Tough and Self-Healing Waterborne Polyurethane Elastomers via Dynamic Hydrogen Bonds Design for Flexible Conductive Substrate Applications.

Balancing the mechanical strength and self-healing performance of polyurethane (PU) remains a significant challenge in achieving excellent self-repairing PU materials. In this study, a self-healing waterborne PU elastomer was designed from a bionic concept by incorporating 2'-deoxythymidine (2'-dT) and isophorone diamine (IPDA) into the polymer chain. The loose stacking of IPDA's irregular cycloaliphatic structure resulted in the irregular arrangement of urethane bonds in the hard domain. The formation of sextuple hydrogen bonds between 2'-dT and urethane bonds, as well as quadruple hydrogen bonds between urethane bonds themselves, enhanced the mechanical properties of the material. The multiple hydrogen bonds can dissociate, recombine, and dissipate energy, thereby improving the material's repair capability. The hierarchical self-assembly of hydrogen bonds enabled the PU to achieve a tensile strength of 15.3 MPa and toughness of 100.75 MJ/m3. The prepared PU film is highly transparent and has a transmittance of more than 90%. Additionally, it can undergo rapid repair under high temperatures or under trace solvent conditions. When used as a flexible conductive substrate, it quickly restored the conductivity and enhanced the material's lifespan after surface damage. This environmentally friendly and self-healing waterborne PU elastomer will hold broad application prospects in the field of flexible electronic devices.

An injectable hydrogel based on hyaluronic acid prepared by Schiff base for long-term controlled drug release.

Drug-loaded injectable hydrogels have been studied widely in biomedical technology while the stable long-term controlled drug release and cytotoxicity are challenges. In this work, an injectable hydrogel with good swelling resistance was in situ synthetized using aminated hyaluronic acid (NHA) and aldehyde ß-cyclodextrin (ACD) via Schiff base reaction. The composition, morphology and mechanical property were characterized with FTIR, 13C NMR, SEM and rheology test, respectively. Voriconazole (VCZ) and Endophthalmitis was selected as a model drug and disease, respectively. The drug release, cytotoxicity and antifungal properties were detected in vitro. The results showed a long-term (> 60 days) drug release was realized, the NHA/ACD2/VCZ presented a zero-order release in the later stage. The cytotoxicity of NHA/ACD was detected by live/dead staining assay and Cell Counting Kit-8 (CCK-8). The survival rate of adult retina pigment epithelial cell line-19 (ARPE-19) was over 100 % after 3 d, it indicated a good cytocompatibility. The antifungal experiment presented samples had antifungal property. Biocompatibility in vivo proved NHA/ACD2 had no adverse effects on ocular tissues. Consequently, the injectable hydrogel based on hyaluronic acid prepared by Schiff base reaction provides a new option for long-term controlled drug release in the course of disease treatment from a material perspective.

Graphene Oxide/Styrene-Butadiene Latex Hybrid Aerogel with Improved Mechanical Properties by PEI Grafted GO and CNT.

Graphene oxide aerogel (GOA) has wide application prospects due to its low density and high porosity. However, the poor mechanical properties and unstable structure of GOA have limited its practical applications. In this study, polyethyleneimide (PEI) was used to graft onto the surface of GO and carbon nanotubes (CNTs) to improve compatibility with polymers. Composite GOA was prepared by adding styrene-butadiene latex (SBL) to the modified GO and CNTs. The synergistic effect of PEI and SBL, resulted in an aerogel with excellent mechanical properties, compressive resistance, and structural stability. When the ratio of SBL to GO and GO to CNTs was 2:1 and 7:3, respectively, the obtained aerogel performance was the best, and the maximum compressive stress was 784.35% higher than that of GOA. The graft of PEI on the surface of GO and CNT could improve the mechanical properties of the aerogel, with greater improvements observed with grafting onto the surface of GO. Compared with GO/CNT/SBL aerogel without PEI grafting, the maximum stress of GO/CNT-PEI/SBL aerogel increased by 5.57%, that of GO-PEI/CNT/SBL aerogel increased by 20.25%, and that of GO-PEI/CNT-PEI/SBL aerogel increased by 28.99%. This work not only provided a possibility for the practical application of aerogel, but also steered the research of GOA in a new direction.

Regulation mechanism of magnetic field on pectinase and its preliminary application in postharvest sapodilla (Manilkara zapota).

In this study, regulation mechanism of magnetic field on pectinase was investigated and it was preliminarily applied in postharvest sapodilla. Results indicated pectinase activity decreased by 44 % when treated by magnetic field (3 mT, 0.5 h) with kinetic parameters Vmax/Km decreasing from 0.799 to 0.366 min. The optimal temperature (48 °C) and pH (4.8) of pectinase was not altered by magnetic field but Ca2+ at 0.05 mol/L strengthened its regulation effect. Ultraviolet and fluorescence spectra suggested tyrosine and tryptophan residues in treated pectinase became more hydrophobic while opposite in phenylalanine. CO, CNH, COO- groups in pectinase were also influenced, resulting in decreased ß-sheet (from 53 % to 49 %), increased random coil (from 20 % to 22 %) and ß-turn content (from 27 % to 29 %). More importantly, the firmness of treated sapodilla remained 45 % of maximum at 12 days' storage. Our findings provided new insights to illustrate the role of magnetic field in fruit preservation.

Structurally Stable, High-Strength Graphene Oxide/Carbon Nanotube/Epoxy Resin Aerogels as Three-Dimensional Skeletal Precursors for Wave-Absorbing Materials.

Three-dimensional (3D) graphene oxide aerogel (GOA) is one of the best fillers for composites for microwave absorption. However, its further development has been hindered by the poor mechanical properties. Methodology to improve the mechanical properties of the aerogel remains an urgent challenge. Herein, graphene oxide/carbon nanotube/epoxy resin composite aerogel (GCEA) was successfully prepared by a facile method. The results showed that the prepared GCEA with the hierarchical and 3D cross-linked structures exhibited excellent compression performance, structural and thermal stability, high hydrophilicity, and microwave absorption. The prepared GCEA recovered from multiple large strain cycles without significant permanent deformation. The minimum reflection loss (RL) was -39.60 dB and the maximum effective absorption bandwidth (EAB) was 2.48 GHz. The development of the enhanced GO aerogels will offer a new approach to the preparation of 3D microwave-absorbing skeletal materials with good mechanical properties.

The Positive Effect of ZnS in Waste Tire Carbon as Anode for Lithium-Ion Batteries.

There is great demand for high-performance, low-cost electrode materials for anodes of lithium-ion batteries (LIBs). Herein, we report the recovery of carbon materials by treating waste tire rubber via a facile one-step carbonization process. Electrochemical studies revealed that the waste tire carbon anode had a higher reversible capacity than that of commercial graphite and shows the positive effect of ZnS in the waste tire carbon. When used as the anode for LIBs, waste tire carbon shows a high specific capacity of 510.6 mAh·g-1 at 100 mA·g-1 with almost 97% capacity retention after 100 cycles. Even at a high rate of 1 A·g-1, the carbon electrode presents an excellent cyclic capability of 255.1 mAh·g-1 after 3000 cycles. This high-performance carbon material has many potential applications in LIBs and provide an alternative avenue for the recycling of waste tires.

Investigation of Carbon Nanotube Grafted Graphene Oxide Hybrid Aerogel for Polystyrene Composites with Reinforced Mechanical Performance.

The rational design of carbon nanomaterials-reinforced polymer matrix composites based on the excellent properties of three-dimensional porous materials still remains a significant challenge. Herein, a novel approach is developed for preparing large-scale 3D carbon nanotubes (CNTs) and graphene oxide (GO) aerogel (GO-CNTA) by direct grafting of CNTs onto GO. Following this, styrene was backfilled into the prepared aerogel and polymerized in situ to form GO-CNTA/polystyrene (PS) nanocomposites. The results of X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy indicate the successful establishment of CNTs and GO-CNT and the excellent mechanical properties of the 3D frameworks using GO-CNT aerogel. The nanocomposite fabricated with around 1.0 wt% GO-CNT aerogel displayed excellent thermal conductivity of 0.127 W/m∙K and its mechanical properties were significantly enhanced compared with pristine PS, with its tensile, flexural, and compressive strengths increased by 9.01%, 46.8%, and 59.8%, respectively. This facile preparation method provides a new route for facilitating their large-scale production.

Effects of different "rigid-flexible" structures of carbon fibers surface on the interfacial microstructure and mechanical properties of carbon fiber/epoxy resin composites.

In order to comprehend the influence of different "rigid-flexible" structures on the interface strength of carbon fiber(CF)/epoxy composites, CNTs was firstly chemically grafted on CFs surface, and then polyamide (PA) was grafted onto CF-CNTs surface through varying anionic polymerization time of caprolactam [CF-CNTs-PAn (n = 6 h, 12 h, 24 h)]. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy indicated the successful establishment of CNTs and PA. TGA demonstrated the different grafting amounts of CF-CNTs-PAn (n = 6 h, 12 h and 24 h). SEM images revealed a compactness and uniform coverage of the CNTs/PA, with increasing polymerization time, the CF and CNTs surface was covered by a thick layer of PA. The surface energy increased and then decreased. The optimal interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of the CF/epoxy composites with a polymerization time of 12 h (CF-CNTs-PA12h) was 86.7 and 85.4 MPa, which was 77.6% and 45.7% higher than that of untreated CF/epoxy composite. As the polymerization time grew, the impact toughness and tensile strength of CF/epoxy composites enhanced and conductivity of CF/epoxy composite reduced. In addition, the mechanisms of reinforcement and toughening were also illuminated. This work would provide a certain theoretical basis for the preparation and applications of high-performance CF composites with different structures.

The unidirectional causality influence of factors on PM2.5 in Shenyang city of China.

Air quality issue such as particulate matter pollution (PM2.5 and PM10) has become one of the biggest environmental problem in China. As one of the most important industrial base and economic core regions of China, Northeast China is facing serious air pollution problems in recent years, which has a profound impact on the health of local residents and atmospheric environment in some part of East Asia. Therefore, it is urgent to understand temporal-spatial characteristics of particles and analyze the causality factors. The results demonstrated that variation trend of particles was almost similar, the annual, monthly and daily distribution had their own characteristics. Particles decreased gradually from south to north, from west to east. Correlation analysis showed that wind speed was the most important factor affecting particles, and temperature, air pressure and relative humidity were key factors in some seasons. Path analysis showed that there was complex unidirectional causal relationship between particles and individual or combined effects, and NO2 and CO were key factors affecting PM2.5. The hot and cold areas changed little with the seasons. All the above results suggests that planning the industrial layout, adjusting industrial structure, joint prevention and control were necessary measure to reduce particles concentration.

Low-cost urchin-like silicon-based anode with superior conductivity for lithium storage applications.

Poor rate and cycling performance are the most critical drawbacks for Si-based anodes on account of their inferior conductivity and colossal volumetric expansion during lithiation/delithiation. Here we report the fabrication of structurally-integrated urchin-like Si anode, which provides prominent structural stability and distinguished electron and ion transmission pathways for lithium storage. The inexpensive solid Si waste from organosilane industry after acid-washed and further ball-milling serves as the pristine Si-source in this work. Carbon nanotubes (CNTs) are in-situ grown outside Si microparticles, resulting in an urchin-like structure (Si/CNTs). The optimized Si/CNTs presents ascendant invertible capacity and rate performance, achieving up to 920 mAh g-1 beyond 100 cycles at 100 mA g -1, and a capacity of 606.2 mAh g-1 at 1 A g -1 after long cycling for 1000 cycles. The proposed scalable synthesis can be adopted to advance the performance of other electrode materials with inferior conductivity and enormous volume expansions during cycling.

Microwave assisted copolymerization of sodium alginate and dimethyl diallyl ammonium chloride as flocculant for dye removal.

Flocculant made from natural polymers has the advantages of abundant source, affordable cost and environmental friendliness. In this work, a binary flocculant (sodium alginate-dimethyl diallyl ammonium chloride, SAD) was successfully prepared using microwave assisted free radical copolymerization technique. Based on the flocculation properties of yellow 7GL dye, the synthetic process was optimized with the amount of initiator was 0.8 wt% (equal molar ratio of ammonium peroxydisulfate and sodium bisulfite as complex initiator), sodium alginate: dimethyl diallyl ammonium chloride = 1:1 (molar ratio), and the microwave irradiation time was 18 min at the power of 280 W. The experimental results show that the color removal ratio was 73.5% at the SAD dosage of 425 mg/L for the 100 mg/L yellow 7GL simulated wastewater. The SAD also maintained excellent decolorization ratios under a wide range of flocculant dosage and environmental pH. The flocculation mechanism might be the combination of charge neutralization and bridging effect. The prepared SAD flocculant has the virtues of simple synthesis process, ecofriendliness and high decolorization ratio, which make it broad application prospect in the treatment of dye wastewater.

Structural and Magnetic Properties of Rare Earth Doped Multilayer Nanocable Arrays.

The structure and anisotropic magnetization of One-dimensional (1D) Nd/Co/PA66 coaxial nanocables prepared by a low cost physical infiltration and electrodeposition methods are investigated. The preparation of Co nanotubes, Co/PA66 two-layer nanotubes and Nd/Co/PA66 three-layer nanocales is described, respectively. The structure, chemical composition and magnetic properties of various nanomaterials were investigated. The results show that the magnetic properties were affected by the rare earth metal Nd and the structural properties. The residual magnetization ratio of Nd/Co/PA66 nanocables is the biggest due to the synergistic effect of Nd and Co. In addition, the magnetization processes of the nanostructure were discussed in detail. We believe that these methods may provide an idea for ferromagnetic alloys and permanent magnet material and suitable for future applications in perpendicular recording media.

Hydroxyl-Terminated Triazine Derivatives Grafted Graphene Oxide for Epoxy Composites: Enhancement of Interfacial and Mechanical Properties.

An effective approach to the fabrication of progressive epoxy nanocomposites by the incorporation of hydroxyl-terminated dendrimers functionalized graphene oxide (GO-TCT-Tris) is reported. The relationship between surface grafting, chemical construction, morphology, dispersion, and interfacial interaction as well as the corresponding mechanical properties of the composites were studied in detail. It was shown that hydroxyl-terminated triazine derivatives have been resoundingly bonded onto the GO surface through covalent bonding, which effectively improved the dispersion and compatibility of GO sheets in epoxy resin. The tensile and flexural tests manifested that the GO-TCT-Tris/epoxy composites exhibited greater tensile/flexural strength and modulus than either the pure epoxy or the GO/epoxy composites. For GO-TCT-Tris (0.10 wt%)/epoxy composite, the tensile strength and elastic modulus increased from 63 ± 4 to 89 ± 6 MPa (41.27%) and from 2.8 ± 0.1 to 3.6 ± 0.2 GPa (28.57%), and the flexural strength and modulus increased from 106 ± 5 to 158 ± 6 MPa (49.06%) and from 3.0 ± 0.1 to 3.5 ± 0.2 GPa (16.67%), respectively, compared to the pure epoxy matrix. Moreover, the fractographic analysis also illustrated the ameliorative interfacial interaction between GO-TCT-Tris and epoxy matrix.

Preparation and Magnetic Properties of Nd/FM (FM=Fe, Co, Ni)/PA66 Three-Layer Coaxial Nanocables.

A new preparation method of three-layer coaxial nanocables has been developed in this work. Nd/FM (FM=Fe, Co, Ni)/PA66 three-layer coaxial nanocables were assembled successfully from outer to inner layer by layer. PA66 nanotubes which served as the outer shell were prepared by polymer solution wetting AAO template. Ferromagnetic metals and Nd were deposited into pre-prepared PA66 nanotubes to be served as the middle layer and inner core, respectively. The results show that the structure has effects on the magnetic properties, and the nanocable preparation allows each layer, length, and thickness of the nanocables to be tuned.

Effect of Each Layer on Anisotropic Magnetic Properties of Nd/Fe/Polyamide 66 Three-Layer Coaxial Nanocables.

One-dimensional (1D) Nd/Fe/polyamide 66 (Nd/Fe/PA66) three-layer coaxial nanocable arrays with high aspect ratio and highly anisotropic magnetization were successfully prepared via layer-by-layer deposition in the anodic aluminum oxide template. The morphology, chemical composition, and magnetic properties of Nd/Fe/PA66 nanocables were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and vibrating sample magnetometry . The effects of 1D nanocables on the magnetic properties of the assembled ordered arrays have been systematically investigated. The structural properties of these nanostructures are investigated as a function of the geometrical parameters. The magnetic anisotropy of Nd/Fe/PA66 nanocables has been significantly enhanced owing to the doped Nd that possesses a larger spin-orbital coupling and leads to a synergistic effect with Fe to enhance anisotropy energy.

Synthesis and flocculation performance of a chitosan-acrylamide-fulvic acid ternary copolymer.

The flocculant made from natural polymers gained prominence in recent years due to its eco-friendliness and low cost. In this study, two natural polymers of chitosan and fulvic acid were successfully grafted with a synthetic monomer of acrylamide as a new type of flocculant. The prepared chitosan-acrylamide-fulvic acid (CAMFA) exhibited an excellent capacity to remove three typical dyes, the color removal ratios were 97.0%, 91.6%, and 38.2%, respectively, at the dosage of 283mg/L for 100mg/L of acid blue 113, reactive black 5 and methyl orange. The main flocculation mechanisms were charge neutralization and bridging effect. CAMFA showed nice flocculation performance with solubility in pure water, high removal efficiency, broad pH effectiveness scope, and a wide flocculation window. The ternary copolymer based on natural polymers is a promising candidate as a flocculant from the perspective of effectiveness, operation simplicity and cost.

In vitro study of wear of Ceramage and IPS e.max Press / 口腔疾病防治

Objective @#To compare the wear of Ceramage and IPS e.max Press offering foundation for nonmetallic materials selection in clinical. @*Methods @#20 class I cavities were prepared in the approximal flattened sides of the extracted human maxillary first molars. The cavities were divided into 2 groups randomly, and then restored with Ceramage or IPS e.max Press. Inlays were prepared according to the manufactures’ instructions with indirect methods and cemented with Varolink N. The non-wear extracted maxillary third molars were used as antagonistic enamel cusps after standardized prepared. After the self-made wear-testing device concluded 200,000 cycles under a load of 20 N, the wear depth of specimens and antagonistic enamel cusps was assessed by Kavo PREP assistant.@*Results @# The wear in Ceramage group was (298.30 ± 40.02) μm, while the wear of normal enamel was (206.60 ± 49.17) μm. The wear in IPS e.max Press group was (212.90 ± 61.21) μm, while the wear of normal enamel was (217.00 ± 25.10) μm. The wear of IPS e.max Press inlays was higher than Ceramage inlays (P < 0.05). Ceramage inlays showed higher wear than normal enamel (P < 0.05), while IPS e.max Press inlays was not statistically different from the normal enamel (P > 0.05). @*Conclusions @#Ceramage has more wear than IPS e.max Press. Ceramage shows higher wear compared with normal enamel, while IPS e.max Press has lower antagonistic war compared with normal enamel.

Preparation of pure chitosan film using ternary solvents and its super absorbency.

Chemical modification and graft copolymerization were commonly adopted to prepare super absorbent materials. However, physical microstructure of pure chitosan film was optimized to improve the water uptake capacity in this study. Chitosan films with micro-nanostructure were prepared by a ternary solvent system. The optimal process parameters are 1% acetic acid water solution: dioxane: dimethyl sulfoxide=90: 2.5: 7.5 (v/v/v) with chitosan concentration at 1.25% (w/v). The water uptake capacity of the chitosan film prepared under the optimal process parameters was 896g/g. The prepared chitosan films also exhibited high water uptake capacity in response to external stimuli such as temperature, pH and salt. This finding may provide another way for improving the water absorbency. The pure chitosan film may find potential applications especially in the fields of hygienic products and biomedicine due to its super water absorbency and nontoxicity.

Fabrication and biocompatibility of poly(l-lactic acid) and chitosan composite scaffolds with hierarchical microstructures.

The scaffold microstructure is crucial to reconstruct tissue normal functions. In this article, poly(l-lactic acid) and chitosan fiber (PLLA/CTSF) composite scaffolds with hierarchical microstructures both in fiber and pore sizes were successfully fabricated by combining thermal induced phase separation and salt leaching techniques. The composite scaffolds consisted of a nanofibrous PLLA matrix with diameter of 50-500nm, and chitosan fibers with diameter of about 20µm were homogenously distributed in the PLLA matrix as a microsized reinforcer. The composite scaffolds also had high porosity (>94%) and hierarchical pore size, which were consisted of both micropores (50nm-10µm) and macropores (50-300µm). By tailoring the microstructure and chemical composition, the mechanical property, pH buffer and protein adsorption capacity of the composite scaffold were improved significantly compared with those of PLLA scaffold. Cell culture results also revealed that the PLLA/CTSF composite scaffolds supported MG-63 osteoblast proliferation and penetration.

The effect of fiber size and pore size on cell proliferation and infiltration in PLLA scaffolds on bone tissue engineering.

The scaffold microstructure has a great impact on cell functions in tissue engineering. Herein, the PLLA scaffolds with hierarchical fiber size and pore size were successfully fabricated by thermal-induced phase separation or combined thermal-induced phase separation and salt leaching methods. The PLLA scaffolds were fabricated as microfibrous scaffolds, microfibrous scaffolds with macropores (50-350 µm), nanofibrous scaffolds with micropores (100 nm to 10 µm), and nanofibrous scaffolds with both macropores and micropores by tailoring selective solvents for forming different fiber size and pre-sieved salts for creating controlled pore size. Among the four kinds of PLLA scaffolds, the nanofibrous scaffolds with both macropores and micropores provided a favorable microenvironment for protein adsorption, cell proliferation, and cell infiltration. The results further confirmed the significance of fiber size and pore size on the biological properties, and a scaffold with both micropores and macropores, and a nanofibrous matrix might have promising applications in bone tissue engineering.