In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electrom...In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electromagnetic interference(EMI)shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy.Water-soluble polyamic acid(PAA)was chosen to match the oriented freeze-drying method to acquire oriented pores,and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure.By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers,the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics(R=0.22).The asymmetric conductive net-work also greatly preserved the thermal insulation properties of PI.The thermal conductivity(TC)of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K).In addition,owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process,the composite foam showed satisfactory compressive strength.The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures,which has great potential in cuttingedge applications such as advanced aircraft.展开更多
Conjugated microporous polymers(CMPs)have attracted considerable attention as potential organic anode materials for sodium-ion batteries(SIBs)due to their flexible chemical structure,high porosity,environmental friend...Conjugated microporous polymers(CMPs)have attracted considerable attention as potential organic anode materials for sodium-ion batteries(SIBs)due to their flexible chemical structure,high porosity,environmental friendliness,and cost effectiveness.However,the inherent shortcomings of organic electrodes,such as low conductivity,high solubility in electrolyte,narrow material utilization,etc.,limit their further development.In this work,we successfully prepared a novel porous polyimide PPD containing multicarbonyl active centers via the polycondensation of pyromellitic dianhydride(PMDA)and2,6-diaminoanthraquinone(DAAQ).The stable conjugated structure and multiple redox centers give the polymer high reversible specific capacity(244.6 m Ah/g after 100 cycles at 100 m A/g),ultra-long cycle stability(100.7 m Ah/g after 2000 cycles at 1.0 A/g),and predominant rate capability.Meanwhile,the sodium storage mechanism of the electrode materials during the charging and discharging process is investigated by ex-situ XPS/FTIR analysis.Due to the exceptional electrochemical properties and simple synthesis method,this work may shed light on the preparation of polyimide-based anodes for high specific capacity and rate capability secondary batteries.展开更多
Hydrophobic nanofiber composite membranes comprising polyimide and metal-organic frameworks are developed for desalination via direct contact membrane distillation(DCMD).Our study demonstrates the synthesis of hydroph...Hydrophobic nanofiber composite membranes comprising polyimide and metal-organic frameworks are developed for desalination via direct contact membrane distillation(DCMD).Our study demonstrates the synthesis of hydrophobic polyimides with trifluoromethyl groups,along with superhydrophobic UiO-66(hMOF)prepared by phenylsilane modification on the metal-oxo nodes.These components are then combined to create nanofiber membranes with improved hydro ph obi city,ensuring long-term stability while preserving a high water flux.Integration of hMOF into the polymer matrix further increases membrane hydrophobic properties and provides additional pathways for vapor transport during MD.The resulting nanofiber composite membranes containing 20 wt%of hMOFs(PI-1-hMOF-20)were able to desalinate hypersaline feed solution of up to 17 wt%NaCl solution,conditions that are beyond the capability of reverse osmosis systems.These membranes demonstrated a water flux of 68.1 kg m^(-2)h^(-1) with a rejection rate of 99.98%for a simulated seawater solution of 3.5 wt%NaCl at 70℃,while maintaining consistent desalination performance for 250 h.展开更多
It is urgent to develop high-performance polyimide(PI)films that simultaneously exhibit high transparency,exceptional thermal stability,mechanical robustness,and low dielectric to fulfil the requirements of flexible d...It is urgent to develop high-performance polyimide(PI)films that simultaneously exhibit high transparency,exceptional thermal stability,mechanical robustness,and low dielectric to fulfil the requirements of flexible display technologies.Herein,a series of fluorinated polyimide films(FPIs)were fabricated by the condensation of 5,5′-(perfluoropropane-2,2-diyl)bis(isobenzofuran-1,3-dione)(6FDA)and the fluorinated triphenylmethane diamine monomer(EDA,MEDA and DMEDA)with heat-crosslinkable tetrafluorostyrene side groups,which was incorporated by different numbers of methyl groups pendant in the ortho position of amino groups.Subsequently,the FPI films underwent heating to produce crosslinking FPIs(C-FPIs)through the self-crosslinking of double bonds in the tetrafluorostyrene.The transparency,solvent resistance,thermal stability,mechanical robustness and dielectric properties of FPI and C-FPI films can be tuned by the number of methyl groups and crosslinking,which were deeply investigated by virtue of molecular dynamics(MD)simulations and density functional theory(DFT).As a result,all the films exhibited exceptional optically colorless and transparent,with transmittance in the visible region of 450-700 nm exceeding 79.9%,and the cut-off wavelengths(λ_(off))were nearly 350 nm.The thermal decomposition temperatures at 5% weight loss(T_(d5%))for all samples exceeded 504℃.These films exhibited a wide range of tunable tensile strength(46.5-75.1 MPa).Significantly,they showed exceptional dielectric properties with the dielectric constant of 2.3-2.5 at full frequency(10^(7)-20 Hz).This study not only highlights the relationship between the polymer molecular structure and properties,but offer insights for balancing optical transparency,heat resistance and low dielectric constant in PI films.展开更多
Designing and fabricating a compatible low-reflectivity electromagnetic interference(EMI)shielding/high-temperature resistant infrared stealth material possesses a critical significance in the field of military.Hence,...Designing and fabricating a compatible low-reflectivity electromagnetic interference(EMI)shielding/high-temperature resistant infrared stealth material possesses a critical significance in the field of military.Hence,a hierarchical polyimide(PI)nonwoven fabric is fabricated by alkali treatment,in-situ growth of magnetic particles and"self-activated"electroless Ag plating process.Especially,the hierarchical impedance matching can be constructed by systematically assembling Fe_(3)O_(4)/Ag-loaded PI nonwoven fabric(PFA)and pure Ag-coated PI nonwoven fabric(PA),endowing it with an ultralowreflectivity EMI shielding performance.In addition,thermal insulation of fluffy three-dimensional(3D)space structure in PFA and low infrared emissivity of PA originated from Ag plating bring an excellent infrared stealth performance.More importantly,the strong bonding interaction between Fe_(3)O_(4),Ag,and PI fiber improves thermal stability in EMI shielding and high-temperature resistant infrared stealth performance.Such excellent comprehensive performance makes it promising for military tents to protect internal equipment from electromagnetic interference stemmed from adjacent equipment and/or enemy,and inhibit external infrared detection.展开更多
Designing and manufacturing compatible multi-band stealth materials remains a great challenge. In this work, a silver-metalized polyimide photochromic composite foam is successfully fabricated by self-activating elect...Designing and manufacturing compatible multi-band stealth materials remains a great challenge. In this work, a silver-metalized polyimide photochromic composite foam is successfully fabricated by self-activating electroless silver-plating on the surface of the polyimide skeleton and followed by applying a photochromic coating on the upper surface. The effective loading of silver nanoparticles facilitates the rational construction of a conductive network in foam, improving the efficient dissipation of incident electromagnetic waves. In addition, the interconnected conductive network successfully endows it with an excellent Joule heating capability, which can be employed to effectively remove ice and/or mitigate the impact of water vapor on radar stealth performance in cold and wet weather. Besides, the low emissivity silver plating combined with superior thermal insulation of foam enables the material with excellent infrared stealth performance. Moreover, the modulation of self-adaptive photochromic coating brings a prominent visual stealth performance under different sunlight backgrounds. As a result, such excellent radar and infrared stealth performance combined with the adaptive color-switching capability provides the foam with great potential for preparing compatible multi-band materials.展开更多
In high-frequency electrical energy systems,polyimide(PI)composite insulation materials need to possess a low dielectric constant,sufficient thermal conductivity,and robust interfacial adhesion to ensure reliable perf...In high-frequency electrical energy systems,polyimide(PI)composite insulation materials need to possess a low dielectric constant,sufficient thermal conductivity,and robust interfacial adhesion to ensure reliable performance under elevated temperatures and pressures.These aspects are crucial for preventing local overheating and electrical breakdown,thereby ensuring reliable equipment operation.Traditional PI insulation materials often exhibit high dielectric constants and pronounced dielectric losses,compromising their insulation efficiency.In this study,molecular dynamics simulations were employed to incorporate polyhedral oligomeric silsesquioxanes(POSS)into PI through physical blending and chemical bonding to enhance dielectric properties.Key parameters of the PI/POSS composite system,including dielectric constant,thermal conductivity,glass transition temperature,Young’s modulus,Poisson’s ratio,and interfacial adhesion energy,were systematically evaluated for both doping methods.The degradation behavior of the PI composites under high-temperature and electric field conditions was also simulated to elucidate degradation pathways and product distributions,providing insights for designing low-dielectric insulation materials.Doping with POSS significantly reduces the dielectric constant of PI,thereby improving insulation performance,thermal stability,mechanical strength,and interfacial adhesion.At an optimal POSS doping ratio,the thermal conductivity of PI is enhanced.Compared with the physical blending system,the chemical bonding system yields more substantial improvements across all evaluated properties.Under high-temperature and strong electric field conditions,POSS doping enhances interfacial adhesion and thermal stability,effectively suppressing the cleavage of key chemical bonds,reducingCOemissions,and increasing the formation of oxygen-containing intermediates and water molecules,which contributes to improved environmental sustainability.展开更多
Aqueous zinc-ion hybrid capacitors(ZIHCs)are promising electrochemical energy storage systems with advantages of high-energy density,low cost,safety and environmental friendliness.However,application of carbon-based c...Aqueous zinc-ion hybrid capacitors(ZIHCs)are promising electrochemical energy storage systems with advantages of high-energy density,low cost,safety and environmental friendliness.However,application of carbon-based cathodes is limited by their low-energy density due to the lack of active sites.Herein,a chemisorption sites modulating strategy is proposed to construct nitrogen-doped polyimide carbon nanoflowers with abundant oxygen vacancies and carbonyl functionalization via high-temperature calcination and subsequent acid processing.The synergistic effect of oxygen vacancies,carbonyl groups,enhanced surface area and porous structure enables stable zinc-ion storage with high capacity.Remarkably,the carbon materials can circulate 20,000 cycles stably at a current density of 2 A·g^(-1).After 10,000 cycles at a high rate of 3 A·g^(-1),a capacity retention rate of 64%can still be achieved.The as-prepared ZIHCs provide an energy density of 65.61 Wh·kg^(-1)at the power density of 197.82 W·kg^(-1).Current research shows that polyimide-derived carbon material synthesized by acid activation provides a new idea for developing cathodes in aqueous ZIHCs.展开更多
Enhancing the mechanical properties is crucial for polyimide films,but the mechanical properties(Young's modulus,tensile strength,and elongation at break)mutually constrain each other,complicating simultaneous enh...Enhancing the mechanical properties is crucial for polyimide films,but the mechanical properties(Young's modulus,tensile strength,and elongation at break)mutually constrain each other,complicating simultaneous enhancement via traditional trial-and-error methods.In this work,we proposed a materials genome approach to design and screen phenylethynyl-terminated polyimides for films with enhanced mechani-cal properties.We first established machine learning models to predict Young's modulus,tensile strength,and elongation at break to explore the chemical space containing thousands of candidate structures.The accuracies of the machine learning models were verified by molecular dynamics simulations on screened polyimides and experimental testing on three representative polyimide films.The performance advantages of the best-selected polyimides were analyzed by comparing well-known polyimides based on molecular dynamics simulations,and the structural rationale was revealed by"gene"analysis and feature importance evaluation.This work provides a cost-effective strategy for designing polyimide films withenhancedmechanical properties.展开更多
Polyimide(PI)is widely used in high-tech fields such as microelectronics,aerospace,and national defense because of its excellent optical properties,high-and low-temperature resistance,and good dimensional stability.To...Polyimide(PI)is widely used in high-tech fields such as microelectronics,aerospace,and national defense because of its excellent optical properties,high-and low-temperature resistance,and good dimensional stability.To achieve the desired properties of PI,the monomers 2,6-diaminopyrimidin-4-ol(DAPD)and 6-(2,3,5,6-tetrafluoro-4-vinylphenoxy)pyrimidin-2,4-diamine(DAFPD),which contains crosslinkable functional groups,were designed and synthesized successfully and copolymerized with 4,4'-oxydianiline(ODA)and 4,4-hexafluoroisopropylphthalic anhydride(6FDA).The prepared PI film(PI-3),with rigid backbones and loose packing had excellent heat resistance(Td5%=489℃)and optical properties(T450=82%).Furthermore,a crosslinked PI film(c-PI-3)with more heat-resistant(Td5%=524℃)and better mechanical properties(σ=125.46MPa),can be obtained through thermal crosslinking of tetrafluorostyrene.In addition,the changes in the properties caused by the proportion of DAFPD added during copolymerization are discussed comprehensively.This study provides a promising candidate for heat-resistant PI materials.展开更多
High performance is always the research objective in developing triboelectric nanogenerators(TENGs)for future versatile applications.In this study,flexible triboelectric membranes were prepared based on polyimide(PI)m...High performance is always the research objective in developing triboelectric nanogenerators(TENGs)for future versatile applications.In this study,flexible triboelectric membranes were prepared based on polyimide(PI)membranes doped with barium titanate(BTO)nanoparticles and multi-walled carbon nanotubes(MWCNTs).The piezoelectric BTO nanoparticles were incorporated to boost the electric outputs by the synergistic effect of piezoelectricity and triboelectricity and MWCNTs were incorporated to provide a microcapacitor structure for enhancing the performance of TENGs.When the mass fraction of the BTO nanoparticle was 10%and the mass fraction of the MWCNT was 0.1%,the corresponding TENG achieved optimum electric outputs(an open-circuit voltage of around 65 V,a short-circuit current of about 20.0μA and a transferred charge of about 25.0 nC),much higher than those of the TENG with a single PI membrane.The TENG is potentially used to supply energy for commercial light-emitting diodes and as self-powered sensors to monitor human physical training conditions.This research provides a guideline for developing TENGs with high performance,which is crucial for their long-term use.展开更多
Modified polyimides(MPIs)possess excellent thermal stability,chemical stability,and mechanical properties,and are considered to be a kind of dielectric material for high-frequency communication.Enhancing the rigidity ...Modified polyimides(MPIs)possess excellent thermal stability,chemical stability,and mechanical properties,and are considered to be a kind of dielectric material for high-frequency communication.Enhancing the rigidity of the polymer chains and intermolecular interactions can ensure low D_(k)/D_(f)at high frequency,which is attributed to the effective restriction of dipole orientations.However,it is difficult to achieve tight chain packing in an overly rigid polymer chain,whereas an overly flexible polymer chain might be insufficient to restrain small-scale molecular motions below T_(g).To balance the trade-off between the rigidity of the polymer chains and tight chain packing,MPI was developed with a rigidsoft structure based on a naphthalene-alkyl-based diamine.On the one hand,incorporating the soft unit can enhance the movability of polymer chains to achieve dense chain packing for polyimides(PIs).On the other hand,the presence of rigid aromatic units can enhance intermolecular interactions and further restrict the motion of polar imide groups below T_(g).As a result,the resultant MPI can prevent small-scale molecular motion below T_(g).In contrast to the reference PI-TFMB-6FDA,D_(k)/D_(f)is significantly reduced from 2.72/0.0075 to 2.73/0.005 at a high frequency of 10 GHz Furthermore,the rigid-soft structure endows PIs with good thermoplasticity owing to the good chain flexibility above T_(g).In addition,PIs based on rigid-soft structures can preserve favorable thermal stability.展开更多
The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme conditions.An important challenge to be solved urgently is the reduction of imidiza...The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme conditions.An important challenge to be solved urgently is the reduction of imidization temperature.In this work,twelve kinds of polyimide films with different chain rigidity were prepared at low temperature of 200℃,in the absence or presence of imidazole used as the catalyst.The molecular rigidity and free volume were theoretically calculated,and relationship between structure and properties were systematically studied.The results show that imidization reaction under low temperatures is significantly affected by the rigidity of molecula r chains.The rigid structure of polyimide is not conducive to the low-temperature imidization,but this adverse effect can be eliminated by adding catalyst,resulting the notably increased imidization degree.The optical and thermal properties can be improved to a certain extent for the chemically catalyzed system,resulting in relatively higher heat resistance and thermal stability.While the mechanical performance could be determined by com plicating factors,greatly different from polyimide films prepa red by high temperature method.To investigate aggregation structures of film s,the effect of chain rigidity and catalyst on the stacking or orientation of molecular chains was further elaborated.This wo rk can contribute to the understanding of chemically catalyzed imidization that is rarely reported in the existing research,and will provide guidance for the low-temperature preparation of high-performance polyimides.展开更多
Silicon-based materials have demonstrated remarkable potential in high-energy-density batteries owing to their high theoretical capacity.However,the significant volume expansion of silicon seriously hinders its utiliz...Silicon-based materials have demonstrated remarkable potential in high-energy-density batteries owing to their high theoretical capacity.However,the significant volume expansion of silicon seriously hinders its utilization as a lithium-ion anode.Herein,a functionalized high-toughness polyimide(PDMI) is synthesized by copolymerizing the 4,4'-Oxydiphthalic anhydride(ODPA) with 4,4'-oxydianiline(ODA),2,3-diaminobenzoic acid(DABA),and 1,3-bis(3-aminopropyl)-tetramethyl disiloxane(DMS).The combination of rigid benzene rings and flexible oxygen groups(-O-) in the PDMI molecular chain via a rigidness/softness coupling mechanism contributes to high toughness.The plentiful polar carboxyl(-COOH) groups establish robust bonding strength.Rapid ionic transport is achieved by incorporating the flexible siloxane segment(Si-O-Si),which imparts high molecular chain motility and augments free volume holes to facilitate lithium-ion transport(9.8 × 10^(-10) cm^(2) s^(-1) vs.16 × 10^(-10) cm^(2) s~(-1)).As expected,the SiO_x@PDMI-1.5 electrode delivers brilliant long-term cycle performance with a remarkable capacity retention of 85% over 500 cycles at 1.3 A g^(-1).The well-designed functionalized polyimide also significantly enhances the electrochemical properties of Si nanoparticles electrode.Meanwhile,the assembled SiO_x@PDMI-1.5/NCM811 full cell delivers a high retention of 80% after 100 cycles.The perspective of the binder design strategy based on polyimide modification delivers a novel path toward high-capacity electrodes for high-energy-density batteries.展开更多
A series of transparent crosslinked colorless polyimide(CPI)films are prepared from 3,3',4,4'-biphenyltetracarboxylic dianhydride(BPDA),2,2'-bis(trifluoro-methyl)benzidine(TFMB),and 4,4'-oxydianiline(O...A series of transparent crosslinked colorless polyimide(CPI)films are prepared from 3,3',4,4'-biphenyltetracarboxylic dianhydride(BPDA),2,2'-bis(trifluoro-methyl)benzidine(TFMB),and 4,4'-oxydianiline(ODA)by thermal imidization,incorporating varying contents of 2,2'-(1,3-phenylene)bis(2-oxazoline)(1,3-PBO)as the crosslinking agent.Following the incorporation of the crosslinking structure,the CPI films show good optical transparency(approximately 85%winthin visible light range),enhanced glass transition temperature(from 325℃to 341℃),and improved thermal stability,and tensile strength.Notably,compared with the pristine uncrosslinked CPI,these crosslinked CPI films significantly increase in elongation at break(from 5.4%to 44.2%).Furthermore,the new approach ensures that crosslinked CPIs improve heat resistance and mechanical properties,while avoiding the embrittlement of materials.This study also offeres straightforward preparation methods for optically transparent crosslinked polyimides without additional processing steps.All these results make this approach can effectively improve the competitive performance of the CPI films for potential applications in microelectronic and optoelectronic fields.展开更多
As a nonmetallic charge carrier,ammonium ion(NH_(4)^(+))has garnered significant attention in the construction of aqueous batteries due to its advantages of low molar mass,small hydration size and rapid diffusion in a...As a nonmetallic charge carrier,ammonium ion(NH_(4)^(+))has garnered significant attention in the construction of aqueous batteries due to its advantages of low molar mass,small hydration size and rapid diffusion in aqueous solutions.Polymers are a kind of potential electro-active materials for aqueous NH_(4)^(+)storage.However,traditional polymer electrodes are typically created by covering the bulky collectors with excessive additives,which could lead to low volume capacity and unsatisfactory stability.Herein,a nanoparticle-like polyimide(PI)was synthesized and then combined with MXene nanosheets to synergistically construct an additive-free and self-standing PI@MXene composite electrode.Significantly,the redox-active PI nanoparticles are enclosed between conductive MXene flakes to create a 3D lamination-like network that promotes electron transmission,while theπ-πinteractions existing between PI and MXene contribute to the enhanced structural integrity and stability within the composite electrode.As such,it delivers superior aqueous NH_(4)^(+)storage behaviors in terms of a notable specific capacity of 110.7 mA·h·cm^(–3) and a long lifespan with only 0.0064%drop each cycle.Furthermore,in-situ Raman and UV–Vis examinations provide evidence of reversible and stable redox mechanism of the PI@MXene composite electrode during NH_(4)^(+)uptake/removal,highlighting its significance in the area of electrochemical energy storage.展开更多
Easy hydrolysis in alkaline environments limits the use of polyimide fibers in environmental protection. The hydrolysis resistance levels of polyimide fibers can be improved by crosslinking of the macromolecular chain...Easy hydrolysis in alkaline environments limits the use of polyimide fibers in environmental protection. The hydrolysis resistance levels of polyimide fibers can be improved by crosslinking of the macromolecular chains. In this work, crosslinked polyimide fibers(CPI fibers) were produced by intrinsic carboxyl decarboxylation for the first time. The thermal stability of the polyimide fibers containing the intrinsic carboxyl groups(PIC fibers) was studied, and the temperature of the decarboxylation-crosslinking reaction was determined to be 450 ℃. The PIC fibers were hotdrawn to initiate thermal crosslinking of the carboxyl groups and molecular chain orientation at high temperature. The CPI fibers had high tensile strengths(0.72-1.46 GPa) and compressive strengths(401-604 MPa). The oriented macromolecules and chemically crosslinked structure improved the tightness of the molecular chains and endowed the CPI fibers with excellent hydrolytic resistance. The CPI-50 fiber did not dissolve in a 0.5 wt% NaOH solution during heating at 90 ℃ for 10 h, and the tensile strength retention reached 87% when treated in 0.5 wt% NaOH solutions at 90 ℃ for 1 h, providing a guarantee for its application in alkaline corrosive environments.展开更多
Metallic copper is widely used as current collector(CC) for graphite anode of lithium-ion batteries(LIBs) due to its high electrical conductivity and electrochemical stability. However, the large volume density of com...Metallic copper is widely used as current collector(CC) for graphite anode of lithium-ion batteries(LIBs) due to its high electrical conductivity and electrochemical stability. However, the large volume density of commercial copper foil(~8.9 g·cm^(-3)) limits the increase of energy density of battery. Here, copper-coated porous polyimide(Cu@PPI) was prepared by vacuum evaporation as collector for the graphite anode. The sandwich structure connects the copper metal on both sides of the collector with excellent electrical conductivity. Compared to commercial Cu foil, Cu@PPI has lighter mass(≤3.9 mg for disc of 12 mm diameter versus 9.9 mg of ~10 μm Cu foil) and lower volume density(≤3.3 g·cm^(-3)). In addition, the porous structure allows of better adhesion of reactive substances and electrochemical properties than pure Cu foils. It is estimated that the energy density of Cu@PPI should be much higher than that of Cu foil. This strategy should be applicable for other current collectors.展开更多
The compatibility of the gate dielectrics with semiconductors is vital for constructing efficient conducting channel for high charge transport.However,it is still a highly challenging mission to clearly clarify the re...The compatibility of the gate dielectrics with semiconductors is vital for constructing efficient conducting channel for high charge transport.However,it is still a highly challenging mission to clearly clarify the relationship between the dielectric layers and the chemical structure of semiconductors,especially vacuum-deposited small molecules.Here,interfacial molecular screening of polyimide(Kapton)dielectric in organic field-effect transistors(OFETs)is comprehensively studied.It is found that the semiconducting small molecules with alkyl side chains prefer to form a high-quality charge transport layer on polyimide(PI)dielectrics compared with the molecules without alkyl side chains.On this basis,the fabricated transistors could reach the mobility of 1.2 cm^(2) V^(−1)s^(−1) the molecule with alkyl side chains on bare PI dielectric.What is more,the compatible semiconductor and dielectric would further produce a low activation energy(E_(A))of 3.01 meV towards efficient charge transport even at low temperature(e.g.,100 K,0.9 cm^(2) V^(−1)s^(−1)).Our research provides a guiding scheme for the construction of high-performance thin-film field-effect transistors based on PI dielectric layer at room and low temperatures.展开更多
Accurate detection of uric acid(UA)is crucial for diagnosing gout,yet traditional sweat-based UA sensors continue to face challenges posed by complex and costly electrode fabrication methods,as well as weakly hydrophi...Accurate detection of uric acid(UA)is crucial for diagnosing gout,yet traditional sweat-based UA sensors continue to face challenges posed by complex and costly electrode fabrication methods,as well as weakly hydrophilic substrates.Here,we designed and developed simple,low-cost,and hydrophilic sweat UA detection sensors constructed by carbon electrodes and cellulose paper substrates.The carbon electrodes were made by carbonized polyimide films through a simple,one-step laser engraving method.Our electrodes are porous,possess a large specific surface area,and are flexible and conductive.The substrates were composed of highly hydrophilic cellulose paper that can effectively collect,store,and transport sweat.The constructed electrodes demonstrate high sensitivity of 0.4μA Lμmol^(-1)cm^(-2),wide linear range of 2–100μmol/L.In addition,our electrodes demonstrate high selectivity,excellent reproducibility,high flexibility,and outstanding stability against mechanical bending,temperature variations,and extended storage periods.Furthermore,our sensors have been proven to provide reliable results when detecting UA levels in real sweat and on real human skin.We envision that these sensors hold enormous potential for use in the prognosis,diagnosis,and treatment of gout.展开更多
基金supported by the Natural Science Foundation of Shanxi Province(Nos.20210302123015 and 20210302123035)the Opening Project of State Key Laboratory of Polymer Materials Engineering(Sichuan University)(No.sklpme2022-4-06)the Open Foundation of China-Belarus Belt and Road Joint Laboratory on Electromagnetic Environment Effect(No.ZBKF2022030301).
文摘In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electromagnetic interference(EMI)shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy.Water-soluble polyamic acid(PAA)was chosen to match the oriented freeze-drying method to acquire oriented pores,and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure.By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers,the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics(R=0.22).The asymmetric conductive net-work also greatly preserved the thermal insulation properties of PI.The thermal conductivity(TC)of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K).In addition,owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process,the composite foam showed satisfactory compressive strength.The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures,which has great potential in cuttingedge applications such as advanced aircraft.
基金supported by National Natural Science Foundation,China(Nos.52071132,U21A20284 and 52261135632)Natural Science Foundation of Henan,China(Nos.232300421080,242300421035)+2 种基金Program for Innovative Team(in Science and Technology)in University of Henan Province,China(No.24IRTSTHN006)Key Scientific Research Programs in Universities of Henan Province,China–Special Projects for Basic Research(No.23ZX008)the Natural Science Foundation of Hunan Province,China(No.2023JJ50287)。
文摘Conjugated microporous polymers(CMPs)have attracted considerable attention as potential organic anode materials for sodium-ion batteries(SIBs)due to their flexible chemical structure,high porosity,environmental friendliness,and cost effectiveness.However,the inherent shortcomings of organic electrodes,such as low conductivity,high solubility in electrolyte,narrow material utilization,etc.,limit their further development.In this work,we successfully prepared a novel porous polyimide PPD containing multicarbonyl active centers via the polycondensation of pyromellitic dianhydride(PMDA)and2,6-diaminoanthraquinone(DAAQ).The stable conjugated structure and multiple redox centers give the polymer high reversible specific capacity(244.6 m Ah/g after 100 cycles at 100 m A/g),ultra-long cycle stability(100.7 m Ah/g after 2000 cycles at 1.0 A/g),and predominant rate capability.Meanwhile,the sodium storage mechanism of the electrode materials during the charging and discharging process is investigated by ex-situ XPS/FTIR analysis.Due to the exceptional electrochemical properties and simple synthesis method,this work may shed light on the preparation of polyimide-based anodes for high specific capacity and rate capability secondary batteries.
基金supported by the Australian Research Council Discovery Early Career Researcher Award Scheme(DE220100135 and DE220100435)。
文摘Hydrophobic nanofiber composite membranes comprising polyimide and metal-organic frameworks are developed for desalination via direct contact membrane distillation(DCMD).Our study demonstrates the synthesis of hydrophobic polyimides with trifluoromethyl groups,along with superhydrophobic UiO-66(hMOF)prepared by phenylsilane modification on the metal-oxo nodes.These components are then combined to create nanofiber membranes with improved hydro ph obi city,ensuring long-term stability while preserving a high water flux.Integration of hMOF into the polymer matrix further increases membrane hydrophobic properties and provides additional pathways for vapor transport during MD.The resulting nanofiber composite membranes containing 20 wt%of hMOFs(PI-1-hMOF-20)were able to desalinate hypersaline feed solution of up to 17 wt%NaCl solution,conditions that are beyond the capability of reverse osmosis systems.These membranes demonstrated a water flux of 68.1 kg m^(-2)h^(-1) with a rejection rate of 99.98%for a simulated seawater solution of 3.5 wt%NaCl at 70℃,while maintaining consistent desalination performance for 250 h.
基金financially supported by the Natural Science Foundation of Shandong Province(Nos.ZR2021ME055,ZR2022QB170 and ZR2022MB034)the Foundation(No.GZKF202128)of State Key Laboratory of Biobased Material and Green Papermaking,Qilu University of Technology,Shandong Academy of Sciencesthe Development Program Project of Young Innovation Team of Institutions of Higher Learning in Shandong Province.
文摘It is urgent to develop high-performance polyimide(PI)films that simultaneously exhibit high transparency,exceptional thermal stability,mechanical robustness,and low dielectric to fulfil the requirements of flexible display technologies.Herein,a series of fluorinated polyimide films(FPIs)were fabricated by the condensation of 5,5′-(perfluoropropane-2,2-diyl)bis(isobenzofuran-1,3-dione)(6FDA)and the fluorinated triphenylmethane diamine monomer(EDA,MEDA and DMEDA)with heat-crosslinkable tetrafluorostyrene side groups,which was incorporated by different numbers of methyl groups pendant in the ortho position of amino groups.Subsequently,the FPI films underwent heating to produce crosslinking FPIs(C-FPIs)through the self-crosslinking of double bonds in the tetrafluorostyrene.The transparency,solvent resistance,thermal stability,mechanical robustness and dielectric properties of FPI and C-FPI films can be tuned by the number of methyl groups and crosslinking,which were deeply investigated by virtue of molecular dynamics(MD)simulations and density functional theory(DFT).As a result,all the films exhibited exceptional optically colorless and transparent,with transmittance in the visible region of 450-700 nm exceeding 79.9%,and the cut-off wavelengths(λ_(off))were nearly 350 nm.The thermal decomposition temperatures at 5% weight loss(T_(d5%))for all samples exceeded 504℃.These films exhibited a wide range of tunable tensile strength(46.5-75.1 MPa).Significantly,they showed exceptional dielectric properties with the dielectric constant of 2.3-2.5 at full frequency(10^(7)-20 Hz).This study not only highlights the relationship between the polymer molecular structure and properties,but offer insights for balancing optical transparency,heat resistance and low dielectric constant in PI films.
基金support from the National Natural Science Foundation of China(52373077,52003106,52103074,52233006,52161135302)the Research Foundation Flanders(G0F2322N)Innovation Program of Shanghai Municipal Education Commission(2021-01-07-00-03-E00108).
文摘Designing and fabricating a compatible low-reflectivity electromagnetic interference(EMI)shielding/high-temperature resistant infrared stealth material possesses a critical significance in the field of military.Hence,a hierarchical polyimide(PI)nonwoven fabric is fabricated by alkali treatment,in-situ growth of magnetic particles and"self-activated"electroless Ag plating process.Especially,the hierarchical impedance matching can be constructed by systematically assembling Fe_(3)O_(4)/Ag-loaded PI nonwoven fabric(PFA)and pure Ag-coated PI nonwoven fabric(PA),endowing it with an ultralowreflectivity EMI shielding performance.In addition,thermal insulation of fluffy three-dimensional(3D)space structure in PFA and low infrared emissivity of PA originated from Ag plating bring an excellent infrared stealth performance.More importantly,the strong bonding interaction between Fe_(3)O_(4),Ag,and PI fiber improves thermal stability in EMI shielding and high-temperature resistant infrared stealth performance.Such excellent comprehensive performance makes it promising for military tents to protect internal equipment from electromagnetic interference stemmed from adjacent equipment and/or enemy,and inhibit external infrared detection.
基金supported by the National Natural Science Foundation of China(Nos.52373077,52003106,52233006,and 52161135302)the Research Foundation Flanders(No.G0F2322N)+1 种基金the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.SJCX23_1236)the Innovation Program of Shanghai Municipal Education Commission(No.2021-01-07-00-03-E00108).
文摘Designing and manufacturing compatible multi-band stealth materials remains a great challenge. In this work, a silver-metalized polyimide photochromic composite foam is successfully fabricated by self-activating electroless silver-plating on the surface of the polyimide skeleton and followed by applying a photochromic coating on the upper surface. The effective loading of silver nanoparticles facilitates the rational construction of a conductive network in foam, improving the efficient dissipation of incident electromagnetic waves. In addition, the interconnected conductive network successfully endows it with an excellent Joule heating capability, which can be employed to effectively remove ice and/or mitigate the impact of water vapor on radar stealth performance in cold and wet weather. Besides, the low emissivity silver plating combined with superior thermal insulation of foam enables the material with excellent infrared stealth performance. Moreover, the modulation of self-adaptive photochromic coating brings a prominent visual stealth performance under different sunlight backgrounds. As a result, such excellent radar and infrared stealth performance combined with the adaptive color-switching capability provides the foam with great potential for preparing compatible multi-band materials.
基金financially supported by the Natural Science Foundation of Shandong Province(No.ZR2021ME011)State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources(No.LAPS20001)。
文摘In high-frequency electrical energy systems,polyimide(PI)composite insulation materials need to possess a low dielectric constant,sufficient thermal conductivity,and robust interfacial adhesion to ensure reliable performance under elevated temperatures and pressures.These aspects are crucial for preventing local overheating and electrical breakdown,thereby ensuring reliable equipment operation.Traditional PI insulation materials often exhibit high dielectric constants and pronounced dielectric losses,compromising their insulation efficiency.In this study,molecular dynamics simulations were employed to incorporate polyhedral oligomeric silsesquioxanes(POSS)into PI through physical blending and chemical bonding to enhance dielectric properties.Key parameters of the PI/POSS composite system,including dielectric constant,thermal conductivity,glass transition temperature,Young’s modulus,Poisson’s ratio,and interfacial adhesion energy,were systematically evaluated for both doping methods.The degradation behavior of the PI composites under high-temperature and electric field conditions was also simulated to elucidate degradation pathways and product distributions,providing insights for designing low-dielectric insulation materials.Doping with POSS significantly reduces the dielectric constant of PI,thereby improving insulation performance,thermal stability,mechanical strength,and interfacial adhesion.At an optimal POSS doping ratio,the thermal conductivity of PI is enhanced.Compared with the physical blending system,the chemical bonding system yields more substantial improvements across all evaluated properties.Under high-temperature and strong electric field conditions,POSS doping enhances interfacial adhesion and thermal stability,effectively suppressing the cleavage of key chemical bonds,reducingCOemissions,and increasing the formation of oxygen-containing intermediates and water molecules,which contributes to improved environmental sustainability.
基金supported by the National Natural Science Foundation of China(Nos.52272211 and 52072145)the Funding of Jilin Province Development and Reform Commission(Nos.2024C018-11 and 2020C026-2)+3 种基金the Scientific and Technological Developing Project of Jilin Province(Nos.20230508046RC,20240602023RC,YDZJ202101ZYTS185 and YDZJ202201ZYTS372)Jilin Talent Development Funding(No.2021Y027)the Funds for Special Projects of the Central Government in Guidance of Local Science and Technology Development(No.202002017JC)the Research Program on Science and Technology from the Education Department of Jilin Province(Nos.JJKH20220439KJ and JJKH20210550KJ).
文摘Aqueous zinc-ion hybrid capacitors(ZIHCs)are promising electrochemical energy storage systems with advantages of high-energy density,low cost,safety and environmental friendliness.However,application of carbon-based cathodes is limited by their low-energy density due to the lack of active sites.Herein,a chemisorption sites modulating strategy is proposed to construct nitrogen-doped polyimide carbon nanoflowers with abundant oxygen vacancies and carbonyl functionalization via high-temperature calcination and subsequent acid processing.The synergistic effect of oxygen vacancies,carbonyl groups,enhanced surface area and porous structure enables stable zinc-ion storage with high capacity.Remarkably,the carbon materials can circulate 20,000 cycles stably at a current density of 2 A·g^(-1).After 10,000 cycles at a high rate of 3 A·g^(-1),a capacity retention rate of 64%can still be achieved.The as-prepared ZIHCs provide an energy density of 65.61 Wh·kg^(-1)at the power density of 197.82 W·kg^(-1).Current research shows that polyimide-derived carbon material synthesized by acid activation provides a new idea for developing cathodes in aqueous ZIHCs.
基金supported by the National Key R&D Program of China(No.2022YFB3707302)the National Natural Science Foundation of China(Nos.52394271 , 52394270).
文摘Enhancing the mechanical properties is crucial for polyimide films,but the mechanical properties(Young's modulus,tensile strength,and elongation at break)mutually constrain each other,complicating simultaneous enhancement via traditional trial-and-error methods.In this work,we proposed a materials genome approach to design and screen phenylethynyl-terminated polyimides for films with enhanced mechani-cal properties.We first established machine learning models to predict Young's modulus,tensile strength,and elongation at break to explore the chemical space containing thousands of candidate structures.The accuracies of the machine learning models were verified by molecular dynamics simulations on screened polyimides and experimental testing on three representative polyimide films.The performance advantages of the best-selected polyimides were analyzed by comparing well-known polyimides based on molecular dynamics simulations,and the structural rationale was revealed by"gene"analysis and feature importance evaluation.This work provides a cost-effective strategy for designing polyimide films withenhancedmechanical properties.
基金supported by the National Key Research and Development Program of China(No.2022YFB3603101)。
文摘Polyimide(PI)is widely used in high-tech fields such as microelectronics,aerospace,and national defense because of its excellent optical properties,high-and low-temperature resistance,and good dimensional stability.To achieve the desired properties of PI,the monomers 2,6-diaminopyrimidin-4-ol(DAPD)and 6-(2,3,5,6-tetrafluoro-4-vinylphenoxy)pyrimidin-2,4-diamine(DAFPD),which contains crosslinkable functional groups,were designed and synthesized successfully and copolymerized with 4,4'-oxydianiline(ODA)and 4,4-hexafluoroisopropylphthalic anhydride(6FDA).The prepared PI film(PI-3),with rigid backbones and loose packing had excellent heat resistance(Td5%=489℃)and optical properties(T450=82%).Furthermore,a crosslinked PI film(c-PI-3)with more heat-resistant(Td5%=524℃)and better mechanical properties(σ=125.46MPa),can be obtained through thermal crosslinking of tetrafluorostyrene.In addition,the changes in the properties caused by the proportion of DAFPD added during copolymerization are discussed comprehensively.This study provides a promising candidate for heat-resistant PI materials.
基金National Natural Science Foundation of China(No.52103267)。
文摘High performance is always the research objective in developing triboelectric nanogenerators(TENGs)for future versatile applications.In this study,flexible triboelectric membranes were prepared based on polyimide(PI)membranes doped with barium titanate(BTO)nanoparticles and multi-walled carbon nanotubes(MWCNTs).The piezoelectric BTO nanoparticles were incorporated to boost the electric outputs by the synergistic effect of piezoelectricity and triboelectricity and MWCNTs were incorporated to provide a microcapacitor structure for enhancing the performance of TENGs.When the mass fraction of the BTO nanoparticle was 10%and the mass fraction of the MWCNT was 0.1%,the corresponding TENG achieved optimum electric outputs(an open-circuit voltage of around 65 V,a short-circuit current of about 20.0μA and a transferred charge of about 25.0 nC),much higher than those of the TENG with a single PI membrane.The TENG is potentially used to supply energy for commercial light-emitting diodes and as self-powered sensors to monitor human physical training conditions.This research provides a guideline for developing TENGs with high performance,which is crucial for their long-term use.
基金supported by the National Natural Science Foundation of China(Nos.U20A20340 and 52001068)Key-Area Research and Development Program of Guangdong Province(No.2020B010182001)+3 种基金Dongguan Key Research&Development Program(No.20231200300192)Science and Technology Projects in Guangzhou(No.2025A04J3832)Foshan Introducing Innovative and Entrepreneurial Teams(No.1920001000108)Guangzhou Hongmian Project(No.HMJH-2020-0012)。
文摘Modified polyimides(MPIs)possess excellent thermal stability,chemical stability,and mechanical properties,and are considered to be a kind of dielectric material for high-frequency communication.Enhancing the rigidity of the polymer chains and intermolecular interactions can ensure low D_(k)/D_(f)at high frequency,which is attributed to the effective restriction of dipole orientations.However,it is difficult to achieve tight chain packing in an overly rigid polymer chain,whereas an overly flexible polymer chain might be insufficient to restrain small-scale molecular motions below T_(g).To balance the trade-off between the rigidity of the polymer chains and tight chain packing,MPI was developed with a rigidsoft structure based on a naphthalene-alkyl-based diamine.On the one hand,incorporating the soft unit can enhance the movability of polymer chains to achieve dense chain packing for polyimides(PIs).On the other hand,the presence of rigid aromatic units can enhance intermolecular interactions and further restrict the motion of polar imide groups below T_(g).As a result,the resultant MPI can prevent small-scale molecular motion below T_(g).In contrast to the reference PI-TFMB-6FDA,D_(k)/D_(f)is significantly reduced from 2.72/0.0075 to 2.73/0.005 at a high frequency of 10 GHz Furthermore,the rigid-soft structure endows PIs with good thermoplasticity owing to the good chain flexibility above T_(g).In addition,PIs based on rigid-soft structures can preserve favorable thermal stability.
基金financially supported by the National Key Research and Development Program of China(No.2022YFB3603105)Key Programs of the Chinese Academy of Sciences(No.ZDRW-CN-2023-3-2)+1 种基金the National Natural Science Foundation of China(No.51803221)Natural Science Foundation of Beijing Municipality(No.2202068)。
文摘The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme conditions.An important challenge to be solved urgently is the reduction of imidization temperature.In this work,twelve kinds of polyimide films with different chain rigidity were prepared at low temperature of 200℃,in the absence or presence of imidazole used as the catalyst.The molecular rigidity and free volume were theoretically calculated,and relationship between structure and properties were systematically studied.The results show that imidization reaction under low temperatures is significantly affected by the rigidity of molecula r chains.The rigid structure of polyimide is not conducive to the low-temperature imidization,but this adverse effect can be eliminated by adding catalyst,resulting the notably increased imidization degree.The optical and thermal properties can be improved to a certain extent for the chemically catalyzed system,resulting in relatively higher heat resistance and thermal stability.While the mechanical performance could be determined by com plicating factors,greatly different from polyimide films prepa red by high temperature method.To investigate aggregation structures of film s,the effect of chain rigidity and catalyst on the stacking or orientation of molecular chains was further elaborated.This wo rk can contribute to the understanding of chemically catalyzed imidization that is rarely reported in the existing research,and will provide guidance for the low-temperature preparation of high-performance polyimides.
基金supported by the National Natural Science Foundation of China (51673017)the National Natural Science Foundation of China (21404005)+1 种基金the Fundamental Research Funds for the Central Universities (XK1802-2)the Natural Science Foundation of Jiangsu Province (BK20150273)。
文摘Silicon-based materials have demonstrated remarkable potential in high-energy-density batteries owing to their high theoretical capacity.However,the significant volume expansion of silicon seriously hinders its utilization as a lithium-ion anode.Herein,a functionalized high-toughness polyimide(PDMI) is synthesized by copolymerizing the 4,4'-Oxydiphthalic anhydride(ODPA) with 4,4'-oxydianiline(ODA),2,3-diaminobenzoic acid(DABA),and 1,3-bis(3-aminopropyl)-tetramethyl disiloxane(DMS).The combination of rigid benzene rings and flexible oxygen groups(-O-) in the PDMI molecular chain via a rigidness/softness coupling mechanism contributes to high toughness.The plentiful polar carboxyl(-COOH) groups establish robust bonding strength.Rapid ionic transport is achieved by incorporating the flexible siloxane segment(Si-O-Si),which imparts high molecular chain motility and augments free volume holes to facilitate lithium-ion transport(9.8 × 10^(-10) cm^(2) s^(-1) vs.16 × 10^(-10) cm^(2) s~(-1)).As expected,the SiO_x@PDMI-1.5 electrode delivers brilliant long-term cycle performance with a remarkable capacity retention of 85% over 500 cycles at 1.3 A g^(-1).The well-designed functionalized polyimide also significantly enhances the electrochemical properties of Si nanoparticles electrode.Meanwhile,the assembled SiO_x@PDMI-1.5/NCM811 full cell delivers a high retention of 80% after 100 cycles.The perspective of the binder design strategy based on polyimide modification delivers a novel path toward high-capacity electrodes for high-energy-density batteries.
文摘A series of transparent crosslinked colorless polyimide(CPI)films are prepared from 3,3',4,4'-biphenyltetracarboxylic dianhydride(BPDA),2,2'-bis(trifluoro-methyl)benzidine(TFMB),and 4,4'-oxydianiline(ODA)by thermal imidization,incorporating varying contents of 2,2'-(1,3-phenylene)bis(2-oxazoline)(1,3-PBO)as the crosslinking agent.Following the incorporation of the crosslinking structure,the CPI films show good optical transparency(approximately 85%winthin visible light range),enhanced glass transition temperature(from 325℃to 341℃),and improved thermal stability,and tensile strength.Notably,compared with the pristine uncrosslinked CPI,these crosslinked CPI films significantly increase in elongation at break(from 5.4%to 44.2%).Furthermore,the new approach ensures that crosslinked CPIs improve heat resistance and mechanical properties,while avoiding the embrittlement of materials.This study also offeres straightforward preparation methods for optically transparent crosslinked polyimides without additional processing steps.All these results make this approach can effectively improve the competitive performance of the CPI films for potential applications in microelectronic and optoelectronic fields.
基金supported by the National Natural Science Foundation of China(52002157)the Undergraduate Research&Practice Innovation Program of Jiangsu Province(202310289033Z).
文摘As a nonmetallic charge carrier,ammonium ion(NH_(4)^(+))has garnered significant attention in the construction of aqueous batteries due to its advantages of low molar mass,small hydration size and rapid diffusion in aqueous solutions.Polymers are a kind of potential electro-active materials for aqueous NH_(4)^(+)storage.However,traditional polymer electrodes are typically created by covering the bulky collectors with excessive additives,which could lead to low volume capacity and unsatisfactory stability.Herein,a nanoparticle-like polyimide(PI)was synthesized and then combined with MXene nanosheets to synergistically construct an additive-free and self-standing PI@MXene composite electrode.Significantly,the redox-active PI nanoparticles are enclosed between conductive MXene flakes to create a 3D lamination-like network that promotes electron transmission,while theπ-πinteractions existing between PI and MXene contribute to the enhanced structural integrity and stability within the composite electrode.As such,it delivers superior aqueous NH_(4)^(+)storage behaviors in terms of a notable specific capacity of 110.7 mA·h·cm^(–3) and a long lifespan with only 0.0064%drop each cycle.Furthermore,in-situ Raman and UV–Vis examinations provide evidence of reversible and stable redox mechanism of the PI@MXene composite electrode during NH_(4)^(+)uptake/removal,highlighting its significance in the area of electrochemical energy storage.
基金financially supported by the Scientific Research Innovation Plan of Shanghai Education Commission (No. 2019-01-07-00-03-E00001)the National Natural Science Foundation of China (Nos. U21A2087 and 21975040)the Natural Science Foundation of Shanghai (No. 21ZR1400200)。
文摘Easy hydrolysis in alkaline environments limits the use of polyimide fibers in environmental protection. The hydrolysis resistance levels of polyimide fibers can be improved by crosslinking of the macromolecular chains. In this work, crosslinked polyimide fibers(CPI fibers) were produced by intrinsic carboxyl decarboxylation for the first time. The thermal stability of the polyimide fibers containing the intrinsic carboxyl groups(PIC fibers) was studied, and the temperature of the decarboxylation-crosslinking reaction was determined to be 450 ℃. The PIC fibers were hotdrawn to initiate thermal crosslinking of the carboxyl groups and molecular chain orientation at high temperature. The CPI fibers had high tensile strengths(0.72-1.46 GPa) and compressive strengths(401-604 MPa). The oriented macromolecules and chemically crosslinked structure improved the tightness of the molecular chains and endowed the CPI fibers with excellent hydrolytic resistance. The CPI-50 fiber did not dissolve in a 0.5 wt% NaOH solution during heating at 90 ℃ for 10 h, and the tensile strength retention reached 87% when treated in 0.5 wt% NaOH solutions at 90 ℃ for 1 h, providing a guarantee for its application in alkaline corrosive environments.
基金supported by the 2019 Foshan Science and Technology Innovation Team(No.1920001000108)Guangdong Basic and Applied Basic Research Foundation(No.2021A1515111103)+2 种基金Guangzhou Science and Technology Plan Project(No.202201010867)Science and Technology Major Project of Guangdong Province(No.220110165851234)the National Key R&D Program of China(No.2020YFB0408100).
文摘Metallic copper is widely used as current collector(CC) for graphite anode of lithium-ion batteries(LIBs) due to its high electrical conductivity and electrochemical stability. However, the large volume density of commercial copper foil(~8.9 g·cm^(-3)) limits the increase of energy density of battery. Here, copper-coated porous polyimide(Cu@PPI) was prepared by vacuum evaporation as collector for the graphite anode. The sandwich structure connects the copper metal on both sides of the collector with excellent electrical conductivity. Compared to commercial Cu foil, Cu@PPI has lighter mass(≤3.9 mg for disc of 12 mm diameter versus 9.9 mg of ~10 μm Cu foil) and lower volume density(≤3.3 g·cm^(-3)). In addition, the porous structure allows of better adhesion of reactive substances and electrochemical properties than pure Cu foils. It is estimated that the energy density of Cu@PPI should be much higher than that of Cu foil. This strategy should be applicable for other current collectors.
基金financial support from National Key Research and Development Program(Nos.2021YFA0717900,2022YFE0124200)National Natural Science Foundation of China(Nos.62004138,52273190,61905121,U2241221)Haihe Laboratory of Sustainable Chemical Transformations.
文摘The compatibility of the gate dielectrics with semiconductors is vital for constructing efficient conducting channel for high charge transport.However,it is still a highly challenging mission to clearly clarify the relationship between the dielectric layers and the chemical structure of semiconductors,especially vacuum-deposited small molecules.Here,interfacial molecular screening of polyimide(Kapton)dielectric in organic field-effect transistors(OFETs)is comprehensively studied.It is found that the semiconducting small molecules with alkyl side chains prefer to form a high-quality charge transport layer on polyimide(PI)dielectrics compared with the molecules without alkyl side chains.On this basis,the fabricated transistors could reach the mobility of 1.2 cm^(2) V^(−1)s^(−1) the molecule with alkyl side chains on bare PI dielectric.What is more,the compatible semiconductor and dielectric would further produce a low activation energy(E_(A))of 3.01 meV towards efficient charge transport even at low temperature(e.g.,100 K,0.9 cm^(2) V^(−1)s^(−1)).Our research provides a guiding scheme for the construction of high-performance thin-film field-effect transistors based on PI dielectric layer at room and low temperatures.
基金funded by Guangdong Basic and Applied Basic Research Foundation(No.2023A1515011388)Guangzhou City Industrial Science&Technology Projects(No.202201010059)+2 种基金the fund from Guangxi China Tobacco Industry Co.,Ltd.(No.2022450000340057)the fund for the construction of Bengbu-SCUT Research Center for Advanced Manufacturing of Biomaterials(No.20210190)The National Key Research and Development Program of China(No.2018YFC1902102)。
文摘Accurate detection of uric acid(UA)is crucial for diagnosing gout,yet traditional sweat-based UA sensors continue to face challenges posed by complex and costly electrode fabrication methods,as well as weakly hydrophilic substrates.Here,we designed and developed simple,low-cost,and hydrophilic sweat UA detection sensors constructed by carbon electrodes and cellulose paper substrates.The carbon electrodes were made by carbonized polyimide films through a simple,one-step laser engraving method.Our electrodes are porous,possess a large specific surface area,and are flexible and conductive.The substrates were composed of highly hydrophilic cellulose paper that can effectively collect,store,and transport sweat.The constructed electrodes demonstrate high sensitivity of 0.4μA Lμmol^(-1)cm^(-2),wide linear range of 2–100μmol/L.In addition,our electrodes demonstrate high selectivity,excellent reproducibility,high flexibility,and outstanding stability against mechanical bending,temperature variations,and extended storage periods.Furthermore,our sensors have been proven to provide reliable results when detecting UA levels in real sweat and on real human skin.We envision that these sensors hold enormous potential for use in the prognosis,diagnosis,and treatment of gout.
