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A Self-Reporting Photocatalyst for Online Fluorescence Monitoring of High Throughput RAFT Polymerization
摘要： Translating controlled/living radical polymerization (CLRP) from batch to the high throughput production of polymer libraries presents several challenges in terms of both polymer synthesis and characterization. Although recently there have been significant advances in the field of low volume, high throughput CLRP, techniques able to simultaneously monitor multiple polymerizations in an 'online' manner have not yet been developed. Here, we report our discovery that 5,10,15,20-tetraphenyl-21H,23H-porphine zinc (ZnTPP) is a self-reporting photocatalyst that can mediate PET-RAFT polymerization as well as report on monomer conversion via changes in its fluorescence properties. This enables the use of a microplate reader to conduct high throughput 'online' monitoring of PET-RAFT polymerizations performed directly in 384-well, low volume microtiter plates.
关键词： photochemistry,polymerization,online monitoring,PET-RAFT
更新于2025-09-23 15:22:29
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Systematic λ/21 resolution achieved in nanofabrication by two-photon-absorption induced polymerization
摘要： Photopolymerization, based on two-photon absorption in resins, has been recognized as one of the enabling technologies to fabricate three-dimensional micro/nanostructures with a sub-diffraction-limit resolution. This work focuses on improving the spatial resolution using femtosecond laser, λ=780 nm, with a systematic nanofabrication process which we developed. We discuss the factors influencing the spatial resolution, including the laser intensity, the exposure time, and the scanning speed by fabricating polymerized-voxels, nano-lines, and suspended nano-fibers in a photoresist based on a methyl-methacrylate monomer. We show that a resolution of ~36 nm, corresponding to ~λ/21, is achieved. Stable 3D microstructures can be fabricated by using our custom made set up.
关键词： Voxel,Resolution,Two Photon Polymerization,Micro/Nanostructures,Femtosecond Laser,Suspended Polymerized Fibers
更新于2025-09-23 15:22:29
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Photoinitiator Free Resins Composed of Plant-Derived Monomers for the Optical μ-3D Printing of Thermosets
摘要： In this study, acrylated epoxidized soybean oil (AESO) and mixtures of AESO and vanillin dimethacrylate (VDM) or vanillin diacrylate (VDA) were investigated as photosensitive resins for optical 3D printing without any photoinitiator and solvent. The study of photocross-linking kinetics by real-time photorheometry revealed the higher rate of photocross-linking of pure AESO than that of AESO with VDM or VDA. Through the higher yield of the insoluble fraction, better thermal and mechanical properties were obtained for the pure AESO polymer. Here, for the first time, we validate that pure AESO and mixtures of AESO and VDM can be used for 3D microstructuring by employing direct laser writing lithography technique. The smallest achieved spatial features are 1 μm with a throughput in 6900 voxels per second is obtained. The plant-derived resins were laser polymerized using ultrashort pulses by multiphoton absorption and avalanche induced cross-linking without the usage of any photoinitiator. This advances the light-based additive manufacturing towards the 3D processing of pure cross-linkable renewable materials.
关键词： polymerization (2PP),vanillin dimethacrylate,photocross-linking,direct laser writing,acrylated epoxidized soybean oil,two-photon,optical 3D printing,nanolithography,multi-photon processing,vanillin diacrylate
更新于2025-09-23 15:22:29
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Conductive Fused Porphyrin Tapes on Sensitive Substrates by a Chemical Vapor Deposition Approach
摘要： Oxidative polymerization of nickel(II) 5,15-diphenyl porphyrin and nickel(II) 5,15-bis(di-3,5-tert-butylphenyl) porphyrin by an oxidative chemical vapor deposition (oCVD) approach yields multiply fused porphyrin oligomers in thin film form. The oCVD technique enables the formation, deposition and p-doping of conjugated poly(porphyrins) coatings in a single step without the use of solvents or post-treatments. The decisive reactions and side reactions during the oCVD process are evidenced by high-resolution mass spectrometry. Due to the highly conjugated structure of the fused porphyrin tapes the thin films exhibit an electrical conductivity of 3.6×10–2 S·cm–1 and strong absorption in the visible to near-infrared spectral region. The formation of smooth conjugated poly(porphyrins) thin films, even on sensitive substrates, is demonstrated by their successful deposition and patterning on glass, silicon and printer paper. The ability to form conductive poly(porphyrins) thin films could enable the design of a new category of optoelectronic devices using the oCVD approach.
关键词： Chemical Vapor Deposition,Polymerization,Oxidative Coupling,Porphyrins,Thin Films
更新于2025-09-23 15:22:29
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UV-Induced Crosslinking of Poly[2-(2’-Norbornenyl)-2-Oxazoline]s
摘要： A 2-oxazoline monomer bearing a norbornenyl functionality in the side-chain was prepared from the reaction of 5-norbornene-2-carbonitrile and 2-ethanol amine. This monomer could be successfully polymerized using a 2-oxazolinium-based macroinitiator that was in-situ generated from the methyl cation-initiated oligomerization of 2-ethyl-2-oxazoline. This polymer could be subjected to polymeranalogous reactions involving the alkene groups of the norbornenyl side-chains: A proof-of-concept was established by utilizing the polymers in photoresists that were crosslinked by thiol-ene reactions involving bisfunctional thiols. Photoinitiators for the UV-induced thiol-ene reaction were required in catalytic amounts only. After development, the resists exhibited reproduction of the geometric patterns with a resolution of 30 μm.
关键词： cationic polymerization,polymer photochemistry,microwave-assisted polymerization,poly(2-oxazoline)s,photoresist,thiol-ene reaction
更新于2025-09-23 15:21:21
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3-Hydroxyflavone and N-phenylglycine in High Performance Photoinitiating Systems for 3D Printing and Photocomposites Synthesis
摘要： In this work, we propose to use 3-hydroxyflavone as a versatile high performance visible light photoinitiator (PIs) in combination with an amino acid (N-phenylglycine) for the free radical polymerization (FRP) of methacrylates in thick samples or composites upon visible light exposure (Light-Emitting Diode LED@405 nm or LED@477 nm). The high originality of this approach is the use of safer compounds in photoinitiating systems (flavone derivative/amino acid). 3-Hydroxyflavone can also be used in three-component systems with an iodonium salt and an amine for the cationic polymerization of epoxides upon exposure to near UV light LED@385 nm. Also interestingly, a charge transfer complex CTC between N-phenylglycine NPG and iodonium salt gives also remarkable initiating performance for free radical polymerization of methacrylates upon mild light irradiation conditions (LED@405 nm). High polymerization initiating abilities are found and high final reactive function conversions are obtained. The use of the new proposed initiating systems as materials for laser write or 3D printing experiments was also especially carried out with the formation of printed green fluorescent photopolymers. This green fluorescence obtained with naturally occurring 3-hydroxyflavone compound can be ascribed to the excited state intramolecular proton transfer ESIPT character. A full picture of the included photochemical mechanisms is given. Remarkably, 3-hydroxyflavone is also very efficient for photocomposites synthesis with glass fibers (thick samples with good depth of cure) using UV or LED@395 nm conveyor.
关键词： 3D printing,Cationic polymerization,Light-Emitting Diodes (LEDs),Free radical polymerization,photoinitiators,composites
更新于2025-09-23 15:21:21
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Effect of the photoactivation method on composite resin cure.
摘要： For composite resins to obtain good properties, they must present a high degree of conversion and minimal polymerization contraction. To minimize this contraction, alternative photoactivation techniques have been suggested. The objective of this study was to compare the hardness of a photoactivated composite resin using the pulse-delay, soft start and conventional techniques, in thicknesses of 1, 2 and 3 mm in the irradiated surface and in the opposite surface. Photoactivation was performed with halogen light for 20 seconds in the conventional and soft start techniques. In the pulse-delay technique, each increment of 1 mm was photoactivated for 3 seconds with a final photoactivation of 40 seconds. The samples were stored in an oven at 37°C for one week and submitted to the Vickers microhardness test. The results were submitted to ANOVA and the Tukey’s test with a level of significance of 5%. It was concluded that the hardness was higher with photoactivation of 40 seconds, and for the techniques that had the photoactivation time of 20 seconds (conventional and soft start), there was no difference in terms of hardness. Therefore, the hardness is not influenced by the technique, but rather, by the polymerization time.
关键词： Polymerization,Hardness,Composite Resin
更新于2025-09-23 15:21:21
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Flexible electrochromic tungsten/iron mixed oxide films synthesized by an atmospheric pressure plasma jet
摘要： Flexible electrochromic organo-tungsten- iron oxide (WFexOyCz) films are rapidly deposited onto flexible (60 Ω/□ polyethylene terephthalate/indium tin oxide; PET/ITO) substrates by a low temperature-atmospheric pressure-plasma polymerization method with an atmospheric pressure plasma jet (APPJ) for a short exposed duration of 48 s. The precursor vapors of tungsten hexacarbonyl [W(CO)6] and biscyclopentadienyl iron [ferrocene; Fe(C5H5)2] are mixed with O2 gases at various gas flow rates, injected into air plasma jet and sprayed onto PET/ITO substrates at room temperature (~23oC) and at atmospheric pressure (1.013 × 105 Pa). Flexible electrochromic WFexOyCz films are synthesized with a specific addition of oxygen gases with superior lithium electrochromic properties as demonstrated by a potential sweep alternating between -1 V and 2 V at a scan rate of 40 mV/s in a 1 M LiClO4-propylene carbonate electrolyte. With amorphous WFexOyCz films produced with an APPJ by adding oxygen gases at a specific flow rate of 0.5 sccm, a high value in oxygen deficiency up to 0.189 allows more Li+ ions to intercalate into and deintercalate out of the film. Significant coloration and bleaching are proven by the high values in optical transmittance modulation (ΔT) of up to 70.3%, optical density (ΔOD) up to 0.77 and color efficiency (η) up to 61.3 cm2/C, at a wavelength of 800 nm, respectively.
关键词： Electrochromic materials,Iron oxide,Tungsten oxide,Flexible electrochromic film,Atmospheric pressure plasmas,Plasma polymerization
更新于2025-09-23 15:21:21
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Ketone derivatives as photoinitiators for both radical and cationic photopolymerizations under visible LED and application in 3D printing
摘要： Six ketones (abbreviated as ketones 1-6) varying by the substitution pattern of the central cyclohexanones and the choice of the peripheral groups (thiophene or furane) were synthesized and proposed as unprecedented visible light sensitive photoinitiators, in combination with an amine and an iodonium salt, for the free radical polymerization of acrylates upon LED irradiation at 405 nm. For the photopolymerization of acrylates carried out as thin samples in laminate, all these ketones showed high photoinitiating abilities. Conversely, when tested as photoinitiators for thick samples, compared to the other 4 ketones, ketone 3 and ketone 5 both based onpiperidin-4-one as the central core and comprising furanes as peripheral groups proved to be the most efficient photoinitiators. Notably, the highest final polymerization conversion of Ebecryl 40, a tetrafunctional polyether acrylate, could be obtained using these two photoinitiators. The high photoreactivity of ketone 3 was highlighted by the steady state photolysis experiments. Meanwhile, ketone 3 could also promote the cationic polymerization of epoxides upon LED irradiation at 405 nm, in the presence of an iodonium salt. Interestingly, some 3D patterns could also be fabricated by free radical polymerization of Ebecryl 40 while using the ketone 3-based photoinitiating system.
关键词： free radical polymerization,ketones,cyclohexanone,photolysis,3D printing,cationic polymerization,LED,photoinitiating system
更新于2025-09-23 15:21:01
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Exploiting Wavelength Orthogonality for Successive Photoinduced Polymerization-Induced Self-Assembly and Photo-Crosslinking
摘要： We report a facile benchtop process for the synthesis of cross-linked polymeric nanoparticles by exploiting wavelength-selective photochemistry to perform orthogonal photoinduced polymerization-induced self-assembly (Photo-PISA) and photo-crosslinking processes. We first established that the water-soluble photocatalyst, zinc meso-tetra(N-methyl-4-pyridyl) porphine tetrachloride (ZnTMPyP) could activate the aqueous PET-RAFT dispersion polymerization of hydroxypropyl methacrylate (HPMA). This photo-PISA process could be conducted under low energy red light (λ max = 595 nm, 10.2 mW/cm2) and without deoxygenation due to the action of the singlet oxygen quencher, biotin (vitamin B7), which allowed for the synthesis of a range of nanoparticle morphologies (spheres, worms, and vesicles) directly in 96-well plates. To perform wavelength selective nanoparticle cross-linking, we added the photoresponsive monomer, 7-[4-(trifluoromethyl)coumarin] methacrylamide (TCMAm) as a comonomer without inhibiting the evolution of the nanoparticle morphology. Importantly, under red light, exclusive activation of the photo-PISA process occurs, with no evidence of TCMAm dimerization under these conditions. Subsequent switching to a UV source (λ max = 365 nm, 10.2 mW/cm2) resulted in rapid cross-linking of the polymer chains, allowing for retention of the nanoparticle morphology in organic solvents. This facile synthesis of cross-linked spheres, worms, and vesicles demonstrates the utility of orthogonal light-mediated chemistry for performing decoupled wavelength selective chemical processes.
关键词： photoinduced polymerization-induced self-assembly,wavelength orthogonality,polymeric nanoparticles,photo-crosslinking,PET-RAFT polymerization
更新于2025-09-23 15:21:01