Polymer Matrix Research Articles

Ultraviolet-cured heat-resistant and stretchable gel polymer electrolytes for flexible and safe semi-solid lithium-ion batteries

Lithium-ion (Li-ion) batteries assembled with gel polymer electrolytes (GPEs) are predicted to increase battery energy density while maintaining battery safety. In this work, poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) is successfully used as a polymer matrix to prepare a new kind of GPE (PHHNT) by ultraviolet (UV) curing technology. The polymer network structure formed by photopolymerization technology significantly enhances the tensile properties of the electrolyte. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) improves the concentration and transport efficiency of lithium ions in the electrolyte as well as the ionic conductivity (1.22 × 10−3 S cm−1) of the GPEs. In addition, the unique tubular structure of the halloysite nanotube (HNT) and the opposite charges carried by the inner and outer surfaces provide additional channels for the lithium salt and facilitate its dissociation. This enhances the expedited movement of Li+ inside the electrolyte, while simultaneously improving the electrochemical and thermal durability of the electrolyte. The assembled LiFePO4 (LFP)/PHHNT/Li battery has an initial discharge-specific capacity of 140.5 mAhg−1 at a current density of 0.5C, showing a high capacity retention rate of 89 % after 120 cycles. The design of this composite material significantly improves the overall performance of the electrolyte and is more suitable for flexible and safe solid-state Li-ion batteries.

Polypy: A Framework to Interpret Polymer Properties from Mass Spectroscopy Data.

Mass spectroscopy (MS) is a robust technique for polymer characterization, and it can provide the chemical fingerprint of a complete sample regarding polymer distribution chains. Nevertheless, polymer chemical properties such as polydispersity (Pd), average molecular mass (Mn), weight average molecular mass (Mw) and others are not determined by MS, as they are commonly characterized by gel permeation chromatography (GPC). In order to calculate polymer properties from MS, a Python script was developed to interpret polymer properties from spectroscopic raw data. Polypy script can be considered a peak detection and area distribution method, and represents the result of combining the MS raw data filtered using Root Mean Square (RMS) calculation with molecular classification based on theoretical molar masses. Polypy filters out areas corresponding to repetitive units. This approach facilitates the identification of the polymer chains and calculates their properties. The script also integrates visualization graphic tools for data analysis. In this work, aryl resin (poly(2,2-bis(4-oxy-(2-(methyloxirane)phenyl)propan) was the study case polymer molecule, and is composed of oligomer chains distributed mainly in the range of dimers to tetramers, in some cases presenting traces of pentamers and hexamers in the distribution profile of the oligomeric chains. Epoxy resin has Mn = 607 Da, Mw = 631 Da, and polydispersity (Pd) of 1.015 (data given by GPC). With Polypy script, calculations resulted in Mn = 584.42 Da, Mw = 649.29 Da, and Pd = 1.11, which are consistent results if compared with GPC characterization. Additional information, such as the percentage of oligomer distribution, was also calculated and for this polymer matrix it was not possible to retrieve it from the GPC method. Polypy is an approach to characterizing major polymer chemical properties using only MS raw spectra, and it can be utilized with any MS raw data for any polymer matrix.

Development of Bioactive Hybrid Poly(lactic acid)/Poly(methyl methacrylate) (PLA/PMMA) Electrospun Fibers Functionalized with Bioglass Nanoparticles for Bone Tissue Engineering Applications.

Hybrid scaffolds that are based on PLA and PLA/PMMA with 75/25, 50/50, and 25/75 weight ratios and functionalized with 10 wt.% of bioglass nanoparticles (n-BG) were developed using an electrospinning technique with a chloroform/dimethylformamide mixture in a 9:1 ratio for bone tissue engineering applications. Neat PLA and PLA/PMMA hybrid scaffolds were developed successfully through a (CF/DMF) solvent system, obtaining a random fiber deposition that generated a porous structure with pore interconnectivity. However, with the solvent system used, it was not possible to generate fibers in the case of the neat PMMA sample. With the increase in the amount of PMMA in PLA/PMMA ratios, the fiber diameter of hybrid scaffolds decreases, and the defects (beads) in the fiber structure increase; these beads are associated with a nanoparticle agglomeration, that could be related to a low interaction between n-BG and the polymer matrix. The Young's modulus of PLA/PMMA/n-BG decreases by 34 and 80%, indicating more flexible behavior compared to neat PLA. The PLA/PMMA/n-BG scaffolds showed a bioactive property related to the presence of hydroxyapatite crystals in the fiber surface after 28 days of immersion in a Simulated Body Fluids solution (SBF). In addition, the hydrolytic degradation process of PLA/PMMA/n-BG, analyzed after 35 days of immersion in a phosphate-buffered saline solution (PBS), was less than that of the pure PLA. The in vitro analysis using an HBOF-1.19 cell line indicated that the PLA/PMMA/n-BG scaffold showed good cell viability and was able to promote cell proliferation after 7 days. On the other hand, the in vivo biocompatibility evaluated via a subdermal model in BALC male mice corroborated the good behavior of the scaffolds in avoiding the generation of a cytotoxic effect and being able to enhance the healing process, suggesting that the materials are suitable for potential applications in tissue engineering.

Sustainable Lignin-Reinforced Chitosan Membranes for Efficient Cr(VI) Water Remediation.

The pollution of aquatic environments is a growing problem linked to population growth and intense anthropogenic activities. Because of their potential impact on human health and the environment, special attention is paid to contaminants of emerging concern, namely heavy metals. Thus, this work proposes the use of naturally derived materials capable of adsorbing chromium (VI) (Cr(VI)), a contaminant known for its potential toxicity and carcinogenic effects, providing a sustainable alternative for water remediation. For this purpose, membranes based on chitosan (CS) and chitosan/Kraft lignin (CS/KL) with different percentages of lignin (0.01 and 0.05 g) were developed using the solvent casting technique. The introduction of lignin imparts mechanical strength and reduces swelling in pristine chitosan. The CS and CS/0.01 KL membranes performed excellently, removing Cr(VI) at an initial 5 mg/L concentration. After 5 h of contact time, they showed about 100% removal. The adsorption process was analyzed using the pseudo-first-order model, and the interaction between the polymer matrix and the contaminant was attributed to electrostatic interactions. Therefore, CS and CS/KL membranes could be low-cost and efficient adsorbents for heavy metals in wastewater treatment applications.

Investigating Permselectivity in PVDF Mixed Matrix Membranes Using Experimental Optimization, Machine Learning Segmentation, and Statistical Forecasting.

This research examines the correlation between interfacial characteristics and membrane distillation (MD) performance of copper oxide (Cu) nanoparticle-decorated electrospun carbon nanofibers (CNFs) polyvinylidene fluoride (PVDF) mixed matrix membranes. The membranes were fabricated by a bottom-up phase inversion method to incorporate a range of concentrations of CNF and Cu + CNF particles in the polymer matrix to tune the porosity, crystallinity, and wettability of the membranes. The resultant membranes were tested for their application in desalination by comparing the water vapor transport and salt rejection rates in the presence of Cu and CNF. Our results demonstrated a 64% increase in water vapor flux and a salt rejection rate of over 99.8% with just 1 wt % loading of Cu + CNF in the PVDF matrix. This was attributed to enhanced chemical heterogeneity, porosity, hydrophobicity, and crystallinity that was confirmed by electron microscopy, tensiometry, and scattering techniques. A machine learning segmentation model was trained on electron microscopy images to obtain the spatial distribution of pores in the membrane. An Autoregressive Integrated Moving Average with Explanatory Variable (ARIMAX) statistical time series model was trained on MD experimental data obtained for various membranes to forecast the membrane performance over an extended duration.

The Development of Biocomposite Filaments for 3D Printing by Utilizing a Polylactic Acid (PLA) Polymer Matrix Reinforced with Cocoa Husk Cellulose Fibers.

Vegetable fibers are increasingly used in biocomposites, but there is a need for further development in utilizing by-products like cocoa husks. Three-dimensional printing, through Fused Filament Fabrication (FFF), is advancing rapidly and may be of great interest for applying biocomposite materials. This study focuses on developing innovative and fully biodegradable filaments for the FFF process. PLA filaments were prepared using cellulose fibers derived from cocoa husks (5% mass ratio). One set of filaments incorporated fibers from untreated husks (UCFFs), while another set utilized fibers from chemically treated husks (TCFFs). The fabricated materials were analyzed using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) techniques, and they were also tested for tensile strength. ANOVA reveals that both UCFFs and TCFFs significantly predict tensile strength, with the UCFFs demonstrating an impressive R2 value of 0.9981. The optimal tensile strength for the filament test specimens was 16.05 MPa for TCFF8 and 13.58 MPa for UCFF8, utilizing the same printing parameters: 70% infill and a layer thickness of 0.10 mm. Additionally, there was an 18% improvement in the tensile strength of the printed specimens using the filaments filled with chemically treated cocoa husk fibers compared to the filaments with untreated fibers.

Implementation of Smartphone-Assisted Colorimetric Assay for Metabolite Measurement in Plant Extract: An Example of Controlled Release from a Polymer Matrix

Implementation of Smartphone-Assisted Colorimetric Assay for Metabolite Measurement in Plant Extract: An Example of Controlled Release from a Polymer Matrix

Transparent and Colorless Luminescent Solar Concentrators Based on ZnO Quantum Dots for Building-Integrated Photovoltaics.

Scientific interest in luminescent solar concentrators (LSCs) has reemerged mainly due to the application of semiconductor quantum dots (QDs) as highly efficient luminophores. Recently, LSCs have become attractive proposals for Building-Integrated photovoltaics (BIPV) since they could help conventional photovoltaics to improve sunlight harvesting and reduce production costs. However, most of the modern LSCs rely on heavy-metal QDs which are highly toxic and may cause environmental concerns. Additionally, their absorption spectra give them a characteristic color limiting their potential application in BIPV. Herein, we fabricated transparent and colorless LSCs by embedding nontoxic and cost-effective zinc oxide quantum dots (ZnO QDs) in a PMMA polymer matrix (ZnO-LSC), preserving the QD optical properties and PMMA transparency. The synthesized colloidal ZnO QDs have an average size of 5.5 nm, a hexagonal wurtzite crystalline structure, a broad yellow photoluminescent signal under ultraviolet excitation, and are highly visibly transparent at the employed concentrations (>95% in wavelengths above 400 nm). The optical characterization of the fabricated ZnO-LSCs showed a good visible transparency of 80.3% average visible transmission (AVT), with an LSC concentration factor (C) of 1.02. An optimal device (ZnO-LSC-O) could reach a C value of 2.66 with the combination of optical properties of colloidal ZnO QDs and PMMA. Finally, simulations of the performance of silicon solar cells coupled to the fabricated and optimal LSCs under standard AM 1.5G illumination were performed employing the software COMSOL Multiphysics. The fabricated ZnO-LSC achieved a simulated maximum power conversion efficiency (PCE) of 3.80%, while the optimal ZnO-LSC-O reached 5.45%. Also, the ZnO-LSC generated a maximum power of 15.02 mW and the ZnO-LSC-O generated 40.33 mW, employing the same active area as the simulated solar cell directly illuminated, which generated 14.39 mW. These results indicate that the ZnO QD-based LSCs may be useful as transparent photovoltaic windows for BIPV applications.

Advanced Dentistry Biomaterials Containing Graphene Oxide.

The aim of this study was to obtain three experimental resin-based cements containing GO and HA-Ag for posterior restorations. The samples (S0, S1, and S2) shared the same polymer matrix (BisGMA, TEGDMA) and powder mixture (bioglass (La2O3 and Sr-Zr), quartz, GO, and HA-Ag), with different percentages of graphene oxide (0%, 0.1%, 0.2% GO) and silver-doped hydroxyapatite (10%, 9.9%, 9.8% HA-Ag). The physical-chemical properties (water absorption, degree of conversion), mechanical properties (DTS, CS, FS), structural properties (SEM, AFM), and antibacterial properties (Staphylococcus aureus, Enterococcus faecalis, Streptococcus mutans, Porphyromonas gingivalis, and Escherichia coli) were investigated. The results showed that the mechanical properties, except for the diametral tensile test, increased with the rise in the %GO. After 28 days, water absorption increased with the rise in the %GO. The surface structure of the samples did not show major changes after water absorption for 28 days. The antibacterial effects varied depending on the samples and bacterial strains tested. After increasing the %GO and decreasing the %HA-Ag, we observed a more pronounced antibacterial effect. The presence of GO, even in very small percentages, improved the properties of the tested experimental cements.

Raman spectroscopic stress mapping of single high modulus carbon fibre composite fragmentation in compression

Fragmentation of high modulus carbon fibres is relevant to the failure mechanisms of advanced polymer matrix composites in compression. In situ spatially-resolved Raman spectroscopy during the fragmentation of model single fibre composites is used to map local stress distributions during failure events. The characteristic graphitic band (the G band) located around 1580 cm−1 is associated with the in-plane carbon-carbon bonds; this band shifts its position, and can be calibrated, with the local axial stress in the fibre. The analysis maps the evolution of local stresses with increasing overall composite compression strain, identifying a series of critical events, including fibre fracture, interfacial debonding, and the formation of inter-fragment ‘wedges’. Fitting shear lag models provides interfacial shear strength values. Multiple failure maps of two examples of high modulus PAN carbon fibres (M46J and M55J) demonstrate the possibility of local fragment bending due to fragment end contact. A timeline of potential fragmentation events is proposed for carbon fibres undergoing compression.

Curing process, mechanical property and thermal stability of acrylic polyurethane/Fe2O3 nanocomposite coatings

The effect of Fe2O3 nanoparticles (NPs) on the curing and properties of acrylic polyol HSU 1168 based coating were investigated. The SEM images showed that Fe2O3 NPs with the content £ 2 wt.% were dispersed regularly in the polymer matrix. The obtained results indicated that Fe2O3 NPs slowed down the curing process of acrylic polyol coating. Without nanoparticles, the neat HSU 1168 based coating has completely cured after 96 hours, whereas in the presence of 2 wt.% Fe2O3 NPs in coating matrix it needed 120 hours for a full curing. In addition, the relative hardness of nanocomposite coating has reduced with increasing the Fe2O3 NPs content. Without nanoparticles, the relative hardness of neat acrylic polyol coating was 0.88, whereas it was 0.75 when 4 wt.% Fe2O3 NPs was added into the coating matrix. Besides, incorporation of Fe2O3 NPs into the acrylic polyol coating also enhanced its abrasion resistance and impact resistance with 2 wt.% Fe2O3 NPs being the best content (i.e. 200 kG.cm of impact resistance and 408.8 L/mil of abrasion resistance). On the other hand, incorporation of Fe2O3 NPs into the coating matrix improved its thermal stability. The starting temperature for degradation of nanocomposite coating (with 2 wt.% Fe2O3 NPs) was 15 oC higher than that of the neat coating (without nanoparticles)

Facile Fabrication of Hydroxyapatite and Bentonite Encapsulated Biopolymeric Hybrid Composites for Selective Removal of Methylene Blue

AbstractDyeing industries release their hazardous dyeing effluents into the environment which affects the human health and ecosystem. Hence, the removal of dye from waste‐water is mandatory one. In this present study, focus on the fabrication of bio‐clay‐ceramic hybrid composites by dispersing bentonite (BT) clay and ceramic hydroxyapatite (HA) into alginate (Alg) and gelatin (Gel) polymeric matrixes by in‐situ method which gives BTHAAlg and BTHAGel hybrid composites for methylene blue (MB) removal. The various adsorption influencing parameters such as shaking time, adsorbent dosage, pH and initial MB concentration were optimized under batch method. The highest MB adsorption capacities of BTHAAlg and BTHAGel composites were found to be 43.70 and 47.50 mg/g respectively with optimized conditions of 100 mg/L of initial MB concentration, 40 min shaking time and 0.1 g dosages. In pH studies, the high MB adsorption capacity of bio‐clay‐ceramic composites were noticed at pH 11. The characterization techniques like FTIR, SEM and EDAX analysis were performed to find the physico‐chemical properties of bio‐clay‐ceramic composites. The equilibrium data of hybrid composites towards MB adsorption was well fitted with Langmuir isotherm model than D‐R and Fruendlich models because of higher r and low sd values. The negative values of ▵Go at three different temperatures (303, 313 and 323 K) indicate that the spontaneous nature of MB adsorption, while positive values of ΔHo and ΔSo revealed that the MB adsorption onto hybrid composites was endothermic in nature and more randomness occurred at solid/liquid interfaces. In kinetic studies, the MB adsorption onto hybrid composites was well fitted with pseudo‐second‐order and intra‐particle diffusion models. The electrostatic attraction and hydrogen bonding plays a dominant role in MB adsorption onto BTHAAlg and BTHAGel bio‐clay‐ceramic composites. The regeneration studies proposed that the hybrid composites can be reusable upto five cycles. Hence, the developed bio‐clay‐ceramic hybrid composites were act as best adsorbents for MB removal.

Single‐Anion Conductive Solid‐State Electrolytes with Hierarchical Ionic Highways for Flexible Zinc‐Air Battery

Flexible zinc‐air batteries are leading power sources for next‐generation smart wearable electronics. However, flexible zinc‐air batteries suffer from the highly‐corrosive safety risk and limited lifespan due to the absence of reliable solid‐state electrolytes (SSEs). Herein, a single‐anion conductive SSE with high‐safety is constructed by incorporating a highly amorphous dual‐cation ionomer into a robust hybrid matrix of functional carbon nanotubes and polyacrylamide polymer. The as‐fabricated SSE obtains dual‐penetrating ionomer‐polymer networks and hierarchical ionic highways, which contribute to mechanical robustness with 1200% stretchability, decent water uptake and retention, and superhigh ion conductivity of 245 mS·cm‐1 and good Zn anode reversibility. Remarkably, the flexible solid‐state zinc‐air batteries delivers a high specific capacity of 764 mAh·g‐1 and peak power density of 152 mW·cm‐2 as well as sustains excellent cycling stability for 1050 cycles (350 hours. This work offers a new paradigm of OH‐ conductors and broadens the definition and scope of OH‐ conductors.

Single-Anion Conductive Solid-State Electrolytes with Hierarchical Ionic Highways for Flexible Zinc-Air Battery.

Flexible zinc-air batteries are leading power sources for next-generation smart wearable electronics. However, flexible zinc-air batteries suffer from the highly-corrosive safety risk and limited lifespan due to the absence of reliable solid-state electrolytes (SSEs). Herein, a single-anion conductive SSE with high-safety is constructed by incorporating a highly amorphous dual-cation ionomer into a robust hybrid matrix of functional carbon nanotubes and polyacrylamide polymer. The as-fabricated SSE obtains dual-penetrating ionomer-polymer networks and hierarchical ionic highways, which contribute to mechanical robustness with 1200% stretchability, decent water uptake and retention, and superhigh ion conductivity of 245 mS·cm-1 and good Zn anode reversibility. Remarkably, the flexible solid-state zinc-air batteries delivers a high specific capacity of 764 mAh·g-1 and peak power density of 152 mW·cm-2 as well as sustains excellent cycling stability for 1050 cycles (350 hours. This work offers a new paradigm of OH- conductors and broadens the definition and scope of OH- conductors.

Polyvinyl alcohol nanofibrous mat impregnated with ClCNTs/Fe2O3 nanocomposite for absorption of diesel oil in water

Abstract Oil contamination is one of the main sources of water pollution in the world. In this study, a sorption material that showed great promise as an absorbent for diesel oil in aqueous solution was developed. Chlorinated carbon nanotubes (CNTs) previously synthesized using a chemical vapor deposition (CVD) method were loaded with iron oxide nanoparticles via a co-precipitation method. The sorption materials were prepared by embedding ClCNTs/Fe2O3 nanocomposite into a polyvinyl alcohol (PVA) polymer matrix via electrospinning. The PVA mat containing only ClCNTs was also prepared for comparison and the maximum sorption capacity of 9.7 g/g was obtained. The optimum concentration of ClCNTs/Fe2O3 nanocomposite that gave uniform, and well-distributed nanofibers was 0.5 wt.%. Crosslinking the PVA/ClCNTs/Fe2O3 nanofiber mat with glutaraldehyde (GA) resulted in increased absorption capacity for oil of ~ 9.4 g/g in comparison with an absorption capacity of ~ 7.6 g/g attained with a pure nanofiber mat. The crosslinked nanofiber mat remained stable even after 60 min of oil absorption which proves that crosslinking assisted in increasing the affinity of PVA for oil by reducing the amount of OH groups through acetal formation making PVA less soluble to water. The oil sorption capacity of the prepared materials was not maintained even after two cycles indicating poor reusability. 

Heavy metals remediation using MOF5@GO composite incorporated mixed matrix ultrafiltration membrane

A polysulfone-based mixed matrix membrane (MMM) was prepared by incorporation of MOF5@GO composite in the polymer matrix. The prepared membrane was characterized by permeability, scanning electron microscopy, Fourier transform infrared spectroscopy, zeta potential, X-ray photoelectron spectroscopy, atomic force microscope, molecular weight cut-off and average pore radius. MMM exhibits enhanced permeability, pore size, surface roughness and molecular weight cut-off compared to polysulfone membrane. Pure water permeability of M−0.5 enhanced from 37.9 to 59.5 L/m2h.bar, which corroborated an increase in molecular weight cut-off from 46.9 to 74.1 kDa and pore radius from 66.9 to 75.4 Å as MOF5@GO composite was incorporated in polysulfone polymer matrix. At neutral pH, the optimized MMM (M−0.5) shows –22.7 mV zeta potential facilitating the adsorption of heavy metals. The M−0.5 membrane exhibits 95–99 % rejection of Pb, Cu, Zn and Cd at 2 bar pressure with enhanced permeate flux (∼116 L/m2h) compared to the polysulfone membrane. M−0.5 membrane shows better antifouling properties than the polysulfone membrane. Among the heavy metals studied, lead and copper showed the maximum rejection. The MMM shows 99 % rejection of lead and copper and breakthrough time of 12 and 9 h, respectively for a small membrane area (0.0012 m2). Thus, the prepared low-pressure driven mixed matrix ultrafiltration membrane was suitable and competent for heavy metal rejection. A modified convection-adsorption model based on the first principle was used to predict the long-term filtration performance of the membrane. The same model was used to generate the performance curve for scaling up the process.

4D Printing of Magneto‐Thermo‐Responsive PLA/PMMA/Fe3O4 Nanocomposites with Superior Shape Memory and Remote Actuation

AbstractThis study presents the development and 4D printing of magnetic shape memory polymers (MSMPs) utilizing a composite of polylactic acid (PLA), polymethyl methacrylate (PMMA), and Fe3O4 nanoparticles. The dynamic mechanical analysis reveals that the integration of Fe3O4 maintains the broad thermal transition without significantly affecting α‐relaxation time, indicating high compatibility and homogeneous distribution of the nanoparticles within the polymer matrix. Field emission scanning electron microscopy further confirms the high compatibility of PLA and PMMA phases as well as uniform dispersion of Fe3O4 nanoparticles, essential for the effective transfer of heat during the shape memory process. Significantly, the incorporation of magnetic nanoparticles enables remote actuation capabilities, presenting a substantial advancement for biomedical applications. 4D‐printed MSMP nanocomposites exhibit exceptional mechanical properties and rapid, efficient shape memory responses under both inductive and direct heating stimuli, achieving 100% shape fixity and 100% recovery within ≈85 s. They are proposed as promising candidates for biomedical implants, specifically for minimally invasive implantation of bone scaffolds, due to their rapid remote actuation, biocompatibility, and mechanical robustness. This research not only demonstrates the 4D printability of high‐performance MSMPs but also introduces new possibilities for the application of MSMPs in regenerative medicine.

Color-tunable ultralong-lifetime room temperature phosphorescence using phenylalanine derivative doped poly(vinyl alcohol) films

Doping chromophores in polymer matrixes to deliver room temperature phosphorescence (RTP) is well established. However, there are few examples of polymer-based RTP materials with ultralong phosphorescent lifetimes (>4 s) and afterglow (>30 s) under ambient conditions. We report a series of ultralong-lived RTP films by doping Phenylalanine (Phe) derivatives in a poly (vinyl alcohol) (PVA) matrix. The phosphorescence lifetime and efficiency of these films can be increased by introducing pentaerythritol (PER), an effect that is attributed to enhanced hydrogen-bonding interactions. The Fmoc-L-Phe@PER/PVA film exhibits a phosphorescence lifetime of 4.42 s and an afterglow duration of 46 s. Co-doping the PVA system with (Rhodamine B and Sulforhodamine B sodium salt) fluorescent dyes allows an adjustment of the afterglow from blue to red and pink. These films have been successfully applied in flexible luminescent materials, silk-screen printing, and multicolor afterglow light-emitting diode (LED) arrays.

In Situ Processing to Achieve High-Performance Epoxy Nanocomposites with Low Graphene Oxide Loading

Modifying the polymer matrix by nanoparticles can be a promising approach to improve the performance of fiber-reinforced polymer (FRP) composites. Organic solvents are usually used for dispersing graphene oxide (GO) well in the polymer matrix. In this study, a green, facile, and efficient approach was developed to prepare epoxy/GO nanocomposites. In situ polymerization is used for synthesizing nanocomposites, eliminating the need for organic solvents and surfactants. By loading just 0.6 wt% of GO into the epoxy resin, Young’s modulus, tensile strength, and toughness improved by 38%, 46%, and 143%, respectively. Fractography analysis indicates smooth fracture surfaces of pure resin that changed to highly toughened fracture surfaces in this nanocomposite. Plastic deformation, crack pinning, and deflection contributed to improving the toughness of the nanocomposites. FTIR investigations show that amide bonding was created by the reaction of the carboxylic acid groups in GO with some amine groups in the curing agent during the dispersion processes.

Transient radical species and oxygen colorimetric indicators grounded on phenothiazinium dyes

This study investigates four phenothiazinium dyes including methylene blue (MB) and three analogues containing auxochrome variation 2–4 as oxygen colorimetric indicators prepared by their incorporation into two types of oxygen permeable materials containing: a) polyvinyl alcohol substrate with additional TiO2 photocatalysts (PhOxIn), and b) carboxymethylcellulose polymer matrix containing glucose and KOH (ChOxIn). In vacuum packages where volumetric concentrations of oxygen were below 0.01 %, the leuco forms of the tested phenothiazinum dyes were readily oxidised, initiating the colour turn from white to blue. The redox processes involved were explored by experimental electron paramagnetic resonance EPR and UV–vis spectroscopic methods and further supported by theoretical quantum chemistry. The EPR experiments showed that the chemical oxidation of the leuco-form of the phenothiazinium dyes 1–4 produced transient aminyl radical species with the single electron mainly located at the nitrogen atom of the heterocyclic core. The formation of these transient aminyl species was also perceived by UV–vis spectroscopy, their absorption maxima situated in the 552–592 nm range being also supported by TD-DFT theoretical calculations.