Light-induced Polymerization Research Articles

Design of a surface-functionalized power-free microchip for extracellular vesicle detection utilizing UV grafting

As a biomarker for various diseases, extracellular vesicles (EV) in bodily fluids have received attention. In this study, poly(2-aminoethyl methacrylate hydrochloride) (PAEMA) was grafted onto a poly(dimethylsiloxane) power-free microchip by UV light-induced graft polymerization and anti-CD 63 antibody for EV capture was immobilized. Thus, a surface-functionalized power-free microchip (SF-PF microchip), which enables simple and rapid EV detection was fabricated. There was a correlation between the amount of antibody immobilized and the EV detection signal intensity, and both the amount and the signal intensity showed a maximum at 0.5 mol/L of AEMA concentration in feed for grafting. The sample volume required for EV detection was 1.0 μL and the time required for detection was 13 min. The SF-PF microchip would contribute to a point-of-care testing application.

Visible Light-Induced Transformation of Polymer Networks

Light-responsive polymeric networks have shown diverse applications as spatiotemporally tunable materials. Herein, we present a straightforward and facile strategy to fabricate photoexpandable/transformable-polymer networks (PET-PNs) that can undergo a growth mechanism via visible light-induced radical polymerization. Our PET-PN fabrication and its subsequent photogrowth process is based on using a trithiocarbonate chain transfer agent, dibenzyl trithiocarbonate (DBTTC), that can be activated by either photoredox catalysis or direct photolysis (photoiniferter) mechanisms. We first demonstrated the use of a photoredox catalyst (5,10,15,20-tetraphenyl-21H,23H-porphine zinc (ZnTPP) for initiating the reversible addition–fragmentation chain-transfer (RAFT) polymerization of a cross-linkable system consisting of difunctional monomers (i.e., tetra(ethylene glycol) diacrylate (TEGDA)) alongside with a monofunctional monomer (i.e., oligo(ethylene glycol) methyl ether acrylate) (OEGA)) under red LED light (λ max =...

Wavelength-Tunable Light-Induced Polymerization of Cyanoacrylates Using Photogenerated Amines

Cyanoacrylate photopolymerization has already been described, but it generally requires the use of organometallic photoinitiators and highly reactive monomers, which often leads to photoinitiator–monomer mixtures with limited stability. In this work we report a method to tackle these limitations, which relies on the use of amines bearing photoremovable protecting groups as light-responsive nucleophilic cyanoacrylate initiators. By exploiting the versatility of amine photorelease strategies, we have developed a series of all-organic initiators that (a) enable fast, on demand photocuring of commercial formulations of various cyanoacrylates, including less reactive, biologically relevant long alkyl chain monomers; (b) show wavelength tunability along the UV–vis spectrum and good thermal stability in the dark; and (c) lead to polymeric materials with excellent adhesive behavior. Because of this combination of properties, photogenerated amines appear as ideal candidates to bring cyanoacrylate photopolymerization into real application, especially in the biomedical field.

Photoinitiated Polymerization-Induced Self-Assembly via Visible Light-Induced RAFT-Mediated Emulsion Polymerization.

Aqueous emulsion polymerization is one of the most commonly used techniques in industry for the production of polymer latexes. In this contribution, we present photoinitiated polymerization-induced self-assembly (photo-PISA) based on aqueous visible light-induced reversible addition-fragmentation chain transfer (RAFT)-mediated emulsion polymerization at room temperature. A wide range of morphologies including spheres, worms, and vesicles have been achieved at room temperature by modulating reaction parameters. Additionally, this method enables access to inorganic nanoparticles-loaded vesicles by adding inorganic nanoparticles at the beginning of the polymerization. Finally, an oxygen-tolerant RAFT-mediated emulsion polymerization has been developed, allowing the synthesis of polymer nano-objects at low volumes (e.g., in a 96-well plate). This study is expected to expand the scope of photo-PISA for the preparation of various block copolymer nano-objects in water at room temperature.

Enhanced reduction of polymerization-induced shrinkage stress via combination of radical ring opening and addition fragmentation chain transfer

The combination of vinylcyclopropanes with an ester-activated vinyl sulfonate ester in a light-induced radical polymerization shows high reactivity accompanied by a significant increase in conversion and it leads to an enhanced reduction of polymerization-induced shrinkage stress.

Preparation of Pt/WO3-coated polydimethylsiloxane membrane for transparent/flexible hydrogen gas sensors

Abstract For sustainable hydrogen energy generation systems, safe, repeatable, and cost-effective hydrogen gas-leakage monitoring is required. In this study, transparent and flexible hydrogen gas sensor membranes that satisfy the above requirements were prepared. Pt/WO3-thin films were deposited on the surface of polydimethyl siloxane (PDMS) membranes previously modified with hydroxyethyl acrylamide (HEAAm) via ultraviolet light-induced graft polymerization. Such grafted HEAAm provided an acid- and heat-resistant hydrophilic surface, where hydrogen gasochromic Pt/WO3 particles can be deposited to form a thin film. The thus prepared Pt/WO3 thin film-coated PDMS membranes show significant colorimetric response toward hydrogen gas.

A 3D Printable Thermal Energy Storage Crystalline Gel Using Mask-Projection Stereolithography.

Most of the phase change materials (PCMs) have been limited to use as functional additions or sealed in containers, and extra auxiliary equipment or supporting matrix is needed. The emergence of 3D printing technique has dramatically advanced the developments of materials and simplified production processes. This study focuses on a novel strategy to model thermal energy storage crystalline gels with three-dimensional architecture directly from liquid resin without supporting materials through light-induced polymerization 3D printing technique. A mask-projection stereolithography printer was used to measure the 3D printing test, and the printable characters of crystalline thermal energy storage P(SA-DMAA) gels with different molar ratios were evaluated. For the P(SA-DMMA) gels with a small fraction of SA, the 3D fabrication was realized with higher printing precision both on milli- and micro- meter scales. As a comparison of 3D printed samples, P(SA-DMAA) gels made by other two methods, post-UV curing treatment after 3D printing and UV curing using conventional mold, were prepared. The 3D printed P(SA-DMAA) gels shown high crystallinity. Post-UV curing treatment was beneficial to full curing of 3D printed gels, but did not lead to the further improvement of the crystal structure to get higher crystallinity. The P(SA-DMAA) crystalline gel having the highest energy storage enthalpy was developed, which reached 69.6 J·g−1. Its good thermoregulation property in the temperature range from 25 to 40 °C was proved. The P(SA-DMAA) gels are feasible for practical applications as one kind of 3D printing material with thermal energy storage and thermoregulation functionality.

Pressure-Induced Transition of Bisamide-Substituted Diacetylene Crystals from Nonphotopolymerizable to Photopolymerizable State.

Mechanoresponsive diacetylenes (DAs) exhibiting a transition of crystalline orientation from light-inert to light-active state upon applied force are reported. Amide units are introduced to DAs where hydrogen bonding is utilized to control intermolecular interactions. Application of external pressure (2-150 MPa) to DAs results in an emergence of new crystal phases with changing the d-spacing which possibly reduces the reaction barrier. Accordingly, the dramatic crystalline transition from "perfectly off" to "on" state to undergo the light-induced topochemical polymerization of bulk DA crystals is obtained. Subsequent UV irradiation at a wavelength of 254 nm enables the polymerization of the pressed region, changing its color from white to blue which suggests the selective formation of polydiacetylene (PDA) polymorphs. In addition, by utilizing the mechanoresponsive crystallinity with low-enough activation pressure, a new strategy for PDA patterning is demonstrated based on the selective transfer of information by means of force to a DA film. This phenomenon can be applicable to a new nanoimprinting technique where no mechanical deformation of resist materials but phase transition is induced by the mold.

Plasma Deposition and UV Light Induced Surface Grafting Polymerization of NIPAAm on Stainless Steel for Enhancing Corrosion Resistance and Its Drug Delivery Property.

When stainless steel is implanted in human bodies, the corrosion resistance and biocompatibility must be considered. In this study, first, a protective organic silicone film was coated on the surface of stainless steel by a plasma deposition technique with a precursor of hexamethyldisilazane (HMDSZ). Then, ultraviolet (UV) light-induced graft polymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AAc) in different molar ratios were applied onto the organic silicone film in order to immobilize thermos-/pH-sensitive composite hydrogels on the surface. The thermo-/pH-sensitive composite hydrogels were tested at pH values of 4, 7.4 and 10 of a phosphate buffer saline (PBS) solution at a fixed temperature of 37 °C to observe the swelling ratio and drug delivery properties of caffeine which served as a drug delivery substance. According to the results of Fourier Transformation Infrared (FTIR) spectra and a potential polarization dynamic test, the silicone thin film formed by plasma deposition not only improved the adhesion ability between the substrate and hydrogels but also exhibited a high corrosion resistance. Furthermore, the composite hydrogels have an excellent release ratio of up to 90% of the absorbed amount after 8h at a pH of 10. In addition, the results of potential polarization dynamic tests showed that the corrosion resistance of stainless steel could be improved by the HMDSZ plasma deposition.

3D Printable Energy Storage Crystalline Gels Using Mask-Projection Stereolithography

Phase change materials (PCMs) are considered one of the most reliable latent heat storage and thermoregulation materials. In this paper, a vinyl monomer is used as phase change material to synthesize gel. Using the light-induced polymerization 3D printing technique, we synthesize the energy storage gel and shape it on 3D printers at the same time. iBox Nano and Lumi Forge are used to print our crystalline gels through mask-projection stereolithography. By adjusting layer thickness, exposure time and first layer settings, gels are shaped into several formations successfully. Infrared images, DSC and WAXS test indicate the printed objects have phase transition behaviors and can provide energy storage capacity. Also, the effects of monomer ratios on phase change enthalpy and phase transition temperature are investigated.

Hyperbranched Polymers by Light-Induced Self-Condensing Vinyl Polymerization.

Hyperbranched polymers (HBPs), a unique class of dendritic macromolecules, have received continuous interest from macromolecular scientists due to their inherent properties such as high level of functional terminal units, high solubility, and low viscosity. Despite enormous efforts devoted to the synthesis of HBPs by traditional methods such as single and double monomer strategies involving step-growth polymerization and self-condensing vinyl polymerization (SCVP) processes, there have been limited attempts to employ light-induced processes. Photochemical methods, however, exhibit distinct advantages not characteristically disclosed by traditional ones, such as spatial and temporal control, low energy, and site-specific activation. This review, after a brief summary of the conventional methods, presents the unique features and the key functionalities of the inimers for photoinduced SCVP and strategies for preparing HBPs.

Dual cure composites: Could body temperature offset the absence of light activation?

Dual cure composites contain both chemically and light-induced polymerization initiators, taking advantage of both processes; however, some studies have suggested that in order to obtain a complete polymerization of the sample it is necessary to light activate the material. Indeed, there is controversy in the literature about the effective polymerization of dual composites in deeper cavity, where light can be strongly attenuated. On the other hand, other studies hypothesized that light activation could determine a rapid increment of the viscosity of the material, blocking the movement of free radicals and avoiding a perfect polymerization. The aim of this study is to evaluate through the thermal analysis and thermogravimetry if dual composite samples, cured only by chemical reaction for 1 h at body temperature of 37 °C, are characterized by the same properties of samples light cured for 40 s at room temperature. The thermogravimetric curve (TGA), the differential thermal analysis and the first derivative of loss of mass (DTG) have been analyzed. The average temperature at which 5% of mass loss occurred and the percentage of the average mass loss between 250 and 350 °C have been recorded. Results have shown that both groups were characterized by a similar thermal stability, compatible with a good polymerization degree and no statistically significant differences have been found.

Optical and Thermomechanical Properties of Doped Polyfunctional Acrylate Copolymers.

Three different polyfunctional acrylate monomers—trimethylolpropantriacrylate (TMPTA), pentaerythritol triacrylate (PETA) and di(trimethylolpropane) tetraacrylate (DTTA)—have been used as comonomers in combination with a reactive resin consisting of poly(methylmethacrylate), dissolved in its monomer methylmethacrylate. Phenanthrene has been added to form a guest–host system. The level of phenanthrene present may be adjusted to tailor the refractive index in the system. Prior to curing, the shear rate and temperature-dependent viscosity as a function of the composition were measured. It could be demonstrated that, with respect to different shaping methods, a tailor-made flow behaviour can be adjusted. After thermally-induced polymerization, the resulting optical (refractive index, optical transmittance) and thermomechanical (glass transition behavior, Vickers hardness) properties were characterized. A significant refractive index increase—up to a value close to 1.56 (@589 nm)—under the retention of good optical transmittance was able to be obtained. In addition, the photopolymerization behaviour was investigated to overcome the undesirable oxygen inhibition effect during the light-induced radical polymerization of acrylates. The level of acrylate units in the copolymer can compensate for the plasticizing effect of the dopant phenanthrene, enabling higher concentrations of the dopant in the guest–host system and therefore larger refractive index values suitable for polymer waveguide fabrication.

Facile preparation of thermoresponsive fluorescent silica nanopaprticles based composites through the oxygen tolerance light-induced RAFT polymerization

Poly(NIPAM-AcFl)/SiO2 nanomaterials were successfully prepared through a convenient oxygen tolerance light-induced RAFT polymerization. The successful preparation of the resulting Poly(NIPAM-AcFl)/SiO2 nanocomposites have been confirmed based on various characterization data. These Poly(NIPAM-AcFl)/SiO2 nanocomposites showed temperature responsive coil-to-globule transition behavior in aqueous solution, because of the hydrophilic and hydrophobic transformation of the H-bond when the temperature was greater than the lower critical solution temperature (LCST). More importantly, this facile RAFT polymerization based on photocatalysis would pave the way for the fabrication of other polymer/inorganic nanomaterials with great application potential in different fields. Compared with the traditional surface-initiated radical polymerization, our method possesses the advantages of no metal contamination, room temperature reaction condition and the oxygen tolerance properties could be the promising facile way for preparation of various nanocomposites.

A novel light-induced ATRP for the preparation of water dispersible fluorescent nanodiamonds and their biological imaging applications

Carbon-based fluorescent nanoparticles are considered to be new promising nontoxic fluorescence probes which suitable for various bioimaging and biomedical applications. However, the synthesis and production of such high-quality fluorescent carbon-based nanoparticles is still challenging, and its most application potential is unexplored. In this work, we introduce a facile light-induced surface-initiated atomic transfer radical polymerization (SI-ATRP) method to fabricate the nanodiamonds (NDs) based fluorescence probes in the absence of transition metal ligands. In this sample way, the Fluorescein was employed and played the role as the fluorescent signal and photocatalyst simultaneously for its photochemical property. Besides, the poor dispersibility of pristine NDs was also obviously improved by modifying with PEGMA, and the modified NDs (FNDs-polyPEGMA) display good dispersion and biocompatibility via characterization methods. A series of characterization techniques were also carried out to confirm the successful fabrication of fluorescent NDs after polymerization. Through our investigation, the as prepared FNDs-polyPEGMA nanoparticles with high dispersibility and stable green fluorescence could be the potentially used fluorescent probes in biomedical application.

High-resolution 3D photopolymerization assisted by upconversion nanoparticles for rapid prototyping applications

Three-dimensional (3D) rapid prototyping technology based on near-infrared light-induced polymerization of photocurable compositions containing upconversion nanomaterials has been explored. For this aim, the rationally-designed core/shell upconversion nanoparticles NaYF4:Yb3+,Tm3+/NaYF4, with the distinct ultraviolet-emitting lines and unprecedentedly high near-infrared to ultraviolet conversion efficiency of {eta }_{{bf{UC}}}^{({bf{UV}})}=2{boldsymbol{ % }} have been used. The upconverted ultraviolet photons were capable to efficiently activate photoinitiators contained in light-sensitive resins under moderate intensities of NIR excitation below 10 W cm−2 and induce generation of radicals and photopolymerization in situ. Near infrared-activated polymerization process, both at the millimeter and sub-micron scales, was investigated. Polymeric macro- and microstructures were fabricated by means of near infrared laser scanning photolithography in the volume of liquid photocurable compositions with focused laser light at 975 nm wavelength. Examination of the polymerization process in the vicinity of the nanoparticles shows strong differences in the rate of polymer shell growth on flat and edge nanoparticle sides. This phenomenon mainly defines the resolution of the demonstrated near infrared - ultraviolet 3D printing technology at the micrometer scale level.

Light-Induced Step-Growth Polymerization of AB-Type Photo-Monomers at Ambient Temperature.

We introduce two AB-type monomers able to undergo a facile catalyst-free photoinduced polycycloaddition of photocaged dienes, enabling rapid Diels-Alder ligations under UV-irradiation (λmax = 350 nm) at ambient temperature, closely adhering to Carother's equation established by a careful kinetic study (17800 g mol-1 < Mw < 24700 g mol-1). The resulting macromolecules were in-depth analyzed via size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. Additionally, SEC hyphenated to high resolution-electrospray ionization-mass spectrometry (HR-ESI-MS) enabled the careful mapping of the end group structure of the generated polymers. Furthermore, we demonstrate that both monomer systems can be readily copolymerized. The study thus demonstrates that Diels-Alder ligation resting upon photocaged dienes is a powerful tool for accessing step-growth polymers.

Enhanced Photodecomposition of Methylene Blue in Water with Sr1−xKxTiO3−δ@PC-polyHIPEs under UV and Visible Light

Photocatalytic method was investigated to remove water pollutant methylene blue (MB) produced in textile, plastic, and dye industries. PC-polyHIPEs were prepared by light-induced polymerization of dopamine in transparent polyHIPEs which were synthesized by polymerization within high internal phase emulsions. Sr1-xKxTiO3-δ (x = 0–0.5) nanoparticles were incorporated and adhered to PC-polyHIPEs to form Sr1-xKxTiO3-δ@PC-polyHIPEs for the first time. The catalysts were characterized by XRD, FTIR, TGA, UV-Vis DRS, and SEM and their photocatalytic properties for MB decomposition were measured over UV-Vis spectrometer. The PC-polyHIPEs were of interconnected porous structure with around 100 μm pores and 30 μm windows. Sr1−xKxTiO3−δ@PC-polyHIPEs showed excellent MB decomposition activity under either UV or visible light although Sr1−xKxTiO3−δ alone worked only under UV light. When x = 0.3, Sr1−xKxTiO3−δ@PC-polyHIPEs showed the highest photocatalytic performance due to the existence of more oxygen vacancies. When the water solution with 50 mg L−1 MB and 1.6 gcat. L−1 Sr0.7K0.3TiO3−δ@PC-polyHIPEs was exposed to visible light for 160 min at room temperature, 88.3% of MB was decomposed. After being used for eight cycles, 87.6% activity of fresh Sr0.7K0.3TiO3−δ@PC-polyHIPEs still remained. The influences of salinity, temperature, and catalyst concentration on the catalytic activity were studied. For MB decomposition under visible light, the activation energy of Sr0.7K0.3TiO3−δ@PC-polyHIPEs was calculated to be 12.3 kJ mol−1 and the kinetics analysis revealed that the photocatalysis followed the second-order reaction. These findings demonstrated that Sr1−xKxTiO3−δ@PC-polyHIPEs were an effective candidate for real application in decomposition of MB in water.

Study on the enhanced adsorption properties of lysozyme on polyacrylic acid modified TiO2 nano-adsorbents

The adsorption and immobilization of enzymes onto solid carriers has been focused on due to their many advantages, such as improved stability against a thermal or organic solvent and a good cycle usability. TiO2 nanoparticles is one of excellent nano-adsorbents owing to its excellent biocompatibility, non-inflammatory, and abundant surface hydroxyl groups, which are convenient to be combined with various functional groups. In this paper polyacrylic acid (PAA) modified TiO2 nanoparticles were synthesized through an in situ light-induced polymerization of acrylic acid on the surface of TiO2 nanoparticles. The structure and surface physicochemical properties of the PAA/TiO2 nanoparticles were characterized by TEM, XRD, FT-IR, Zeta potential measurements and TG-DSC. The experimental results showed that the isoelectric point of PAA/TiO2 significantly reduced to 1.82 compared with that of pure TiO2 nanoparticles (6.08). In the adsorption tests of lysozyme (Lyz), the PAA/TiO2 nanoparticles displayed enhanced adsorption activity compared with pristine TiO2. The maximum adsorption capacity of PAA/TiO2 for Lyz was 225.9 mg g−1 under the optimum conditions where the initial concentration of Lyz was 300 mg ml−1, the addition amount of PAA/TiO2 was 6.4 mg, the adsorption time was 30 min and the pH value was 7.0. The sodium dodecyl sulfate (SDS, 0.5%) presented the best efficiency (76.86%) in the removal of adsorbed Lyz, and the PAA/TiO2 nanoparticles showed excellent adsorption stability based on five cyclic adsorption–desorption tests. The fitting calculation results of the adsorption isotherm and the thermodynamics indicated the adsorption was an exothermic, entropy increasing, spontaneous and monomolecular layer adsorption process.

A mild route to entrap papain into cross-linked PEG microparticles via visible light-induced inverse emulsion polymerization

Entrapment of enzymes into a cross-linked network is an effective way to enable their recycling. In order to obtain a satisfied recovery of enzyme activity, a mild encapsulating condition is highly required due to the delicate nature of enzymes. Herein, a facile and mild visible light-induced inverse emulsion polymerization technique was developed for in situ entrapment of enzyme. In this method, poly (ethylene glycol) diacrylate (PEGDA) was dissolved in phosphate buffer saline and used as disperse phase, while continuous phase was composed of liquid paraffin, photoinitiators (isopropylthioxanthone and ethyl 4-dimethylaminobenzoate) and emulsifier (Span 80 and Tween 80). Under the irradiation of visible light, PEGDA could be cross-linkedly polymerized and formed microparticles with diameter ranged from 0.75 to 6.5 μm. When the glutaraldehyde cross-linked papain was added into disperse phase, it could be in situ entrapped into the microparticles after the visible light-induced inverse emulsion polymerization. The immobilized papain exhibited higher activity in a wide range of temperature and pH than free papain. Moreover, the immobilized papain could maintain 60% of its initial activity even after ten cycles of usage. This simple and mild strategy to in situ entrapment of enzymes has potential application in fields such as biocatalyst, biosensor and drug delivery.