Dual-functional Separators Regulating Ion Transport Enabled by 3D-Reinforced Polyimide Microspheres Protective Layer for Dendrite-Free and High-Temperature Lithium Metal Batteries.

High-energy-density lithium metal batteries (LMBs) are confronted with crucial concerns of security and a short cycle lifespan caused by the uncontrollable formation of lithium (Li) dendrites. The poor thermal stability and heterogeneous Li deposition of conventional polyolefin separators often cause battery short circuiting and thermal runaway in LMBs. Herein, a novel dual-functional PE composite separator (PI-COOH/PE) coated by carboxyl polyimide (PI) microspheres is fabricated by an etching-acidification method. The three-dimensional (3D) high-temp PI microsphere with rich carboxyl groups on the surface improve the security of LMBs at extremely high temperatures and facilitate the formation of a stable and uniform SEI layer, which contributes to accelerating the Li+ transport and stabilizing the formation of the SEI layer. Consequently, the Li symmetric cell assembled with the (PI-COOH)/PE separator exhibits stable overpotential over 3000 h, and the corresponding Li//NCM811 full cells also show a high-level discharge capacity of 146.6 mAh g-1 at 5 C. Meanwhile, it also demonstrates outstanding cycling stability and thermal safety, which can survive continuously over 160 min at 140 °C (vs 21 min for PE). The above results indicate the (PI-COOH)/PE separator constructed by a low-cost and industrial-friendly strategy simultaneously addresses high-temperature stability and dendrite resistance.

Improving Interfacial and Compressive Properties of Polyimide Fiber by Constructing Inorganic Layers on Fiber Surface.

The compressive performance of organic fiber has always been a key problem, limiting its development. In this paper, silicon oxide, alumina, and titanium oxide particles were separately deposited on the surface of high-strength and high-modulus polyimide (PI) fibers to form a structural supporting shell by using a magnetron sputtering method. The theoretical thickness was calculated by thermogravimetric analysis in good agreement with the actual thickness determined from scanning electron microscopy. The mechanics, surface, and interface properties of the measured fibers were analyzed mainly from the aspects of surface energy, interfacial shear strength (IFSS), and compression strength. The results showed that after magnetron sputtering, the inorganic shells were uniformly deposited on the surface of PI fiber, resulting in an increase in the content of inorganic elements as well as the roughness. As a result, the surface energy and IFSS of silica-coated fiber was increased by 174 and 85.6%, respectively, and compression strength was increased by 45.7%. This study provides a new approach for improving the interface property and compression strength of high-strength and high-modulus PI-fiber-reinforced composites.

Retina-inspired organic neuromorphic vision sensor with polarity modulation for decoding light information.

The neuromorphic vision sensor (NeuVS), which is based on organic field-effect transistors (OFETs), uses polar functional groups (PFGs) in polymer dielectrics as interfacial units to control charge carriers. However, the mechanism of modulating charge transport on basis of PFGs in devices is unclear. Here, the carboxyl group is introduced into polymer dielectrics in this study, and it can induce the charge transfer process at the semiconductor/dielectric interfaces for effective carrier transport, giving rise to the best device mobility up to 20 cm2 V-1 s-1 at a low operating voltage of -1 V. Furthermore, the polarity modulation effect could further increase the optical figures of merit in NeuVS devices by at least an order of magnitude more than the devices using carboxyl group-free polymer dielectrics. Additionally, devices containing carboxyl groups improved image sensing for light information decoding with 52 grayscale signals and memory capabilities at an incredibly low power consumption of 1.25 fJ/spike. Our findings provide insight into the production of high-performance polymer dielectrics for NeuVS devices.

Thermostable and nonflammable polyimide/zirconia compound separator for lithium-ion batteries with superior electrochemical and safe properties.

Separators are applied to segregate cathode and anode, and provide ion transport channels in lithium-ion batteries (LIBs). Nevertheless, present commercial polyolefin separators represent high thermal shrinkage and inferior electrolyte wettability, seriously limiting wider development of LIBs. In this work, we prepared zirconia (ZrO2) nanolayer encapsulated polyimide (PI) nanofiber compound separator through in-situ polar adsorption and hydrolysis strategy. The obtained PI/ZrO2 compound separator has superior thermal stability, electrolyte wettability and flame retardance in comparison with polypropylene (PP) separator. The shrinkage ratio of prepared PI/ZrO2 compound separator is 0 even at 300 °C, while the PP separator significantly shrank at 160 °C. Furthermore, the ionic conductivity of PI/ZrO2 separator reaches up to 1.32 mS cm-1, far higher than 0.34 mS cm-1 of PP separator. Besides, the coin batteries of LiNi0.8Co0.1Mn0.1O2 (NCM811)/electrolyte-separator/lithium (Li) assembled with PI/ZrO2 compound separator exhibit enhanced rate performance, high discharge capacity retention rate of 88.3% after 100 cycles at 1C and excellent battery safety performance even at 140 °C. Thus, combined with its advantages, such as preparation, thermostability, electrolyte wettability, electrochemical property and safety, the PI/ZrO2 compound separator exhibits promising prospect in the application of commercial LIBs.

Long non-coding RNA TUG1 promotes osteosarcoma cell proliferation and invasion through inhibition of microRNA-212-3p expression.

[This retracts the article DOI: 10.3892/etm.2018.6216.].

High-Temperature-Induced Shape Memory Copolyimide.

A series of polyimide (PI) films with a high-temperature-induced shape memory effect and tunable properties were prepared via the facile random copolymerization of 4,4'-oxydianiline (ODA) with 4,4'-(hexafluoroisopropyl)diphthalic anhydride (6FDA) and 4,4'-oxydiphthalic anhydride (ODPA). The trigger temperature can be controlled from 294 to 326 °C by adjusting the ratio of monomers. The effects of monomer rigidity on the chain mobility, physical properties, and shape memory performance of as-prepared copolyimide were systematically investigated. The introduction of ODPA could enhance the mobility of PI macromolecular chains, which made chain entanglement more likely to occur and increased the physical crosslinking density, thereby improving the PI's shape recovery up to 97%. Meanwhile, the existence of 6FDA enabled PI films to set quickly at low temperatures with a shape fixation of 98%. The shape memory cycling characteristics of the polyimide films are also studied, and the relationship between the PI chemical structure and the film properties are further discussed.

Enhanced Impact Properties of Hybrid Composites Reinforced by Carbon Fiber and Polyimide Fiber.

A series of hybrid fiber-reinforced composites were prepared with polyimide fiber and carbon fiber as the reinforcement and epoxy resin as the matrix. The influence of stacking sequence on the Charpy impact and flexural properties of the composites as well as the failure modes were studied. The results showed that hybrid fiber-reinforced composites yielded nearly 50% increment in Charpy impact strength compared with the ones reinforced by carbon fiber. The flexural performance was significantly improved compared with those reinforced solely by polyimide fibers and was greatly affected by the stacking sequence. The specimens with compressive sides distributed with carbon fiber possessed higher flexural strength, while those holding a sandwich-like structure with carbon fiber filling between the outer layers displayed a higher flexural modulus.

Effect of a "Zn Bridge" on the Consecutively Tunable Retention Characteristics of Volatile Random Access Memory Materials.

Polyimide memory materials with a donor-acceptor structure based on a charge-transfer mechanism exhibit great potential for next-generation information storage technology due to their outstanding high-temperature resistance and good dimensional and chemical stability. Precisely controlling memory performance by limited chemical decoration is one of core challenges in this field. Most reported work mainly focuses on designing novel and elaborate electron donors or acceptors for the expected memory behavior of polyimides; this takes a lot of time and is not always efficacious. Herein, we report a series of porphyrinated copolyimides coPI-Znx (x=5, 10, 20, 50, 80), where x represents the mole percentage of Zn ion in the central core of the porphyrin. Experimental and theoretical analysis indicate that the Zn ion could play a vital bridge role in promoting the formation and stabilization of a charge-transfer complex by enhancing the hybridization of local and charge transfer (HLCT) excitations of porphyrinated polyimides, endowing coPI-Znx with volatile random access memory performance and continuously tunable retention time. This work could provide one simple strategy to precisely regulate memory performance merely by altering the metal content in porphyrinated polyimides.

Zinc Ion Triggered Controllable Binary/Ternary Memory Conversion Behaviors in Polyimides Containing Pendant Porphyrin Group.

Compared with typical binary polymeric memory materials, functional polymers with ternary memory performance possess significant potential to achieve ultra-high-density data storage. The reported ternary memory polymers are normally driven by dual-mechanism. However, the involved thermodynamically unstable mechanisms (field-induced conformation change or conductive filament formation/fracture) may result in the poor reliability of memory devices under high-temperature working atmosphere. Another strategy to realize ternary memory is introducing charge trapping/de-trapping mechanism by attaching charge trap atom/group at electron donor, which is proved not always effective. Moreover, the synergistic two mechanisms may have difficulty for clarifying the relationship between memory performance and chemical structures, which is the core issue of polymer memory materials. Besides, some multi-level memory materials need the cooperative participation of artificially setting compliance current, which is the extension of typical binary memory and may cause a more complicated technique and logic circuit. Herein, based on charge-transfer mechanism, a concise and effective strategy to realize ternary memory application is proposed. By inserting a Zn ion, the charge-transfer process occurring in electron donors can lead to the novel electrical tri-stability memory behaviors. This work can provide a novel idea for achieving reliable and intrinsic ternary high-density data storage applications.

A Janus nanofiber-based separator for trapping polysulfides and facilitating ion-transport in lithium-sulfur batteries.

Endowing separators with the polysulfide-blocking function is urgently needed for high-performance lithium-sulfur (Li-S) batteries. Thus far, most of the reported research has focused on modifying conventional polyolefin separators but with poor thermal stability and low ionic conductivity. To address these issues, herein we report a Janus separator based on a thermally stable polymeric nanofabric designed with abilities to trap polysulfides and facilitate the transport of Li+ simultaneously. This Janus separator possesses a configuration of a carbon nanofiber (CNF) layer toward the sulfur cathode and the polyimide (PI) nanofabric toward the Li metal anode. It is demonstrated that the conductive CNF layer can effectively anchor and convert the polysulfides; meanwhile, the excellent wettability with liquid electrolytes and the highly porous structure of the PI nanofiber layer significantly promote the Li+-transport. In addition, the Janus separator presents notable advantages in thermal dimensional stability benefiting from the PI nanofabric. As a result, the Li-S battery armed with the Janus separator shows a high initial capacity (1393 mA h g-1 at 0.1 A g-1), stable cycling performance (822 mA h g-1 at 1 A g-1) and high coulombic efficiency of 99.6%.

In Situ Armoring: A Robust, High-Wettability, and Fire-Resistant Hybrid Separator for Advanced and Safe Batteries.

Development of nonflammable separators with excellent properties is in urgent need by next-generation advanced and safe energy storage devices. However, it has been extremely challenging to simultaneously achieve fire resistance, high mechanical strength, good thermomechanical stability, and low ion-transport resistance for polymeric separators. Herein, to address all these needs, we report an in situ formed silica@silica-imbedded polyimide (in situ SiO2@(PI/SiO2)) nanofabric as a new high-performance inorganic-organic hybrid separator. Different from conventional ceramics-modified separators, this in situ SiO2@(PI/SiO2) hybrid separator is realized for the first time via an inverse in situ hydrolysis process. Benefiting from the in situ formed silica nanoshell, the in situ SiO2@(PI/SiO2) hybrid separator shows the highest tensile strength of 42 MPa among all reported nanofiber-based separators, excellent wettability to the electrolyte, good thermomechanical stability at 300 °C, and fire resistance. The LiFePO4 half-cell assembled with this hybrid separator showed a high capacity of 139 mAh·g-1@5C, which is much higher than that of the battery with the pristine PI separator (126.2 mAh·g-1@5C) and Celgard-2400 separator (95.1 mAh·g-1@5C). More importantly, the battery showed excellent cycling stability with no capacity decay over 100 cycles at the high temperature of 120 °C. This study provides a novel method for the fabrication of high-performance and nonflammable polymeric-inorganic hybrid battery separators.

The design of a multifunctional separator regulating the lithium ion flux for advanced lithium-ion batteries.

Herein, we design a controllable approach for preparing multifunctional polybenzimidazole porous membranes with superior fire-resistance, excellent thermo-stability, and high wettability. Specifically, the recyclable imidazole is firstly utilized as the eco-friendly template for micropores formation, which is an interesting finding and has tremendous potential for low-cost industrial production. The unique backbone structure of the as-prepared polybenzimidazole porous membrane endows the separator with superb thermal dimensional stability at 300 °C. Most significantly, the inherent flame retardancy of polybenzimidazole can ensure the high security of lithium-ion batteries, and the existence of polar groups of imidazole can regulate the Li+ flux and improve the ionic conductivity of lithium ions. Notably, the cell with a polybenzimidazole porous membrane presents higher capability (131.7 mA h g-1) than that of a commercial Celgard membrane (95.4 mA h g-1) at higher charge-discharge density (5C), and it can work normally at 120 °C. The fascinating comprehensive properties of the polybenzimidazole porous membrane with excellent thermal-stability, satisfying wettability, superb flame retardancy and good electrochemical performance indicate its promising application for high-safety and high-performance lithium-ion batteries.

Robust polyimide nanofibrous membrane with porous-layer-coated morphology by in situ self-bonding and micro-crosslinking for lithium-ion battery separator.

Herein, we demonstrate a strategy to improve the tensile strength, thermal safety issues, and electrochemical performance of an as-synthesized polyimide separator. By spraying the solution of a specific chemical constituent on both sides of a poly(amic acid) non-woven membrane followed by thermal treatment, a novel polyimide nanofibrous membrane with porous-layer-coated morphology was successfully fabricated by in situ self-bonding and micro-crosslinking technique. The self-bonding and micro-crosslinking techniques improve the tensile strength of the nanofiber membranes from 5 MPa to 28 MPa by forming a crosslinked network structure, thereby reducing the risk of nanofiber disassembly during long-term operation. The rigid structure and aromatic groups in the polyimide chain enable the separator to have outstanding thermal dimensional stability at temperatures as high as 300 °C and thermal stability (5% weight loss at about 528 °C). Additionally, the unique flame retarding capability of polyimide ensures high security of the battery as well. Notably, the lithium-ion battery using porous-layer-coated polyimide separator exhibits a much higher capability (129.9 mA h g-1, 5C) than that using a Celgard-2400 separator (95.2 mA h g-1, 5C) and could work steadily at 120 °C, thus implying promising application in next generation high-safety and high-performance lithium-ion batteries.

Long non-coding RNA TUG1 promotes osteosarcoma cell proliferation and invasion through inhibition of microRNA-212-3p expression.

Taurine upregulated gene 1 (TUG1), a long non-coding RNA (lncRNA), has recently been suggested to be associated with the development of osteosarcoma (OS), but the underlying molecular mechanism still remains largely unclear. In the present study, it was revealed that TUG1 was significantly upregulated whereas miR-212-3p was significantly downregulated in OS tissues and cell lines, when compared with adjacent non-tumor tissues and normal osteoblasts cell lines, respectively. An inverse association between the TUG1 and miR-212-3p expression was also observed in OS tissues. Furthermore, TUG1 directly interacted with miR-212-3p and negatively regulated the expression of miR-212-3p in OS cells. In vitro experiments further indicated that inhibition of TUG1 suppressed the proliferation and invasion of OS cells. Furthermore, knockdown of miR-212-3p eliminated the suppressive effects of TUG1 inhibition on the proliferation and invasion of OS cells. Taken together, these findings demonstrate that TUG1 promotes OS cell proliferation and invasion by inhibition of miR-212-3p expression, thus suggesting that TUG1 may become a potential therapeutic target for OS.

Copolymer dielectrics with balanced chain-packing density and surface polarity for high-performance flexible organic electronics.

The ever-increasing demand for flexible electronics calls for the development of low-voltage and high-mobility organic thin-film transistors (OTFTs) that can be integrated into emerging display and labeling technologies. Polymer dielectrics with comprehensive and balanced dielectric properties (i.e., a good balance between their insulating characteristics and compatibility with organic semiconductors) are considered particularly important for this end. Here, we introduce a simple but highly efficient strategy to realize this target by using a new type of copolymer as dielectrics. Benefiting from both high chain packing density guaranteeing dielectric properties and surface polarity optimizing molecular packing of organic semiconductors, this rationally designed copolymer dielectric endows flexible OTFTs with high mobility (5.6 cm2 V-1 s-1), low operating voltage (3 V) and outstanding stability. Further, their applicability in integrated circuits is verified. The excellent device performance shows exciting prospects of this molecular-scale engineered copolymer for the realization of plastic high-performance integrated electronics.

Downregulation of TACC3 inhibits tumor growth and migration in osteosarcoma cells through regulation of the NF-κB signaling pathway.

TACC3, a member of the transforming acidic coiled-coil protein (TACC) family, is a multifunctional protein that is involved in various biological functions, including proliferation and differentiation of tumor cells, cancer progression and metastasis. The aims of the present study were to examine whether TACC3 expression is associated with the proliferation and migration of osteosarcoma (OS) cells and to investigate the potential underlying molecular mechanisms of TACC3 in OS. First, the levels of mRNA and protein expression in OS cell lines by reverse transcription-quantitative polymerase chain reaction and western blotting, respectively were examined. Second, the effects of TACC3 knockdown and overexpression on the proliferative, migratory and invasive capacities of OS cells were investigated. Finally, western blot analysis was employed to detect the potential mechanism of TACC3 in osteosarcoma. TACC3 expression was significantly increased in osteosarcoma tissues and cell lines, compared to matched controls. The knockdown of TACC3 was able to significantly inhibit the proliferation, migration and invasion of osteosarcoma cells, whereas the overexpression of TACC3 was able to promote cell proliferation and migration. Mechanistically, TACC3 may promote the migration and invasion of osteosarcoma cells via through nuclear factor-κB signaling. These data suggest that TACC3 has an important part in the progression of osteosarcoma and may serve as a potential target for gene therapy.

Berberine alleviates oxidative stress in rats with osteoporosis through receptor activator of NF-kB/receptor activator of NF-kB ligand/osteoprotegerin (RANK/RANKL/OPG) pathway.

Previous studies suggested that oxidative stress is related to the onset and development of osteoporosis. Moreover, it was demonstrated that berberine has a protective effect against oxidative stress-induced injuries. In this study, we aimed to investigate the effect and mechanism of action of berberine on rats with induced osteoporosis. Sixty 8-week-old female Wistar rats were randomly divided into the following 6 groups: control saline-treated, osteoporosis saline-treated, 3 osteoporosis berberine-treated groups (Ber 5, 10, and 20 mg/kg/body weight, respectively), and osteoporosis alendronate-treated (ALD) group. Osteoporosis was induced by bilateral ovariectomy. All treatments were performed for 8 weeks. The bone mineral density (BMD), serum alkaline phosphatase (ALP), osteocalcin, calcium, phosphorus, superoxide dismutase (SOD), methylenedioxyamphetamine (MDA), and glutathione peroxidase (GSH-Px) level was determined in the rat femur tissue. The gene and protein expression of osteoprotegerin (OPG) and receptor activator of nuclear factor kappa-B ligand (RANKL) was analyzed by quantitative reverse transcription PCR and Western blot, respectively. The BMD, SOD and GSH⁃Px levels, and the expression of OPG were significantly lower in osteoporosis compared to control group (all p < 0.05). The serum levels of osteocalcin, ALP, and MDA, and the expression of RANKL were significantly higher in osteoporosis compared to control group (all p < 0.05). Berberine, especially the high doses of berberine, effectively increased SOD, GSH⁃Px, and OPG levels as well as decreased serum osteocalcin, ALP, MDA and RANKL levels in berberine-treated osteoporosis groups (all p < 0.05). To conclude, oxidative stress may promote the development of osteoporosis in rats through the RANK/RANKL/OPG pathway. The antioxidative effect of berberine reduces the development of osteoporosis in rats to some extent.

Synthesis of silver nanocubes with controlled size using water-soluble poly(amic acid) salt as the intermediate via a novel ion-exchange self-assembly technique.

Here, we report for the first time on the successful fabrication of monodispersed silver nanocubes with regular shape and controlled size in the solid phase via a novel ion-exchange self-assembly technique by using water-soluble poly(amic acid) salt as the intermediate and silver nitrate as the metal precursor. By simply altering the annealing times at high temperature, the size of the silver nanocubes could be finely tuned in the range of 90-160 nm in the present case. Further attempts with different metal salts show that the present method is also feasible for other metal species and might be universal.

Interfacial growth of controllable morphology of silver patterns on plastic substrates.

Controllable growth of newly born silver nanoparticles to fractal, cauliflower-like, microscale disks and continuous silver layers with high conductivity and reflectivity on plastic substrates has been developed via solid-liquid interfacial reduction and growing of ion-doped polymeric films. Such approaches involve polyimide (PI) films as substrates, its corresponding silver-ion-doped precursors as solid oxidants, and facile immersion of ion-doped polymeric films in aqueous reducing solution. The solution reducing process belongs to liquid-solid interfacial reduction processes, during which silver ions doped in polymeric matrix transformed to newly born silver nanoparticles which further aggregated and migrated along the liquid-solid interface to form dendrite, cauliflower-like and lamella disk-like architecture and/or severely compact continuous silver nanolayers with highly reflective and conductive properties. Time-dependent morphology evolutions of silver particles were traced by scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). This strategy can also extend to synthesis of many other metals on polymeric films while maintaining outstanding metal-polymer adhesion based on incorporation of various metal ions, and may offer an opportunity to fabricate large scale, high-output, cost-effective processes for metal patterns on flexible polymeric substrates.

Incorporation of silver nanoparticles into the bulk of the electrospun ultrafine polyimide nanofibers via a direct ion exchange self-metallization process.

This paper reports our works on the preparation of the silver-nanoparticle-incorporated ultrafine polyimide (PI) ultrafine fibers via a direct ion exchange self-metallization technique using silver ammonia complex cation ([Ag(NH(3))(2)](+)) as the silver precursor and pyromellitic dianhydride (PMDA)/4,4'-oxidianiline (4,4'-ODA) polyimide as the matrix. The polyimide precursor, poly(amic acid) (PAA), was synthesized and then electrospun into ultrafine fibers. By thermally treating the silver(I)-doped PAA ultrafine fibers, where the silver(I) ions were loaded through the ion exchange reactions of the carboxylic acid groups of the PAA macromolecules with the [Ag(NH(3))(2)](+) cations in an aqueous solution, ultrafine polyimide fibers embedded with silver nanoparticles with diameters less than 20 nm were successfully fabricated. The fiber-electrospinning process, the ion exchange process, and various factors influencing the hybrid ultrafine fibers preparation process such as the thermal treatment atmospheres and the thermal catalytic oxidative degradation effect of the reduced silver nanoparticles were discussed. The ultrafine fibers were characterized by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA).