Photocuring Behaviors of UV-Curable Perfluoropolyether-Based Fluoropolymers with and without Tertiary Amine

UV-curable perfluoropolyether (PFPE)-based fluoropolymer (PFPE-DMA) was synthesized and the photocuring behaviors of PFPE-DMA/HDDA systems with and without tertiary triethyl amine (TEA) were investigated using photo-DSC under air and nitrogen atmospheres. Photo-DSC analysis revealed that N2 purging and the presence of TEA mitigated oxygen inhibition in the photopolymerization of the UV-curable free-radical PFPE-DMA/ HDDA system. In addition, TEA synergistically acted as a coinitiator or photosynergist under nitrogen atmosphere, which increased the cure rate and percentage conversion for the photopolymerization of PFPE-DMA/ HDDA. TEA acted as both oxygen scavenger and photosynergist. The results presented here demonstrate that investigating the photocuring behaviors of PFPE-DMA/HDDA systems is very helpful to determine the optimal curing conditions for the PFPE-DMA fluoropolymer.

PHOTOCURING STUDY OF NEW DENTAL RESINS BASED ON MULTIFUNCTIONAL ACRYLIC ISOCYANURATE BY PHOTOCALORIMETRY

Photocuring of new dental resins composed of tri(2-hydroxyethyl) isocyanurate triacrylate (THITA) alone and its mixtures with trimethylolpropane triacrylate (TMPTA) or pentaerythritol triacrylate (PETA) initiated by camphorquinone/amine system was studied by photocalorimetry. Among several different amines as coinitiators, 2-ethyl-4-dimethylaminobenzoate (AM-3), N,N-dimethylbenzylamine (AM-5) and 2,4,6-[tri(dimethylaminomethyl)]phenol (AM-6) are most effective. Upon irradiation, photopolymerization can occur immediately and no induction period appears in N-2 nor in air. Comparing the THITA/TMPTA and THITA/PETA mixtures, the parameters of photopolymerization and hardness of photocured samples show a small difference and only change slightly with varying molar ratios of mixture. In the presence of inorganic filler, the hardness of photocuring resins is almost the same as that for commercial products.

Lithium bis(trifluoromethanesulfonyl)imide blended in polyurethane acrylate photocurable solid polymer electrolytes for lithium-ion batteries

The increased demand of electronic devices promotes the development of advanced and more efficient energy storage devices, such as batteries. Lithium-ion batteries (LIBs) are the most studied battery systems due to their high performance. Among the different battery components, the separator allows the control of lithium ion diffusion between the electrodes. To overcome some drawbacks of liquid electrolytes, including safety and environmental issues, solid polymer electrolytes (SPEs) are being developed. In this work, a UV photocurable polyurethane acrylate (PUA) resin has been blended with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) up to 30 wt% LiTFSI content to reach a maximum ionic conductivity of 0.0032 mS/cm at room temperature and 0.09 mS/cm at 100 ℃. Those values allowed applying the developed materials as photocurable SPE in Swagelok type Li/C-LiFePO_(4) half-cells, reaching a battery discharge capacity value of 139 mAh.g^(−1) at C/30 rate. Those results, together with the theoretical studies of the discharge capacity at different C-rates and temperatures for batteries with LiTFSI/PUA SPE demonstrate the suitability of the developed photocurable SPE for LIB applications.

Reparation and Performance Testing of Free Radical Photocurable Passivation Film Modified by Titanate Coupling Agent for Hot-plated Aluminum-zinc Steel Plate

To study the effect of free radical photocurable passivation film modified by titanate coupling agent for hot-plated aluminum-zinc plate,trimethylpropane triacrylate(TMPTA)and 2-phenoxyethyl acrylate were used as active diluents,a mixture of modified epoxy acrylate and modified polyester acrylate in a certain proportion was used as an oligomer,2-methyl-1-[4-(methylothyl)benzene]-2-morpholine acetone(907)was used as a free radical photoinitiator,isopropyl thioxanthone(ITX)was used as sensitizer,and bis(dioctyl phosphate acyl)titanate ethyltitanate acrylamide chelate(FD-812)was used as corrosion inhibitor modifier.After UV-curing,the passivation film was characterized by neutral salt spray test,electrochemical testing and other methods.The general performance of the passivation film may meet the requirements of downstream users of hot aluminum-zinc steel plate.The neutral salt spray test,electrochemical testing and microscopic surface morphology analysis of passivation film are in agreement.The introduction of titanate components may effectively promote the photocuring of free radicals.There have been few reports on the titanate coupling which is added to UV-curing coating formula.The titanate coupling agent contains acrylamide groups and terminal amine groups,acrylamide group has oligomer and crosslinking monomer,the terminal tertiary amine groups can provide hydrogen protons,reduce oxygen polymerization,and a phosphating film is formed on the surface of the metal substrate to improve the adhesion and corrosion resistance of the coating.

UV-LED Curing Cationic Passivation Film for the Surface of Hot-Dip Aluminum-Zinc Coated Steel Plate

The surface treatment technology of hot aluminum-zinc steel plate and UV curing technology may be effectively combined in the present research. According to different light curing mechanisms, different formulations from UV curing surface treatment agents can be applied to the surface treatment of hot aluminum-zinc steel plate, mainly including 3-ethyl-3-benzoxy-methyl oxacyclobutane (TCM 104) and 3,4-epoxy-cyclohexylformic acid -3',4'-epoxy-cyclohexyl methyl ester (UVR 6110) as active diluents, high molecular weight polyfunctional oxacyclobutane as oligomer, triaryl sulfonium salt as a cationic photoinitiator, and an anthracene compound as a sensitizer. 385 nm LED lamp used as a radiation resource, the effects of the proportion of active diluent, the type and amount of photoinitiator, the amount of sensitizer, the curing temperature, and the amount of nano-SiO2 on the photocuring rate were investigated by photoper-scanning differential calorimetry (Photo-DSC). The experimental results show that the system has the fastest photocuring rate under the conditions of 8:2 ratio of TCM 104 to UVR 6110, 2.5% photoinitiator, 0.6% sensitizer, 0.2% nano-SiO2 additive, and 80˚C curing temperature. Based on addition of the appropriate number of various additives, the cationic photocuring surface treatment solution was prepared and further coated on the hot-dip galvalume steel plates. After curing, the passivation films were characterized by neutral salt spray test (NSST), Fourier transform infrared spectroscopy (FT-IR), electrochemical testing and other methods. The results show that the formulations could be cured at an energy of 150 mJ/cm2, and the overall performance of the passivation film could meet with the requirements of the downstream users.

Melt and One-Pot Solution Synthesis of Thermally Stable, Organosoluble and Photocurable Acidic Polyimides

Polyimides are well known for their high chemical and thermal stability. However, a few polyimide samples have been reported which are completely soluble in such environmentally friendly and common organic solvent as propyleneglycol monomethyl ether acetate (PGMEA). In this work thermally stable, organosoluble and photocurable acidic polyimides were synthesized by simple and cost effective one-pot solution method. They polyimides obtained by this method showed much higher thermal stability (1 wt% loss temperature 345°C) than melt polymerized polyimides owing to the photocrosslinking reactions by the terminal double bonds.

Hydrogen self-supplying initiators excited by visible light for the fabrication of transparent films

Unimolecular Type Ⅱ radical photoinitiators(PIs) have received significant attention in photocuring owing to the fact that they improve the sustainability of the overall process compared with traditional Type Ⅱ radical photoinitiators. However, the photopolymerization efficiency of unimolecular Type Ⅱ radical photoinitiators is hindered by their short excitation wavelengths,poor photon capture abilities, and inefficient photobleaching performance. Herein, we report a coumarin-based self-sufficient initiator(C-NA), which is designed by integrating “hydrogen donor” and “hydrogen acceptor” into the coumarin framework and used for single-component visible light curing. C-NA exhibits a visible light absorbance and high molar extinction coefficient and is completely photobleached under the irradiation of 405 nm light-emitting diodes(LEDs). The formation of free radicals arises from the transfer of hydrogen from the diethylamino group to the coumarin framework, together with a highly efficient photodegradation process of C-NA. Finally, C-NA was successfully applied to prepare a transparent film material. Therefore,C-NA offers new insights into the design of promising unimolecular Type Ⅱ radical photoinitiators for photocuring.

A novel gatifloxacin-loaded intraocular lens for prophylaxis of postoperative endophthalmitis

Postoperative endophthalmitis(POE)has been the most threatening complication after cataract surgery,which perhaps can be solved by the antibiotic-loaded intraocular lens(IOL).However,most drug-loaded IOLs demonstrate insufficient drug quantity,short release time,increased implantation-related difficulties or other noticeable drawbacks.To prevent POE and to address these deficiencies,a drug-loaded copolymer IOL,prepared from poly(urethane acrylate)prepolymer,isobornyl methacrylate(IBOMA),N-vinyl-2-pyrrolidone(NVP),Irgacure 819,RUVA-93,and gatifloxacin(GAT),was rapidly fabricated via photocuring and by using a 3D-printed mold.This composite displayed an outstanding and controllable GAT release behavior in vitro,a high light transmittance,and a moderate refractive index.Also,it demonstrated improved strain stress and elongation compared with the reference commercial acrylic IOL material.In vivo tests demonstrated satisfying released drug concentration at the early treatment stage.In vitro and in vivo studies further confirmed the remarkable bacterial inhibition and prevention of POE by the proposed IOL,which also displayed good biocompatibility.These findings suggested that the GAT-loaded IOL could be a promising implant to prevent and cure POE,also the proposed methods could inspire more designs for various medical applications.

Hyaluronic acid methacrylate/laponite hydrogel loaded with BMP4 and maintaining its bioactivity for scar-free wound healing

Scar-free wound healing is a challenging process due to the excessive deposition of extracellular matrix and collagen.To overcome this issue,hydrogels with superior biochemical and mechanical properties have been used in combination with medicinal compounds as wound dressings.In this study,a novel composite hydrogel consisting of double-crosslinked photocurable hyaluronic acid methacrylate(HAMA)and Laponite(Lap)loaded with bioactive bone morphogenetic protein 4(BMP4)was developed and thoroughly characterized for its properties such as degradation,morphology,porosity,compression,skin adhesion and load release.The effect of the HAMA/Lap/BMP4 hydrogel was evaluated through both in vitro and in vivo experiments.In the in vivo rabbit ear-scar model,the HAMA/Lap/BMP4 hydrogel dressing was found to reduce scar-related expressions ofα-SAM and decrease the ratio of collagenΙ/III in wounded tissue.Additionally,histopathological examination indicated that the HAMA/Lap/BMP4 hydrogel-treated groups exhibited enhanced wound repair and increased levels of collagen maintenance compared to other standard groups,ultimately leading to scarless wound healing.Therefore,this sustained-release photocurable HAMA/Lap/BMP4 hydrogel offers a therapeutic approach for scar-free wound healing.

Natural polymer-derived photocurable bioadhesive hydrogels for sutureless keratoplasty

Keratoplasty is the gold standard treatment for visual impairment caused by corneal damage.The use of suturing as the bonding method is the source of many complications following keratoplasty.Currently available corneal adhesives do not have both adequate adhesive strength and acceptable biocompatibility.Herein,we developed a photocurable bioadhesive hydrogel which was composed of gelatin methacryloyl and oxidized dextran for sutureless keratoplasty.The bioadhesive hydrogel exhibited high light transmittance,resistance to enzymatic degradation and excellent biocompatibility.It also had higher adhesive strength than commercial adhesives(fibrin glue).In a rabbit model of lamellar keratoplasty,donor corneal grafts could be closely bonded to the recipient corneal bed and remained attached for 56 days by using of this in situ photopolymerized bioadhesive hydrogel.The operated cornea maintained transparent and noninflamed.Sutureless keratoplasty using bioadhesive hydrogel allowed rapid graft re-epithelialization,typically within 7 days.In vivo confocal microscopic and histological evaluation of the operated cornea did not show any apparent abnormalities in terms of corneal cells and ultrastructure.Thus,this bioadhesive hydrogel is exhibited to be an appealing alternative to sutures for keratoplasty and other corneal surgeries.

Marginal sealing around integral bilayer scaffolds for repairing osteochondral defects based on photocurable silk hydrogels

Osteochondral repair remains a major challenge in current clinical practice despite significant advances in tissue engineering.In particular,the lateral integration of neocartilage into surrounding native cartilage is a difficult and inadequately addressed problem that determines the success of tissue repair.Here,a novel design of an integral bilayer scaffold combined with a photocurable silk sealant for osteochondral repair is reported.First,we fabricated a bilayer silk scaffold with a cartilage layer resembling native cartilage in surface morphology and mechanical strength and a BMP-2-loaded porous subchondral bone layer that facilitated the osteogenic differentiation of BMSCs.Second,a TGF-β3-loaded methacrylated silk fibroin sealant(Sil-MA)exhibiting biocompatibility and good adhesive properties was developed and confirmed to promote chondrocyte migration and differentiation.Importantly,this TGF-β3-loaded Sil-MA hydrogel provided a bridge between the cartilage layer of the scaffold and the surrounding cartilage and then guided new cartilage to grow towards and replace the degraded cartilage layer from the surrounding native cartilage in the early stage of knee repair.Thus,osteochondral regeneration and superior lateral integration were achieved in vivo by using this composite.These results demonstrate that the new approach of marginal sealing around the cartilage layer of bilayer scaffolds with Sil-MA hydrogel has tremendous potential for clinical use in osteochondral regeneration.

Visible light-curable polymers for biomedical applications

Photocurable systems, which offer advantages such as microfabrication and in situ fabrication, have been widely used as dental restorative materials. Because the visible light-curable(VLC) system causes no biological damage, it is popular as a dental material and is being investigated by many researchers for other medical applications. Here, the principle of the VLC system is explained and recent progress in key components including photoinitiators, monomers, macromers, and prepolymers is discussed. Finally, biomedical applications for drug delivery and soft tissue engineering are reviewed. Considering the recent development of VLC systems, its importance in the field of medical applications is expected to continue to increase in the future.

Modeling and measurement of curing properties of photocurable polymer containing magnetic particles and microcapsules

In microstereolithography,three-dimensional microstructures are created by scanning an ultraviolet laser on a photocurable resin and stacking several such layers to form the desired structure.By mixing different types of particles in the resin,the formed microstructures exhibit various physical properties.For example,the magnetism and density of the microstructure can be controlled by adding magnetic particles and microcapsules to the resin.This method has been used to fabricate magnetic micromachines.Although such functional resins are useful,the incorporated magnetic particles and microcapsules can affect the fabrication resolution,making it difficult to fabricate microstructures with high precision.Thus,it is necessary to understand the effects of such microparticles and microcapsules on the fabrication process.In this study,we propose a simple model of curing resins containing magnetic particles and microcapsules to explain the effects of the magnetic particles and microcapsules.The proposed model can explain the observed curing characteristics of a resin that contains particles for all concentrations as well as for different types of magnetic particles and microcapsules.Finally,using the proposed model,we discuss how to improve the characteristics of resins containing microparticles to realize the high-resolution fabrication of three-dimensional microstructures with desirable material properties.

Highly Porous Crosslinked Poly(ester-anhydride) Microspheres with High Loading Efficiency

Microparticles with diameter within the range of Dn = 26-38 μm were prepared from functional poly（ester- anhydride）s with different amount of allyl groups in the side chains, using emulsion solvent evaporation technique. Porous structure was obtained as the effect of photocrosslinking of aUyl groups. 2,2-Dimetoxy-2-phenylacetophenone （DMPA） （0.5 wt%-10 wt%） was used as a photoinitiator. The crosslinking was carried out by UV irradiation during the solvent evaporation. Effectiveness of the crosslinking was characterized by the content of insoluble part of samples and it was in the range of 18%-75%. Porosity of microparticles （in the range of 76%-88%） depended on the functionality of poly（ester- anhydride）s and amount of the photoinitiator used. The most porous particles were obtained with use of 0.5 wt% of DMPA. Their flow ability expressed by Carr＇s index was excellent, and their theoretical mass mean aerodynamic diameters were acceptable for use in pulmonary drug delivery. The most porous particles were loaded with p-nitroaniline, theophilline or doxycycline. The loading efficiencies of drugs in porous microspheres were higher compared to nonporous ones. The porosity of loaded microparticles was slightly decreased, however their flow ability was still very good.