Photosensitive Polymer Research Articles

ОПТИЧНІ ТА ФОТОХІМІЧНІ ВЛАСТИВОСТІ ПОЛІМЕРІВ НА ОСНОВІ 2-(4-МЕТАКРИЛОКСИСТИРИЛ)ХІНОЛІНУ

The design and synthesis of new polymer materials with controlled and predictable properties is still a challenge. Photoactive chromophore can be incorporated into a polymer in several different ways: guest-host systems, main chain polymers and side chain polymers. While none of these options are not perfect and each has its advantages and disadvantages. However, the chromophore functionalized polymers were found to be more effective due to: high concentration of the chromophores can be introduced; polymers with chromophore moiety show increased stability of poling induced SHG activity and decrease of the orientation relaxation process; absence of phase separation lessens the scattering losses; such techniques as plasma etching, optically induced index changes, laser ablation, electrical poling can be applied; multilayer phormation assists in easy integration with electronic and optical components. The principles of design of various molecular photoswitches and logical devices, in particular, those based on the photoisomerization reaction of diarylethylenes have been actively investigated in recent years. Azasubstituted diarylethylenes (DAE) styrylquinolines containing a central double bond and an endocyclic nitrogen atom, have become the subject of interest due to their ability to reversible transformations (photoisomerization and protonation). In this work, photosensitive polymers were synthesized by radical polymerization of corresponding styrylquinoline derivatives with comonomers methyl methacrylate (MMA) using asobisisobutyronitrile (AIBN) as radical initiator. We present results obtained for thin films of the methacrylic polymers incorporating styrylquinoline side-group as optically active molecule. Synthesis of 2-(4-methacryloxystyryl)quinolone and 2-(4-methacryloxystyryl)-6-methoxyquinoline was described. The polymers were obtained by free radical polymerization of methacrylic monomers in dimethylformamide with azobisisobutyronitrile as initiator. The products of polymerization were characterized and evaluated by 1HNMR, UV spectroscopy. Glass transition temperatures were characterized by DSC method. It was found 133°C, 110°C, 130°C, 112°C for P1, P1MMA, P2, P2MMA respectively. Their optical and photochemical properties as well as temperature dependence of the photoluminescence of diarylethylenes have been investigated.

Low solid loading, low viscosity, high uniform shrinkage ceramic resin for stereolithography based additive manufacturing

In this work, a three-dimensional (3D) ceramic scaffold of barium titanate (BaTiO3) is realized by stereolithographic (SLA) of BaTiO3 powder and photopolymer with a high resolution and followed by a controlled thermal treatment. The photosensitive polymer in the resin mixture plays a vital role in dispersing ceramic powders and supporting complex structures cured by ultraviolet (UV) laser. The fabricated BaTiO3 and photopolymer composite part shows homogeneous dispersion of BaTiO3 microparticles. With a controlled thermal treatment, the photopolymer was carefully removed from the composite during the debinding process. Further sintering of the debinded ceramic parts at 1100 ℃, 1200 ℃, and 1300 °C shows a huge-volume shrinkage of up to 98.25% at a low concentration of ceramic powders (10 wt%). The sintered BaTiO3 ceramic parts are structurally intact with SEM images showing uniform microstructures with a relative density of 73.48%. The ultra-high shrinkage rate in this process provides a way to create complex 3D ceramic scaffolds with higher resolution than the SLA printing resolution. With the success of sintering ultralow solid loading ceramic-polymer composites, low-cost SLA 3D printers could be used to manufacture various ceramic parts with an improved resolution. This process allows widely application of 3D printed ceramics parts in the area of biomedical, aerospace, automotive, and energy fields.

Direct UV laser writing system to photolithographically fabricate optimal microfluidic geometries: Experimental investigations

Ultraviolet (UV) photolithography is utilised to obtain required geometric features on a substrate coated with photosensitive polymer by impinging beam of UV light. Using this fabrication technique, dimensions in the order of sub-micron range can be achieved effectively. However, the conventional photolithography is quite complex, tardy and inefficient approach, specially to achieve higher dimensions (>50 µm). In this work, optimization for fabrication of microchannels using a custom PC based UV (405 nm) Direct Laser Writing (DLW) system for photolithography has been performed. Liquid photoresist and dry film photoresist of various thicknesses are used on the substrate and the patterns are fabricated using the DLW system. The geometry of developed pattern is observed using profilometry and imaging techniques to understand how the width and depth of pattern is being affected by the varying parameters (laser intensity and stage speed), and their optimal values for desired width and depth have been identified. Parameters for developing (developer solution and time) are analysed for both types of photoresists and their effect of mould dimensions have also been studied.

Повышение эффективности полимерного нанокомпозита для формирования фотонных структур методом оптической записи

In this work, the conditions for optimizing an optical recording material based on photosensitive acrylate-urethane nanocomposites with silicon oxide nanoparticles, for efficient Bragg gratings recording by multibeam interference method is presented. It was shown that the choice of the most effective monomers and their concentrations in the nanocomposite which depends on their structure and polymerization rate, followed by determination of the optimal recording radiation intensity for the given composition, makes it possible to adjust the conditions for component diffusion and redistribution, and hence, the formation of regions with different refractive indices in the recording medium. These results can be useful for creating complex 2D and 3D photonic structures based on the targeted modification of photosensitive polymer nanocomposites with different properties (luminescent, nonlinear optical, etc.).

Engineering an adhesive based on photosensitive polymer hydrogels and silver nanoparticles for wound healing.

Hemostasis, wound closure and prevention of infection are critical to wound healing after an injury. Skin adhesives have been used to seal incisions, thus aiding primary wound healing, as well as creating a barrier to microbes. We constructed a skin adhesive with antibacterial and hemostatic activities (AHAs) for wound management. The adhesive was made by using methacrylated hyaluronan-polyacrylamide (MHA-PAAm) hydrogels, integrated with silver nanoparticles (AgNPs) and bonded to gelatin. Because of the three-dimensional network structure of the hydrogels, nanoscale particles can be encapsulated into their voids; the AgNPs, through sustained delivery of silver ions, endow the adhesives with sustained broad-spectrum antibacterial activity. Furthermore, due to the introduction of MHA which can be crosslinked by visible light, the polyacrylamide hydrogel matrix can be formed through photo crosslinking. In addition, gelatin can be bonded to both the hydrogel matrix and host tissues because of the interaction between carboxyl and amino-moieties. Our animal studies demonstrated that the AHAs which possess tissue adhesive and antibacterial properties were easy to stretch, and were able to stop bleeding in rat tail amputation and liver injury models. AHAs enhance wound granulation tissue formation, vascular tissue formation, and collagen formation, as well as alleviate inflammation. These properties promoted wound closure in rat wound infection models, promising great potential for applying AHAs in clinical uses.

Efficient suppression of amyloid-β peptide aggregation and cytotoxicity with photosensitive polymer nanodots.

The deposition of amyloid plaques resulting from the aggregation of amyloid-β (Aβ) peptides is closely related to Alzheimer's disease (AD). With the development of various therapeutic methods, the oxidative modification of Aβ has emerged as a fascinating noninvasive photo-therapeutic intervention for treating AD by altering the Aβ aggregation tendency. Herein, we report the photo-triggered inhibition of Aβ aggregation and cytotoxicity by utilizing polymer nanodots (Pdots) modified with rose bengal (RB), methylene blue (MB), and riboflavin (RF). Experimental results demonstrate that these functionalized Pdots manifest a superior suppression effect on Aβ aggregation under irradiation. This can be attributed to the formation of reactive oxygen species (ROS) (i.e., singlet oxygen (1O2)), resulting in the oxygenation of Aβ and the change of Aβ aggregation tendency. Especially, RB-Pdots manifest better biocompatibility and higher 1O2 productivity. In a word, this hybridized nanostructure will provide a promising platform for the noninvasive photo-therapeutic treatment of AD in the future.

Local Optical Chirality Induced by Near-Field Mode Interference in Achiral Plasmonic Metamolecules.

When circularly polarized light interacts with a nanostructure, the optical response depends on the geometry of the structure. If the nanostructure is chiral (i.e., it cannot be superimposed on its mirror image), then its optical response, both in near-field and far-field, depends on the handedness of the incident light. In contrast, achiral structures exhibit identical far-field responses for left- and right-circular polarization. Here, we show that a perfectly achiral nanostructure, a plasmonic metamolecule with trigonal D3h symmetry, exhibits a near-field response that is sensitive to the handedness of light. This effect stems from the near-field interference between the different plasmonic modes sustained by the plasmonic metamolecule under circularly polarized light excitation. The local chirality in a plasmonic trimer is then experimentally evidenced with nanoscale resolution using a molecular probe. Our experiments demonstrate that the optical near-field chirality can be imprinted into the photosensitive polymer, turning an optical chirality into a geometrical chirality that can be imaged using atomic force microscopy. These results are of interest for the field of polarization-sensitive photochemistry.

Structure and optical properties of the photosensitive hybrid Ti-contained polymer materials for photonics

Titanium-containing interpenetrating polymer networks (Ti-IPNs) based on the cross-linked polyurethane, poly (hydroxyethyl methacrylate) and poly (titanium oxide) have been synthesized. First poly (titanium oxide) was synthesized by sol-gel method in the presence of 2-hydroxyethyl methacrylate at different molar ratio of Ti (OPri)4/H2O. The results obtained by method of optical spectrophotometry shows that the light transmission coefficients (T, %) of titanium-containing interpenetrating polymer networks samples was 90.7–91.0% at λ = 650 nm. According to EPR data, UV irradiation in the air at room temperature of Ti-IPN samples is accompanied by appearance of signal of paramagnetic centers with broad isotropic signal at g1 = 2.010 and also noticeably splitted signal at g2 = 2.003 and g3 = 1.967. First and second of them can be ascribed to the oxygen-containing “hole scavenger”, while the third one is associated with the Ti3+ paramagnetic ions. The low rate of the electron–hole pair recombination at room temperature in the air demonstrates efficient separation of the charged particles in the hybrid material. X-ray diffraction analysis indicates that Ti-IPN sample have an amorphous structure. UV-induced charge separation and subsequent charge recombination in Ti-IPNs cause the changes in short-range order in the arrangement of polymer macrochains.

Fabrication of 3D conjugated polymer structures via vat polymerization additive manufacturing

Conjugated polymers are a class of electroactive active material that have been studied for their potential in advanced sensing and actuation technologies. Conventional methods to fabricate conjugated polymer transducers produce devices with planar morphologies that limit fabricated devices to simplistic linear or bending modes of operation. To overcome this limitation, this work develops a photosensitive polypyrrole formulation and light-based additive manufacturing method capable of realizing three-dimensional conjugated polymer structures with micro-scale features. The electroactivity and strain sensing properties of the photosensitive polymer formulation are reported to show the early development of this method towards new sensing and actuation technologies.

Light-Induced Structuring of Photosensitive Polymer Brushes

We investigate light-induced irreversible structuring of surface topographies in poly(3-sulfopropyl methacrylate/potassium salt) (PSPMK) brushes on flat solid substrates prepared by surface-initiat...

Synthesis of Photosensitive Cyclopropane-Containing Polymers

New cyclopropyl methacrylate monomers were prepared, their radical polymerization was performed, and the composition and structure of the polymers obtained, containing reactive UV-sensitive fragments, were determined. Experiments on photochemical cross-linking revealed photosensitivity of the polymers synthesized. The materials based on them are optically transparent and can be used in microelectronics and optics.

Preparation of hydroxypropyl cellulose-poly (2-Methacryloyloxyethyl phosphorylcholine) coating for the analysis of proteins by capillary electrophoresis

We reported a new method for preparing coated capillaries in this paper. First, we combined hydroxypropyl cellulose (HPC) and 2-Methacryloyloxyethyl phosphorylcholine (MPC) to form hydroxypropyl cellulose-poly (2-Methacryloyloxyethyl phosphorylcholine) (HPC-PMPC) by atom transfer radical polymerization (ATRP). Then the photosensitive polymer diazoresin (DR) was used as a linker to the inner wall of the capillary, and finally exposed to ultraviolet light to form a stable covalent bond coating. Protein adsorption on the inner surface of capillary was effectively inhibited. The cytochrome c (Cyt-c), lysozyme (Lys), ribonuclease A (RNase A) and bovine serum albumin (BSA) were separated obviously using capillary electrophoresis (CE) within 15 minutes and showed good stability and repeatability.

Polymer M-Z Thermal Optical Switch at 532-nm Based on Wet Etching and UV-Writing Waveguide.

Polymer thermal optical switches have low power consumption and 532 nm is the communication window of polymer fiber. Polymer thermal optical switches at 532 nm are rarely reported, because of switching extinction ratio properties that are restricted by modes of the waveguide. Single mode waveguide at 532 nm is hard to fabricate due to the dissolution of core and cladding materials. A polymer M-Z thermal optical switch at 532 nm was first demonstrated based on the wet etching method. The proposed thermal optical switch was consisted of silica substrate, photosensitive polymer core, and cladding material. The device was fabricated and tested with the power consumption of 6.55mW, extinction of 4.8 dB, and switching time of 0.23 ms (rise)/0.28 ms (down). An optimized switch structure combining with the UV-writing technique and graphene thermal conduction layer was proposed based on the experiments above. A side electrode was designed to reduce the power consumption and the switching time. The optimized device was calculated to have a power consumption of 1.5 mW. The switching time of the UV-writing device was simulated to be 18.2 μs (rise) and 85 μs (down). The device is promising in the wearable device and laser radar area.

Biomimetic Designer Scaffolds Made of D,L-Lactide-ɛ-Caprolactone Polymers by 2-Photon Polymerization.

Traditionally tissue engineering (TE) strategy relies on three components: cells, signaling systems (e.g., growth factors), and extracellular matrix (ECM). Nowadays the combination of cells, signaling systems, an artificial ECM, and appropriate bioreactor systems has recently been defined as the “Tissue Engineering Quadriad”1 taking into consideration the fundamental role of the dynamic physiological environment. Not surprisingly, the establishment of an artificial ECM with the necessary flexibility seems to be a mission impossible without advanced materials and fabrication techniques. This claim applies to therapeutic (regeneration) as well as diagnostic (disease-modeling) approaches. To meet the challenge to mimic the hierarchical structured and complex milieu of the natural ECM it was tried in this study to combine a flexible photosensitive polymer platform based on (D,L)-lactide-ɛ-caprolactone methacrylate (LCM) with a nanoscale rapid prototyping technique based on two-photon polymerization (2-PP). Polyesters, such as poly-ɛ-caprolactone or poly-(D, L)-lactide, are very popular candidates for mimicking the ECM, because of their adjustable biophysical and biochemical properties. 2-PP represents a versatile lithographic method for the generation of scaffolds with defined size and shape, due to a spatial resolution <100 nm. This unique performance enables the fabrication of mathematically defined structures (scaffolds) based on triply periodic minimal surfaces with a tailor-made stiffness, permeability, and degradation behavior. Especially the Schwarz P minimal surface, which divides the interior of a scaffold into two intertwining labyrinths, plays an important role in generating custom-made or designer scaffolds. This review gives an overview of materials, techniques, and appropriate geometries to establish a conceptual framework to engineer such scaffolds. Furthermore, selected application scenarios in bone and tumor TE were introduced in the sense of a first proof of principle to show the high potential of this concept in therapeutic (regeneration) and diagnostic (disease-modeling) approaches.Impact StatementIn tissue engineering (TE), the establishment of cell targeting materials, which mimic the conditions of the physiological extracellular matrix (ECM), seems to be a mission impossible without advanced materials and fabrication techniques. With this in mind we established a toolbox based on (D,L)-lactide-ɛ-caprolactone methacrylate (LCM) copolymers in combination with a nano–micromaskless lithography technique, the two-photon polymerization (2-PP) to mimic the hierarchical structured and complex milieu of the natural ECM. To demonstrate the versatility of this toolbox, we choose two completely different application scenarios in bone and tumor TE to show the high potential of this concept in therapeutic and diagnostic application.

Beyond grayscale lithography: inherently three-dimensional patterning by Talbot effect

Abstract There are a growing number of applications where three-dimensional patterning is needed for the fabrication of micro- and nanostructures. Thus far, grayscale lithography is the main technique for obtaining a thickness gradient in a resist material that is exploited for pattern transfer by anisotropic etch. However, truly three-dimensional structures can only be produced by unconventional lithography methods such as direct laser writing, focused ion beam electrodeposition, colloidal sphere lithography, and tilted multiple-pass projection lithography, but at the cost of remarkable complexity and lengthiness. In this work, the three-dimensional shape of light, which is formed by Talbot effect diffraction, was exploited to produce inherently three-dimensional patterns in a photosensitive polymer. Using light in the soft X-ray wavelength, periodic three-dimensional structures of lateral period 600 nm were obtained. The position at which the sample has to be located to be in the Fresnel regime was simulated using an analytical implementation of the Fresnel integrals approach. Exploiting the light shape forming in diffraction effects thus enables the patterning of high-resolution three-dimensional nanostructures over a large area and with a single exposure pass – which would be otherwise impossible with conventional lithographic methods.

Selective Electroless Copper Deposition by Using Photolithographic Polymer/Ag Nanocomposite

This paper presents a novel, direct, selective, vacuum-free, and low-cost method of electroless copper deposition, allowing additive patterning of nonconductive surfaces. Ag nanoparticles (NPs) synthesized inside a photosensitive polymer are acting as seeds for electroless copper deposition. The resulting copper film surface morphology was studied with scanning electron microscopy. Copper films were shown to display a rough grainlike structure, covering substrate uniformly with good metal-substrate adhesion. Copper thickness was studied as a function of the plating time, temperature, and Ag NPs seed concentration. A maximal copper thickness of ${0.44}\,\pm \,{0.05}~\mu \text{m}$ was achieved when plated at 30 °C with 0.4 M Ag(I). The minimum feature resolution of copper patterns, grown with 0.025- and 0.1-M silver salt, is attained down to ${10}~\mu \text{m}$ . The maximum electrical conductivity of the copper film prepared with 0.025-, 0.1-, and 0.4-M Ag(I) approaches ( ${0.8}\,\pm \,0.1) \times {10}^{{7}}$ S/m, ( ${1.1}\,\pm \,{0.1}) \times {10}^{{7}}$ S/m and ( ${1.6}\,\pm \, {0.4}{)} \times {10}^{{7}}$ S/m, respe- ctively. Electroless copper interconnections and LED circuit on glass substrate were fabricated as a proof of concept demonstrators.

Preparation and electrical conductivity of metal and photosensitive polymer composite film

In-situ photochemical synthesis and spin casting were used to fabricate a metal and photosensitive polymer composite film on insulation substrates in this study. The metal salt/photosensitive polymer solution consists of polyethylene glycol diacrylate(PEGDA) as the monomer, a mixture of 50% 1-hydroxycyclohexyl-phenyl ketone and 50% benzophenone as the photo initiator, ethanol as the reducing agent, pyrrole as the organic electrolyte, and silver nitrate (AgNO3) as the conductor. The resulting composite liquid was spin coated onto a glass substrate, irradiated by ultraviolet–visible light so that silver particles were in-situ synthesized by photo polymerization, and treated thermally to form a silver nanoparticle/polymer composite film. As shown in the results, the sheet electrical resistance of the as-prepared composite film formed with 12.5 wt% of AgNO3; irradiation by 3 J/cm2 of ultraviolet–visible light, which produced an Ag particle size of about 24 nm; and thermal treatment at 250 °C for 30 min would be less than 2 Ω/sq, as measured with a four-probe points of sheet electrical resistance meter. This implies that the electrical continuity path on the surface of the as-prepared composite is induced by Ostwald ripening. The composite prepared in this study promises application in electronics and communication to prevent electromagnetic interference (EMI) and radio frequency interference (RFI).

Preparation of two novel Schiff base polymers and their Eu (III)/Yb (III) complexes

A series of novel Schiff base photosensitive polymers with coordination property were synthesized through a condensation reaction. Then using the Schiff base photosensitive polymers as macromolecular ligands, a series of polymer rare-earth complexes were prepared through a coordination reaction. The structure of the polymer and their corresponding complex was performed by means of Fourier transform infrared and ultraviolet spectroscopy; the fluorescence properties of the complex were mainly investigated by fluorescence spectroscopy, and the thermal property was investigated by differential scanning calorimetry and thermogravimetric analysis. The luminescence properties of the europium (Eu) (III)/ytterbium (Yb) (III) complex in dimethylformamide solutions were investigated. The experimental results show that the complexes have fine thermal stability and all the europium (III)/ytterbium (III) complexes exhibit characteristic photoluminescence peaks in the visible region and the results indicate that the complexes are promising in the field of light-emitting materials and can be further mixed with a suitable polymer to form functional rare-earth polymers.

Toxicity and photosensitizing assessment of gelatin methacryloyl-based hydrogels photoinitiated with lithium phenyl-2,4,6-trimethylbenzoylphosphinate in human primary renal proximal tubule epithelial cells

Gelatin methacryloyl (GelMA) and lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) photoinitiator are commonly used in combination to produce a photosensitive polymer but there are concerns that must be addressed: the presence of unreacted monomer is well known to be cytotoxic, and lithium salts are known to cause acute kidney injury. In this study, acellular 10% GelMA hydrogels cross-linked with different LAP concentrations and cross-linking illumination times were evaluated for their cytotoxicity, photosensitizing potential, and elastic moduli. Alamar Blue and CyQuant Direct Cell viability assays were performed on human primary renal proximal tubule epithelial cells (hRPTECs) exposed to extracts of each formulation. UV exposure during cross-linking was not found to affect extract cytotoxicity in either assay. LAP concentration did not affect extract cytotoxicity as determined by the Alamar Blue assay but reduced hRPTEC viability in the CyQuant Direct cell assay. Photocatalytic activity of formulation extracts toward NADH oxidation was used as a screening method for photosensitizing potential; longer UV exposure durations yielded extracts with less photocatalytic activity. Finally, elastic moduli determined using nanoindentation was found to plateau to approximately 20-25 kPa after exposure to 342 mJ/cm2 at 2.87 mW of UV-A exposure regardless of LAP concentration. LAP at concentrations commonly used in bioprinting (<0.5% w/w) was not found to be cytotoxic although the differences in cytotoxicity evaluation determined from the two viability assays imply cell membrane damage and should be investigated further. Complete cross-linking of all formulations decreased photocatalytic activity while maintaining predictable final elastic moduli.

Comparative Analysis of Wollastonite‐Diopside Glass‐Ceramic Structures Fabricated via Stereo‐Lithography

One key feature of digital light processing consists of the high flexibility in the design of highly porous reticulated scaffolds. In the present paper, the authors report recent experiences concerning two glasses, both converted into wollastonite‐diopside (CaSiO3–CaMgSi2O6) glass‐ceramics by viscous flow sintering of fine powders (&lt;45 μm) with concurrent crystallization. Glass particles are homogeneously dispersed in a photosensitive polymer, selectively hardened, layer‐by‐layer, by exposure to visible light, forming diamond cell lattices. The printing accuracy is slightly influenced by the glass chemistry, whereas the shape maintenance, after firing at 1100 °C, is observed for both compositions. The newly developed scaffolds are compared to other glass‐ceramic scaffolds, previously developed on the basis of the starting glass: the adoption of a new design does not determine any substantial degradation of mechanical properties.