamine moiety is shortened to 0.29 ns, from the lifetime of 3.17 ns. We attribute this quenching effect to the intramolecular electron spin–spin interaction between the nitroxide radical and the photoexcited rhodamine chromophore. Nanosecond transient absorption spectra confirm the REISC in RB-TEMPO, indicated by the detection of the rhodamine chromophore triplet excited state; the lifetime was determined as 128 ns, which is shorter than the native rhodamine triplet state lifetime (0.58 μs). The zero-field splitting (ZFS) parameters of the triplet state of the chromophore were determined with the pulsed laser excited time-resolved electron paramagnetic resonance (TREPR) spectra. RB-TEMPO was used as a photoinitiator for the photopolymerization of pentaerythritol triacrylate (PETA). These studies are useful for the design of heavy atom-free triplet photosensitizers, the study of the ISC, and the electron spin dynamics of the radical-chromophore systems upon photoexcitation.

Novel metal oxide/polymer composite photocatalysts prepared by photocuring with common metal oxide particles (ZnO or CeO2) and acrylic ester monomers have been investigated for the first time. Metal oxide particles were fully integrated with the acrylate polymer network based on the crosslink of poly ethylene glycol diacrylate (noted below as Poly-PEG) by photopolymerization upon mild light source (LED@405 nm) irradiation. The prepared metal/oxide composite showed excellent performance in the photodegradation of Acid Black dye (used as a benchmark pollutant) in an aqueous environment. Indeed, under UV lamp irradiation for 60 min, the degradation of Acid Black reached 59% and 56%, in the presence of 10 wt% ZnO/Poly-PEG and 3 wt% CeO2/poly PEG, respectively. Markedly, the new reported photocatalysts have offered much better performance over the conventional TiO2 photocatalytic material used as a control (39% degradation using 1 wt% TiO2/poly PEG). In turn, the new proposed metal oxide/polymer composites were further characterized by a range of analytical characterization methods, including the swelling test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), dynamic mechanical analysis (DMA), UV–visible diffuse reflectance spectroscopy, and electron spin resonance analysis. The results showed that the new photocatalysts demonstrated excellent water adsorption properties, high-temperature resistance, and excellent recyclability, which were very suitable for wide application and in line with the concept of green chemistry.

Photopolymerization is a growing field with an extensive range of applications and is environmentally friendly owing to its energy-efficient nature. Such light-assisted curing methods were initially used to cure the coatings. However, it has become common to use photopolymerization to produce 3D objects, such as bridges or dental crowns, as well as to cure dental fillings. In this study, polymer nanocomposites containing inorganic nanofillers (such as zinc nano-oxide and zinc nano-oxide doped with two wt.% aluminum, titanium nano-oxide, kaolin nanoclay, zirconium nano-oxide, aluminum nano-oxide, and silicon nano-oxide) were fabricated and studied using Real Time FT-IR to investigate the effects of these nanoadditives on the final conversion rates of the obtained nanocomposites. The effects of the fillers on the viscosity of the produced nanocomposites were also investigated, and 3D prints of the selected nanocomposites were presented.

International audience; The design of photoinitiating systems activable in the visible range and under low light intensity is an active research field supported by the vast applications of photopolymerization. In the search for new dyes that can exhibit panchromatic absorptions, anthraquinone has been identified as a promising scaffold. Over the years, numerous modifications have been carried out on this scaffold by molecular engineering, enabling to design water-soluble, panchromatic or photobleachable dyes. In this review, an overview of the recent advances concerning photopolymerization with anthraquinone-based photoinitiating systems is given.

In this study, capability of Terahertz (THz) spectroscopy for determination of thermal properties of phase change materials (PCM) in an acrylated polyurethane coating investigated. Spherical shaped mesoporous silica materials (MPSs) are prepared as a template for stearic acid (SA). SA was impregnated into MPSs for investigate its PCM properties. Surface of MPSs was modifed with 3-(Trimethoxysilyl)propyl methacrylate (MEMO) to add acrylate functionality to form covalently bond to polyurethane (PU)-based composite UV matrix to avert leakage problem. Finally, this resin was photopolymerized and its change in thermal properties was determined by both conventional Diferential Scanning Calorimetry (DSC) and THz. DSC results show that the heating process phase change enthalpy is measured between 20.83 J/g and 136.80 J/g, and the freezing process phase change enthalpy is found between 13.55 J/g and 181.13 J/g by DSC. The thermal properties of phase changing behavior of the sample were also analyzed by Terahertz Time Domain Spectroscopy (THz-TDS). Besides the phase changes THz spectroscopy has shown the temperature dependent variation in the host matrix, also fnal PCM sample. Comparison of the data suggest that THz Spectroscopy is a fairly strong technique for characterization of phase changing materials even in very complex resin environment and it is a strong complementary technique especially following the temperature dependent properties close to room temperature.

The development of multifunctional dressing materials with beneficial properties for wound healing has become a recent focus of research. Many studies are being conducted to incorporate active substances into dressings to positively impact wound healing processes. Researchers have investigated various natural additives, including plant extracts and apiproducts such as royal jelly, to enhance the properties of dressings. In this study, polyvinylpyrrolidone (PVP)-based hydrogel dressings modified with royal jelly were developed and analyzed for their sorption ability, wettability, surface morphology, degradation, and mechanical properties. The results showed that the royal jelly and crosslinking agent content had an impact on the physicochemical properties of the hydrogels and their potential for use as innovative dressing materials. This study investigated the swelling behavior, surface morphology, and mechanical properties of hydrogel materials containing royal jelly. The majority of the tested materials showed a gradual increase in swelling ratio with time. The pH of the incubated fluids varied depending on the type of fluid used, with distilled water having the greatest decrease in pH due to the release of organic acids from the royal jelly. The hydrogel samples had a relatively homogeneous surface, and no dependence between composition and surface morphology was observed. Natural additives like royal jelly can modify the mechanical properties of hydrogels, increasing their elongation percentage while decreasing their tensile strength. These findings suggest possible future applications in various fields requiring high flexibility and elasticity.

Paper is one of the oldest commodities used by mankind, having helped record its history throughout the ages. However, to talk about paper today, is to talk about something that goes beyond the simple matrix of cellulose fibers used as a support for printing and writing. Due to its biodegradability, recyclability, renewable character, and properties in general, paper is currently exploited in a wide range of applications, such as sensors or diagnostic papers. Yet, one of its most important applications is as a packaging material. To do this, papers are usually coated with a polymer in order to improve their water and air barrier properties. Most coating formulations are still based on polymers obtained from non-renewable sources, such as poly(ethylene-vinyl alcohol) (PEVOH) and polyvinylidene chloride (PVDC). In addition, these formulations rely on the use of volatile organic compounds (VOCs) as organic solvents (e.g. chloroform). With advances made in biomass refining, new biologically sourced and biodegradable polymers, such as poly(lactic acid) (PLA) and poly(hydroxyalkanoates) (PHAs), have been used to replace traditional polymers. However, despite their "greener" characteristics, even these polymers rely on application techniques that require the use of VOCs as solvents. An expedient way to functionalize paper, and of easy industrialization, is the application of photopolymerizable coatings. This type of coatings can be formulated without the use of traditional organic solvents, and the curing process is initiated by the incidence of light (usually UV), which can occur in a few seconds. Many of the monomers and other components used in the formulation of this type of coatings can come from renewable sources, also helping to reduce the current dependence on non-renewable sources. Therefore, the goal of this PhD was the functionalization of paper through the application of photopolymerizable coatings that would give this substrate new functionalities such as hydrophobicity and cholesteric properties. In this context, this work focused on the development of solvent-free formulations, giving priority to the use of renewable raw materials. The study started with the development of a solvent-free photopolymerizable coating based on a copolymer of two acrylic monomers, namely 2-ethylhexyl acrylate and isobornyl methacrylate in a molar ratio of 0.64/0.36, in order to obtain a paper with hydrophobic properties. Two formulations consisting of 50 and 60 wt% copolymer, a mixture of the monomers (in the same molar proportion as the copolymer), and the photoinitiator (PI) darocur 1173 were studied. The application of these formulations resulted in a significant increase in the hydrophobicity of the paper (water contact angle values greater than 120°, and a decrease in water adsorption with Cobb values of 11 g/m2), while maintaining (if not improving) the other properties of the paper, namely the mechanical and air barrier properties. In the same vein, a second solvent-free formulation was developed with the aim of also improving the hydrophobicity of the paper. The formulation was based on tung oil (a highly unsaturated vegetable oil) and Darocur 1173 (PI). The coated papers had their hydrophobicity significantly improved, evidenced by an increase in the water contact angle values from about 71 ° (uncoated paper) to 127 ° and a significant decrease in water absorption, as determined by the Cobb test, from 108 to 17 g/m2 after a curing time of only 15 s. Moreover, with this short curing time, the paper's optical properties (namely whiteness, gloss and opacity) were maintained, and its mechanical properties (namely tensile and burst strength) improved. The last formulation developed is part of a preliminary study, in which the cholesteric properties of aqueous hydroxypropylcellulose (HPC) mixtures were combined with a photopolymerizable system consisting of 2-hydroxyethyl methacrylate (HEMA, monomer) and benzophenone (PI). The aim of these formulations was to develop paper-based moisture sensors capable of changing their color when exposed to atmospheric moisture. The concentration of HPC (65, 68, and 68 wt%) and the HEMA:water ratio (1:2, 1.4:1, 1:1, 1:1.4, 1:2), were adjusted to produce cholesteric papers capable of exhibiting homogeneous color and appropriate moisture response. Preliminary test of exposure of said papers to atmospheres of high relative humidity (95 %) revealed that the color change (ΔE) increased with exposure time, being the color change clearly perceptible (ΔE between 13 and 16). However, further studies are needed in order to better adjust the moisture response of the developed sensors. In summary, the work developed throughout this thesis highlights the possibility of using conventional solvent-free photopolymerizable coatings to manufacture paper-based products with new functionalities. Not only can the formulations developed be easily applied to paper, but the possibility of using renewable materials and short irradiation times allows paper functionalization in an efficient, scalable and environmentally friendly way. This is undoubtedly a promising strategy for developing new paper products with innovative properties. O papel é uma das mais antigas comodidades utilizadas pela humanidade, tendo ajudado a registar a sua História ao longo dos tempos. Contudo, falar de papel hoje em dia, é falar de algo que vai além da simples matriz de fibras de celulose utilizada como suporte para impressão e escrita. Devido à sua biodegradabilidade, reciclabilidade, caráter renovável e propriedades em geral, o papel é atualmente explorado numa vasta gama de aplicações, como por exemplo, em sensores ou papéis de diagnóstico. No entanto, uma da sua aplicação mais importante é como material de embalagem. Para tal, os papéis são normalmente revestidos com um polímero de modo a melhorar as suas propriedades de barreira à água e ao ar. A maioria das formulações de revestimento baseia-se ainda em polímeros obtidos de fontes não renováveis, tais como o poli(álcool etileno vinílico) (PEVOH) e o poli(cloreto de vinilideno) (PVDC). Além disso, estas formulações dependem da utilização de compostos orgânicos voláteis (COV) como solventes orgânicos (ex. clorofórmio). Com os avanços alcançados na refinação da biomassa, novos polímeros de origem biológica e biodegradáveis, como o poli(ácido láctico) (PLA) e os poli(hidroxialcanoatos) (PHAs), têm vindo a ser utilizados para substituir os polímeros tradicionais. No entanto, apesar das suas características "mais verdes", mesmo estes polímeros dependem de técnicas de aplicação que requerem a utilização de COVs como solventes. Uma forma expedita de funcionalização do papel, e de fácil industrialização, é a aplicação de revestimentos fotopolimerizáveis. Este tipo de revestimentos pode ser formulado sem o uso dos solventes orgânicos tradicionais, sendo o processo de cura iniciado pela incidência de luz (por norma UV), que pode ocorrer em poucos segundos. Muitos dos monómeros e demais componentes usados na formulação deste tipo de revestimentos podem provir de fontes renováveis, ajudando também a reduzir a atual dependência em fontes não-renováveis. Portanto, o objetivo deste doutoramento foi a funcionalização do papel através da aplicação de revestimentos fotopolimerizáveis que conferissem a este substrato novas funcionalidades como hidrofobicidade e propriedades colestéricas. Nesse contexto, este trabalho centrou-se no desenvolvimento de formulações sem solventes, dando prioridade à utilização de matérias-primas renováveis. O estudo começou com o desenvolvimento de um revestimento fotopolimerizável sem solventes baseado num copolímero de dois monómeros acrílicos, nomeadamente o acrilato de 2-etilhexilo e o metacrilato de isobornilo numa proporção molar de 0,64/0,36, no sentido de obter um papel com propriedades hidrofóbicas. Foram estudadas duas formulações que consistiam em 50 e 60 wt% de copolímero, uma mistura dos monómeros (na mesma proporção molar que o copolímero), e o fotoiniciador (PI) darocur 1173. A aplicação destas formulações resultou num aumento significativo da hidrofobicidade do papel (valores de ângulo de contacto com a água superiores a 120 °, e um decréscimo da adsorção de água com valores de Cobb de 11 g/m2), mantendo (se não melhorando) as outras propriedades do papel, nomeadamente as propriedades mecânicas e de barreira ao ar. Na mesma linha, foi desenvolvida uma segunda formulação sem solventes com o objetivo de melhorar também a hidrofobicidade do papel. A formulação foi baseada em óleo de tungue (um óleo vegetal altamente insaturado) e Darocur 1173 (PI). Os papéis revestidos tiveram a sua hidrofobicidade significativamente melhorada, evidenciada pelo aumento dos valores do ângulo de contacto com água de cerca de 71 ° (papel não revestido) para 127 ° e pela diminuição significativa da absorção de água, determinada pelo teste Cobb, de 108 para 17 g/m2, após um tempo de cura de apenas 15 s. Além disso, com este curto tempo de cura, as propriedades óticas do papel (nomeadamente brancura, brilho e opacidade) foram mantidas e as suas propriedades mecânicas (nomeadamente resistência à tração e à rutura) melhoradas. A última formulação desenvolvida faz parte de um estudo preliminar, em que as propriedades colestéricas de misturas aquosas de hidroxipropilcelulose (HPC) foram combinadas com um sistema fotopolimerizável constituído por 2-hidroxietil metacrilato (HEMA, monómero) e benzofenona (PI). O objetivo destas formulações visou o desenvolvimento de sensores de humidade baseados em papel capazes de alterar a sua cor quando expostos à humidade atmosférica. A concentração de HPC (65, 68, e 68 % em massa) e o rácio HEMA:água (1:2, 1.4:1, 1:1, 1:1.4, 1:2), foram ajustados para produzir papéis colestéricos capazes de exibir uma cor homogénea e uma resposta adequada à humidade. O teste preliminar de exposição dos referidos papéis a atmosferas de elevada humidade relativa (95 %) revelou que a mudança de cor (ΔE) aumentou com o tempo de exposição, sendo a mudança de cor claramente percetível (ΔE entre 13 e 16). Contudo, é necessário realizar mais estudos de forma a ajustar melhor a resposta à humidade dos sensores desenvolvidos. Em suma, o trabalho desenvolvido ao longo desta tese destaca a possibilidade de utilizar revestimentos fotopolimerizáveis sem solventes convencionais para fabricar produtos à base de papel com novas funcionalidades. Não só as formulações desenvolvidas podem ser facilmente aplicadas no papel, mas a possibilidade de utilizar materiais renováveis e tempos de irradiação curtos permite a funcionalização do papel de uma forma eficiente, escalável e amiga do ambiente. Esta é sem dúvida uma estratégia promissora para o desenvolvimento de novos produtos de papel com propriedades inovadoras. Programa Doutoral em Engenharia Química

Il mio Progetto di dottorato si è incentrato sul potenziamento di strategie sintetiche in soluzione per la produzione di colloidi con applicazioni come materiali colloidali. Esso si è strutturato in due linee di ricerca all’apparenza differenti ma concettualmente interconnesse tra loro. In primo luogo, lo sviluppo di una procedura sintetica di nanocristalli colloidali CsPbBr3 che fosse intrinsecamente scalabile, versatile e affidabile ad ogni scala. L’aspetto fondamentale su cui verte è stata l’introduzione di un turbo-emulsore, il cui utilizzo non è mai stato riportato nel campo dei nanocristalli. Per prima cosa, abbiamo corroborato il suo contributo innovative rispetto all’agitazione magnetica generalmente utilizzata, dimostrando che per volumi superiori al litro, il suo utilizzo diventa indispensabile. Successivamente, abbiamo approfonditamente studiato l’impatto di differenti parametri sintetici sulle proprietà delle risultanti dispersioni colloidali, acquisendo un punto di vista completo e controllabile a nostro favore sul meccanismo con cui avviene il processo: incremento della viscosità del mezzo di reazione, effetto della temperature, sostituzione dei leganti acidi e amminici. Abbiamo inoltre ottimizzato un processo di recupero degli scarti di sintesi che permette di riutilizzarli quasi direttamente per riprodurre la sintesi, senza diminuire la qualità dei materiali ottenuti. Infine, abbiamo testato preliminarmente I materiali in celle solari, evidenziando una maggiore compatibilità con il campo dell’indoor, e abbiamo depositato una domanda di brevetto per scintillatori nanocompositi ultraveloci che preservano le loro proprietà sotto irradiazione da raggi gamma fino ad 1 MGy. La seconda linea di ricerca parallela consiste nello sviluppo di un approccio fotochimico per la trasformazione di micelle formate da surfattanti commerciali in oggetti nanometrici stabilizzati core-shell che possono essere applicati in rilascio controllato di farmaci, catalisi o imaging. Ci siamo avvalsi della formazione di un sistema semi-interpenetrato tra il surfattante ramificato tween 80, commerciale, economico e non tossico, e il co-surfattante designer APE-4 (2-(tetrahydropyranyl)oxy tetraethylene glycol methacrylate) di facile accesso sintetico, per stabilizzare lo specifico colloide associativo che si forma. Per prima cosa, abbiamo ottimizzato l’efficienza del processo di fotopolimerizzazione sotto irraggiamento a 365 nm, in modo che fosse più rapido dello sblocco del gruppo tetraidropiranico competitivo, con I seguenti metodi: utilizzo di un reattore fotochimico a flusso, accoppiamento di un fotoiniziatore molto efficiente con un opportuno sensibilizzatore, infine introduzione di un fotoiniziatore più polare, maggiormente compatibile con la shell micellare (4-HBP, 4-hydroxybenzophenone). L’ultimo aspetto, implementato con l’utilizzo di agitazione magnetica durante l’irraggiamento, ha dimostrato di raggiungere il 100 % di resa di fotopolimerizzazione. Per concludere, abbiamo esteso la generalità del metodo introducendo due ulteriori co-surfattanti, (AME-3, methoxy triethylene glycol methacrylate, and ABE-3, benzoxyl triethylene glycol methacrylate). Siamo passati ad un irraggiamento centrato intorno a 254 nm per evitare la necessità di un fotoiniziatore, estendendo la generalità e attivando la polimerizzazione radicalica direttamente sul doppio legame della funzionalità metacrilica. Per entrambe le specie, si è dimostrata la completa conversione a polimero e la resistenza della dispersione ottenuta alla dissoluzione da parte di un solvente organico. My research was centred on the enhancement of synthetic strategies via wet methods intended for production of colloids having applications as functional materials. The overall project is composed by two distinct but conceptually connected research lines. Firstly, the development of unprecedentedly scalable, versatile and reliable synthetic strategy for high quality colloidal CsPbBr3 nanocrystals. The key advantage of the method is the original introduction of a high shear homogenizer. We firstly corroborated the improvement with respect to generally used magnetic stirring, showcasing its requirement when working with volumes that exceed 1 L. Successively, we deeply studied the impact of processing parameters on the properties of colloidal dispersions to gain a full insight and completely rule over the synthetic mechanism: increased medium viscosity, temperature, acid and amine ligands substitution during synthesis. We also optimized a waste recovery process that allows to almost directly reuse unreacted species remaining after the synthesis to perform the reaction again and without decreasing output nanocrystals properties. Finally we preliminary tested these materials in solar cells, deducing better compatibility with indoor target and patented a new type of nanocomposite scintillator able to preserve its properties to gamma irradiation doses up to 1 MGy. The second research line deals with the development of photochemical approaches for the transformation of micelles of commercially available surfactants into crosslinked core-shell amphiphilic nano-hosts, intended for applications in controlled release, catalysis and imaging. We exploited the formation of a semi-interpenetrated network between the branched, cheap, commercial tween 80 and the photopolymerized co-surfactant APE-4 (2-(tetrahydropyranyl)oxy tetraethylene glycol methacrylate) to freeze the specific association colloid formed. We firstly optimized efficiency of photopolymerization process under 365 nm irradiation over the parasite tetrahydropyran cleavage testing photopolymerization under microflow chemistry conditions, then coupling a more efficient photoinitiator with a proper sensitizer, eventually introducing a more polar and compatible with pegylated shell photoinitiator (4-HBP, 4-hydroxybenzophenone). The last modification, along with the employment of magnetic stirring during irradiation, demonstrated to be the turning points to achieve 100 % yield of photopolymerization. In conclusion, we extended the generality of the method designing and using two further co- surfactants (AME-3, methoxy triethylene glycol methacrylate, and ABE-3, benzoxyl triethylene glycol methacrylate), with 254 nm irradiation to avoid the necessity of photoinitiation and directly exciting methacrylate group. For both species, 100 % yield was observed and the obtained dispersion demonstrated to resist to organic solvent dissolution.

Providing a 3D environment that mimics the native extracellular matrix is becoming increasingly important for various applications such as cell function studies, regenerative medicine, and drug discovery. Among the most critical parameters to consider are the scaffold’s complicated micro-scale geometry and material properties. Therefore, stereolithography based on photopolymerization is an emerging technique because of its ability to selectively form volumetric structures from liquid resin through localized polymerization reactions. However, one of the most important parameters of the scaffold is biocompatibility, which depends not only on the material but also on the exposure conditions and post-processing, which is currently underestimated. To investigate this systematically, microporous scaffolds with pore sizes of 0.05 mm3 corresponding to a porosity of 16,4% were fabricated using the stereolithography printer Asiga PICO2 39 UV from the widely used resins FormLabs Clear and Flexible. The use of various polymers is usually limited for cells because, after wet chemical development, the non-negligible amount of remaining monomers intertwined in the photopolymerized structures is significantly toxic to cells. Therefore, the aim of this research was to find the best method to remove monomers from the 3D scaffold by additional UV exposure. For this purpose, a Soxhlet extractor was used for the first time, and the monomers were immersed in different alcohols. A Raman microspectroscopy was also used to investigate whether different post-processing methods affect DC (cross-linking) to find out if this specifically affects the biocompatibility of the scaffolds. Finally, mesenchymal stem cells from rat dental pulp were examined to confirm the increased biocompatibility of the scaffolds and their ability to support cell differentiation into bone tissue cells.

Novel 3D printing techniques enable the development of medical devices with drug delivery systems that are tailored to the patient in terms of scaffold shape and the desired pharmaceutically active substance release. Gentle curing methods such as photopolymerization are also relevant for the incorporation of potent and sensitive drugs including proteins. However, retaining the pharmaceutical functions of proteins remains challenging due to the possible crosslinking between the functional groups of proteins, and the used photopolymers such as acrylates. In this work, the in vitro release of the model protein drug, albumin–fluorescein isothiocyanate conjugate (BSA–FITC) from differently composed, photopolymerized poly(ethylene) glycol diacrylate (PEGDA), an often employed, nontoxic, easily curable resin, was investigated. Different PEGDA concentrations in water (20, 30, and 40 wt %) and their different molecular masses (4000, 10,000, and 20,000 g/mol) were used to prepare a protein carrier with photopolymerization and molding. The viscosity measurements of photomonomer solutions revealed exponentially increasing values with increasing PEGDA concentration and molecular mass. Polymerized samples showed increasing medium uptake with an increasing molecular mass and decreasing uptake with increasing PEGDA content. Therefore, the modification of the inner network resulted in the most swollen samples (20 wt %) also releasing the highest amount of incorporated BSA–FITC for all PEGDA molecular masses.

Digital light processing (DLP) 3D printing is rapidly advancing and has emerged as a powerful additive manufacturing approach to fabricate analytical microdevices. DLP 3D-printing utilizes a digital micromirror device to direct the projected light and photopolymerize a liquid resin, in a layer-by-layer approach. Advances in vat and lift design, projector technology, and resin composition, allow accurate fabrication of microchannel structures as small as 18 × 20 µm. This review describes the latest advances in DLP 3D-printing technology with respect to instrument set-up and resin formulation and highlights key efforts to fabricate microdevices targeting emerging (bio-)analytical chemistry applications, including colorimetric assays, extraction, and separation.

Surface imprinting used for protein recognition in functional cavities is highly effective in imprinting biomacromolecules to avoid template encapsulation during the formation of a molecularly imprinted polymer (MIP) matrix. Herein, we introduce a facile surface-imprinting method based on two-step spin-coating and photopolymerization to design highly efficient imprinted sites on polymeric films to detect trypsin (TRY). Well-distributed template imprinting is successfully achieved for maximized sensing responses by controlling the composition of functional monomers and crosslinkers in the precursor solution and the concentration of TRY in the imprinting solution. The MIP film exhibits higher sensitivity (−841 ± 65 Hz/(μg/mL)) with a coefficient of determination of 0.970 and a higher imprinting factor of 4.5 in a 0.24 µg/mL TRY solution compared to the nonimprinted polymer (NIP) film. Moreover, the limit of detection and limit of quantification are calculated to be 25.33 and 84.42 ng/mL, respectively. Finally, the selectivity coefficient is within the range of 3.90–6.78 for TRY against other proteins. These sensing properties are superior to those of the corresponding nonimprinted polymer matrix. Thus, the proposed facile surface-imprinting method is highly effective for protein imprinting with high sensitivity and selectivity.

International audience; Visible light photopolymerization has extensively been studied during the last decades since alternatives to UV processes have to be found rapidly. Indeed, based on the Minamata Convention, Hg irradiation setups must be suppressed from industrial applications. Even if the use of visible light is beneficial in terms of depth of cure and safety for the manipulator, photopolymerization in water is still far aside to the other polymerization processes. At present, only few visible light photoinitiators are soluble in water, speeding down the development of greener polymerization processes. In this review, an overview of the recent advances on water-soluble photoinitiating systems is provided. Even if water-solubility is a key parameter to polymerize in water, the monomer conversion that can be achieved is also important. For these reasons, comparisons with reference photoinitiating systems soluble in water is provided.

This work demonstrated a workable approach for the synthesis of a re-healing polyaniline-modified epoxy resin coating material via photopolymerization. The prepared coating material exhibited low water absorption, allowing it to be used as an anti-corrosion protective layer for carbon steel. First, graphene oxide (GO) was synthesized through the modified Hummers’ method. It was then mixed with TiO2 to extend its light response range. The structural features of the coating material were identified using scanning electron microscopy (SEM), X ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT IR). The corrosion behavior of the coatings and the pure resin layer were tested by using electrochemical impedance spectroscopy (EIS) and the potentiodynamic polarization curve (Tafel). The presence of TiO2 reduced the corrosion potential (Ecorr) toward lower values in 3.5% NaCl at room temperature, which was due to the photocathode of titanium dioxide. The experimental results indicated that GO was successfully compounded with TiO2 and that GO effectively improved the light utilization capacity of TiO2. The experiments showed that the presence of local impurities or defects can reduce the band gap energy, resulting in a lower Eg for the 2GO:1TiO2 composite (2.95 eV) compared to that of TiO2 alone (3.37 eV). After applying visible light to the coating surface, the change in the Ecorr value of the V-composite coating was 993 mV and the value of Icorr decreased to 1.993 × 10−6 A/cm2. The calculated results showed that the protection efficiency of the D-composite and V-composite coatings on composite substrates was approximately 73.5 and 83.3%, respectively. More analyses revealed that under visible light, the coating had better corrosion resistance. This coating material is expected to be a candidate for carbon steel corrosion protection.

Biocompatible and conductive polymer hydrogels are the subject of intensive research in the bioengineering field because of their use in bioelectronic devices and for the fabrication of electro-responsive tissues and drug delivery systems. In this study, we report the synthesis of conductive composite hydrogels consisting of a poly(N-isopropylacrylamide) (PNIPAM) matrix embedding carboxyl-functionalized multi-walled carbon nanotubes (MWCNT-COOH) using a two-step photopolymerization method. Thermo-responsive hydrogels with controlled hydrophilicity and conductivity were prepared by varying the carbon nanotube concentration in the range 0.5–3 wt%. The thermal response of the PNIPAM-based composite hydrogels was measured by differential scanning calorimetry with both ultrapure water and PBS solution as swelling liquid. Results show that the endothermic peak associated with the temperature-induced volume phase transition (VPT) shifts to higher temperatures upon increasing the concentration of the nanotubes, indicating that more energy is required to dissociate the hydrogen bonds of the polymer/filler network. In PBS solution, the swelling ratios and the VPT temperatures of the composite hydrogels are reduced because of salt-induced screening of the oppositely charged polymer/filler assembly, and the electrical resistivity decreases by a factor of 10 with respect to the water-swollen hydrogels.

In this paper, epoxy-acrylate structural adhesives tapes (SATs) were obtained from Bisphenol A-based liquid epoxy resin and epoxy acrylic resins (EARs). A new method of EARs preparation, i.e., the free radical bulk photopolymerization process (FRBP), was studied in detail. The influence of methacrylic monomers (methyl methacrylate, ethyl methacrylate, butyl methacrylate, lauryl methacrylate, (2-acetoacetoxy)ethyl methacrylate) and vinyl monomers (N-vinylpyrrolidone and styrene) on the FRBP process of base monomers (i.e., butyl acrylate, glycidyl methacrylate and 2-hydroxyethyl acrylate) was investigated. The kinetics of photopolymerization process was monitored by photo-differential scanning calorimetry method. The properties of the obtained EARs (viscosity and average molecular weights), as well as monomers conversion using 1H NMR, were determined. It was revealed that styrene significantly decreases the photopolymerization rate and increases the final monomers conversion (+27%). However, the resulting tetrapolymers BA-co-GMA-co-HEA-co-STY have low molecular weights and low polydispersity (2.2). Methacrylate monomers with shorter aliphatic chains (

International audience; Photopolymerization under visible light has known major breakthroughs in recent years due to the development of new irradiation setups based on Light-Emitting Diodes (LEDs) enabling now to polymerize resins with low light intensities but also by the urgent need to develop efficient photoinitiating systems perfectly fitting the light sources currently under use in 3D printers. If the use of visible light is the key parameter to increase the thickness of the polymerized films, visible light photoinitiators are also strongly colored compounds that can adversely impact the future use of photopolymers for daily applications. Indeed, colorless coatings are highly desired by industry, what can not currently be achieved by use of visible light photoinitiators. To address this issue, the development of photobleachable photoinitiating systems has become an active research field. In this review, an overview of the recent advances on photobleachable photoinitiators is provided. Face to the difficulty to access to these highly desired structures, a wide range of structures have been explored and an overview of the different structures is given.

The dithiocarbamate groups are known to act as photoinitiators in the free radical polymerization of vinyl monomers. The photolability of this group is due to the rupture of the C – S bond by UV irradiation. The C – S bond is photo chemically cleaved at around 254 – 366 nm. Synthesis of polyacrylamide was initiated by the use of such photoinitiators through radical polymerization process. Living radical polymerization of acrylamide (AM) through the use of N,N-Diethyl dithiocarbamato-( 1,2 )-propanediol( DCPD ) was also studied. The photoinitiator DCPD was synthesized from sodium N,N-Diethyldithiocarbamate(NaSR) and 3-chloro-1,2-propanediol(CPD).The role of the monomer concentration and reaction time on the conversion of acrylamide to polyacrylamide(PAM) was investigated. It was found that percentage conversion of AM increased both with the rise in concentration of monomer and reaction time. The living radical nature of the polyacrylamide (PAM) was ascertained by the polymerization of acrylonitrile(AN) with PAM to form PAM-b-PAN block copolymer. The PAM and PAM-b-PAN were characterized by FTIR, 1H-NMR, Thermogravimetry.

To improve the performance of lead-free piezoelectric composites, the functionalization of the filler particles has been suggested as a successful strategy in several recent reports. The details of the functionalization process, however, are not clear, nor is its influence on the dielectric properties of the composites. This study reports a systematic investigation of the functionalization process parameters of barium titanate nanoparticles (BTONP) with 3-(trimethoxysilyl)propyl methacrylate (TMSPM) used as a linker to an acrylate-based matrix polymer. Functionalization process temperature, time, functionalization agent ratio, solvent, and catalyst influence on the functionalization degree were measured by thermogravimetric analysis (TGA), elemental analysis, and Fourier-transform infrared (FTIR) spectroscopy. Elevated temperature and average functionalization time led to the highest functionalization degree in the form of a TMSPM monolayer on the particle surface. Three solvents, with and without catalysts, were investigated and two types of functionalized BTONP were selected for composite manufacturing. To this end, the functionalized particles were used to manufacture 10 vol.% BTONP/photopolymer UV light-curable composite suspensions. After solidification of the suspensions by exposure to UV light, the microstructure and dielectric properties of the resulting composites were investigated. It was seen that functionalization improves the dispersion of particles, increases suspension viscosity, and decreases the curing depth and dielectric properties.

International audience; Photopolymerization is facing a revolution with the development of cheap and easily available LEDs that enable to polymerize in safe and energy-saving conditions. Bodipy constitutes a unique class of renowned dyes that are well-known for to their high photoluminescence quantum yields, their exceptional molar extinction coefficients combined with a narrow absorption and emission band. In the constant search for new photoinitiating systems activable under low-light intensity and in the visible range, bodipys have been identified as a promising scaffold for the design of photoinitiators. Recently, several difluoroborane derivatives such as boranils, squaraine-derived structures or 2phenacylbenzoxazole difluoroboranes have been proposed, expending the scope of application of photopolymerization. In this review, the different bodipys, boranils, squaraine-based difluoroborate complexes and 2-phenacylbenzoxazole difluoroboranes used to elaborate photoinitiating systems and reported to date are presented. Efficiency of the newly developed photoinitiators will be compared to that of reference photoinitiating systems.

In the last few years, 3D printing has evolved from its original niche applications, such as rapid prototyping and hobbyists, towards many applications in industry, research and everyday life. This involved an evolution in terms of equipment, software and, most of all, in materials. Among the different available 3D printing technologies, the light activated ones need particular attention from a chemical point of view, since those are based on photocurable formulations and in situ rapid solidification via photopolymerization. In this article, the chemical aspects beyond the preparation of a formulation for light-induced 3D printing are analyzed and explained, aiming at giving more tools for the development of new photocurable materials that can be used for the fabrication of innovative 3D printable devices. Graphical abstract

Σκοπός της παρούσας διπλωματικής εργασίας ήταν η αξιολόγηση του βαθμού πολυμερισμού μιας προθερμασμένης ρητίνης που χρησιμοποιήθηκε ως υλικό συγκόλλησης για έμμεσες αποκαταστάσεις σύνθετης ρητίνης τύπου επενθέτων. Οι συσκευές για τον πολυμερισμό της προθερμασμένης ρητίνης που εξετάσθηκαν ήταν δύο συμβατικές λυχνίες πολυμερισμού και ένα διοδικό λέϊζερ καθώς το διοδικό λέϊζερ μπορεί να είναι μια εναλλακτική πηγή φωτοπολυμερισμού. Η αξιολόγηση του βαθμού πολυμερισμού μέσω της εκτίμησης μετατροπής διπλών δεσμών άνθρακα της προθερμασμένης ρητίνης έγινε με τη συσκευή FTIR spectroscopy., The aim of this study was to evaluate the polymerization efficiency of a preheated resin composite used as a luting agent for indirect restorations light-cured by a blue diode laser. Photopolymerization was followed using three light sources, a diode laser (SiroLaser Blue), and two LED units (Bluephase Style and Valo), diode laser with appropriate setting parameters may be an alternative for photopolymerization of preheated resin composites indicated for luting of indirect composite restorations. Degree of conversion (DC) of the preheated resin composite was evaluated using Fourier transform infrared spectroscopy (FTIR).

Photocuring is a crosslinking process, widely employed to produce polymers in the form of film. As it is an environmentally friendly process, it is particularly interesting for the preparation of sustainable materials and composites. In this work, composite self-standing films were obtained combining microfibrillated cellulose (MFC) and photocured matrices. To understand the influence of the polarity and surface tension of the matrix on the properties of the composite, poly(ethylene glycol) diacrylate was selected as a hydrophilic matrix and soybean oil epoxidized acrylate as a hydrophobic matrix. Furthermore, the weight fraction of MFC also varied. The conversion and rate of the curing reaction, and the water vapor permeability were studied and discussed in the light of the morphology and composition of the composites.

Eine gestörte Knochenregeneration kann durch Krankheiten oder Unfälle hervorgerufen werden, was des Weiteren zum Verlust von Knochen führen kann. Tissue Engineering befasst sich mit der Entwicklung von Materialien, welche zur Herstellung von Implantaten für den Knochenersatz verwendet werden sollen, um die Knochenregeneration zu fördern. Diese Knochenersatzmaterialien können durch lithographiebasierte additive Fertigungsverfahren hergestellt werden. Hier sind (Meth)acrylate die derzeit am weitesten verbreiteten Monomere, da sie eine hohe Reaktivität und gute mechanische Eigenschaften aufweisen. Allerdings werden sie als reizend und teilweise zytotoxisch eingestuft, und ihre Abbauprodukte (Polysäuren) können das umliegende Gewebe schädigen. Daher werden stattdessen Vinylester (VE) verwendet, um diese Probleme zu umgehen. Leider zeigen diese eine verringerte Reaktivität, weshalb die Thiol-En-Polymerisation eingesetzt wird, um diese zu erhöhen. Darüber hinaus weisen die erhaltenen Netzwerke häufig eine hohe Sprödigkeit auf. Aus diesem Grund werden in dieser Arbeit zwei Konzepte zur Verbesserung der Materialeigenschaften, insbesondere der Zähigkeit, vorgestellt.Die Zugabe von z.B. hochmolekularen Polymeren zu einem Thiol-En-System auf VE-basis kann die Zähigkeit des Endmaterials verbessern. Aus diesem Grund wurden verschiedene modifizierte Additive synthetisiert und ihre Auswirkungen auf das Endpolymer bestimmt. Diese Additive basierten auf Poly(ɛ caprolacton), da es bereits als biologisch abbaubares und biokompatibles Polymer verwendet wird und sich in vorherigen Untersuchungen als Zähigkeitsverbesserer erwiesen hat. Um den Einfluss der Additive auf das fertige Polymer zu untersuchen, wurden Zugversuche, DMTA- und photorheologische RT-FT-NIR-Messungen durchgeführt. Diese Experimente zeigten einen Anstieg der Zähigkeit, alle Tgs lagen weit über der Körpertemperatur und diese Additive führten nicht zu einer signifikanten Verringerung der Reaktivität.Zusätzlich wurde die Herstellung von interpenetrierenden Polymernetzwerken (IPNs) betrachtet. Hier wurde das rigide Netzwerk auf seine (thermo)mechanischen Eigenschaften untersucht und anschließend optimiert. Ebenfalls wurde der Einfluss des flexiblen Netzerkes mit zunehmender Menge auf das rigide Netzwerk untersucht. Hierbei zeigten DMTA Messungen, dass alle Tgs weit oberhalb der Körpertemperatur lagen und die Zähigkeit der Materialien deutlich verbessert werden konnte. Diese Ergebnisse zeigten, dass die Verwenung von modifiziertem PCL als Zähigkeitsverbesserer und auch IPNs als Herstellungsverfahren für Knochenersatzmaterialien geeignet sind., Diseases or accidents can lead to disturbed bone regeneration or loss of bone. In order to promote bone regeneration, tissue engineering is concerned with the development of materials for manufacturing artificial bone replacement materials. These can be produced by lithography-based additive manufacturing technologies. In this area, (meth)acrylates are currently the most advanced monomers. They combine favorable reactivity and mechanical properties. However, they are irritating and sometimes cytotoxic, and their degradation products (poly acids) can damage surrounding tissue. Therefore, vinyl esters (VEs) are used to circumvent these problems. Unfortunately, they lead to a decrease in reactivity, which is why thiol-ene polymerization is used to boost it. In addition, the networks are often highly brittle. This work presents two concepts to improve the material properties, especially the toughness. On the one hand, high molecular weight polymers can be added to a vinyl ester-based thiol-ene system to improve the toughness of the final material. Therefore, different modified toughness-enhancing additives were synthesized. These additives were based on poly(ε caprolactone), as it is already used as a biodegradable and biocompatible polymer and has been shown to be a toughness-enhancing motif. Tensile tests, DMTA measurements, and RT-FT NIR photorheological measurements were performed to investigate the influence of toughness enhancers on the final polymer. These experiments showed increased elongation at break with no loss in tensile strength. It was also demonstrated that all Tgs were far above body temperature and that the addition of toughness enhancers did not significantly decrease reactivity. In addition, the formation of interpenetrating polymer networks (IPNs) has been investigated. The hard network was investigated for its (thermo)mechanical properties and subsequently optimized. Furthermore, the flexible network was generated, and its influence on the hard network with increasing amounts was determined. Here, excellent results were generated as well. The glass transition temperatures were above body temperature, and the toughness of the materials could be significantly increased. These results demonstrate the applicability of modified PCL as a toughness enhancer and IPNs as a suitable method for manufacturing bone graft substitutes.

The possibility of exploiting visible light to induce polymerizations is extremely appealing from a technological point of view as it improves the sustainability of the overall process. To achieve this objective, it is necessary to employ single- or multicomponent systems containing a photoinitiator, and in some cases, a photosensitizer in combination. Due to their long-lived excited states and reversible redox properties, transition metal complexes are a valid choice to be applied in photoinitiating systems, often exhibiting enhanced conversions compared to purely organic compounds. This review presents an overview of the transition metal complexes exploited in photopolymerization reactions. Particular attention will be devoted to recent applications in 3D printing, highlighting the possible challenges that need to be faced to achieve highly efficient and more sustainable processes.

3D-Druck und Frontalpolymerisation sind zwei hochaktuelle Themen in Industrie und Wissenschaft mit schier endloser Anwendungsvielfalt. Für beide spezialisierten Technologien stellt die kationische Polymerisation ein leistungsfähiges Werkzeug dar, um ausgehend von verschiedenen Monomeren ein breites Feld von Materialien herzustellen. Epoxide werden häufig verwendet, da diese Monomerklasse eine gute Haftung auf den meisten Materialien, eine hohe Beständigkeit gegen Chemikalien und definierte Materialeigenschaften bietet. Iodoniumperfluorierte Antimonate und Tetraphenylborate sind die am weitesten verbreitete Klasse von Photoinitiatoren, die in Frontalpolymerisation verwendet werden, während die Sulfonium-Äquivalente aufgrund hoher thermischen Stabilität in 3D Druckanwendungen hervorstechen.Im ersten Teil dieser Arbeit wurden Atome aus den Gruppen 14 bis 16 des Periodensystems der Elemente als neuartige Kationen in Onium-basierten Photoinitiatoren untersucht, da die Einführung einer positiven Ladung und die daraus resultierende Umwandlung in Oniumsalze gut erforscht ist, viele Klassen umfasst und diese leicht zugänglich sind. Unter Verwendung handelsüblicher Epoxidharze zeigen Thiopyrylium-, Bismutonium- und Pyryliumsalze eine gute Reaktivität und hohen Epoxidgruppenumsatz in der klassischen kationischen Photopolymerisation. Andererseits ergeben sich durch die Einführung von Bismut- und Sauerstoff-basierten Oniumsalzen neue vielversprechende Initiatorkandidaten für die Frontalpolymerisation. Der Vorteil Bismuthonium-basierter Systeme liegt in der hervorragenden Lagerstabilität der Formulierungen, die per Frontalpolymerisation auf Knopfdruck ausgehärtet werden können.Der zweite Teil konzentriert sich auf die Erforschung neuartiger Anionen in Onium-basierten Photoinitiationen. Umfangreiche Forschungen in den Bereichen ionische Flüssigkeiten und Elektrolyte für Lithium-Ionen-Batterien machten viele boratbasierte Supersäuren zugänglich. Cyanid-ligierte Borane sind von besonderem Interesse aufgrund des niedrigeren Molekulargewichts im Vergleich zu modernen Boraten und weniger teuren, kommerziellen Ausgangsmaterialien. Die neuen Borate übertreffen alle kommerziellen Systeme in einem breiten Temperaturbereich mit hervorragenden Epoxidgruppenumsätzen. Das Cyanid-ligierte Boran eignet sich hervorragend für frontale Anwendungen und ergibt transparente Proben im Gegensatz zu den getesteten kommerziellen Systemen, die schwarze Proben produzieren. Einfacher synthetischer Zugang, ausreichende Lagerstabilität der Formulierungen, hohe Reaktivität und gute Frontalparameter machen Cyanid-ligierte Iodoniumborate zu einer überzeugenden Alternative zu aktuellen State-of-the-Art-Initiatoren.Im dritten Teil dieser Arbeit wird die ringöffnende Metathesepolymerisation ROMP und ihr effizienter Härtungsprozess unter Anwendung metallbasierter Initiatoren herausgefordert. Mit einer anhaltenden Abkehr von Schwermetallen in der Materialherstellung sind Pyryliumsalze eine überzeugende Alternative für metallfreie ROMP. Nach Modifikation der aktuellsten Pyrylium-Photoredox-Mediatoren für ROMP werden neuartige und hocheffiziente Systeme erhalten. Die resultierenden alkoxylierten Pyryliumhexafluorphosphate zeigen eine außergewöhnliche Effizienz bei der metallfreien ROMP von Norbornen in Lösung, wobei ein Umsatz von 98 %, ein hohes Molekulargewicht und enge Polydispersitäten erreicht werden., 3D-printing and frontal polymerization are two hot topics with a seemingly endless variety of applications. For both highly specialized technologies, cationic polymerization represents a powerful tool to produce a broad field of materials starting from various monomers. Epoxides are frequently used since this monomer class provides great adhesion to most materials, high resistance towards chemicals and well-defined material properties. Iodonium perfluorinated antimonates and tetraphenylborates are the most widespread class of photoinitiators used in frontal polymerization applications, while sulfonium equivalents excel in 3D-printing applications due to their enhanced thermal stability. Within the first part of this thesis, atoms from group 14 to 16 in the periodic table of elements were explored as novel cations in onium-based photoinitiators since the introduction of a positive charge and the resulting transformation into onium salts is well researched and many classes are easily accessible. Using commercial epoxy resins, thiopyrylium-, bismuthonium-, and pyrylium salts show good reactivity and high epoxy group conversions in classical cationic photopolymerization. On the other hand, the introduction of bismuth- and oxygen-based onium salts, new potent initiator candidates arise for frontal polymerization. The advantage of bismuthonium-based systems is the outstanding pot life of the formulations, which can be cured at the press of a button via frontal polymerization.The second part focuses on the exploration of novel anions in onium-based photoinitiations. Extensive research in the fields of ionic liquids and lithium ion battery electrolytes, made many borate-based superacids available. Cyanide-ligated boranes are of special interest due to lower molecular weight compared to state-of-the-art borates and less expensive commercial starting materials. The new borates outperform all commercial systems in a broad range of temperatures with excellent epoxy group conversions. The cyanide-ligated borane is exceptionally suited for frontal applications and produces transparent specimens in contrast to the tested commercial systems, which are black. Easy synthetic access, sufficient pot life of formulations, high reactivity and good frontal parameters make cyanide-ligated iodonium borates a compelling alternative to current state-of-the-art initiators.Within the third part of this work, ring-opening metathesis polymerization ROMP and its potent curing process incorporating metal-based initiators is challenged. With a continuing shift away from heavy metals in material production, pyrylium salts are a compelling alternative for metal-free ROMP. After modification of the state-of-the-art pyrylium photoredox mediators for ROMP, novel and highly efficient systems are obtained. The resulting alkoxylated pyrylium hexafluorophosphates show exceptional performance in metal-free ROMP of norbornene in solution achieving 98% conversion, high molecular weight and narrow polydispersities.

Vitrimers brought new properties in thermosets by allowing their reshaping, self-healing, reprocessing, and network rearrangement without changing structural integrity. In this study, epoxidized castor oil (ECO) was successfully used for the straightforward synthesis of a bio-based solvent-free vitrimer. The synthesis was based on a UV-curing process, which proceeded at low temperatures in the absence of any solvents, and within a short time. Real time Fourier-transformed infrared spectroscopy and photo-DSC were exploited to monitor the cationic photocurable process. The UV-cured polymer networks were able to efficiently undergo thermo-activated bond exchange reactions due to the presence of dibutyl phosphate as a transesterification catalyst. Mechanical properties, thermal resistance, glass transition temperature, and stress relaxation were investigated as a function of the amount of transesterification catalyst. Mechanical properties were determined by both DMTA and tensile tests. Glass transition temperature (Tg) was evaluated by DMTA. Thermal stability was assessed by thermogravimetric analysis, whilst vitrimeric properties were studied by stress relaxation experiments. Overall, the ECO-based vitrimer showed high thermal resistance (up to 200 °C) and good mechanical properties (elastic modulus of about 10 MPa) and can therefore be considered as a promising starting point for obtaining more sustainable vitrimers.

Refereed/Peer-reviewed 3D printing is an attractive method to accurately construct artificial organs or alternative materials with complicated structures and functional performance. Naturally derived hydrogels have emerged as promising materials for the preparation of biomimetic 3D organization or scaffolds by 3D printing due to their good biocompatibility, high water content, and fascinating 3D network. However, the poor printing properties and weak structural stability of naturally derived hydrogels limit their applications. In this study, photopolymerizable hydrogels are designed based on maleic chitosan (MCS) and thiolated sodium hyaluronate (SHHA). The Michael addition between MCS and SHHA improves the viscosity of the mixed solution. Moreover, it benefits the 3D printing process, followed by photopolymerization (acrylate-thiol step-chain polymerization and acrylate–acrylate chain polymerization) to form a stable covalent network rapidly. The rheological property, swelling behaviors, microstructure, and in vitro degradation are tuned by adjusting the molar ratio of the thiol group and acrylate group. In addition, MCS/SHHA hydrogel scaffolds with good accuracy and enhanced structural stability are prepared using extrusion-based 3D printing and photopolymerization technology. The hydrogels display excellent cytocompatibility and can support adherence of L929 cells, which can be used as prospective materials for tissue engineering applications.

This perspective gives an overview of recent progress in thefield of photocured polymer composites based on variousforms of nanocelluloses, with a focus on cellulose nanofibrils. The manufacturing processes and performances of these nanocellulosecomposites are detailed, comprising solvent-assisted mixing processes, emulsification, coating and casting processes, preformimpregnation, and 3D printing. Attention is also paid to life-cycle engineered approaches to improve their sustainability. Thesematerialsfind applications in numerous domains, primarily as protective coatings but also as diffusion barrier composites andfilmsfor packaging and encapsulation of electronics, as composite hydrogels for biomedical applications, and as membranes for battery technologies.

Vanillin acrylate-based thermo-responsive shape memory photopolymers with high thermal stability, tunable mechanical properties, and antimicrobial activity have been developed. Photocurable resins containing one of the three commercial vanillin derivatives, vanillin diacrylate, vanillin dimethacrylate, and vanillin hydroxypropane dimethacrylate, and 1,3-benzenedithiol were tested. The results of dual curing systems with different ratios of thiol and acrylate (1:1 and 0.5:1) were compared. The reduction of thiol content increased the rate of photocuring, improved the mechanical performance of polymers (Young’s modulus was increased from 1.4–3.5 to 3952.3–11339.4 MPa), and their heat resistance (the 10% weight loss increased from 277–327 to 294–341 °C). All polymers were able to return to their primary shape after deformation and maintain their temporary shape at a temperature lower than their glass transition temperature (–3–46 °C). Furthermore, allpolymer films exhibited significant antibacterial activity against Escherichia coli and Staphylococcus aureus (cell reduction reached 99.8–100% after 24 h) and antifungal activity against Aspergillus flavus and Aspergillus niger (cell reduction reached 72.3–100% after 24 h).

Photolatent base catalysts exhibiting ideal structural properties for the straightforward manufacturing of thiol–epoxy vitrimers equipped with spatially resolved dynamic properties.

A number of photoinitiators are available in chemical industry, but less of them in biomedicine or clinical therapy due to the limitation of their cytotoxicity and biocompatibility. Thus, it is urgently necessary to find non-toxic or low-toxic photoinitiators to meet clinical demands. Aceanthrenequinone (AATQ) is a novel photosensitizer with high-photoinitiating ability, but no reports contribute, to date, to its cytotoxicity and biocompatibility. Here, primary cells and various cell lines were exposed to different concentrations of AATQ with or without irradiation. AATQ had the similar photoinitiating conversion efficiency to the extensively used bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (BAPO) and higher one than 9,10-phenanthrenequinone (PANQ) with the similar extent of polymerization in depth within a certain range, but displayed much lower cytotoxicity than BAPO under non-irradiation or irradiation. The biocompatibility of BisGMA/TEGDMA polymer prepared by AATQ was superior to that of PANQ, but inferior to that of camphorquinone (CQ) although the far lower dose of AATQ is enough to initiate polymerization of monomer than that of CQ. Hence, AATQ offers a valuable alternative in applications of industrial or biomedical areas.

International audience; Photoinitiating systems activable under visible light are the focus of numerous studies, and this interest is directly related to the higher light penetration that can be obtained in this spectral range. Reactivity of the photoinitiating systems is another major concern of photopolymerists and this issue can be addressed by investigating new structures of dyes. In this field, naphthoquinones have only been scarcely examined as visible light photoinitiators of polymerization. Besides, since 2015, different strategies have been developed to design photoinitiators with naphthoquinone, and promising results have been obtained, positively paving the way for future developments. In this review, an overview of the different photoinitiators comprising a naphthoquinone unit is given and polymerization efficiencies of these new structures are compared to those of reference compounds.

Herein, mono- and disubstituted thioxanthones have been synthesized and introduced as photosensitizers of iodonium salt for cationic and free-radical photopolymerization of epoxy and an acrylate monomer, respectively. Photoinitiation activity of these molecules was verified during photopolymerization processes performed upon exposure to visible LEDs of 420, 455, and 470 nm. The kinetics of the photopolymerization processes was followed using FT-IR spectroscopy. Moreover, the developed compounds were proposed as strongly reducing metal-free photoredox catalysts in organocatalyzed atom transfer radical polymerization (ATRP). Thioxanthone derivatives (with alkyl halide) efficiently activate the ATRP of methyl methacrylate using a visible LED as an irradiation source. The formed polymers in the ATRP process were characterized by SEC. Apart from studying the photopolymerization processes with the participation of obtained thioxanthones, absorption, fluorescence, as well as electrochemical properties of thioxanthone derivatives were investigated. Furthermore, the performance of studied compounds in 3D printing applications was also examined. The most important result of this study is the design and possible application of photosensitizers/photocatalysts for photopolymerization processes.

Currently, hydrogel materials are being widely developed and investigated. Factors affecting their properties may be mentioned, such as the types and the amounts of the reagents used for the synthesis of the hydrogel matrix and modifiers; thus, the main aim of the investigations was to check the impact of the amount of photoinitiator applied during the UV-induced polymerization of polyvinylpyrrolidone-based hydrogels incorporated with vitamin C and Aloe vera juice. The experiments that were performed were focused on determining the hydrogels’ swelling capability, behavior in simulated body fluids, hydrophilicity, chemical structure (using FT-IR spectroscopy), as well as their surface morphology and roughness. It was proven that developed materials had relatively rough surfaces, they did not degrade in simulated physiological liquids, and their swelling ratios in these media were 2.0–3.0 g/g. The only change in the pH of the incubation media—a slight decrease—was caused by the release of the modifiers into the tested liquids. Subsequently, it was demonstrated that as the amount of the photoinitiator (2-hydroxy-2-methylpropiophenone) increased, the percentage elongation decreased, and the tensile strength increased. The content of the photoinitiator in the hydrogels also influenced their wettability. All samples showed hydrophilicity; the more photoinitiator in the hydrogel structure, the lower wetting angle for water. Moreover, the greater the amount of 2-hydroxy-2-methylpropiophenone, the smoother and more homogeneous the hydrogel surface; thus, considering the demonstrated physicochemical properties of developed materials, they seem to show application potential for more advanced research regarding the development of innovative dressing materials.

In this study, Poly(N-isopropylacrylamide) (PNIPAM) hydrogels were produced from N-isopropylacrylamide (NIPAM), at three different concentrations of crosslinker, N,N´-methylenebisacrylamide (BIS) (0.50%, 0.35%, and 0.25%) using two types of photoinitiator, a hydrophilic photoinitiator (Irgacure 2959) and a hydrophobic photoinitiator (Irgacure 651). When Irgacure 651 was used photopolymerization process was completed in 20 min compared to two hours with Irgacure 2959. However, the resultant hydrogels were opaque suggesting a heterogeneous structure, which in turn led to low compressive strength. Besides, when hydrogel solution was prepared with Irgacure 651 in water/ethanol mixture 0.25% crosslinker ratio was not sufficient to form a hydrogel. Irgacure 2959 produced homogenous transparent hydrogels with a higher degree of swelling. When the crosslinker ratio decreased swelling capacity increased, but hydrogels became weaker. The decrease in compressive strength was particularly high at the 0.25% crosslinker ratio. The crosslinker ratio or photoinitiator type did not have any significant effect on the phase transition temperature. On the other hand, hydrogel samples prepared with Irgacure 651 in water/ethanol mixture showed a quicker response to swelling and deswelling. In conclusion, in terms of morphology, swelling capacity, and compressive strength the best results were obtained with the crosslinker ratio of 0.35% and Irgacure 2959. © 2022, The Polymer Society, Taipei., Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, TÜBİTAK: 119M355, The authors would like to express appreciation for the support of the Scientific and Technological Research Council of Turkey (TÜBİTAK) [Project Number =119M355].

A series of difunctional epoxy methacrylate resins (EAs) containing at least one epoxy and at least one methacrylate group were synthesized by means of an addition reaction between epoxy-terminated diglycidyl ethers and methacrylic acid. In order to investigate the impact of polymer architecture on the course of addition reactions and further coating properties, several different types of diglycidyl ethers, i.e., linear, containing aliphatic or aromatic rings, with a short or polymeric backbone, were employed in the synthesis. The carboxyl–epoxide addition esterification reactions have been found to, in a relatively straightforward manner, control the extent of acrylation depending on the substrate feed ratio and reaction time. The structure of obtained pre-polymers was evaluated by FT-IR and NMR methods. At the same time, the extent of addition reactions was validated via quantitative analysis, including non-volatile matter content (NV), acid value (PAVs), and epoxy equivalent value (EE) analysis. The modification was carried out in a manner likely to create a compound with one epoxy and one carbon–carbon pendant group. Hence, due to the presence of both functionalities, it is possible to crosslink compositions based on synthesized EAs via two distinct mechanisms: (i) cationic polymerization or (ii) free-radical polymerization. Synthesized epoxy methacrylate pre-polymers were further employed for use in formulate photocurable coating compositions by the cationic or radical process. Furthermore, the photopolymerization behavior and properties of cured coatings were explored regarding some structural factors and parameters. The investigated polymeric materials cure in a short time to obtain coatings with good properties, which is why they can be successfully used to produce protective and decorative coatings for many industries.

The significant development of industry and the growing demand for renewable fuels lead to the accumulation of massive amounts of glycerol as a by-product. Scientists have been trying to use this product as a raw material for several years. One of its uses is in the acquirement of 1,3-propanediol (PDO). This work presents studies on the synthesis of two new urethane acrylate resins obtained from 1,3-propanediol and urethane acrylate oligomers containing isocyanate groups in each molecule. The method for obtaining the resins was presented, considering various conditions of synthesis, i.e., the structure of the carbon chain of the oligomer used, the molar ratio of the reactants, or the use of solvents. The reactions were monitored in real time by FTIR until the disappearance of the NCO groups. Then, polymer films were prepared from the obtained products and cured using UV radiation or thermally. The obtained coatings were tested in terms of the photopolymerization kinetics and properties of the cured coatings. Resultantly, the obtained bio-sourced coatings were observed to be characterized by good functional properties and a short curing duration, both with the use of UV radiation-based or thermal curing. These types of resins obtained using a bioproduct can be employed as eco-friendly film-forming products in the coating industry for many applications. In particular, due to their potential for dual curing methods (UV or thermal), these resins can be used on three-dimensional surfaces, i.e., those in which there is a possibility of the insufficient availability of UV radiation.

An eco-friendly epoxy/thiol-ene photopolymerization (ETEP) process was employed to prepare epoxy bio-composites using a commercial biobased epoxy resin and a woven jute fabric as reinforcement. In this process the components of the thiol-ene system, an allyl-functionalized ditertiary amine curing agent, a multifunctional thiol and a radical photoinitiator, were added to the epoxy resin to produce a polyether–polythioether crosslinked co-network. Moreover, the jute fibers were functionalized with thiol groups using the 3-mercaptopropyl (trimethoxysilane) with the purpose of creating a chemically bonded polymeric matrix/fiber system. The obtained bio-composites prepared with the thiol-functionalized cellulose fibers exhibited an increase up to 52% and 40% in flexural modulus and strength with respect to the non-functionalized counterparts. Under the three-point bending loadings, the composites displayed higher deformation at break and toughness due to the presence of polythioethers in the co-network. The prepared bio-composites developed in this work are excellent candidates to extend the use of cellulose fibers for structural applications.

The synthesis of novel phosphorus-containing telomers (P-telomers) was conducted via a solution-free UV-initiated telomerization process of butyl acrylate, methyl methacrylate, 2-hydroxyethyl acrylate, and styrene, different phosphorus telogens (dimethyl phosphite (DMPh), dibutyl phosphite (DBPh), diphenyl phosphite (DPPh) or dibutyl phosphate (DBP)), and a radical photoinitiator-acylphosphine oxide (APO). The course of the UV-phototelomerization process was monitored by photo-DSC and the chemical structures of telomers were assessed by FTIR. Final UV-photocurable varnish compositions consisted of prepared P-telomer syrups, crosslinking monomer (pentaerythritol triacrylate; PETIA), and a radical UV-photoinitiator (α-hydroxyalkylphenone, HAP). The influence of P- telomers on the optical and mechanical features of coatings was investigated. Relatively the highest hardness and satisfactory scratch values, as well as water and solvent resistance, were observed for varnish based on DMPh-telomers. While the strongest adhesive bond to a glass substrate was reported for DPPh-telomers. It is worth pointing out that the P-telomers did not affect the gloss values of varnishes in comparison to the telomer-free reference sample.

Most commercial dressings with moderate to high exudate uptake capacities are mechanically weaker and/or require a secondary dressing. The current research article focuses on the development of hydrogel-based wound dressings combining mechanical strength with high exudate absorption capacities using acrylate-endcapped urethane-based precursors (AUPs). AUPs with varying poly(ethylene glycol) backbone molar masses (10 and 20 kg mol(-1)) and endcap chemistries are successfully synthesized in toluene, subsequently processed into UV-cured hydrogel sheets and are benchmarked against several commercial wound dressings (Hydrosorb, Kaltostat, and Mepilex Ag). The AUP materials show high gel fractions (>90%) together with strong swelling degrees in water, phosphate buffered saline and simulated wound fluid (12.7-19.6 g g(-1)), as well as tunable mechanical properties (e.g., Young's modulus: 0.026-0.061 MPa). The AUPs have significantly (p < 0.05) higher swelling degrees than the tested commercial dressings, while also being mechanically resistant. The elasticity of the synthesized materials leads to an increased resistance against fatigue. The di- and hexa-acrylated AUPs show excellent in vitro biocompatibility against human foreskin fibroblasts, as evidenced by indirect MTS assays and live/dead cell assays. In conclusion, the processed AUP materials demonstrate high potential for wound healing application and can even compete with commercially available dressings.

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.

Hydrogels are ideal candidates for the sustained local administration of antimicrobial drugs because they have customizable physicochemical properties that allow drug release kinetics to be controlled and potentially address the issue of systemic side effects. Consequently, the purpose of this study was to use 266 nm-pulsed laser beams to photo-crosslink gelatin methacryloyl hydrogels using Irgacure 2959 as a photo-initiator to reduce the curing time and to have an online method to monitor the process, such as laser-induced fluorescence. Additionally, irradiated chlorpromazine was loaded into the hydrogels to obtain a drug delivery system with antimicrobial activity. These hydrogels were investigated by UV–Vis and FTIR absorption spectroscopy, scanning electron microscopy, and laser-induced fluorescence spectroscopy and their structural and morphological characteristics, swelling behavior, and drug release profile were obtained. As a result the morphology, swelling behavior, and drug release profile were influenced by both the energy of the laser beam and the exposure time. The optimal hydrogel was obtained after 1 min of laser irradiation for Irgacure 2959 at 0.05% w/v concentration and gelatin methacryloyl at 10% w/v concentration. The hydrogels loaded with irradiated chlorpromazine show significant antimicrobial activity against Staphylococcus aureus and MRSA bacteria and a non-cytotoxic effect against L929 fibroblast cell lines.

Over a short period of time, electronic assemblies have been dramatically developed with smaller size and lighter weight and 3D printing plays a crucial role in their future production. However, it is difficult to develop epoxy resins and other thermoset resins for this process because of the polymer's liquid state during processing. This work uses a UV curing technique for making flexible epoxy/multi-walled carbon nanotubes (MWCNTs) composites that are suitable for future 3D printing applications. The synthesized carbazole-coated TiO2 nanoparticles, used as a photosensitizer, were characterized by their photoabsorbance, morphology, and surface property before use. The results indicated that the TiO2 nanoparticles coated with 75 wt% carbazole were appropriate for UV-cured flexible epoxy/MWCNT composites because of its fast cure kinetics after irradiation by a UV light source. The epoxy/MWCNT composites displayed low tensile properties because of the agglomeration of MWCNTs inside the epoxy matrix. In addition, the epoxy/MWCNT composites showed slightly lower thermal expansion with high electrical properties with a large amount of MWCNTs in the epoxy composites.