Super Strong and Tough Polybenzimidazole/Metal Ions Coordination Networks: Reinforcing Mechanism, Recyclability, and Anti-Counterfeiting Applications.

Nature has provided many delicate strategies for optimizing the structural characteristics of biological materials. One such strategy is the strengthening and toughening of matrix materials by aduandant and hierarchically arranged non-covalent crosslinking. However, efficient strengthening and toughening of high-performance aromatic polymers by non-covalent bonds has rarely been reported yet. Herein, we report the preparation and characterizations of a metal coordination bonds crosslinked polybenzimidazole (PBI) network. By optimizing the synthetic parameters, the strength of copper ion (Cu2+ ) crosslinked PBI is improved from 87.8 to 218.4 MPa, and the toughness is increased from 19.4 to 111.9 MJ m-3 , corresponding to increments of 148.7 % and 476.8 %, respectively, which surpass all previously reported non-covalent bonds crosslinked high-performance polymers. PBI with varied chain flexibility are then synthesized to deeply understand the stregnening and toughening mechanism. In addition, the glass transition temperature of PBI is dramatically increased by 75 °C after Cu2+ crosslinking. Moreover, the chemical recycling of PBI from crosslinekd network, and the development of a novel high-temperature resistant or high-temperature rewritable anti-counterfeiting films based on Cu2+ crosslinked PBI are also demonstrated. This study is expected to shed light on design principle for future supramolecularly crosslinked and recyclable high-performance polymers.

Lysosome-targetable selenium-doped carbon nanodots for in situ scavenging free radicals in living cells and mice.

Lysosome-targetable selenium-doped carbon nanodots (Lyso-Se-CDs) that can efficiently scavenge lysosomal •OH in living cells and mice were designed in this research. Se-CDs with redox-responsive fluorescence (λex = 379 nm, λem = 471 nm, quantum yield = 7.1%) were initially synthesized from selenocystine by a facile hydrothermal method, followed by the surface modification with morpholine, a lysosome targeting moiety. The as-synthesized Lyso-Se-CDs exhibited excellent colloidal stability, efficient scavenging abilities towards •OH, low biotoxicity, as well as good biocompatibility and lysosome targetability. Due to these desirable properties, Lyso-Se-CDs had been successfully utilized for rescuing cells from elevated lysosomal •OH levels. More importantly, Lyso-Se-CDs efficiently relieved phorbol 12-myristate 13-acetate (PMA) triggered ear inflammation in live mice. These findings reveal that Lyso-Se-CDs are potent candidates for treating •OH-related inflammation.

High Performance Microfiltration Composite Membranes Based on Phenolphthalein Poly(ether sulfone) Nanofibrous Substrate with Hydrophilic Coating.

In the present paper, Phenolphthalein poly(ether sulfone) (PES-C) nanofibrous membranes were prepared via solution-blowing technology and polyvinylpyrrolidone (PVP) which would be converted to stable gels by reaction with potassium persulfate (K2S2O8) was immobilized on the surface of nanofibers. The influence factors such as PVP concentration and depositing time were optimized to obtain the composite nanofibrous membranes. The membranes were characterized by Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), Wide-angle X-ray diffraction (WAXD), X-ray photoelectron spectroscopy (XPS) and Water contact angles (WCA), etc. The hydrophilicity of the composite membrane was significantly enhanced by immobilizing Polyvinylpolypyrrolidone (PVPP) on the surface of nanofibers. Furthermore the filtration experiment of starch suspension and oil-water separation test were executed and the anti-fouling properties of the modified membranes were evaluated with the flux recovery ratio (FRR%). The results showed that membranes with PVPP-modified had a more excellent and stability antifouling performances compared with the original membranes. Generally, this work provides a simple and useful method to improve anti-fouling properties of PES-C nanofibrous membranes which had great potential application in microfiltration.

Mussel-adhesive-inspired fabrication of multifunctional silver nanoparticle assemblies.

The assembly of metal nanoparticles (NPs) has attracted a great deal of attention recently because of their collective properties that could not be exhibited by individual NPs. Here a one-step approach was reported for the fabrication of spherical silver NP assemblies (AgNAs). The formation of AgNAs simply included the stirring of silver ammonia and 3,4-dihydroxy-l-phenylalanine (DOPA) in aqueous solution at room temperature, in which DOPA acted as a reductant for AgNPs first because of its reducing ability and then directed the assembly of AgNPs into AgNAs. The AgNAs exhibited hierarchical structure with controllable sizes ranging from 180 to 610 nm by adjusting the concentrations of reagents. The two individual components, AgNPs and polyDOPA, also allowed AgNAs with multiple functions as demonstrated in this study of durable catalytic activity, high SERS sensitivity, and good antioxidant properties. The thin polyDOPA layer coated on AgNAs further offered the opportunity to modify the surface of AgNAs. The results presented here may provide a green and facile approach to designing multifunctional NP assemblies.

The past, present and future of high-performance fibers.

This paper summarizes the recent progress of diverse high-performance fibers in their properties, applications and the challenges.

Conjugated Microporous Polymers-Based Catalytic Membranes with Hierarchical Channels for High-Throughput Removal of Micropollutants.

Engineering a catalytic membrane capable of efficiently removing emerging organic microcontaminants under ultrahigh flux conditions is of significance for water purification. Herein, drawing inspiration from the functional attributes of lymphatic vessels involved in immunosurveillance and fluid transport with minimal energy consumption, a novel hierarchical porous catalytic membrane is engineered. This membrane, based on an innovative nitrogen-rich conjugated microporous polymer (polytripheneamine, PTPA), is synthesized using an electrospinning coupled in situ polymerization approach. The resulting bioinspired membrane with hierarchical channels comprises a thin layer (≈1.7 µm) of crosslinked PTPA nanoparticles covering the interconnected electrospun nanofibers. This unique design creates an intrinsic microporous angstrom-confined system capable of activating peroxymonosulfate (PMS) to generate 98.7% singlet oxygen (1O2), enabling durable and highly efficient degradation of microcontaminants. Additionally, the presence of a thin layer of mesoporous structure between PTPA nanoparticles and macroporous channels within the interwoven nanofibers enhances mass transfer efficiency and facilitates high flux rates. Notably, the prepared hierarchical porous organic catalytic membrane demonstrates enduring high-efficiency degradation performance with a superior permeance (>95% and >2500 L m-2 h-1 bar-1) sustained over 100 h. This work introduces an innovative pathway for the design of high-performance catalytic membranes for the removal of emerging organic microcontaminants.

Investigation of the photocatalytic activity of magnetically recoverable g-C3N4/CoFe2O4/Bi2MoO6 particles for purifying tetracycline antibiotics: synthesis, characterization, ecotoxicity analysis, and plant toxicity test.

To purify water polluted by tetracycline antibiotics, a new visible light-driven magnetically recoverable photocatalyst, g-C3N4/CoFe2O4/Bi2MoO6, was prepared in this study, and it effectively removed tetracycline antibiotics. Its rapid recycling was achieved by external magnets, which greatly increased material utilization. After four repeated uses, the degradation rate of tetracycline antibiotics by the g-C3N4/CoFe2O4/Bi2MoO6 composite photocatalyst remained at a high level, and the magnetic separation performance remained stable. Subsequently, it was further discovered that the degradation mechanism of this photocatalytic system was consistent with a double Z-type mechanism, which enabled two transport channels for photogenerated electrons, and was favorable for the separation of the photogenerated electron-hole pairs and prolonged the lifetime of the photogenerated carriers. The active substances playing an important role in the photocatalytic system were ˙O2- and h+. In addition, the possible intermediates in the photocatalytic process were detected by GC-MS analysis, and a degradation mechanism was proposed. The ecotoxicity of the degradation products and intermediates was evaluated using the Toxicity Estimation Software Tool (TEST), and the mung bean seed cultivation test was carried out to visually and efficiently illustrate that the g-C3N4/CoFe2O4/Bi2MoO6 photocatalyst can effectively degrade antibiotics, with low ecotoxicity of the degradation products. This provides a new idea for the removal of organic pollutants using light energy.

Effects of three parameters on the diameter of electrospun poly(ethylene oxide) nanofibers.

The combined use of two techniques namely electrospray and spinning is made use in a highly versatile technique called electrospinning, which produces the diameter of polymer fibers range from nanometer to sub-micron. In this work, we have studied effects of adding LiCl on the morphology and diameter of electrospun poly(ethylene oxide), and we have also evaluated systematically the effect of three important solution parameters on the morphology of electrospun poly(ethylene oxide): molecular weight, solution viscosity and electrical conductivity. We find that molecular weight is strongly correlated with the formation of bead defects in the fibers, the smaller molecular weight, the more beads defect density. As a result, the fibers have beads-in-string structures. Electrical conductivity increases, then decreases as molecular weight increases. Solution viscosity has been found to most strongly affect fiber size, with fibers diameter increasing with increasing solution viscosity according to a power law relationship. In addition, we find evidence that solution viscosity and electrical conductivity affect the interesting morphology of the electrospun nanofibers, and result in doubling and forming membrances phenomena.

Study on morphology and characterization of poly(mphenylene isophtalamide)/multi-walled carbon nanotubes composite nanofibers by electrospinning.

Electrospinning technique is the main method of preparing polymer nanofiber simply, directly and continuously at present. In this work, electrospinning blend solution was prepared by in-situ polymerization using acid-modified multi-walled carbon nanotubes (MWNTs), m-phenylenediamine (MPD) and isophthaloyl chloride (IPC). And then composite nanofibers were prepared by electrospinning. MWNTs played an important role in nanofiber's properties. The effects of MWNTs on the morphology and characterization of the MWNTs/PMIA composite nanofibers were investigated. Scanning electron microscopy (SEM), thermal gravimetric analyzer (TGA), and X-ray diffraction (XRD) were utilized to characterize the MWNTs/PMIA nanofibers morphology and properties. The experimental results indicated that the nanofibers diameter decreased and solution dynamic viscosity increased with increasing MWNTs contents. XRD data demonstrated that PMIA composite nanofibers had the same crystal type as the pure PMIA nanofiber, and crystallinity was improved with increasing MWNTs loading. Transmission electron microscopy (TEM) was used to confirm MWNTs aligned along the axis of composite nanofibers.

Facile strategy to prepare polyimide nanofiber assembled aerogel for effective airborne particles filtration.

Polyimide nanofiber (PINF) aerogel materials have received extensive attention as heat insulation, sensors and filtration media due to their excellent thermodynamic properties and unique porous structure. However, PINF must be difficult to disperse in organic solvents (dioxane or dimethyl sulfoxide) and dimensional instability has been regarded as issues that limits the preparation of PINF aerogels, especially in the water. So, it is of great significance to prepare polyimide aerogels with stable structure using water as a dispersant. In this work, the electrospun polyimide nanofiber precursor (polyamic acid (PAA) nanofiber (PAANF)) is uniformly dispersed in water, and triethylamine is added to terminated PAA oligomer as a binder. The resultant PINF aerogel has excellent mechanical properties with outstanding elasticity and a maximum compressive stress of 7.03 kpa at 50% strain. Furthermore, due to the extremely high porosity (98.4%) and hierarchical porous structure, the aerogel exhibits a high filtration efficiency (99.83%) for PM2.5, while the pressure drop is lower than that of the corresponding nanofiber membrane materials, which will facilitate its application in high temperature filtration and other fields.

Mechanically Robust and Spectrally Selective Convection Shield for Daytime Subambient Radiative Cooling.

As a passive cooling strategy, radiative cooling is becoming an appealing approach to dissipate heat from terrestrial emitters to the outer space. However, the currently achieved cooling performance is still underperforming due to considerable solar radiation absorbed by the emitter and nonradiative heat transferred from the surroundings. Here, we proposed a mechanically robust and spectrally selective convection shield composed of nanoporous composite fabric (NCF) to achieve daytime subambient radiative cooling. By selectively reflecting ∼95% solar radiation, transmitting ∼84% thermal radiation, and suppressing the nonradiative heat transferred from warmer surroundings, the NCF-based radiative cooler demonstrated an average daytime temperature reduction of ∼4.9 °C below the ambient temperature, resulting in an average net radiative cooling power of ∼48 W/m2 over a 24 h measurement. In addition, we also modeled the potential cooling capacity of the NCF-based radiative cooler and demonstrated that it can cover the cooling demands of energy-efficient residential buildings in most regions of China. Excellent spectral selectivity, mechanical strength, and weatherability of the NCF cover enable a much broader selection for the emitters, which is promising in the real-world deployment of direct daytime subambient radiative cooling.

Ginsenoside Rb1 Lessens Gastric Precancerous Lesions by Interfering With ß-Catenin/TCF4 Interaction.

Background: Seeking novel and effective therapies for gastric precancerous lesions (GPL) is crucial to reducing the incidence of gastric cancer. Ginsenoside Rb1 (GRb1) is a major ginsenoside in ginseng and has been proved to possess multiple bioactivities. However, whether GRb1 could protect against GPL and the underlying mechanisms have not been explored. Methods: We evaluated the effects of GRb1 on gastric precancerous lesions in rats on macroscopic, microscopic and ultramicroscopic levels. Then, an antibody array was employed to screen differential expression proteins (DEPs). Validation for the targeting DEP and investigation for the possible mechanism was conducted using immunohistochemistry, qRT-PCR, TUNEL apoptosis assay, immunoprecipitation and immunoblotting. Results: GRb1 was found to reverse intestinal metaplasia and a portion of dysplasia in the MNNG-induced GPL rats. The antibody array assay revealed seven DEPs in GPL rats as compared to control rats (5 DEPs were up-regulated, while two DEPs were down-regulated). Among the DEPs, ß-catenin, beta-NGF and FSTL1 were significantly down-regulated after GRb1 administration. Our validation results revealed that enhanced protein expression and nuclear translocation of ß-catenin were present in animal GPL samples. In addition, analysis of human gastric specimens demonstrated that ß-catenin up-regulation and nuclear translocation were significantly associated with advanced GPL pathology. GRb1 intervention not only decreased protein expression and nuclear translocation of ß-catenin, but interfered with ß-catenin/TCF4 interaction. Along with this, declined transcriptional and protein expression levels of downstream target genes including c-myc, cyclin D1 and Birc5 were observed in GRb1-treated GPL rats. Conclusion: GRb1 is capable of preventing the occurrence and progression of GPL, which might be contributed by diminishing protein expression and nuclear translocation of ß-catenin and interfering with ß-catenin/TCF4 interaction.

Yuan­zhi­san inhibits tau protein aggregation in an Aß1­40­induced Alzheimer's disease rat model via the ubiquitin­proteasome system.

Yuan­zhi­san (YZS) is a classic type of Traditional Chinese Medicine, which has been reported to aid in the treatment of Alzheimer's disease (AD). The present study aimed to investigate the effects of YZS on tau protein aggregation, a hallmark of AD pathology, and its possible mechanisms. The results demonstrated that YZS improved learning and memory abilities, and decreased the severity of AD pathology in ß­amyloid (Aß1­40)­induced AD rats. Moreover, YZS administration inhibited the hyperphosphorylation of tau protein at Ser199 and Thr231 sites. Several vital enzymes in the ubiquitin­proteasome system (UPS), including ubiquitin­activating enzyme E1a/b, ubiquitin­conjugating enzyme E2a, carboxyl terminus of Hsc70­interacting protein, ubiquitin C­236 terminal hydrolase L1 and 26S proteasome, were all significantly downregulated in AD rats, which indicated an impaired enzymatic cascade in the UPS. In addition, it was identified that YZS treatment partly increased the expression levels of these enzymes in the brains of AD rats. In conclusion, the present results suggested that YZS could effectively suppress the hyperphosphorylation of tau proteins, which may be partially associated with its beneficial role in restoring functionality of the UPS.

Dynamic rheological studies of poly(p-phenyleneterephthalamide) and carbon nanotube blends in sulfuric acid.

We have studied the dynamic scanning of liquid-crystalline (LC) poly(p-phenyleneterephthalamide) sulfuric acid (PPTA-H(2)SO(4)) solution, and its blend with single-walled carbon nanotubes (SWNTs), by using a flat plate rotational rheometer. The effects of weight concentration and molecular weight of PPTA, as well as operating temperature, on dynamic viscoelasticity of the PPTA-H(2)SO(4) LC solution system are discussed. The transition from a biphasic system to a single-phase LC occurs in the weight concentration range of SWNTs from 0.1% to 0.2%, in which complex viscosity reaches the maximum at 0.2 wt% and the minimum at 0.1 wt%, respectively, of SWNTs. With increasing SWNT weight concentration, the endothermic peak temperature increases from 73.6 to 79.9 degrees C. The PPTA/SWNT/H(2)SO(4) solution is in its plateau zone and storage modulus (G') is a dominant factor within the frequency (omega) range of 0.1-10 rad/s. As omega increases, the G' rises slightly, in direct proportion to the omega. The loss modulus (G'') does not rise as a function of omega when omega < 1 s(-1), then when omega > 1 s(-1) G'' increases faster than G', yet not in any proportion to the omega.

Hyper-Cross-Linked Polymers-Derived Porous Tubular Carbon Nanofibers@TiO2 toward a Wide-Band and Lightweight Microwave Absorbent at a Low Loading Content.

An enormous challenge exists in the achievement of one-dimensional (1D) dielectric carbon composite high-performance microwave absorbents at a low filling ratio. Porous/core-shell dual microstructures have been considered as the potential candidate for designing remarkable microwave absorbers with strong absorption and wide band. Herein, novel multiple-structured tubular carbon nanofibers@TiO2 (TCNFs@TiO2) hybrids were constructed via the sequential steps of hydrolysis and pyrolysis. The dielectric properties of the as-prepared composites can be tuned by adjusting the relative content of the TiO2 shell and carbonaceous temperature to enhance the impedance matching behavior. Notably, the minimum reflection loss (RLmin) value reaches up to -61.2 dB with an effective absorption bandwidth (EAB) of 3.2 GHz at 3 mm, and the EAB can cover 5.3 GHz with a thickness of merely 2 mm when 1.3 mL of tetrabutyl titanate (TBT) and 700 °C pyrolysis temperature are optimized, respectively. Delightedly, the mixing ratio is only 10 wt %, outperforming that of the most-related composites. The heterogeneous interfaces in TCNFs-TiO2 are beneficial for the interfacial polarization relaxation. Besides, the hybrids are enriched with numerous pores to favor the lightweight absorbers. The desirable design in the microstructure can provide a promising route in wide-band and lightweight microwave absorbents.

The Construction of a Hydrophilic Inorganic Layer Enables Mechanochemically Robust Super Antifouling UHMWPE Composite Membrane Surfaces.

In this study, a facile and effective method is adopted to prepare mechanochemically robust super antifouling membrane surfaces. During the process, vinyl trimethoxy silane (VTMS) was used as the reactive intermediate for coupling the hydrophilic inorganic SiO2 nanoparticle layer on to the organic ultra-high-molecular-weight polyethylene (UHMWPE) membrane surface, which created hierarchical nanostructures and lower surface energy simultaneously. The physical and chemical properties of the modified UHMWPE composite membrane surface were investigated. FTIR and XPS showed the successful chemical grafting of VTMS and SiO2 immobilization, and this modification could effectively enhance the membrane's surface hydrophilicity and filtration property with obviously decreased surface contact angle, the pure water flux and bovine serum albumin (BSA) rejection were 805 L·m-2·h-1 and 93%, respectively. The construction of the hydrophilic nano-SiO2 layer on the composite membrane surface for the improvement of membrane antifouling performance was universal, water flux recovery ratio values of BSA, humic acid (HA), and sodium alginate (SA) were all up to 90%. The aim of this paper is to provide an effective approach for the enhancement of membrane antifouling performance by the construction of a hydrophilic inorganic layer on an organic membrane surface.

Mechanical strong stretchable conductive multi-stimuli-responsive nanocomposite double network hydrogel as biosensor and actuator.

Multi-stimuli- responsive mechanical strong stretchable hydrogel has grabbed extensive attention in recent years. Here, a novel stretchable conductive biocompatible near-infrared light(NIR)-/thermal-/pH-/ionic concentration- responsive carboxymethyl chitosan (CMCTs)/graphene oxide (GO)/poly(N-isopropylacrylamide)(PNIPAm) nanocomposite double network hydrogel was fabricated through a simple one-pot in situ free radical polymerization, which is initiated by ultraviolet (UV) light and using N-(3-dimethylaminopropyl)-N-ethylcarbodiimidehydrochloride (EDC) and N,N'-bis(acryloyl)cystamine (BAC) as cross-linkers respectively, instead of toxic organic molecules. When the concentration of CMCTs, GO, EDC and BAC is 22.50, 0.103, 7.50 and 0.467 mg/mL respectively, the obtained hydrogel sample owns the highest tensile strength of 1046 kPa at failure strain of 1286% and a corresponding compressive stress of 2.37 MPa at deformation of 90%. Besides, these hydrogels have an obvious pH-/thermal-/ionic concentration-responsive properties depending on the concentration of the above mentioned factors, and their good conductive property makes them as candidate material for healthcare biosensors. Finally, we attempt to design a novel thermal-/NIR-responsive double network structure bilayer hydrogel, which has the potential use as remote actuator in dangerous places in the future.

Tough robust dual responsive nanocomposite hydrogel as controlled drug delivery carrier of asprin.

Smart mechanical strong hydrogels have gained increasing attention in the last decade. A novel tough robust biocompatible and dual pH- and temperature- responsive poly (N-isopropylacrylamide)/clay (Laponite XLS)/gold nanoparticles (Au-S-S NPs)/caboxymethyl chitosan (CMCTs) nanocomposite hydrogel was synthesized by a facile one-pot in situ free radical polymerization, using clay and Au-S-S NPs as the cross-linkers instead of toxic organic molecules. By tuning the crucial factors, concentration of Au-S-S NPs, CMCTs and clay, the obtained hydrogels exhibited the highest tensile stress of 535.5 kPa at the breaking deformation of 1579.5%. Furthermore, these synthesized hydrogels were tough enough and simultaneously owned a fast recoverability after unloaded in 15 min at room temperature. Moreover, effects of the above factors on swelling and swelling-shrinking behaviors of the prepared hydrogels were investigated in detail. In addition, these designed hydrogels also possessed a controlled drug release property of asprin by adjusting their inner crosslink density. Owing to this property, they could be used as the potential drug delivery carriers in future.

Vitrimer Chemistry Assisted Fabrication of Aligned, Healable, and Recyclable Graphene/Epoxy Composites.

The alignment is a key factor to fully exploit the potential of graphene in reinforcement of polymer composites. However, it is still a challenge to orientate graphene in thermosets because of the insoluble and infusible features of the later. In this paper, we report a facile and scalable hot press method to fabricate aligned graphene nanoplate (GnP)/epoxy composites by utilizing the dynamic character of epoxy vitrimer. The bond exchange and topological rearrangement associated viscous flow of epoxy vitrimer during hot press allows the spontaneous orientation of GnP in matrix because the 2D structure and volume exclusion effect. SEM images demonstrate the orientation of GnP, while tensile test reveals the significantly increased reinforcement effect of GnP on matrix after hot press. Moreover, the dynamic reaction of epoxy vitrimer confers good healability and recyclability to the aligned composites as confirmed by the nearly fully recovered mechanical properties of the healed sample after cutting, and the recycled sample after grinding. This work is expected to provide new opportunity for fabrication of aligned thermosetting composites.

Mechanically strong dual responsive nanocomposite double network hydrogel for controlled drug release of asprin.

Mechanically strong dual/multi-stimuli-responsive smart hydrogels have attracted extensive attention in recent years. A novel tough, mechanical strong and biocompatible dual pH- and temperature- responsive poly (N-isopropylacrylamide) /clay (laponite XLG)/carboxymethyl chitosan (CMCTs) /genipin nanocomposite double network hydrogel was synthesized through a facile, one-pot free radical polymerization initiated by the ultraviolet light, using clay and the natural molecular-genipin as the cross-linkers instead of toxic organic molecules. Crucial factors, the content of CMCTs, clay and genipin, for synthesizing the mechanical strong hydrogels were investigated. When the content of CMCTs, clay and genipin were 5 wt%, 33.3 wt% and 0.175 wt%, respectively (to the weight of N-isopropylacrylamide), these prepared hydrogels exhibited a high tensile strength of 137.9 kPa at the failure strain of 446.1%. Furthermore, the relationship between swelling and deswelling rate of the synthesized hydrogels and the above crucial factors were also studied. Besides, the synthesized hydrogels displayed a considerable controlled release property of asprin by tuning their inner crosslink density. Owing to this property, they may have great potential in the drug delivery systems.