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The photocatalyst (PC) zinc tetraphenylporphyrin (ZnTPP) is highly efficient for photoinduced electron/energy transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. However, ZnTPP suffers from poor absorbance of orange light by the so-called Q-band of the absorption spectrum (maximum absorption wavelength λ max = 600 nm, at which molar extinction coefficient ε max = 1.0 × 10 4 L/(mol·cm)), hindering photo-curing applications that entail long light penetration paths. Over the past decade, there has not been any competing candidate in terms of efficiency, despite a myriad of efforts in PC design. By theoretical evaluation, here we rationally introduce a peripheral benzo moiety on each of the pyrrole rings of ZnTPP, giving zinc tetraphenyl tetrabenzoporphyrin (ZnTPTBP). This modification not only enlarges the conjugation length of the system, but also alters the a 1 u occupied π molecular orbital energy level and breaks the accidental degeneracy between the a 1 u and a 2 u orbitals, which is responsible for the low absorption intensity of the Q-band. As a consequence, not only is there a pronounced hyperchromic and bathochromic effect ( λ max = 655 nm and ε max = 5.2 × 10 4 L/(mol·cm)) of the Q-band, but the hyperchromic effect is achieved without increasing the intensity of the less useful, low wavelength absorption peaks of the PC. Remarkably, this strong 655 nm absorption takes advantage of deep-red (650–700 nm) light, a major component of solar light exhibiting good atmosphere penetration, exploited by the natural PC chlorophyll a as well. Compared with ZnTPP, ZnTPTBP displayed a 49% increase in PET-RAFT polymerization rate with good control, marking a significant leap in the area of photo-controlled polymerization. [ABSTRACT FROM AUTHOR]

3D inkjet printing is a fast, reliable, and non‐contact bottom–up approach to printing small and large models and is one of the fastest additive manufacturing technologies available. These attributes position inkjet printing as a promising tool for the additive manufacturing of biomaterials, for example, tissue engineering scaffolds. However, due to the stringent technical rheological requirements of current inkjet technologies, there is a lack of photopolymer resins suitable for the inkjet printing of biomaterials. Hence, a novel ink engineered for 3D piezoelectric inkjet printing of biomaterials is designed and developed. The novel resin leverages a biodegradable amino acid phosphorodiamidate matrix copolymerized with a dialkyne ether to modulate the viscosity. Copolymerization with commercially available thiols facilitates the photochemical thiol‐yne curing reaction. The ink exhibits optimal viscosity, eliminating the need for solvents, as well as reliable jetting and sufficiently swift curing kinetics. Furthermore, the formulation is successfully demonstrated in an industrial inkjet printhead. Notably, the resulting materials have low cytotoxicity and, hence, have significant promise in advancing the applications of 3D inkjet printing of biological scaffolds. [ABSTRACT FROM AUTHOR]

The present work focuses on a double process involving additive manufacturing and joining of ceramic-resin green bodies, aiming to overcome the challenges of printing long-span and large-size ceramic specimens. Through partitioned 3D printing, individual green bodies were built and then joined together using either a single-phase slurry (Al 2 O 3) or a double-phase slurry (Al 2 O 3 and ZrO 2). The impact of sintered temperature, photocuring duration time, and sandwich layer thickness on the three-point bending strength of the joined specimens was investigated. The analysis of photocuring depth, thermogravimetry, and composition structure characteristics reveals two significant joining mechanisms, namely initial polymer network joining and ultimate grain bonding and growth joining, which play a crucial role in holding the connection shapes and enhancing the connection strength. Furthermore, the bending strength analysis indicates a positive correlation between sintering temperature and bending strength, while a negative correlation is observed between sandwich layer thickness and bending strength. The photocuring duration time has no significant impact on the bending strength. Finally, the double-phase slurry demonstrates superior connection performance, but the joining strength is decreased to 44.53 % of the sintered substrate specimens due to the presence of joining defects such as flow channel pores and lamellar gaps. These defects have prompted the development of lamellar structures, flow channel pores, and intercrystalline fracture regions, consequently reducing the overall strength. [ABSTRACT FROM AUTHOR]

The integration of 3D printing technology into the production of ceramic membranes has garnered significant interest. Nonetheless, challenges persist in fabricating macroporous supports with both high porosity and strength through 3D printing. In this study, titania nanoparticles were introduced to facilitate the fusion of alumina nanoparticles. This freed the pores occupied by alumina nanoparticles and enhanced the connections between micron-sized alumina particles. Consequently, both the permeability and strength of the ceramic membrane supports were improved. The impact of ceramic slurry composition on photocuring performance, sintering processes, and the addition of titania nanoparticles on the microstructure and properties of the porous ceramic membrane support were investigated. The optimized membrane support featured a pore size of approximately 1.36 µm, achieving a porosity of 42.4% and a pure water permeance of 3700 L·m−2·h−1·bar−1. These findings provide a fundamental groundwork for subsequent endeavors in the development of high-performance ceramic membranes. [ABSTRACT FROM AUTHOR]

Photocuring 3D printing of hydrogels, with sophisticated, delicate structures and biocompatibility, attracts significant attention by researchers and possesses promising application in the fields of tissue engineering and flexible devices. After years of development, photocuring 3D printing technologies and hydrogel inks make great progress. Herein, the techniques of photocuring 3D printing of hydrogels, including direct ink writing (DIW), stereolithography (SLA), digital light processing (DLP), continuous liquid interface production (CLIP), volumetric additive manufacturing (VAM), and two photon polymerization (TPP) are reviewed. Further, the raw materials for hydrogel inks (photocurable polymers, monomers, photoinitiators, and additives) and applications in tissue engineering and flexible devices are also reviewed. At last, the current challenges and future perspectives of photocuring 3D printing of hydrogels are discussed. [ABSTRACT FROM AUTHOR]

This study investigated effects of the different emittance-mode protocols from three light curing units (LCUs): (i) a Laser (Monet); (ii) a quad-wave (PinkWave); (iii) a conventional LED (Elipar S10) on the temperature rise (ΔT) and degree of conversion (DC) when photo-curing fast or conventional bulk-fill resin-based composites (RBC). The aim was to correlate ΔT and DC, and the radiant exposure delivered to RBC specimens. A 3D-printed resin mold of 4 mm depth was filled with two bulk-fill RBCs: Tetric PowerFill® (fast photo-polymerised composite) (TPF) or Tetric EvoCeram® Bulk-Fill (EVO). Three LCUs were used: (i) Monet laser for 1 s and 3 s (MONET-1 s, MONET-3 s); (ii) PinkWave quad-wave used for 3 s in Boost mode (PW-3 s) and for 20 s in standard mode (PW-20 s); (iii) Elipar S10 for 5 s (S10–5 s) and for 20 s in standard mode (S10–20 s). 2-dimensional temperature maps were obtained before, during and for 60 s after the LCU had turned off using a thermal imaging camera. Thermal changes were analysed at five depths: (0, 1, 2, 3, and 4 mm from the top surface of the RBC). The maximum temperature rise (T max) and the mean temperature rise (ΔT) were determined. Cylindrical-shaped specimens were prepared from each material using a stainless-steel split mold (4 × 4 mm) and light-cured with the same protocols. The DC was measured for 120 s and at 1 h after LCU had turned off using Fourier Transform Infrared Spectroscopy (FTIR). Data were analysed using Three-way ANOVA, One-way ANOVA, independent t-tests, and Tukey post-hoc tests (p < 0.05). Radiant exposures delivered by the various irradiation protocols were between 4.5–30.3 J/cm2. Short exposure times from MONET-1 s and PW-3 s delivered the lowest radiant exposures (4.5 and 5.2 J/cm2, respectively) and produced the lowest ΔT and DC. The longer exposure times in the standard modes of PW-20 s, S10–20 s, and MONET-3 s produced the highest T max , ΔT, and DC for both composites. The ΔT range among composites at different depths varied significantly (31.7–49.9 °C). DC of TPF ranged between 30–65% and in EVO between 15.3–56%. TPF had higher T max, ΔT for all depths and DC compared to EVO, across the LCU protocols (p < 0.05), except for PW-20 s and MONET-3 s. The coronal part of the restorations (1–2 mm) had the highest ΔT. There was a positive correlation between ΔT and DC at 4-mm depth after 120 s Longer, or standard, exposure times of the LCUs delivered greater radiant exposures and had higher DC and ΔT compared to shorter or high-irradiance protocols. The fast photo-polymerised RBC had comparatively superior thermal and conversion outcomes when it received a high irradiance for a short time (1–5 s) compared to the conventional Bulk-Fill RBC. [ABSTRACT FROM AUTHOR]

To assess visually and quantitatively the contributions of the adhesive layer photopolymerization and the subsequent resin composite increment to spatio-temporal maps of temperature at five different cavity locations, subjected to two irradiance curing protocols: standard and ultra-high. Caries-free molars were used to obtain 40, 2 mm thick dentin slices, randomly assigned to groups (n = 5). These slices were incorporated within 3D-printed model cavites, 4 mm deep, restored with Adhese® Universal bonding agent and 2 mm thick Tetric® Powerfill resin composite, and photocured sequentially, as follows: G1: control-empty cavity; G2: adhesive layer; G3 composite layer with no adhesive; and G4 composite layer with adhesive. The main four groups were subdivided based on two curing protocols, exposed either to standard 10 s (1.2 W/cm2) or Ultra high 3 s (3 W/cm2) irradiance modes using a Bluephase PowerCure LCU. Temperature maps were obtained, via a thermal imaging camera, and numerically analyzed at 5 locations. The data were analyzed using two-way ANOVA followed by multiple one-way ANOVA, independent t-tests and Tukey post-hoc tests (α = 0.05). T max , ΔT, T int (integrated area under the curve) and time-to-reach-maximum-temperature were evaluated. Two-way ANOVA showed that there was no significant interaction between light-curing time and location on the measured parameters (p > 0.05), except for the time-to-reach-maximum-temperature (p < 0.05). Curing the adhesive layer alone with the 10 s protocol resulted in a significantly increased pulpal roof temperature compared to 3 s cure (p < 0.05). Independent T-tests between G3 and G4, between 3 s and 10 s, confirmed that the adhesive agent caused no significant increases (p > 0.05) on the measured parameters. The ultra-high light-curing protocol significantly increased ΔT in composite compared to 10 s curing (p < 0.05). When the adhesive layer was photocured alone in a cavity, with a 2 mm thick dentin floor, the exothermal release of energy resulted in higher temperatures with a 10 s curing protocol, compared to a 3 s high irradiance. But when subsequently photocuring a 2 mm layer of composite, the resultant temperatures generated at pulpal roof location from the two curing protocols were similar and therefore there was no increased hazard to the dental pulp from the immediately prior adhesive photopolymerization, cured via the ultra-high irradiation protocol. [ABSTRACT FROM AUTHOR]

In the process of photocuring using ceramic slurry, the scattering of ceramic particles is widely acknowledged as the primary cause of deviations. However, when aiming to minimize scattering deviations for the production of intricate structures, it is crucial to also consider deviations resulting from resin shrinkage, an aspect that has been overlooked in previous research. This study successfully reduced scattering deviations by incorporating graphite as a light absorber. This approach enabled the evaluation and analysis of the impact of shrinkage deviations on forming deviations. Experimental results investigating deviations in size and shape across various feature structures demonstrated the substantial impact of shrinkage deviations on the final forming deviations. By combining theoretical analysis with empirical findings, this study proposes a coupled model that accounts for the combined effects of scattering deviations and shrinkage deviations. Additionally, a control method is introduced to enhance forming accuracy by compensating for scattering deviations using shrinkage deviations. Moreover, it elucidates the variation curve of forming deviations with the addition of graphite under different photocuring parameters. Ultimately, this model facilitated the enhancement of ceramic slurry formulation and photocuring process parameters, enabling the high-precision printing of intricate ceramic core molds with incorporated grids. [ABSTRACT FROM AUTHOR]

It is challenging to enhance the stress‐free two‐way shape memory (stress‐free TWSM) effect to obtain a wide range of response temperatures. Herein, a polycaprolactone (PCL)/poly(ω‐pentadecalactone) (PPDL) is photocured under UV light irradiation in the solvent of 1,1,2‐trichloroethane (TCA), to obtain a series of cross‐linked polyesters (CPES). Controlling solvent content (SC) which is removed after the polymerization allows the yielded CPES to perform a regulatable thermodynamic and stress‐free TWSM properties. High SC is beneficial to reduce the degree of chain overlap (C/C*) of PPDL chain segments in the PCL‐based CPES network, then causes the cocrystallization of PCL and PPDL and yielding an additional melting‐transitions (Tm). An enhanced stress‐free TWSM is obtained in high SC samples (CPES‐15‐90), reflected in the attainment of a wide range of response temperature, which means a wider service temperature. The enhancement is reflected in higher reversible strain of high SC samples compared with the samples prepared with low SC when varying high trigger temperature (Thigh). Even at high Thigh, the high SC sample still has reversible strain. Therefore, controlling SC strategy for photocuring copolyester not only provides a new preparation approach for high‐performance shape memory (SM) polymers, but also offers new condensed polymer structure to explore. [ABSTRACT FROM AUTHOR]

Background: The service quality and life of photopolymerized materials are dramatically impaired by shrinkage stress generated during the polymerization process. Several soft-start photocuring protocols including two-step, ramp, and pulse delay have been proposed to reduce the shrinkage stress. However, the mechanism for the shrinkage stress reduction by soft-start photocuring remains largely elusive. Objective: This study aims to explore the mechanism for shrinkage stress reduction in soft-start photocuring protocols and then propose a universal strategy to maximize the stress reduction. Method: A theory-experiment-combined method was developed to investigate the effect of soft-start photocuring protocols on the shrinkage stress evolution. Shrinkage stresses under different protocols were measured by a standardized cantilever beam-based instrument. An improved theoretical model incorporating the evolutions of the reaction kinetics and material properties was developed to predict the shrinkage stress evolution under different curing protocols. Results: Compared to the standard protocol with a constant photo-irradiation, all the soft-start photocuring protocols could effectively reduce the shrinkage stress and the two-step protocol achieved a maximum reduction of 25% among all experimental conditions. The elastic modulus of photopolymers coincided under the same radiant exposure and irradiation intensity. Unlike previous studies focusing on the mechanical properties of the photopolymers, we found that the shrinkage stress reduction by soft-start photocuring protocols could be attributed to a delayed gelation and a reduction in the peak temperature change after gelation. Based on these mechanisms, adding a delay time before the gelation was proposed as an effective strategy to reduce the shrinkage stress, leading to a reduction of up to more than 40% according to the theoretical predictions. Additionally, the timing for introducing the delay and its duration can be effectively and conveniently determined by monitoring the real-time evolution of shrinkage stress in the standard photocuring protocol. Conclusions: This theory-experiment-combined study not only uncovers that the shrinkage stress reduction by soft-start photocuring protocol is attributed to the delay in the gelation and the reduction of the peak temperature change after the gelation but also proposes an effective approach to mitigate shrinkage stress by adding a delay time before the gelation. Such a strategy for maximizing the shrinkage stress reduction while maintaining the mechanical and curing properties is to guide the practical applications of photopolymers. [ABSTRACT FROM AUTHOR]

The aim of this study was to explore the thermal properties of epoxy–acrylate blends for the liquid crystal display (LCD) 3D printing technique. Starting from an epoxy–acrylate blend with a ratio of epoxy to acrylate of 50:50, the effect of adding a reactive monofunctional epoxy diluent was evaluated. The diluent was a resin composed by oxirane, mono[(C12-14 alkyl) methyl] derivatives selected for its low viscosity (i.e., 1.8 Poise) at room temperature and its reactivity. The diluent content varied from 15 to 25 wt% and, for all the formulation, double curing cycles, where thermal curing followed photocuring, were studied. The effect of different curing temperatures was also evaluated. The control of the diluent content and of the curing temperature allowed tailoring of the thermomechanical resin properties while improving the resin's processability. The glass transition ranged from 115.4 °C to 90.8 °C depending on the combination of diluent content and post-curing temperature. The resin developed displayed a faster processing time tested on a reference part with printing time of 4 h and 20 min that was much lower than the printing times (7 and 16 h) observed for the starting formulations. [ABSTRACT FROM AUTHOR]

Currently, purely organic compounds showing ambient phosphorescence with high efficiency (ΦP) and ultra‐long lifetime (τP) are quite rare and often need to be achieved in hydrophilic poly(vinyl alcohol)‐based hosts. This severely limits their applications. Here, we provide a solution to this issue by constructing an ortho‐linked donor‐acceptor (D−A) dyad whose D moiety has not only a long‐lived T1 state to achieve a long τP, but also a Tn state that is close to the S1 state of the dyad to trigger effective spin‐orbit charge transfer intersystem crossing (SOCT‐ISC). The rationality of this strategy was validated by a new phosphor OF‐BCz that is able to show a τP of 1.92 s and a ΦP of 30 % even in a less rigid matrix of poly(methyl methacrylate) (PMMA). Excitingly, OF‐BCz exhibited its potential as both a photocuring initiator and an in situ quality indicator, allowing for the visual detection of defects in photolithographic patterning. [ABSTRACT FROM AUTHOR]

Currently, purely organic compounds showing ambient phosphorescence with high efficiency (ΦP) and ultra‐long lifetime (τP) are quite rare and often need to be achieved in hydrophilic poly(vinyl alcohol)‐based hosts. This severely limits their applications. Here, we provide a solution to this issue by constructing an ortho‐linked donor‐acceptor (D−A) dyad whose D moiety has not only a long‐lived T1 state to achieve a long τP, but also a Tn state that is close to the S1 state of the dyad to trigger effective spin‐orbit charge transfer intersystem crossing (SOCT‐ISC). The rationality of this strategy was validated by a new phosphor OF‐BCz that is able to show a τP of 1.92 s and a ΦP of 30 % even in a less rigid matrix of poly(methyl methacrylate) (PMMA). Excitingly, OF‐BCz exhibited its potential as both a photocuring initiator and an in situ quality indicator, allowing for the visual detection of defects in photolithographic patterning. [ABSTRACT FROM AUTHOR]

The utilization of dynamic cross‐linking represents a highly promising approach in addressing the escalating issues of plastic pollution and fossil resource consumption. Despite being extensively investigated over the past decade, various dynamically cross‐linked polymers (DCPs) predominantly remain confined to the realm of academic research. To serve as a valuable material for practical application, advanced processing is always essential for all kinds of materials. 3D printing (3DP) enables the creation of intricate shapes layer‐by‐layer without relying on molds, thus the integration of 3DP techniques with DCPs holds significant potential to enhance and expand the practical applicability of DCPs. Here, an overview of the fundamental principles underlying DCPs compatible 3DP techniques are provided, namely photocuring 3DP, extrusion‐based 3DP, and laser sintering‐based 3DP. Additionally, a comprehensive summary of representative research works that specifically focus on the application of DCPs in each respective 3DP technique is presented. The performance and dynamic mechanism involved in the corresponding printing process are thoroughly discussed and comprehensively reviewed. Finally, the existing challenges and issues pertaining to further enhancing 3D printability, performance, efficiency, etc., are extensively deliberated upon, while proposing potential directions to address these concerns. [ABSTRACT FROM AUTHOR]

The utilization of 3D printing for fabricating ceramic membranes has garnered increasing attention in recent years. However, the precise preparation of ceramic slurries tailored for this purpose remains an area requiring more systematic research. This paper delves deeper into the photo-curing characteristics of ceramic slurries characterized by high solid content and low viscosity. Employing a mask-curing experimental system, the study investigates the impact of photoinitiators and additives, such as triethanolamine and tartrazine, on the photo-curing performance. Quantitative analysis is carried out, considering various parameters, including curing depth, curing broadening, broadening depth, critical energy, and curing sensitivity. By incorporating diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), triethanolamine (TEOA), and tartrazine at optimized concentrations of 0.1 wt%, 1.5 wt%, and 1.0 wt% respectively, the broadening depth increases significantly, exceeding 200 μm. This effectively meets the curing depth requirements for 3D printing tasks. Consequently, the printed ceramic green body exhibits excellent shape retention, surface flatness (R a < 0.9 μm), as well as ample strength and toughness. These characteristics provide a solid foundation for the subsequent preparation of high-performance ceramic membranes. [ABSTRACT FROM AUTHOR]

The utilization of 3D printing for fabricating ceramic membranes has garnered increasing attention in recent years. However, the precise preparation of ceramic slurries tailored for this purpose remains an area requiring more systematic research. This paper delves deeper into the photo-curing characteristics of ceramic slurries characterized by high solid content and low viscosity. Employing a mask-curing experimental system, the study investigates the impact of photoinitiators and additives, such as triethanolamine and tartrazine, on the photo-curing performance. Quantitative analysis is carried out, considering various parameters, including curing depth, curing broadening, broadening depth, critical energy, and curing sensitivity. By incorporating diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), triethanolamine (TEOA), and tartrazine at optimized concentrations of 0.1 wt%, 1.5 wt%, and 1.0 wt% respectively, the broadening depth increases significantly, exceeding 200 μm. This effectively meets the curing depth requirements for 3D printing tasks. Consequently, the printed ceramic green body exhibits excellent shape retention, surface flatness (R a < 0.9 μm), as well as ample strength and toughness. These characteristics provide a solid foundation for the subsequent preparation of high-performance ceramic membranes. [ABSTRACT FROM AUTHOR]

Although long‐lived triplet charge‐transfer (3CT) state with high energy level has gained significant attention, the development of organic small molecules capable of achieving such states remains a major challenge. Herein, by using the through‐space electronic coupling effect, we have developed a compound, namely NIC‐DMAC, which has a long‐lived 3CT state at the single‐molecule level with a lifetime of 210 ms and a high energy level of up to 2.50 eV. Through a combination of experimental and computational approaches, we have elucidated the photophysical processes of NIC‐DMAC, which involve sequential transitions from the first singlet excited state (S1) that shows a 1CT character to the first triplet excited state (T1) that exhibits a local excited state feature (3LE), and then to the second triplet excited state (T2) that shows a 3CT character (i.e. S1 (1CT)→T1 (3LE)→T2 (3CT)). The long lifetime and high energy level of its 3CT state have enabled NIC‐DMAC as an initiator for photocuring in double patterning applications. [ABSTRACT FROM AUTHOR]

Although long‐lived triplet charge‐transfer (3CT) state with high energy level has gained significant attention, the development of organic small molecules capable of achieving such states remains a major challenge. Herein, by using the through‐space electronic coupling effect, we have developed a compound, namely NIC‐DMAC, which has a long‐lived 3CT state at the single‐molecule level with a lifetime of 210 ms and a high energy level of up to 2.50 eV. Through a combination of experimental and computational approaches, we have elucidated the photophysical processes of NIC‐DMAC, which involve sequential transitions from the first singlet excited state (S1) that shows a 1CT character to the first triplet excited state (T1) that exhibits a local excited state feature (3LE), and then to the second triplet excited state (T2) that shows a 3CT character (i.e. S1 (1CT)→T1 (3LE)→T2 (3CT)). The long lifetime and high energy level of its 3CT state have enabled NIC‐DMAC as an initiator for photocuring in double patterning applications. [ABSTRACT FROM AUTHOR]

The presented work deals with the photocuring of telechelic macromonomers derived from plant-based fatty acids to obtain a soft polymer network. Compositions were made by mixing macromonomers with three different concentrations (0.5, 1, and 2%) of two type I photoinitiators (Omnirad 2022 and Omnirad 819). All formulations were then subjected to photopolymerization studies by applying UV-assisted differential scanning calorimetry (UV-DSC) measurements at isothermal conditions at 37 °C with a narrow light source wavelength of 365 nm and irradiation (light intensity) of 20 and 50 mW/cm2. The percentage conversions, reaction orders, and constants were estimated based on autocatalytic Sestak–Berggen and Avrami models. In this work, for the first time, the influence of the curing conditions on the photopolymerization process, such as the photoinitiator concentration, light intensity, and oxygen presence/absence, were investigated for these novel systems. The results indicated significant differences between the two commercially available photoinitiators and their effects on photopolymerization kinetics. The maximum reaction rate was found to be considerably higher for Omnirad 2022 (which is a blend of three different compounds), especially at a lower light intensity, i.e., 20 mW/cm2, compared to Omnirad 819. However, it led to lower maximum conversion in an air atmosphere. The dynamic thermomechanical analysis (DMTA) revealed that light intensity, photoinitiator concentration, and oxygen presence had a strong effect on the storage modulus and loss modulus values. It was concluded that the chemical structure of the photoinitiator and curing conditions had a strong effect on the photopolymerization kinetics and properties of the prepared soft polymer networks. [ABSTRACT FROM AUTHOR]

The thermal curing of industrial coatings (e.g., car painting and metal coil coatings) is accompanied by a substantial energy consumption due to the intrinsically high temperatures required during the curing process. Therefore, the development of new photochemical curing processes—preferably using visible light—is in high demand. This work describes new diazo‐based cross‐linkers that can be used to photocure acrylic coatings using blue light. This work demonstrates that the structure of the tethered diazo compounds influences the cross‐linking efficiency, finding that side reactions are suppressed upon engineering greater molecular flexibility. Importantly, this work shows that these diazo compounds can be employed as either thermal or photochemical cross‐linkers, exhibiting identical crosslinking performances. The performance of diazo‐cross‐linked coatings is evaluated to reveal excellent water resistance and demonstrably similar material properties to UV‐cured acrylates. These studies pave the way for further usage of diazo‐functionalized cross‐linkers in the curing of paints and coatings. [ABSTRACT FROM AUTHOR]

Considering the current efforts for the development of new antimicrobial coatings from renewable resources suitable for application in environmentally friendly light-based technologies, the dependence of photocuring kinetics of vanillin bis epoxy resin and properties of the resulting coatings on the resin composition and process conditions was investigated. The photocuring rate, cross-linking density, and yield of the insoluble fraction, and thus the rheological, mechanical, and thermal properties of vanillin bis epoxy coatings have been found to be highly dependent on the amount of photoinitiator, solvent, and process temperature. The optimal resin, which ensures the highest thermal and mechanical characteristics of the coating, contained 3 wt% of a photoinitiator, triarylsulfonium hexafluorophosphate salts, and dichloromethane, and it was cured at 45 °C. Real-time photorheometry was shown to be able to be used for simple and quick determination of optimal resin composition and UV curing conditions to obtain coatings with desirable properties. The developed vanillin bis epoxy cross-linked coating is a viable alternative from renewable resources to petroleum-based epoxy analogues. [ABSTRACT FROM AUTHOR]

Thioxanthone derivatives with additional amino groups (TX‐S‐NH3) are synthesized via a simple esterification reaction between TX‐S‐CH2‐COOH and 2‐methylaminoethanol hydrocarbons in a p‐toluene sulfonic acid medium. The TX‐S‐NH3 is characterized by 1H NMR, 13C NMR, FT‐IR, HRMS, ultraviolet‐visible spectrophotometry, and fluorescence spectroscopy. TX‐S‐NH3 has strong absorption in water and ethanol, and the molar extinction coefficients at 395 nm are 2800 and 2780 mol−1L cm−1, respectively. TX‐S‐NH3 shows a low fluorescence quantum yield of 0.109 in deionized water. The maximum mobility of TX‐S‐NH3 in the photocuring product in ethanol is 12.5%. The double bond conversion of TMPTA cured by TX‐S‐NH3 is 60.7% without co‐initiator. TX‐S‐NH3 has excellent curing effects in UV‐curable ink with a light curing time of only 2.3 s. [ABSTRACT FROM AUTHOR]

The photoinduced curing gradients and in-situ lamellar gaps were related to the three-dimensional curing mechanism of stereolithography and researched in this work. Based on the photocuring mathematic theories presented by our team, photoinduced curing gradients were influenced by printing parameters such as laser power and frequency, scanning angle, and printing thickness. Among these curing gradients, the inadequate curing area was the main factor affecting the surface quality and physical properties of ceramics. The in-situ lamellar gaps were derived from the inadequate curing area. The lamellar gap size of green bodies was enlarged in brown bodies (sintering at 1170 ℃) and shrunk in sintered bodies (sintering at 1500 ℃). The correlations between the surface quality and printing parameters were clarified by establishing mathematical formulations of the lamellar gap size. Furthermore, anisotropic volume shrinkage, anisotropic surface topography, and density and hardness evolutions were associated with the wrapped particle density differences induced by the photoinduced curing gradients. Finally, the optimal printing parameters (75% of laser power, laser frequency of 150 kHz, scanning angle of 90º, printing thickness of 25 µm, and scanning speed of 2.5 m/s) were obtained by the orthogonal experimental analysis. This study provides a distinct understanding of the high-quality forming and extreme-performance manufacturing of stereolithography. • The three-dimensional curing mechanisms of stereo-lithography were discovered. • The lamellar gap formation was related to the single-point curing shapes. • The defect mathematical theories of the photo-curing gradients were presented. • The physical property difference was induced by the photo-induced curing gradients. [ABSTRACT FROM AUTHOR]

3D-printing technologies for polymer formulations are experiencing huge development due to the complex and specific geometries that can be created employing additive manufacturing. However, to ensure sustainable growth, it is essential to replace the currently used fossil-based resins with new biosourced alternatives. In this study, tunable bis-allylated compounds were efficiently synthesized from cellulose-derived levoglucosenone via a chemo-enzymatic pathway whose greenness has been assessed by E-factor and Eco-Scale. Subsequently, photocuring was employed as an eco-friendly process to polymerize these compounds with a trifunctional thiol using thiol-ene click chemistry. Real-time techniques such as FT-IR, photo-DSC, and photo-rheology were employed to extensively characterize the UV process. The resulting thermosets were also subjected to a thorough analysis, covering their thermo-mechanical properties and degradation. Owing to the exceptional reactivity of this thiol-ene system, 3-D printed materials were achieved with remarkable precision. [ABSTRACT FROM AUTHOR]

Poly(vinyl alcohol) (PVA)‐based hydrogels have attracted great attention and been widely used in biological tissue engineering. With the development of modern medicine, precision medicine requires the customization of medical materials. However, lacking of photocurable functional groups or the performance of rapid phase transition makes PVA‐based hydrogels difficult to be customizable molded through photocuring 3D printing technique. In this research, customizable PVA‐based hydrogels with high performance through 3D photocurable printing and freezing‐thawing (F‐T) process are obtained. The ability of 3D‐printable is endowed by the introduction of polyvinyl alcohol–styrylpyridine (PVA‐SBQ), which can be photo‐crosslinked quickly without photoinitiator. Meanwhile, the tunable mechanical properties are achieved by adjusting the mass ratio of PVA‐SBQ to PVA, and PVA can offer the physical crosslinking points through freezing‐thawing (F‐T) process. The hydrogels with high resolution are prepared by digital light procession 3D printing with the mass ratio 1:1 of PVA‐SBQ to PVA solution. Attributed to the absence of initiator, and no small molecule residues inside the hydrogels, the hydrogels have good biocompatibility and have the potential to be applicated in the field of biological tissue engineering. [ABSTRACT FROM AUTHOR]

Photonic microspheres containing colloidal arrays are useful as structural colorants in inks and cosmetics. However, low color saturation and low deformability of the microspheres restrict the uses. To overcome the limitations, elastic photonic shells with enhanced color saturation and high deformability using water‐in‐oil‐in‐water (W/O/W) double‐emulsion templates are designed. The elastic shells are produced by photocuring acrylate‐based resin containing non‐close‐packed arrays of silica particles in the middle oil layer. The presence of two concentric interfaces and water‐soluble molecules in the inner and continuous water phases at high concentrations improve the crystalline order of silica particles. In addition, the absence of a relatively disordered core reduces incoherent random scattering, thereby enhancing color saturation. Although the shells themselves are elastically deformable, the liquid core renders them significantly more deformable with small stiffness and negligible hysteresis, which is potentially beneficial for improving the fluidity of suspensions. Moreover, the structural colors of the elastic shells are post‐tunable by osmotic inflation of the semipermeable shells in hypotonic conditions. The high color saturation and high deformability as well as color tunability will provide a new opportunity for structural coloration with the elastic photonic shells as a colorant in inks and cosmetics. [ABSTRACT FROM AUTHOR]

Carbon fiber‐reinforced hollow composites play a vital role in lightweighting modern cars and aircrafts. Fabrication of such hollow composites with seamless internal finish requires sacrificial tooling that can be used under pressure and high temperature. For the very first time, high performance sacrificial tooling that can be used to fabricate fiber‐reinforced hollow composites is produced using photocuring 3D printing technology. This is achieved by developing UV‐curable resins containing highly soluble yet hydrolysable acetal acrylate cross‐linker and hydrophilic 4‐acryloylmorpholine monomer. It is found that the cross‐linker content greatly affects the printing speed. Further, the widely adopted UV post‐curing method is found to have negligible impact on improving the thermal‐mechanical properties of printed structures. After thermal post‐treatment, printed sacrificial tooling exhibits a heat deflection temperature of 112 °C at 0.455 MPa and an average coefficient of linear thermal expansion of 59 ppm °C−1 between 30 and 100 °C. As a result, printed tooling enables fabrication of carbon fiber‐reinforced hollow composites with complex geometry, which shows a tensile strength of 802 MPa and an elastic modulus of 50.2 GPa. [ABSTRACT FROM AUTHOR]

In this work, a bio-based, lightweight, coated cotton fabric by using a cleaner manufacturing method, "photocuring" was proposed in order to be used as an alternative to the conventional heat-, solvent-, and water-based outdoor textile (tarpaulin, tent, etc.) manufacturing. For this purpose, photocurable bio-based phosphorylated oligomer was synthesized with the reaction between a monomethacrylate functional phosphorus containing monomer and epoxidized soybean oil (ESBO). The synthesized phosphorylated ESBO (P-ESBO) oligomer was used in cotton fabric coatings in different proportions and photocured with UV light exposure. The effects of the amount of P-ESBO oligomer in the formulation on the crystalline morphology, mechanical, thermal, surface wettability, flammability, and abrasion resistance properties of the cotton fabrics were all searched. It was revealed that the increasing amount of P-ESBO oligomer in the formulation increases the drapeability and tensile strength of the fabrics with enhanced flame resist property by giving higher char yields. Besides, phosphorylated oligomer also acted as an adhesion promoter between the fabric surface and coating layer resulting a better abrasion resistance property. [ABSTRACT FROM AUTHOR]

The thermoresponsive drug-loaded hydrogels have attracted widespread interest in the field of medical applications due to their ease of delivery to structurally complex tissue defects. However, drug-resistant infections remain a challenge, which has prompted the development of new non-antibiotic hydrogels. To this end, we prepared chitosan-methacrylate (CTSMA)/gelatin (GEL) thermoresponsive hydrogels and added natural phenolic compounds, including tannic acid, gallic acid, and pyrogallol, to improve the efficacy of hydrogels. This hybrid hydrogel imparted initial crosslinking at physiological temperature, followed by photocuring to further provide a mechanically robust structure. Rheological analysis, tensile strength, antibacterial activity against E. coli, S. aureus, P. gingivalis, and S. mutans, and L929 cytotoxicity were evaluated. The experimental results showed that the hybrid hydrogel with CTSMA/GEL ratio of 5/1 and tannic acid additive had a promising gelation temperature of about 37 °C. The presence of phenolic compounds not only significantly (p < 0.05) enhanced cell viability, but also increased the tensile strength of CTSMA/GEL hybrid hydrogels. Moreover, the hydrogel containing tannic acid revealed potent antibacterial efficacy against four microorganisms. It was concluded that the hybrid hydrogel containing tannic acid could be a potential composite material for medical applications. [ABSTRACT FROM AUTHOR]

A series of thermoresponsive shape-memory photopolymers have been synthesized from the mixtures of two biobased monomers, tetrahydrofurfuryl acrylate and tridecyl methacrylate, with the addition of a small amount of 1,3-benzendithiol (molar ratio of monomers 0–10:0.5:0.03, respectively). Ethyl (2,4,6 trimethylbenzoyl) phenylphosphinate was used as photoinitiator. The calculated biorenewable carbon content of these photopolymers was in the range of (63.7–74.9)%. The increase in tetrahydrofurfuryl acrylate content in the photocurable resins resulted in a higher rate of photocuring, increased rigidity, as well as mechanical and thermal characteristics of the obtained polymers. All photopolymer samples showed thermoresponsive shape-memory behavior when reaching their glass transition temperature. The developed biobased photopolymers can replace petroleum-derived thermoresponsive shape-memory polymer analogues in a wide range of applications. [ABSTRACT FROM AUTHOR]

Temperature and light responsiveness are widely exploited stimuli to tune the physico-chemical properties of double network hydrogels. In this work, new amphiphilic poly(ether urethane)s bearing photo-sensitive moieties (i.e., thiol, acrylate and norbornene functionalities) were engineered by exploiting the versatility of poly(urethane) chemistry and carbodiimide-mediated green functionalization procedures. Polymers were synthesized according to optimized protocols maximizing photo-sensitive group grafting while preserving their functionality (approx. 1.0 × 1019, 2.6 × 1019 and 8.1 × 1017 thiol, acrylate and norbornene groups/gpolymer), and exploited to prepare thermo- and Vis-light-responsive thiol-ene photo-click hydrogels (18% w/v, 1:1 thiol:ene molar ratio). Green light-induced photo-curing allowed the achievement of a much more developed gel state with improved resistance to deformation (ca. 60% increase in critical deformation, γL). Triethanolamine addition as co-initiator to thiol-acrylate hydrogels improved the photo-click reaction (i.e., achievement of a better-developed gel state). Differently, L-tyrosine addition to thiol-norbornene solutions slightly hindered cross-linking, resulting in less developed gels with worse mechanical performances (~62% γL decrease). In their optimized composition, thiol-norbornene formulations resulted in prevalent elastic behavior at lower frequency compared to thiol-acrylate gels due to the formation of purely bio-orthogonal instead of heterogeneous gel networks. Our findings highlight that exploiting the same thiol-ene photo-click chemistry, a fine tuning of the gel properties is possible by reacting specific functional groups. [ABSTRACT FROM AUTHOR]

The types of additive technologies and the prospects for their use in the fabrication of products from silicon carbide ceramic materials are considered. The most popular for obtaining parts of complex configurations are additive technologies such as stereolithography, photocuring, inkjet printing, layer-by-layer 3D printing by extrusion of 'inks,' three-dimensional printing, selective laser sintering, selective laser melting, lamination method, layer-by-layer deposition method. [ABSTRACT FROM AUTHOR]

This study investigated the ability of a laser, and a 'quad-wave' LCU, to photo-cure paste and flowable bulk-fill resin-based composites (RBCs). Five LCUs and nine exposure conditions were used. The laser LCU (Monet) used for 1 s and 3 s, the quad-wave LCU (PinkWave) used for 3 s in the Boost and 20 s in the Standard modes, the the multi-peak LCU (Valo X) used for 5 s in the Xtra and 20 s in the Standard modes, were compared to the polywave PowerCure used in the 3 s mode and for 20 s in the Standard mode, and to the mono-peak SmartLite Pro used for 20 s. Two paste consistency bulk-fill RBCs: Filtek One Bulk Fill Shade A2 (3 M), Tetric PowerFill Shade IVA (Ivoclar Vivadent), and two flowable RBCs: Filtek Bulk Fill Flowable Shade A2 (3 M), Tetric PowerFlow Shade IVA (Ivoclar Vivadent) were photo-cured in 4-mm deep x 4-mm diameter metal molds. The light received by these specimens was measured using a spectrometer (Flame-T, Ocean Insight), and the radiant exposure delivered to the top surface of the RBCs was mapped. The immediate degree of conversion (DC) at the bottom, and the 24-hour Vickers Hardness (VH) at the top and bottom of the RBCs were measured and compared. The irradiance received by the 4-mm diameter specimens ranged from 1035 mW/cm2 (SmartLite Pro) to 5303 mW/cm2 (Monet). The radiant exposures between 350 and 500 nm delivered to the top surface of the RBCs ranged from 5.3 J/cm2 (Monet in 1 s) to 26.4 J/cm2 (Valo X), although the PinkWave delivered 32.1 J/cm2 in 20 s 350 to 900 nm. All four RBCs achieved their maximum DC and VH values at the bottom when photo-cured for 20 s. The Monet used for 1 s and the PinkWave used for 3 s on the Boost setting delivered the lowest radiant exposures between 420 and 500 nm (5.3 J/cm2 and 3.5 J/cm2 respectively), and they produced the lowest DC and VH values. Despite delivering a high irradiance, the short 1 or 3-s exposures delivered less energy to the RBC than 20-s exposures from LCUs that deliver> 1000 mW/cm2. There was an excellent linear correlation (r > 0.98) between the DC and the VH at the bottom. There was a logarithmic relationship between the DC and the radiant exposure (Pearson's r = 0.87-97) and between the VH and the radiant exposure (Pearson's r = 0.92–0.96) delivered in the 420-500 nm range. • The spectral radiant powers and the radiant exposures delivered to the RBCs from the LCUs ranged from 5.3 J/cm2 to 32.1 J/cm2. • The effect of high irradiance and short exposure times was material dependant. • There was an excellent correlation (r > 0.98) between both the DC and the VH at the bottom and the radiant exposure. • There was little correlation between the irradiance and the DC or the VH. [ABSTRACT FROM AUTHOR]

To prepare a photocurable ceramic suspension for use in commercialized additive manufacturing equipment, the effects of the rheological properties of zirconia particles added to a binder, and the presence or absence of a silane coupling agent on the particles was evaluated. To this end, three experimental groups (ZSs, ZMs, ZLs) and three control groups (ZS, ZM, ZL) were designed depending on the size of the underlying zirconia particles. The test-group zirconia suspensions were prepared through silanization, which was not applied to the control-group suspensions. Depending on the particle size, viscosity differences between the test and control groups were 16,842, 18,623, and 12,303 mPa·s, respectively. Compared to the other groups, the viscosity of the ZLs group suspension decreased by 70.98–88.04%. This confirmed that the viscosity of the suspensions was affected by the particle size and the presence of silane coating. The dispersion stability of the zirconia suspensions was evaluated over 20 days. A sedimentation test confirmed that the sedimentation rate of the ZLs group was slower than those of the other groups. This study aimed to optimize the suspension manufacturing method to effectively be utilized in further commercializing zirconia three-dimensional (3D) printing and could also help to develop various medical applications. [ABSTRACT FROM AUTHOR]

A deliberately selected end-capping agent was introduced into the precursor to form a low number average molecular weight precursor and meet the need for liquid crystal display (LCD) 3D printing. The influence of number average molecular weight on the photocuring properties of precursor and the physical properties of pyrolysis samples were studied in detail for the first time. The results proved that a relatively low number average molecular weight precursors had low ceramic yields after pyrolysis. As the number average molecular weight of the precursor decreased, the photocuring ability of the precursor photosensitive resin increased. With the decrease in the number average molecular weight of the precursor in the precursor photosensitive resin, the ceramic yield of 3D printed PDCs decreased from 58.4% to 30.2%, and the linear shrinkage increased from 27.2% to 40.3%. The bending strength of the LCD 3D printed specimen reached 61.5 ± 3.7 MPa. The low cost of precursor synthesis and equipment in this study points the way for the preparation of precursor non-oxide ceramic composites and can be conducive to the development and application of LCD 3D printing precursor ceramics. [ABSTRACT FROM AUTHOR]

In this study, hyperbranched polyglycerol (HPG) is synthesized via ring‐opening polymerization of a glycidol monomer. An epoxy group is introduced at the end of HPG through a reaction with epichlorohydrin in a one‐pot process. The number of epoxy groups introduced increase proportional to the amount of boron‐trifluoride‐tetrahydrofuran catalyst used. In addition, acrylate‐functionalized polyglycerol (AG) is synthesized via a reaction of the epoxy group with an acrylic acid, and a maximum of 5.7 acrylate groups are introduced per molecule. AG shows photocuring behavior with the photoinitiator Irgacure 819, while viscosity is adjusted from 18 to 2947 cPs by introducing up to 80 wt% 2‐hydroxyethyl acrylate (2‐HEA). Diluted resin can cure over 97 wt% even with a short UV irradiation period of 20 s. Furthermore, hydrophilicity increases proportional to the amount of 2‐HEA added, and water absorption can be controlled in the range of 30–124 wt%. [ABSTRACT FROM AUTHOR]

In this study, a simple photocuring method is proposed for preparing PDMS elastomers using a homogenous poly(dimethylsiloxane) (PDMS) solution in tert‐butyl acrylate (tBA) as an alternative way of mechanically blending two kinds of PDMS respectively containing vinyl and hydridosilyl groups over a platinum catalyst. Poly(dimethylsiloxane‐co‐methylvinylsiloxane) (PDMSc) with 30 mol% of vinyl moieties is synthesized. The functionalized PDMS is estimated to be soluble in tBA from theoretical calculations of solubility parameters of PDMS and several liquid monomers. The PDMS solution is satisfactorily photocured under a conventional photoinitiator. Initial modulus and strain of the photocured films increase from 144 to 552 MPa and decrease from 3.96 to 1.84, respectively, as the tBA content rises from 5 to 30 wt%. They are extremely transparent in a visible region (T > 94%) regardless of the amount of tBA. The unreacted vinyl groups in PDMSc are inter‐ or intrareacted near 200 °C and γ‐hydrogen transfer reactions from the tert‐butyl groups in poly(tert‐butyl acrylate) occur over 250 °C. One of the photocrosslinked films exhibits outstanding performance as an electroactive polymer in application. In essence, this study will initiate a new methodological research into provision of PDMS elastomers using an easily formulated photocrosslinkable PDMS solution. [ABSTRACT FROM AUTHOR]

Vitrimers have gained attention as materials with recyclability, self-healing, and shape memory properties. The use of bio-based monomers for the synthesis of vitrimers is relevant because of the use of an environmentally friendly strategy. In this work, resins based on 2-hydroxy-2-phenoxypropyl acrylate and acrylated epoxidized soybean oil were designed and tested by real-time photorheometry, Fourier transform infrared spectroscopy (FT-IR), and mechanical testing to determine suitability for digital light processing 3D printing. The synthesis of vitrimer that could have good thermal properties and vitrimeric abilities, such as shape memory, self-healing, and recyclability properties, was investigated. Because of this, the vitrimer could repair cracks and defects and could have a complex design of several parts, which also contributes to recyclability and decreases costs. The rigidity and viscosity of the resins were reduced with an increasing amount of 2-hydroxy-2-phenoxypropyl acrylate-based monomer. The resin that has the highest amounts of hydroxyl and ester groups that are beneficial for transesterification reactions was chosen for vitrimer synthesis in order to show vitrimeric abilities such as self-healing, shape memory properties, reprocessability, and recyclability. The synthesized vitrimer was applied to digital light processing 3D printing and showed shape memory with a recovery ratio of 100%, self-healing and reprocessability with an efficiency of 47 and 31% and recyclability properties. [ABSTRACT FROM AUTHOR]

A novel dual cure photopolymerizable system was developed by combining two plant-derived acrylic monomers, acrylated epoxidized soybean oil and vanillin dimethacrylate, as well as the thiol monomer pentaerythritol tetrakis (3-mercaptopropionate). Carefully selected resin composition allowed the researchers to overcome earlier stability/premature polymerization problems and to obtain stable (up to six months at 4 °C) and selectively-polymerizable resin. The resin demonstrated rapid photocuring without an induction period and reached a rigidity of 317.66 MPa, which was more than 20 times higher than that of the other vanillin-based polymers. Improved mechanical properties and thermal stability of the resulting cross-linked photopolymer were obtained compared to similar homo- and copolymers: Young's modulus reached 4753 MPa, the compression modulus reached 1634 MPa, and the temperature of 10% weight loss was 373 °C. The developed photocurable system was successfully applied in stereolithography and characterized with femtosecond pulsed two-beam initiation threshold measurement for the first time. The polymerization threshold of the investigated polymer was determined to be controlled by the sample temperature, making the footprint of the workstations cheaper, faster, and more reliable. [ABSTRACT FROM AUTHOR]

Chitosan is one of the promising compounds for use in various fields of medicine. However, for successful application, materials based on it must be insoluble in water and have specified physical and mechanical properties. In this work, we studied the interaction of N-methylolacrylamide (NMA) and chitosan upon concentration of the solutions, both under the action of UV radiation and without it, which results in curing of the polymer matrix. The main products, proposed mechanisms of the crosslinking reaction, and the influence of external conditions on these processes have been revealed using NMR, IR, and UV spectroscopy. It was found that the reaction proceeds along three pathways. The main reactions proceed with the amino groups of chitosan, and the hydroxymethyl and vinyl groups of NMA. Studies have shown that for the formation of insoluble materials based on chitosan, the best content in the initial cast solution is 2 wt% of chitosan at 0.25 wt% concentration of NMA. Films formed from such solutions possessed high strength and deformation characteristics, namely an elastic modulus of about 1500 GPa, a strength of about 30 MPa, and an elongation at break of about 100%. [ABSTRACT FROM AUTHOR]

Nano-WO3 particles are expected to find use in new shielding materials because of their significant absorption of near-infrared light in the 1400–1600 nm and 1900–2200 nm bands and high transmittance of visible light. In this study, WO3 was ground and dispersed using high-energy ball-milling to prepare a nano-WO3 dispersion using BYK331 as the dispersant and ethanol as the solvent. The prepared nano-WO3 dispersion was added to a photo-curing system and cured using UV irradiation to form films. The cured films were characterized using FT-IR, SEM, XRD, and TGA. The results showed that the nano-WO3 powder was evenly dispersed in the coating. The infrared blocking rate of the film continuously improved and the visible light transmission rate continuously decreased with increasing amounts of nano-WO3.For the film containing 6 wt%nano-WO3, the infrared blocking rate of the coating is 90%, the visible light transmittance is 70%, the hardness of the coating is 3B, and the adhesion is 3H. The thermal stability of the coating is also improved. [ABSTRACT FROM AUTHOR]

In order to overcome challenges typically encountered during additive manufacturing of ceramics via the polymer precursor route, a novel polymer-derived SiOC/SiC composite system suitable for advanced geometric designs achievable by lithography-based ceramic manufacturing was established. The photoreactive resin system filled with 20 wt% SiC exhibits suitable viscosity characteristics, adequate stability against sedimentation, and a fast photocuring behavior. After printing and pyrolytic conversion, SiC particulates were well-dispersed within the polymer-derived SiOC matrix. A direct comparison with the unfilled polysiloxane-based resin system showed that the addition of particulate SiC increases handleability, reduces shrinkage, and significantly increases critical wall thicknesses up to 5 mm. The biaxial Ball-on-Three-Balls testing methodology yielded a characteristic strength of 325 MPa for SiOC/SiC composites. The results highlight the high potential of particle-filled preceramic polymer systems toward the fabrication of high-performance SiC-based materials by lithography-based additive manufacturing. [ABSTRACT FROM AUTHOR]

In this study, photo-curing kinetics for urethane-acrylate-based photo-inks for 3D printing were evaluated using a photo-differential scanning calorimetry analysis. Initially, the photopolymerization kinetics of di- and monofunctional monomers were separately studied at different temperatures (5–85 °C). Later, the photo-curing kinetics and mechanical properties of photo-inks based on different monomer mixtures (40/60–20/80) were evaluated. The results showed that urethane-dimethacrylate (UrDMA) and urethane-acrylate (UrA) had no light absorption in the region of 280–700 nm, making them a proper crosslinker and a reactive diluent, respectively, for the formulation of 3D-printing photo-inks. The kinetics investigations showed a temperature dependency for the photo-curing of UrDMA, where a higher photopolymerization rate (Rp,max: from 5.25 × 10−2 to 8.42 × 10−2 1/s) and double-bound conversion (DBCtotal: from 63.8% to 92.2%) were observed at elevated temperatures (5–85 °C), while the photo-curing of UrA was independent of the temperature (25–85 °C). Enhancing the UrA content from 60% to 80% in the UrDMA/UrA mixtures initially increased and later decreased the photopolymerization rate and conversion, where the mixtures of 30/70 and 25/75 presented the highest values. Meanwhile, increasing the UrA content led to lower glass transition temperatures (Tg) and mechanical strength for the photo-cured samples, where the mixture of 30/70 presented the highest maximum elongation (εmax: 73%). [ABSTRACT FROM AUTHOR]

• Gamma radiation can induce crosslinking in epoxies containing C = C bonds. • This behavior provides a path to functionally graded materials and adhesives. • Radiation crosslinking is more efficient with multiple types of C = C bonds present. • Composition, radiation dose, crosslink density and T g can be related quantitatively. Ultra-violet (UV) radiation has been used to produce functionally graded materials by locally modulating crosslink density. Functionally graded adhesives are an important subset of functionally graded materials, but photocuring is of limited use when creating structural adhesive joints, most of which involve opaque adherends. As a result of these and other difficulties generating such materials in practice, the advantages of functionally graded adhesives have been reported theoretically, but experimental investigations remain rare. For this reason, our group has focused on dual cure systems sensitive to post-curing via high energy radiation as a means of locally modulating properties. Here, a series of thermally cured epoxy resins are shown to exhibit different levels of sensitivity toward gamma (γ) irradiation as a function of the concentration of a bisphenol-derived unsaturated chain extender incorporated into an epoxy-anhydride network that contains unsaturations as well. It was observed that addition of the chain extender slowed curing and impacted the thermal properties of the cured epoxy networks but greatly favored radiation-induced crosslinking over degradation given the observed shifts in properties. A theory proposed by Shibayama relating T g to crosslink density is applied to better understand the structure and crosslinking behavior of thermally cured epoxies before and after radiation post-curing and provides a useful means to predict radiation-induced changes in performance. The development of such heat / γ radiation dual curable formulations, the understanding of their behavior upon irradiation and the ability to predict key properties via a simple analytical model provides a new perspective for the successful generation of functionally graded materials through methods described in our prior work. [ABSTRACT FROM AUTHOR]

The preparation of functional photopolymer nanocomposites is affected by both the physical and chemical interactions of nanoparticles (NPs) and polymer resin. Some NPs, such as semiconducting metal oxides, may contribute by their photocatalytic behavior and electron transfer, influencing the kinetics of the photopolymerization reaction. This study has investigated the complex effect of titanium dioxide (TiO 2) NPs in anatase and rutile form on the conversion, kinetics, and printability of free-radical and cationic photopolymerization resin. Two different polymorphs of TiO 2 NPs ensured identical chemical properties, but different physical effects related to their varying band gap energies and electron transfer efficiency. These parameters were found to be crucial for influencing the photopolymerization kinetics. While rutile showed a more pronounced enhancement of the free-radical photopolymerization's conversion and kinetics, cationic photopolymerization was favourably affected only by anatase NPs due to the photosensitization effect. These findings are critical in understanding and designing functional nanocomposite materials processed by vat photopolymerization 3D printing that could find use in optical, medical, or environmental applications. [Display omitted] • Anatase and rutile nanoparticles (NPs) can photosensitize cationic polymerization. • Anatase and rutile NPs can directly photoinitiate free-radical polymerization. • Enhanced cationic polymerization occurs for high band-gap energy NPs. • Enhanced free-radical polymerization occurs for low band-gap energy NPs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Four coumarin-carbazole-based oxime esters were synthesized as photoinitiators (PIs). • PIs exhibit excellent adsorption and initiation ability than commercial OXE 02. • PIs can effectively initiate one/two-photon polymerization of LEDs/NIR light. • PIs have outstanding migration stability and cytocompatibility. • PIs with CF 3 group have higher two-photon lithography capability. Photocuring has developed rapidly in recent years owing to its unique "5E" characteristics, especially in the industrial and manufacturing fields, where photoinitiators (PIs) are essential components of the polymerization system. However, most PIs have limited applications in fields that directly contact the human body, such as food packaging or biomedicine, due to migration stability and toxicity. Here, four oxime esters were designed as PIs by using coumarin-carbazole as the conjugate structure, and their properties were optimized by multisite modification of the molecular structure. First, substituents with different electronic properties were introduced at the 4-position of coumarin. The introduction of electron-withdrawing trifluoromethyl redshifted the molecule and better matched the light-emitting diode (LED) emission spectra (i.e., 365–450 nm). In addition, the introduction of long and branched alkyl chains on carbazole increased the solubility of the four PIs. The initiation efficiency of the PIs was improved by inserting long or cyclized alkyl chains at the α-position of C = N double bond. The experimental results demonstrated that these four PIs are superior to the commercial oxime ester OXE 02 in terms of light absorption and initiation ability under LED irradiation. The migration stability and cytocompatibility of these PIs were validated, ensuring a green and safe application in photocuring applications. Furthermore, these PIs exhibited a considerable writing speed and remarkable nanopatterning capabilities under 780 nm laser in two-photon polymerization. These outstanding properties indicated their great potential for applications in diverse areas of photocuring, especially in food packaging, bio-3D printing, tissue engineering, and nano-additive manufacturing. [ABSTRACT FROM AUTHOR]

The use of renewable resources for additive manufacturing has grown significantly as a means of advancing the ongoing shift to a green economy. This study uses bio-oil generated from the rapid pyrolysis of forest waste as a bio-based chemical to partially replace polyethylene glycol to synthesize a new type of bio-oil modified polyurethane acrylate, used in photo-curing 3D printing technology. The study explores the impact of the ratio of bio-oil to polyethylene glycol on the properties of polyurethane resin. As the amount of bio-oil added increases, the molecular weight of polyurethane acrylate decreases. Modified photosensitive resin showcases better suitability for photo-curing 3D printing, with lower viscosity and volume shrinkage, and its printed samples exhibit enhanced mechanical strength and improved thermal stability. In particular, when the bio-oil substitution rate is 20 wt%, the tensile strength of the 3D printed sample increases by 70 %, and the double bond conversion rate reaches 58.07 %. Meanwhile, the hollow and branching structures of 3D printing have the characteristics of high precision and flexibility. Introducing bio-oil into 3D printing technology not only expands the application fields of bio-oil but also provides new considerations for the transition of photosensitive resins from petroleum-based to renewable fields. [Display omitted] • The volume shrinkage rate of photosensitive resin greatly decreased with bio-oil modification. • The viscosity of photosensitive resin was significantly reduced by more than ten times after adding bio-oil. • The tensile strength of the mechanical specimen of 20BPUA resin was increased to 70 % higher than unmodified resin. • Bio-oil-modified polyurethane acrylate photosensitive resin can 3D print flexible structures and complex shapes. [ABSTRACT FROM AUTHOR]

Novel itaconic acid-derived green hyperbranched macromers with polymerizable C=C bonds both in the internal skeleton and periphery were synthesized under mild synthetic conditions. The addition of hyperbranched polymers can make the cured cross-linked network denser and more uniform, and thus, leading to a significant improvement in performance of the coatings. [Display omitted] • Novel itaconic acid-based hyperbranched macromers with C = C bonds both in framework and periphery were designed and synthesized. • Esterification was catalyzed by tetramethylguanidine under mild reaction conditions with simple operations. • The new hyperbranched macromers can effectively promote the photopolymerization performance. • Addition of the hyperbranched macromers leads to a significant improvement in the performance of coatings. A series of hyperbranched polymers derived from biomass itaconic acid was prepared via aliphatic nucleophilic substitution polycondensation reaction under mild conditions by using bis(2-bromoethyl) itaconate and trimeric acid as A 2 and B 3 monomers, respectively, and tetramethylguanidine as catalyst. On this basis, the hyperbranched macromers that contained C = C double bonds in the internal skeleton and the periphery were obtained by further adding A 1 monomer (2-bromoethyl acrylate) directly into the reaction system. The successful synthesis of these macromers were confirmed via proton nuclear magnetic resonance, Fourier transform infrared and gel permeation chromatography. The results of photo-differential scanning calorimetry and rheological experiments showed that these macromers exerted a positive effect on the ultraviolet (UV) curing of commercial resin. The properties of cured splines and coatings, such as mechanical properties, pencil hardness, and thermal stability, were considerably improved with the addition of hyperbranched macromers. They were significantly better than those of linear macromers and macromers that contained polymerizable groups only in the inner framework or their terminal units. The results show that both the inner and terminal C = C double bonds of hyperbranched macromers can participate in UV cross-linking. Thus, such macromers may be used as potential additives for high-performance UV curable coatings. [ABSTRACT FROM AUTHOR]

This investigation focused on the contribution of various silane blends, used as coupling agents, to the ultimate performance of dental nanocomposite dimethacrylate photocurable resins. Initially, the surface of silica nanospheres was silanized with three different silane coupling agents: γ-MPS, APTES, and OTMS, with the grafting rate serving as the index. Fourier Transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) verified the modification of nanosilica. Through orthogonal test experiments on the three silane coupling agents, the optimal modifier concentration, temperature, and time were determined. Subsequently, 15 wt% organomodified SiO 2 nanospheres were incorporated into Bis-GMA/TEGDMA (70/30 by wt%) based resins via a photocuring process. Scanning electron microscopy (SEM) findings revealed a relatively vague interface between inorganic fillers and resins in the polymer composite, especially when reactive silanes like γ-MPS and their corresponding blends were used. The combination of SiO 2 and γ-MPS functional silane blend provided the highest flexural properties and the lowest solubility after storing the nanocomposite in water for 1 week at 37 °C. With these methods, composite resins containing 15 wt% MPS-SiO 2 nanospheres in a Bis-GMA/TEGDMA (70/30 by wt%) mixture exhibited the best comprehensive properties, making them a promising choice for achieving long-term durable restorations in clinical therapies. [ABSTRACT FROM AUTHOR]

Visible light polymerization is a development trend in the field of photocuring. However, most of the reported visible light photoinitiators (PIs) are two-component systems that display limited initiation efficiency due to diffusion restriction and back electron transfer effect. In this study, two one-component visible light PIs (BDNPG-1 and BDNPG-2) are synthesized through combining N -phenylglycine (NPG) moiety with cyclopentanone moiety together. Upon irradiation of blue or green light, they can undergo intermolecular electron transfer followed by proton transfer plus a decarboxylation reaction to produce carbon dioxide and aminoalkyl radicals. This decarboxylation reaction is irreversible so that the intermolecular back electron transfer can be effectively blocked, resulting in a significantly improved photoinitiation efficiency of BDNPG-1 and BDNPG-2 compared with their prototype PI (BDEA) containing no NPG group and the two-component system of BDEA+NPG. Furthermore, both of them have strong two-photon absorption capability and show excellent performance in two-photon polymerization. [Display omitted] • Two one-component benzylidene cyclopentanone visible light photoinitiators (PIs) were synthesized. • They can undergo an irreversible decarboxylation reaction to produce aminoalkyl radicals upon irradiation. • Their photoinitiation efficiency was much higher than their prototype PI BDEA and the combination of BDEA and NPG. • They also showed excellent performance in two-photon polymerization. [ABSTRACT FROM AUTHOR]