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Tailoring the collagen film structural properties via direct laser crosslinking of star-shaped polylactide for robust scaffold formation
摘要： Application of restructured collagen-based biomaterials is generally restricted by their poor mechanical properties, which ideally must be close to those of a tissue being repaired. Here, we present an approach to the formation of a robust biomaterial using laser-induced curing of a photosensitive star-shaped polylactide. The created collagen-based structures demonstrated an increase in the Young’s modulus by more than an order of magnitude with introduction of reinforcing patterns (from 0.15±0.02 MPa for the untreated collagen to 51.2±5.6 MPa for the reinforced collagen). It was shown that the geometrical configuration of the created reinforcing pattern affected the scaffold’s mechanical properties only in the case of a relatively high laser radiation power density, when the effect of accumulated thermomechanical stresses in the photocured regions was significant. Photo-crosslinking of polylactide did not compromise the scaffold’s cytotoxicity and provided fluorescent regions in the collagen matrix, that create a potential for noninvasive monitoring of such materials’ biodegradation kinetics in vivo.
关键词： mechanical properties,collagen,reinforcements,photopolymerization,biocompatible polymers,riboflavin
更新于2025-11-21 11:24:58
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Synthesis of luminescent polymers in the UV light region from dimethacrylate monomer using novel quinoline dyes
摘要： This study aims at thermal and morphological features, as well as the degree of conversion these luminescent polymers obtained using a dimethacrylate monomer, and quinoline dyes as photoinitiator. The photoinitiators provide a ?uorescent propriety to the ?nal polymer. Thermal properties such as thermal stability, steps of mass loss, and glass transition are obtained by thermogravimetry-differential thermal analysis and derivative thermogravimetric and differential scanning calorimetry. Using the mid-infrared spectroscopy, it is possible to calculate the degree of conversion/rate of polymerization; the data indicate that the quinoline derivatives could be used as photoinitiators in lower concentration (0.1%) resulting in solid rigid polymers with higher conversion (74.24, 71.81, 66.36, and 61.09%). The morphological characteristics of polymers are analyzed by scanning electronic microscopy. Finally, solid ultraviolet–visible (UV–vis) analysis shows a bathochromic shift, due to the stabilization of the molecules in the solid state, compared to liquid UV–vis analysis. ? 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47461.
关键词： thermal analysis,quinoline dyes,photopolymerization,luminescent polymers,high conversion
更新于2025-11-14 15:18:02
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Dewetting and photochemical crosslinking of adhesive pads onto lithographically patterned surfaces
摘要： The design of structured adhesive interfaces can be realized by dewetting of a liquid adhesive onto substrates with hydrophilic and hydrophobic domains followed by photochemical crosslinking. The latter allows the creation of well-defined arrays of confined adhesive pads with a controlled geometry. In a first step, the surfaces are covered by a hydrophobic film and lithographically patterned through a mask with an array of spots with diameter of 2 mm. The adhesive can consequently be locally deposited by a dosing syringe and remains confined within the hydrophilic spots. By defining the volume of the adhesive droplets, the contact angle and height of the adhesive pads are controlled through pinning at the hydrophilic/hydrophobic interface, which prevents further spreading. Alternatively, the dip coating and spontaneous dewetting of liquid adhesive over the patterned surface provide a continuous fabrication method for adhesive pad arrays. In a second step, the geometry of the deposited adhesive pads is stabilized by partial crosslinking during different times under UV light. Finally, an adhesive joint is created by applying the counterface followed by full cross-linking. The adhesive strength and mechanical performance are further optimized by considering different crosslinking times and pattern designs.
关键词： adhesives,surfaces and interface,photopolymerization
更新于2025-09-23 15:23:52
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Effect of indirect restorative material and thickness on light transmission at different wavelengths
摘要： Purpose: The aim of this study was to evaluate the influence of indirect restorative material type and thickness on the transmission of different wavelengths from a broad-banded dental curing light. Methods: Four dental indirect restorative materials for computer-aided design and computer-aided manufacturing (CAD/CAM) were evaluated: [RC] resin/ceramic hybrid material (Lava Ultimate), [FC] feldspathic ceramic (VitaBlocs), and two zirconia-based ceramics ([ZK] Katana; and [ZL] Lava). Total loss of irradiance (TL) was measured for blue (WB, 425–490 nm) and violet (WV, 350–425 nm) wavelengths. Specimens of 15 mm with varying thicknesses (0.5, 1.0, 1.5, and 2.0 mm) were fabricated (n = 5). A plasma-arc dental light-curing unit was used (Arc Light-II). To assess TL as a function of wavelength, a software (Spectra Suite v5.1) connected to a spectroradiometer (USB2000) and an integrating sphere (CTSM-LSM-60-SF) was used. Data was subjected to statistical analysis (two-way ANOVA and post-hoc Tukey test, α = 0.05). Results: A 0.5 mm interposition resulted in TL from 50.5 to 67.2%, depending on material. Increased thickness resulted in higher TL for all materials. FC showed less TL compared to ZK. In general, WV showed higher TL than did WB, and WV/WB proportion decreased with increasing thickness. Conclusions: Indirect materials significantly reduced TL, and this effect is greater with increasing thickness. WV showed lower penetration compared to WB.
关键词： Ceramics,Photopolymerization,Irradiance,Composite,Zirconia
更新于2025-09-23 15:23:52
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Thioxanthone-functionalized 1,6-heptadiene as monomeric photoinitiator
摘要： The synthesis of the first photoinitiator (PI) based on thioxanthone (TX) with 1,6-heptadiene structure is described. This PI (TXdMA) absorbs in the near UV–vis region (435–439 nm; with absorption redshift≈50 nm and ε values comparable to TX). Photopolymerization results demonstrate that although TXdMA is not an effective one-component polymerizable photoinitiator, it can successfully initiate photopolymerization of poly(ethylene glycol) diacrylate (PEGDA, Mn = 250 D) and trimethylolpropane triacrylate (TMPTA) in the presence of bis-(4-tert-butylphenyl)-iodonium hexafluorophosphate (Iod) similar to TX/Iod. TXdMA exhibits better migration stability than TX. Absorption, fluorescence, steady state photolysis and cyclic voltammetry experiments are carried out to investigate the photochemical mechanisms.
关键词： Photopolymerization,Monomeric photoinitiators,Fluorescence,Photo differential scanning calorimetry
更新于2025-09-23 15:23:52
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Effects of different molecular chain lengths and side groups on structure and property of UV-curable waterborne cathodic electrophoretic deposition coatings
摘要： A series of UV-curable waterborne cathodic electrophoretic deposition (CED) coatings with various structures were successfully developed by introducing modified acrylic monomer with different molecular chain lengths and side groups. The length of linear chain of the modified monomer had little effect on phase separation of acrylic polymer and easily formed homogeneous structure. Owing to the longer molecular chains, the pencil hardness decreased from 2H to H and the glass transition temperature reduced to 77.7 °C. The hard side groups of the modified monomer in CED coatings exhibited opposite characteristics resulting from the steric hindrance of the rigid groups and the crosslinking network, which were more likely to exhibit partial phase separation. Therefore, the stronger rigidity of the molecular structure improved the particle size to 122.42 nm, the smoothness of the CED cured film and surface contact angle decreased. And the morphology of the films became rough and surface contact angle decreased. Besides, the adhesive force and flexibility of the films could be excellent. The surface rust of the modified CED film is not remarkable under salt spray test. The photopolymerization rate (Rp) and the double bond conversion were evaluated. It was found that the Rp and the conversion obviously decreased with increasing rigid groups in acrylate molecular chains. However, the maximum decomposition temperature of it was higher than the other samples. The residue char yield (Yc) was 5.24 wt%. The stronger rigidity of the molecular structure had better thermal stability and mechanical properties.
关键词： Cathodic electrophoretic deposition coatings,Thermal stability,Photopolymerization rate,Molecular structure
更新于2025-09-23 15:22:29
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3D Printing Amorphous Polysiloxane Terpolymers via Vat Photopolymerization
摘要： Photocuring and vat photopolymerization (VP) additive manufacturing (AM) is reported for two families of fully amorphous poly(dimethyl siloxane) (PDMS) terpolymers containing either diphenylsiloxy (DiPhS) or diethylsiloxy (DiEtS) repeating units. A thiol-functionalized PDMS crosslinker enables rapid crosslinking in air using efficient thiol–ene addition. Differential scanning calorimetry and dynamic mechanical analysis (DMA) confirm the absence of crystallinity for the DiPhS-containing systems, while DMA shows a rubbery plateau extending to greater than 200 °C for the DiEtS-containing system. VP-AM of both photopolymer systems afford well-defined 3D geometries, including high aspect ratio structures, which demonstrate feasibility of these photopolymers for the 3D printing of unique geometric objects that require elastomeric performance to temperatures as low as ?120 °C.
关键词： thiol–ene reaction,elastomers,poly(dimethyl siloxane),vat photopolymerization,siloxane terpolymers,3D printing
更新于2025-09-23 15:22:29
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Experimental investigation and thermo-mechanical modelling for tool life evaluation of photopolymer additively manufactured mould inserts in different injection moulding conditions
摘要： There is a growing interest for integrating additive manufacturing (AM) technology in different manufacturing processes such as injection moulding (IM) due to the possibility of achieving shorter manufacturing times and increased cost effectiveness. This paper evaluates IM inserts fabricated by the AM vat photopolymerisation method. The inserts are directly manufactured with a photopolymer material, integrated on an injection moulding tool and subsequently used for IM. Therefore, particular attention has to be paid in order to develop the soft tooling process chain and the IM experimental procedure as detailed in this study. Different combinations of IM parameters are investigated in this work in order to determine the influence of the various process settings on the inserts’ performance (lifetime, crack propagation, consistency of the mould surface features). The mould inserts were analysed by three-dimensional optical metrology and evaluated with regard to the different surface features that were affected by the IM process. A three-dimensional thermo-mechanical with phase change model for the analysis of the effects of the IM process on the additive manufactured tools was accomplished in the FE software COMSOL Multiphysics. The potential causes for the insert failure are identified both by means of the IM experiments and the numerical model. The developed model could also predict the thermally induced deformations produced in the mould and identify where this phenomenon would eventually lead to defects in the shape of the parts. The influence of three different temperatures of the insert at 25 °C, 50 °C and 100 °C on the failure of the insert was investigated. Also a detailed discussion about the solidification and temperature changes is given.
关键词： Finite element modelling,Vat photopolymerization,Injection moulding,Soft tooling,Additive manufacturing
更新于2025-09-23 15:22:29
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[IEEE 2019 24th Microoptics Conference (MOC) - Toyama, Japan (2019.11.17-2019.11.20)] 2019 24th Microoptics Conference (MOC) - Light-Induced Self-Written Optical Waveguide Fabrication by Near Infrared Continuous Wave Laser Light with Microwatt Power
摘要： We have successfully demonstrated light-induced self-written (LISW) waveguides at a wavelength of 1070 nm and 1310 nm, respectively. Microwatt level photopolymerization threshold value was obtained at both wavelengths. The results show a promising approach for optical interconnection in silicon photonics.
关键词： Photopolymerization,Continuous Wave (CW) laser,Silicon photonics,Near Infrared (NIR),Light-induced self-written (LISW) waveguides
更新于2025-09-23 15:21:01
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Substituent Effects on Photoinitiation Ability of Monoaminoanthraquinonea??Based Photoinitiating Systems for Free Radical Photopolymerization under LEDs
摘要： Three monoamino-substituted anthraquinone derivatives (AAQs), that is, 1-aminoanthraquinone (AAQ), 1-(methylamino)anthraquinone (MAAQ), and 1-(benzamido)anthraquinone (BAAQ), incorporated with various additives [e.g., triethanolamine (TEAOH) and phenacyl bromide (PhC(═O)CH2Br)] are investigated for their roles as photoinitiating systems of free radical photopolymerization of (meth)acrylate monomers upon the exposure to UV to green LEDs. The AAQs-based photoinitiating systems, AAQ/TEAOH/PhC(═O)CH2Br and BAAQ/TEAOH/PhC(═O)CH2Br photoinitiators exhibit the highest efficiency for the free radical photopolymerization of DPGDA under the irradiation of blue LED and UV LED, respectively, which is consistent with the extent of overlap between their absorption spectra and the emission spectra of the LEDs. AAQ/TEAOH/PhC(═O)CH2Br photoinitiator can also initiate the free radical photopolymerization of different (meth)acrylate monomers, with an efficiency dependent on the chemical structures of these monomers.
关键词： LEDs,free radical photopolymerization,aminoanthraquinone,photo initiators
更新于2025-09-23 15:21:01