AbstractToday, controlling the photopolymerization process during the 3D printing in vat photopolymerization is a key challenge. In this work, it is shown that using a relatively limited set of parameter, it is possible to estimate key factors involved in such process. On the basis of 16 formulations containing different concentrations of photoinitiator and UV filter, attempt was made to rationalize the photonic parameters used in the 3D printing process, that is, the depth of penetration Dp and the critical energy Ec. It is shown that the experimental Dp values can be correlated with calculated ones from Bouguer–Beer–Lambert law. Real‐time Fourier‐transform infrared spectroscopy (RT‐FTIR) experiments were performed under similar conditions as in 3D printing. The conversion profiles were used to estimate the Ec values. The limits of this approach was discussed as a function of the UV filter concentration. Finally, the RT‐FTIR curves are exploited to predict the in‐depth conversion of the different 3D printed layers and compared to experimental results obtained by confocal Raman microscopy.
AbstractPhotopolymerization is an energy‐saving and environmentally friendly technology and has been widely applied and continuously developed in various fields since the mid‐20th century. Today, photopolymerization technology has become ubiquitous in every aspect of our lives. This review initially explains the principle of photopolymerization reactions, introducing the process of photopolymerization and the initiation mechanisms of photoinitiators. Then, this review focuses on the applications of photopolymerization technology in thiol‐based click reactions, photoinduced controlled/living polymerizations, three‐dimensional printing, ultraviolet nanoimprint lithography photoresist and hydrogels to demonstrate its irreplaceable role at present.
AbstractPhotopolymerization of thiol–epoxy resins initiated by photobase generators (PBGs) is a very good way to prepare specific polymeric products. However, the lack of near‐UV or visible light emitting diode (LED) light‐sensitive PBGs that can release strong bases to effectively catalyze this reaction and synchronously monitor the polymerization progress still is a problem. In this work, a series of such PBGs are successfully synthesized by modifying common aggregation‐induced emission (AIE) molecules, including triphenylamine and tetraphenylethylene and then neutralizing them with strong bases like 1,8‐diazabicyclo[5.4.0]undec‐7‐ene, 1,5‐diazabicyclo[4.3.0]non‐5‐ene, and 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD). The obtained PBGs show very good light absorption ability from 365 to 405 nm. They can generate free strong bases under near‐UV/visible LED light radiations as a result of photodecarboxylation reaction to catalyze the rapid thiol–epoxy photopolymerization. The TBD‐based PBGs have the best final monomer conversion above 60% due to their strongest alkalinity. Increasing viscosity during the polymerization process can trigger an AIE phenomenon of the PBGs. A linear correlation equation of the AIE intensity with the monomer conversion can be found, which is helpful for quantitatively monitoring the photopolymerization progress. More importantly, qualitative observations of the brightness changes of the resulting AIE lights are very useful to visualize the photopolymerization progress, which may find some applied potential in industry.
Recently many microfluidic systems are increasingly equipped with functional units for ionic controls for various applications. In this review article, we define an ion bridge as a structure that controls current or distribution of ions in a microfluidic system, and summarize the ion bridges in the literature in terms of characteristics, fabrication methods, advantages and disadvantages. The ion bridges play two basic roles, namely to ensure electrical contact in a microfluidic network and mechanically separate a liquid phase from another. More interestingly, the charged surfaces of ion bridges, which can be chemically modified, create new characteristics such as permselectivity and concentration polarization. Asymmetric ion transport as well as ionic conductivity through the ion bridges suggests a variety of applications including sample preconcentration, electroosmotic pump, electrospray ionization, electrically driven valve and many others. This review categorizes the ion bridges into several classes and describes the structures, materials, fundamental functions and applications. 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AbstractThe design and development of photoinitiating systems applicable to visible light delivered from light‐emitting diodes (LEDs) have attracted increasing attention owing to the wide application of photopolymerization. In this study, four aryl glycine derivatives are designed and synthesized, and their applicability as visible light‐sensitive photoinitiators is thoroughly investigated. Specifically, the photoinitiation mechanism of these aryl glycine derivatives, when combined with iodonium salt, is investigated using steady‐state photolysis, fluorescence, and electron paramagnetic resonance spin trapping techniques. It is revealed that radicals can be generated from aryl glycine derivatives/iodonium salt combinations upon exposure to blue LEDs (410 and 445 nm) to induce free radical photopolymerization (FRP) of (meth)acrylates. Additionally, besides FRP, a photobase generator based on one of the investigated aryl glycine derivatives is synthesized and demonstrates the capability to initiate epoxy‐thiol polymerization under light irradiation. The remarkable photolatent characteristics demonstrate the significant potential in broadening the application of aryl glycine derivatives in controlled photopolymerization processes.
Polyampholytic poly(2-aminoethyl methacrylate-co-sulfopropyl methacrylate) (p(AEMA-co-SPMA)) thin films were prepared by self-initiated photopolymerization and photografting (SIPGP) and are demonstrated to be a potential alternative to films prepared from zwitterionic poly(sulfobetaine methacrylate) (pSBMA) for antifouling applications. SIPGP allows polymerization from aqueous solutions containing only monomers, implying that p(AEMA-co-SPMA) thin films can be prepared simply and inexpensively without the risk of introducing potentially toxic substances necessary in many controlled polymerization reactions. For the polymers, wettabilities were studied by contact angle goniometry, the compositions of the films were determined by infrared and X-ray photoelectron spectroscopies, and streaming current measurements were used to assess their net charge. The antibiofouling properties were compared via adsorption of fibrinogen and bovine serum albumin, settlement of algal zoospores, and the growth of sporelings of the marine alga Ulva lactuca. The fouling of the p(AEMA-co-SPMA) copolymer was in several respects similar to that of the zwitterionic pSBMA and suggests that it is potentially suitable for applications under high-salinity conditions, such as marine or physiological environments. ; Funding Agencies|European Communitys Seventh Framework Program FP7/2007-2013 [237997]; Swedish Research Council (VR)Swedish Research Council [2014-04004, 2017-06696, 621-2013-5357]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Carl Tryggers Stiftelse [CTS 15:507]
International audience ; A simple, selective, and sensitive method involving a miniaturized solid phase extraction step based on a monolithic molecularly imprinted polymer (MIP) directly coupled on-line to UV detection was developed for the determination of benzoylecgonine (BZE) in complex biological samples. Monolithic MIPs were prepared into 100 µm internal diameter fused-silica capillaries either by thermal or photopolymerization. While leading to similar selectivities with respect to BZE, photopolymerization has made it possible to produce monoliths of different lengths that can be adapted to the targeted miniaturized application. The homogeneous morphology of these monolithic MIPs was evaluated by scanning electron microscopy prior to measuring their permeability. Their selectivity was evaluated leading to imprinting factors of 2.7 ± 0.1 for BZE and 4.0 ± 0.6 for cocaine (selected as template for the MIP synthesis) with polymers resulting from three independent syntheses, showing both the high selectivity of the MIPs and the reproducibility of their synthesis. After selecting the appropriate capillary length and the setup configuration and optimizing the extraction protocol to promote selectivity, the extraction of BZE present in human urine samples spiked at 150, 250, and 500 ng mL-1 was successfully carried out on the monolithic MIP and coupled directly on-line with UV detection. The very clean-baseline of the resulting chromatograms revealing only the peak of interest for BZE illustrated the high selectivity brought by the monolithic MIP. Limits of detection and quantification of 56.4 ng mL-1 and 188.0 ng mL-1 were achieved in urine samples, respectively. It is therefore possible to achieve analytical threshold in accordance with the legislation on BZE detection in urine without the need for an additional chromatographic separation.
International audience ; A simple, selective, and sensitive method involving a miniaturized solid phase extraction step based on a monolithic molecularly imprinted polymer (MIP) directly coupled on-line to UV detection was developed for the determination of benzoylecgonine (BZE) in complex biological samples. Monolithic MIPs were prepared into 100 µm internal diameter fused-silica capillaries either by thermal or photopolymerization. While leading to similar selectivities with respect to BZE, photopolymerization has made it possible to produce monoliths of different lengths that can be adapted to the targeted miniaturized application. The homogeneous morphology of these monolithic MIPs was evaluated by scanning electron microscopy prior to measuring their permeability. Their selectivity was evaluated leading to imprinting factors of 2.7 ± 0.1 for BZE and 4.0 ± 0.6 for cocaine (selected as template for the MIP synthesis) with polymers resulting from three independent syntheses, showing both the high selectivity of the MIPs and the reproducibility of their synthesis. After selecting the appropriate capillary length and the setup configuration and optimizing the extraction protocol to promote selectivity, the extraction of BZE present in human urine samples spiked at 150, 250, and 500 ng mL-1 was successfully carried out on the monolithic MIP and coupled directly on-line with UV detection. The very clean-baseline of the resulting chromatograms revealing only the peak of interest for BZE illustrated the high selectivity brought by the monolithic MIP. Limits of detection and quantification of 56.4 ng mL-1 and 188.0 ng mL-1 were achieved in urine samples, respectively. It is therefore possible to achieve analytical threshold in accordance with the legislation on BZE detection in urine without the need for an additional chromatographic separation.
International audience ; A simple, selective, and sensitive method involving a miniaturized solid phase extraction step based on a monolithic molecularly imprinted polymer (MIP) directly coupled on-line to UV detection was developed for the determination of benzoylecgonine (BZE) in complex biological samples. Monolithic MIPs were prepared into 100 µm internal diameter fused-silica capillaries either by thermal or photopolymerization. While leading to similar selectivities with respect to BZE, photopolymerization has made it possible to produce monoliths of different lengths that can be adapted to the targeted miniaturized application. The homogeneous morphology of these monolithic MIPs was evaluated by scanning electron microscopy prior to measuring their permeability. Their selectivity was evaluated leading to imprinting factors of 2.7 ± 0.1 for BZE and 4.0 ± 0.6 for cocaine (selected as template for the MIP synthesis) with polymers resulting from three independent syntheses, showing both the high selectivity of the MIPs and the reproducibility of their synthesis. After selecting the appropriate capillary length and the setup configuration and optimizing the extraction protocol to promote selectivity, the extraction of BZE present in human urine samples spiked at 150, 250, and 500 ng mL-1 was successfully carried out on the monolithic MIP and coupled directly on-line with UV detection. The very clean-baseline of the resulting chromatograms revealing only the peak of interest for BZE illustrated the high selectivity brought by the monolithic MIP. Limits of detection and quantification of 56.4 ng mL-1 and 188.0 ng mL-1 were achieved in urine samples, respectively. It is therefore possible to achieve analytical threshold in accordance with the legislation on BZE detection in urine without the need for an additional chromatographic separation.
