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Description: A multi-layer wrinkled structure of MWCNTs/polyimide aerogel-based paper was prepared using a simple method. This paper exhibits excellent responsiveness, thermal stability, and mechanical properties, and can detect the movement of mechanical devices through generated responsiveness. [Display omitted] • Multilayer wrinkled structure MWCNTs/polyimide aerogel-based paper (CPs) was prepared via a single freeze-drying-thermal extrusion-thermal imidization method. • CPs can stably generate electrical responses in high-temperature environments up to 300 °C. • CPs exhibit good tensile strength (CP-1: 117.1 MPa at 25 °C) and stability (1000 cycles). • The response generated by CPs can be utilized to monitor changes in the mechanical device. In recent years, as the electronics industry has driven the development of human civilization, flexible responsive materials have become highly favored in sensing applications. However, most flexible materials are not stable under high-temperature conditions, so only a few flexible responsive materials are suitable for high-temperature and high-strength applications. In this paper, multi-walled carbon nanotubes (MWCNTs) were added as conductive material into poly(amic acid) ammonium salt (PAAS) solutions to prepare MWCNTs/polyimide aerogel-based papers (CPs) by a simple method. The introduction of MWCNTs into the ordered multilayer folded structure of the CPs provided a conductive pathway and improved their thermal stability. When the multilayer folded structure was deformed, the MWCNTs between the layers contacted each other, increasing the number of electron transport channels and providing a larger contact area for the conductive network. When the deformation was removed, the MWCNTs in the interlayer contact zone rapidly separated, providing stable and excellent responsiveness at high temperatures (CP-2: ΔR/R 0 value of up to −0.45 at 300 °C) and favorable stability after 1000 cycles (CP-2: RV retention of 92.4 % at 25 °C and 80.5 % at 300 °C). Therefore, the prepared CPs have great application prospects in the fields of high-temperature mechanical device monitoring, sensing, and alarms. [ABSTRACT FROM AUTHOR]

The irreversible threshold voltage (Vth) shift by polyimide (PI) charging is experimentally demonstrated. The Vth of device without PI electrode is positively moved during the release. Interestingly, the shifted Vth is not recovered to initial value up to one month. The mechanism for the irreversibility is suggested. [ABSTRACT FROM AUTHOR]

This paper introduces a novel, cost-effective solution designed to achieve large absorption bandwidth within the THz spectrum employing a miniaturized, single-layer metamaterial structure. The designed structure features a single circular ring composed of an ohmic resistive sheet with notably higher sheet resistance than traditional metallic resonators. This distinctive design is implemented on a lossy dielectric polyimide substrate with a backing of metallic gold. Our developed absorbing structure demonstrates the capability to achieve a substantial absorption bandwidth ranging from 3.78 to 4.25 THz, maintaining a consistent absorption rate of over 90%. Moreover, we conducted an analysis to assess its absorption performance under various sheet resistance values within the top layer. Additionally, we characterized its angular stability and polarization insensitivity through oblique incident and polarization angle analysis. Finally, an RLC circuital and interference theory approach is adopted to justify its simulated results. The proposed absorber shows potential for a broad spectrum of applications, encompassing communication, imaging, and diverse integrated circuits operating within the THz band. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Silicon carbide (SiC) is a wide-band gap semiconductor that exceeds other semiconducting materials (except diamond) in electrical, mechanical, chemical, and radiation stability. In this paper, we report a novel approach to fabrication of SiC nano films on a Si substrate, which is based on the endotaxial growth of a SiC crystalline phase in a graphite-like carbon (GLC) matrix. GLC films were formed by carbonization of rigid rod polyimide (PI) Langmuir–Blodgett (LB) films on a Si substrate at 1000 °C in vacuum. After rapid thermal annealing of GLC films at 1100 °C and 1200 °C, new types of heterostructures SiC(10 nm)/GLC(20 nm)/Si(111) and SiC(20 nm)/GLC(15 nm)/SiC(10 nm)/Si(111) were obtained. The SiC top layer was formed due to the Si-containing gas phase present above the surface of GLC film. An advantage of the proposed method of endotaxy is that the SiC crystalline phase is formed within the volume of the GLC film of a thickness predetermined by using PI LB films with different numbers of monolayers for carbonization. This approach allows growing SiC layers close to the 2D state, which is promising for optoelectronics, photovoltaics, spintronics. [ABSTRACT FROM AUTHOR]

This paper investigates the properties of 100-nm ZnO thin films prepared by radio frequency (RF) sputtering technique on polyethylene terephthalate (PET) and polyimide (PI) plastic substrates using X-ray diffraction (XRD) patterns to show the proper formation of hexagonal ZnO (002) structure, with ZnO on PET plastic substrate recording higher peak and FWHM compared to ZnO on PI plastic substrate. AFM reveals smooth surface morphologies on both substrates with a root-mean-square (RMS) roughness of below 10 nm. Optical transmittance measures values exceeding 80% in the visible and infrared (IR) regions on each substrate. ZnO on PET records 3.33 eV, and ZnO on PI measures 3.35 eV of optical band gap (Eg) from the Tauc plot. The photoelectrochemical cell (PEC) parameter measurement study shows that ZnO thin films on PET and PI plastic substrates have efficiencies (η = 0.93) and (η = 0.88), respectively. [ABSTRACT FROM AUTHOR]

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the policy tilt and increased investment in research and development in the world, new energy vehicle technology continues to progress and the drive motor power density continues to improve, which puts forward higher requirements for the comprehensive performance of the core insulating material enameled wire enamel for drive motors. Polyimide (PI) has excellent electrical insulation properties, and heat resistance is often used to drive the motor winding insulation. To further improve the corona resistance and insulating properties of PI wire enamel varnish, in this paper, firstly, fluorene groups with a rigid conjugated structure were introduced into the molecular chain of the PI film by molecular structure modulation, and then uniformly dispersed alumina nanoclusters (AOCs) were introduced into the PI matrix by using an in situ growth process to inhibit the migration of high-energy electrons. The quantum size effect of the alumina nanoclusters was exploited to synergistically enhance the suppression and scattering of energetic moving electrons by PI-based composite films. The results show that the breakdown field strength of the PI-based composite film (MPI/1.0 vol% AOC) reaches 672.2 kV/mm, and the corona resistance life reaches 7.9 min, which are, respectively, 1.55 and 2.19 times higher than those of the initial PI film. A PI-based composite film with excellent insulating and corona resistance properties was obtained. [ABSTRACT FROM AUTHOR]

Nonwoven fabrics with appropriate hydrophilicity and potent antimicrobial properties hold important promise for hygiene applications. However, existing materials with certain limitations and complex manufacturing steps, along with the unavoidable use of chemicals in the process, are limited to a certain extent in terms of the balance between comfort and antimicrobial properties. In this paper, a polyimide (PI) fiber was reported to be used for the preparation of PI composite nonwoven fabrics (5-P), which can effectively enhance the surface hydrodynamic and antimicrobial properties of the nonwoven by a one-step plasma treatment on one side. After treatment, the one-sided water contact angle (WCA) changed from 121.5° to 68.5°, and the permeation volume from 0.7 to 2.1 g, with a relative increase of 181.9%. Meanwhile, the reverse osmosis amount was only 0.5 g, achieving rapid permeation while keeping a low reverse osmosis amount. The antimicrobial experiment showed that plasma-treated 5-P exhibited 64.3% and 91.6% inhibitory properties against Escherichia coli and Staphylococcus aureus, respectively. Notably, the production process of antimicrobial 5-P was fast and efficient without the addition of any chemicals. This method has great potential for the industrial preparation of antimicrobial comfort materials on a large scale, which is competitive in the medical, sanitary materials, and personal care fields. [ABSTRACT FROM AUTHOR]

Polyimide‐based dielectric films are widely used in various thin film devices including organic field‐effect transistors (OFETs) owing to their promising thermal/chemical stability, mechanical flexibility, and insulating properties. On the other hand, considerable attention is paid to lowering the process temperature to allow coating on plastic substrates because high‐temperature annealing (≈200 °C) is usually required to convert precursors to polyimide films with those excellent properties. In addition, polyimide‐based dielectric films have low dielectric constants (k) (<4). Therefore, modifying the k properties of polyimide is a critical issue for applications as an insulating thin film for practical transistors. This paper reports a new type of polyimide‐based gate dielectric comprising methacryloyl moiety (PI‐MA) as a side chain for photo‐pattern/processability and high‐k properties. This study shows that the photocured PI‐MA thin films show excellent insulating properties (leakage current densities < 10−8 A cm⁻2 at 4 MV cm⁻1) and high‐k properties (≈8) even without a post‐annealing process. Finally, the use of PI‐MA in printed field‐effect transistors results in high performance with low‐voltage operation (within 5 V) and integrated logic‐gate devices (NOT, NAND, and NOR gates). [ABSTRACT FROM AUTHOR]

With the rapid development of flexible displays and wearable electronics, there are a substantial demand for colorless transparent polyimide (CPI) films with different properties. Traditional trial‐and‐error experimental methods are time‐consuming and costly, and density functional theory based prediction of HOMO‐LUMO gap energy also takes time and is prone to varying degrees of error. Inspired by machine learning (ML) applications in molecular and materials science, this paper proposed a data‐driven ML strategy to study the correlation between microscopic molecular mechanisms and macroscopic optical properties. Based on varying degrees of impact of various molecular features on the cutoff wavelength (λcutoff), the ML algorithm is first used to quickly and accurately predict the λcutoff of CPI. Several new CPI films are then designed and prepared based on the key molecular features, and the predicted values of their λcutoff are effectively verified within the experimental error range. The interpretability provided by the model allows to establish correlations between the nine key descriptors identified and their physicochemical meanings. The contributions are also analyzed to the transparency of polyimide films, thereby giving insight into the molecular mechanisms underlying transparency modulation for CPIs. [ABSTRACT FROM AUTHOR]

This paper introduces a novel, cost-effective solution designed to achieve large absorption bandwidth within the THz spectrum employing a miniaturized, single-layer metamaterial structure. The designed structure features a single circular ring composed of an ohmic resistive sheet with notably higher sheet resistance than traditional metallic resonators. This distinctive design is implemented on a lossy dielectric polyimide substrate with a backing of metallic gold. Our developed absorbing structure demonstrates the capability to achieve a substantial absorption bandwidth ranging from 3.78 to 4.25 THz, maintaining a consistent absorption rate of over 90%. Moreover, we conducted an analysis to assess its absorption performance under various sheet resistance values within the top layer. Additionally, we characterized its angular stability and polarization insensitivity through oblique incident and polarization angle analysis. Finally, an RLC circuital and interference theory approach is adopted to justify its simulated results. The proposed absorber shows potential for a broad spectrum of applications, encompassing communication, imaging, and diverse integrated circuits operating within the THz band. [ABSTRACT FROM AUTHOR]

In order to improve the PI resin's processability and thermal properties, a novel diamine monomer bis(p-aminophenylethynyl)dimethylsilane was designed and synthesized by introducing silicon and alkyne groups in this paper. And a new thermosetting polyimide resin SiOPI with silicon and alkynyl structures in the main chain was prepared using 4,4′-oxobis (phthalic anhydride) (ODPA) as the dianhydride monomer with this diamine monomer. The structures of the diamine monomer and the polyimide were characterized by H nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform infrared spectroscopy (FT-IR), mass spectrometry (MS), and X-ray diffraction (XRD), respectively. The incorporation of silyl groups into the PI increases the flexibility of the resin and provides good solubility and processability. The SiOPI is well soluble in DMF, DMSO and THF. The resin has a viscosity of less than 200 Pa·s at 50–88°C and has a wide processability range. By virtue of the introduction of alkyne groups, the cured polyimide forms dense reticulated structures, analogous to the benzene ring, giving the resin excellent heat resistance and mechanical property. The glass transition temperature (Tg) of SiOPI reached 367°C, and the heat loss temperature at 5% (Td5) is 540.9°C, the heat loss temperature at 10% (Td10) is 592.2°C, and the residual carbon rate at 800°C (R800°C) is 65.76% in a nitrogen atmosphere. The tensile strength of c-SiOPI is 257.6 MPa at room temperature and 232.9 MPa with a retention rate of 90.41% at 300°C, respectively. [ABSTRACT FROM AUTHOR]

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, stannous oxide (SnO) was synthesized by hydrothermal method, and then the obtained SnO was introduced into polyimide matrix by in-situ polymerization method to prepare SnO/PT composite films. The contents of SnO have significant influence on the dielectric constant, dielectric loss, tensile strength and breakdown strength of the film. When the contents of SnO was 1 Owt%, the dielectric constant of the SnO/PT composite film was as high as 456, the dielectric loss was only 0.034, the tensile strength was 65 MPa, and the breakdown strength was 146.9 MV/m, respectively. The introduction of SnO into PT could greatly improve the dielectric properties of the composite PT films, so that it has a good application prospect in energy storage, aerospace, insulation and other fields. [ABSTRACT FROM AUTHOR]

Polyimide (PI) has excellent resistance to high or low temperatures due to its unique molecular structure, and is widely used in advanced electronics and power systems in extreme environments. In recent years, a small amount of studies have been published to modulate the dynamic behavior of PI such as self‐healable, recyclable, and degradable abilities by adjusting the structure of molecular chains and the composition of monomers. However, the conceptual design, formation conditions, and application prospects of dynamic PI are still unclear. In this paper, the new concepts and systems of dynamic PI are introduced from the perspective of the design of molecular structure, the development of regulating performance area, and the application of extreme insulation, based on recent work and other representative work. Specifically, this work appeals to researchers involved in PI synthesis, smart, dielectric, energy storage, and extreme insulation. [ABSTRACT FROM AUTHOR]

• Thermal-force external coupling enhances polyimide molecular chain orientation. • Orientation modulation increases the honeycomb shear strength 10 times to 1.07 MPa. • Excellent thermal performance of polyimide aerogel honeycomb (T d5% >650 °C). • Fabricating integrated lightweight honeycomb structures using the formwork method. Lightweight honeycomb structures are widely used in applications that require high strength-to-weight ratios and low densities, including aircraft, automobiles, and various engine components. However, due to the immaturity of microstructure conditioning techniques and the fact that highly porous structures usually fracture during stretching, it is challenging to obtain both high-strength and lightweight porous structures. Herein, a newly developed multilayer interconnected polyimide aerogel-based paper honeycomb is successfully prepared based on the ice crystal reverse template method and multi-level structure regulation via chemical and physical interactions. The synergistic effect of the hot extrusion-stress strategy and the heat imidization process provides the submicron layer of the paper honeycomb wall with more orderly molecular chain stacking, excellent orientation, and an enhanced folding degree between layers. The prepared polyimide aerogel paper honeycombs have low density (approx. 8–9 kg/m3), good shear strength of 1.07 MPa (W direction) and 0.86 MPa (L direction), excellent specific compressive strength (0.38 MPa), and excellent thermal stability. These integrally molded polyimide paper honeycombs, as sandwich resin-based composite structures, provide a new versatile platform for aerospace and marine applications. [ABSTRACT FROM AUTHOR]

• This paper aims to break through the bottleneck problem that the right-angle can'tbe perfectly machined in the existing photolithography process because of the light diffraction. The tangent treatment of U-shaped corners is carried out in this paper, thus fundamentally reducing the requirement for photolithography process accuracy from the beginning of design. • The equivalent dielectric parameter of substrate can be determined by comparing the experimental data of QWP transmission characteristics with the simulation data obtained by scanning the dielectric parameters under the same design. The proposed equivalent dielectric parameter of the substrate can provide the correct dielectric parameter input for accurate simulation of subsequent designs. • This paper gives a new empirical formula for our multilayer U-shaped metamaterial to help understand the effects of unit cell size, corner tangent size, and equivalent dielectric parameter of substrate on QWP transmission characteristics in the simulation. To overcome the bottleneck problem that the right-angle of metamaterial metal unit cell can't be perfectly machined in the existing photolithography process, the tangent treatment of U-shaped corners is carried out in this paper. Using two layers of U-shaped metamaterial gold unit cell with corner design sandwiched with three polyimide layers, a flexible terahertz quarter-wave plate (QWP) with polarization conversion efficiency of 0.8 and operating bandwidth of 0.2 THz is obtained. The equivalent dielectric parameter of substrate is proposed to provide the correct dielectric parameter input of polyimide for the precise simulation. The influences of the equivalent dielectric parameter, the corner tangent length and the geometric parameters of the metamaterial metal unit cell on the QWP performance are analyzed. To better understand the effects of these parameters on the QWP performance, an empirical formula for multilayer U-shaped metamaterial is given in this paper. This work has good application potential in terahertz wireless communications, terahertz imaging, and terahertz medical diagnostic systems and other fields. [ABSTRACT FROM AUTHOR]

In this paper, two calculation methods, quantum mechanics and molecular dynamics, are used to simulate the polyimides with 12 different molecular structure models. First, a variety of structural parameters that may be related to the dielectric constant are screened out, including free volume fraction, solubility parameters, the most negative atomic net charge, etc. Then, a stepwise regression analysis model is constructed using the parameters and dielectric constant, preliminary identification of property parameters with significant correlation with dielectric constant, and in-depth analysis of the rationality, structure–activity relationship, correlation, and other aspects of the multiple linear regression model. The results indicate that the p-value is less than p = 0.000 < 0.05, and the design of the model has important practical value; There is an inherent relationship between the five structural parameters and the dielectric constant—solubility parameters are positively correlated with end distance/free volume and dielectric constant, while the net charge of the most negative atom, free volume fraction, length of side groups are negatively correlated with dielectric constant. In addition, increasing the free volume of polyimide is more effective than changing the polarity to reduce the dielectric constant of polyimide. [ABSTRACT FROM AUTHOR]

Context: Polyimide (PI) and aramid, as functional polymer materials, have significant application prospects in special fields such as fire prevention and arc resistance. Blends of materials can not only improve the physical and chemical properties of a single material, but also save costs, so in order to improve the performance of polyimide, it is of great practical importance to study the properties of PI and aramid blends. Molecular dynamics simulation results showed that the two materials are compatible. The solubility parameters of PI tend to stabilize when the polymerization degree exceeded 10; aramid-1313 and aramid-1414 tend to stabilize at polymerization degrees of 10 and 15 or more, respectively. On this basis, the binding energy, diffusion coefficient, and mechanical properties of PI/aramid-1313 and PI/aramid-1414 blends with different mass ratios were analyzed. It was found that with the continuous increase of aramid content, the binding energy of the blends continue to improve, limiting the gas molecules diffusion ability. The mechanical properties of the materials also continue to improve. The simulation results provided in this paper can provide theoretical guidance for experiments on PI blends and shorten the research time and cost. Methods: To investigate the properties of PI and aramid blends, the PI/aramid composite system models were constructed using the Amorphous Cell module in Materials Studio software. Subsequently, molecular dynamics simulations of the PI/aramid composite system were performed using the Forcite module, while the interactions between atoms and molecules were described using the COMPASS II force field. [ABSTRACT FROM AUTHOR]

Polyimide (PI) was first discovered to exhibit excellent tribological properties in alkaline environments. PI is widely used because of its low thermal expansion coefficient, excellent mechanical properties, and resistance to high and low temperatures. The high manufacturing cost of PI makes its waste recycling a hot topic. The most common way of recycling is to hydrolyze PI in strong alkaline environments (C(OH−)>2 mol/L). Therefore, the intuition is that the friction performance of PI decline in highly corrosive environments. However, this paper found a counter-intuitive phenomenon. PI exhibits excellent tribological properties in alkaline environments. This paper studied the behavior of ball-on-disk contact between ceramic ball and PI disk tribopair in an alkaline environment. Results show a very low coefficient of friction (COF, 0.013) and wear rate (1.4 × 10−6 mm3/NM) in sodium hydroxide (NaOH) solution with pH = 13 under the average Hertzian contact pressure of 60 MPa. The COF and wear rate decreased by 80% and 63.4%, respectively, compared with those in solutions with pH = 7. The worn surface was characterized to explore the tribological mechanism. NaOH reacts with PI to form a polymer containing sodium ions during the friction process. The polymer adheres to the friction surface and improves the friction performance of PI. The chemical reaction breaks the C–N–C chemical bond of PI, thereby reducing the molecular rigidity and improving the adhesion of the PI surface. This paper provides a new modification method for improving the tribological properties of PI. [Display omitted] • The tribological properties of PI in the alkaline environment with different pH values were studied. • Polyimide was first discovered to exhibit excellent tribological properties in alkaline environments. • The alkaline solution reacts with PI can effectively improve the tribological properties. [ABSTRACT FROM AUTHOR]

Piezoelectric sensors have been widely used in wearable electronic devices with improved integration, which is prone to cause electromagnetic interference (EMI) pollution and affects its operation stability. How to design the materials with integrated piezoelectric sensing and EMI shielding performance is of great significance. In this paper, the Fe 3 O 4 @PPy/PINF (FPN) composite film was prepared by depositing pyrrole (Py) on the surface of Fe 3 O 4 nanoparticles and combining it with polyimide (PI) nanofibrous membrane via vacuum-assisted suction filtration. In addition, after encapsulation with a highly soluble fluorine-containing polyimide (FPI) resin, a structurally stable FPI-Fe 3 O 4 @PPy/PINF (PFPN) composite film was obtained. The prepared PFPN composites show excellent EMI shielding effectiveness (44.58 dB) through the secondary reflection and multiple absorption effects. Remarkably, the value of the absorption coefficient A can reach 0.74, showing outstanding absorption characteristics. In addition, PFPN composite film also shows unexpected piezoelectric properties with high sensitivity of S = 0.8, short response (25 ms) and recovery (45 ms) time. Its piezoelectric output can reach 4.2 V with stable cyclic output property (>15000 times). This kind of composite film with ultra-low reflection characteristics and favorable piezoelectricity presents a wide range of potential applications in the self-powered wearable electronic fields. [ABSTRACT FROM AUTHOR]

Due to the unique ability of Keggin-type polyoxometalate (POM) to remain stable when accepting electrons to form mixed valence POM, organic-POM hybrid materials can complete multi-electron transfer while maintaining structural stability. The organic-POM hybrids photocatalysts prepared using organic materials and POM as raw materials have been developed to form new energy bands and crystal structures. This not only enhances their quantum efficiency and but also expands their visible light response range. Nevertheless, organic-POM hybrids, featuring organic amines as ligands, are prone to photoetching, impeding g-C 3 N 4 's progress in this area. In this paper, the amino group of g-C 3 N 4 was converted into imide ring by solid phase amidation method, which overcame this obstacle and converted g-C 3 N 4 into g-C 3 N 4 based polyimide (CNPI) with enhanced photoelectric properties. XRD, IR spectrum, and XPS data indicate that CNPI is more tightly integrated with potassium phosphotungstate (KPW) than g-C 3 N 4 , demonstrating superior electron transport capabilities and potentiated POM-π interactions. In terms of photocatalytic efficacy, CNPI/KPW-30 % exhibits an impressive degradation rate constant of 0.5458 h−1 for imidacloprid, attributed to its compact microstructure and superior charge transfer capability. While maintaining good photocatalytic stability, the mineralization rate of CNPI/KPW-30 % to imidacloprid was 55.25 %. In addition, h+ and ·O 2 − were identified as active species through trapping agent experiments, and the degradation pathway was advanced by ESR technology analysis. [ABSTRACT FROM AUTHOR]

In the present study, the effect of varying titanium dioxide (TiO2) nanoparticles on the dielectric, thermal, and corrosion characteristics of PI-based composites prepared by spark plasma sintering was investigated. The results obtained revealed that the TiO2 nanoparticles were uniformly dispersed within the PI matrix. Addition of TiO2 into the neat PI markedly reduced its dielectric constant and electrical conductivity by 72.7% and 82.3%, respectively, as well as enhancing its breakdown strength by 16.7% at 8 wt% TiO2 loading. The nanocomposites depict better thermal stability and heat-resistance index characteristics when compared to the PI. Additionally, the produced nanocomposites exhibit improved corrosion resistance than that of the neat PI. The remarkable improvement in the dielectric, thermal stability, and corrosion resistance of the nanocomposites is achieved by better dispersion of the TiO2 particles in the polymer matrix. The enhancement in properties suggests TiO2/PI-based nanocomposites potential for a variety of applications in electrical insulation, thermal management, and harsh environment. [ABSTRACT FROM AUTHOR]

The thermal stability and aging kinetics of polyimides have garnered significant research attention. As a newly developed class of high thermal stability polyimide, the thermal aging characteristics and degradation kinetics of phenylene-capped polyimide prepolymer (PMR350) have not yet been reported. In this article, the thermo-oxidative stability of PMR350 was investigated systematically. The thermal degradation kinetics of PMR350 resin under different atmospheres were also analyzed using the Flynn–Wall–Ozawa method, the Kissinger–Akahira–Sunose method, and the Friedman method. Thermogravimetric analysis (TGA) results revealed that the 5% thermal decomposition temperature (Td5%) of PMR350 in a nitrogen atmosphere was 29 °C higher than that in air, and the maximum thermal degradation rate was 0.0025%/°C, which is only one-seventh of that observed in air. Isothermal oxidative aging results indicated that the weight loss rate of PMR350 and the time-dependence relationship follow a first-order exponential growth function. PMR350 resin thermal decomposition reaction under air atmosphere includes one stage, with a degradation activation energy of approximately 57 kJ/mol. The reaction model g(α) fits the F2 model, and the integral form is given by g(α) = 1/(1 − α). In contrast, the thermal decomposition reaction under a nitrogen atmosphere consists of two stages, with degradation activation energies of 240 kJ/mol and 200 kJ/mol, respectively. The reaction models g(α) correspond to the A2 and D3 models, with the integral forms represented as g(α) = [−ln(1 − α)]2 and g(α) = [1 − (1 − α)1/3]2 due to the oxygen accelerating thermal degradation from multiple perspectives. Moreover, PMR350 resin maintained high hardness and modulus even after thermal aging at 350 °C for 300 h. The results indicate that the resin exhibits excellent resistance to thermal and oxygen aging. This study represents the first systematic analysis of the thermal stability characteristics of PMR350 resin, offering essential theoretical insights and data support for understanding the mechanisms of thermal stability modification in PMR350 and its engineering applications. [ABSTRACT FROM AUTHOR]

As triboelectric nanogenerator (TENG) technology continue to evolve, its application in harsh environments has increasingly captivated the interest of researchers. However, the current research on heat-resistant triboelectric materials remains predominantly focused on the development of tribo-negative materials, with scant attention given to their equally crucial tribo-positive counterparts. In this study, the tribo-positive polyimide (PI) material with enhanced tribo-positivity is developed by integrating amide groups with electron-donating effects into the molecular chain. Furthermore, the TENG devices based on this series of tribo-positive PI materials have demonstrated an open-circuit voltage (VOC) of 242 V, a short-circuit current (ISC) of 8.13 μA, and a transferred charge (QSC) of 117 nC. Notably, these devices also demonstrate the capability to efficiently generate electricity even under elevated temperature conditions. This work not only proposes a potential molecular design strategy for developing high-performance tribo-positive PI materials applicable in TENGs, but also markedly propels the advancement of robust energy-harvesting devices engineered for operation at elevated temperatures. [ABSTRACT FROM AUTHOR]

Redox-active porous organic polymers (POPs) demonstrate significant potential in supercapacitors. However, their intrinsic low electrical conductivity and stacking tendencies often lead to low utilization rates of redox-active sites within their structural units. Herein, polyimide POPs (donated as PMTA) are synthesized in situ on multi-walled carbon nanotubes (MWCNTs) from tetramino-benzoquinone (TABQ) and 1,4,5,8-naphthalene tetracarboxylic dianhydride (PMDA) monomers. The strong π–π stacking interactions drive the PMTA POPs and the MWCNTs together to form a PMTA/MWCNT composite. With the assistance of MWCNTs, the stacking issue and low conductivity of PMTA POPs are well addressed, leading to the obvious activation and enhanced utilization of the redox-active groups in the PMTA POPs. PMTA/MWCNT then achieves a high capacitance of 375.2 F g−1 at 1 A g−1 as compared to the pristine PMTA POPs (5.7 F g−1) and excellent cycling stability of 89.7% after 8000 cycles at 5 A g−1. Cyclic voltammetry (CV) and in situ Fourier-Transform Infrared (FT-IR) results reveal that the electrode reactions involve the reversible structural evolution of carbonyl groups, which are activated to provide rich pseudocapacitance. Asymmetric supercapacitors (ASCs) assembled with PMTA/MWCNTs and activated carbon (AC) offer a high energy density of 15.4 Wh kg−1 at 980.4 W kg−1 and maintain a capacitance retention of 125% after 10,000 cycles at 5 A g−1, indicating their good potential for practical applications. [ABSTRACT FROM AUTHOR]

Abstract This paper introduces a novel, cost-effective solution designed to achieve large absorption bandwidth within the THz spectrum employing a miniaturized, single-layer metamaterial structure. The designed structure features a single circular ring composed of an ohmic resistive sheet with notably higher sheet resistance than traditional metallic resonators. This distinctive design is implemented on a lossy dielectric polyimide substrate with a backing of metallic gold. Our developed absorbing structure demonstrates the capability to achieve a substantial absorption bandwidth ranging from 3.78 to 4.25 THz, maintaining a consistent absorption rate of over 90%. Moreover, we conducted an analysis to assess its absorption performance under various sheet resistance values within the top layer. Additionally, we characterized its angular stability and polarization insensitivity through oblique incident and polarization angle analysis. Finally, an RLC circuital and interference theory approach is adopted to justify its simulated results. The proposed absorber shows potential for a broad spectrum of applications, encompassing communication, imaging, and diverse integrated circuits operating within the THz band.

[Display omitted] • A laser-induced graphene was introduced on the surface of PI nanofiber membrane. • The TENG outputs were improved by the enhanced charge transfer efficiency. • The arrangement of the graphene patterns crucially impacts the charge transfer process. • The TENGs have a great potential in wearable self-powered display systems. In the realm of self-powered systems, the efficacy of triboelectric nanogenerators (TENGs) has garnered significant attention which hold promise for revolutionizing energy supply technologies. However, enhancing their output performance remains a challenge in the field. In this paper, a laser-induced graphene (LIG) pattern was introduced beneath a polyimide (PI) nanofiber membrane, serving as an efficient charge transfer layer (CTL) significantly amplifying the transfer of friction charges, thereby enhancing the charge storage capacity. The inclusion of the LIG pattern in the TENG design has resulted in a remarkable improvement in the outputs. Furthermore, the strategic arrangement of the LIG patterns crucially impacts the charge transfer process, aligned with electrostatic equilibrium principles, and resulting in a structurally stable and cost-effective CTL. When subjected to an external force, the enhanced TENG exhibited a power density sufficient to power small electronics like LED lights and calculators. Finally, wearable self-powered display systems were designed by combing the TENG based on PI nanofiber membranes with the electroluminescent fibers. It is possible to release the functional displays and real-time information transmission, providing an innovative and efficient design idea for the practical application of TENGs as the power supply of microelectronic devices. [ABSTRACT FROM AUTHOR]

The 96 laser-induced multigraphene electrode (96L-MGE) integrated microwell plate (96 L-MGE-MP) is described. Each cell includes separate working, auxiliary, and reference electrodes, and the array sits on a poly-methyl methacrylate (PMMA) well. The 96 electrochemical cells were fabricated by laser ablation of polyimide adhesive tape, which created laser-induced graphene electrodes (L-GE). The microwell was produced using laser ablation of the PMMA sheet as well. The morphology and electrochemical characterization of L-GE were controlled by tuning the laser processing. L-GE fabricated at laser power–laser speed ratios of 0.008–0.02 W s mm–1displayed good electrochemical behaviors. Under the optimal condition of L-GE fabrication, the measured L-GE surface roughness was 475.47 nm. The 96 L-MGE can be fabricated in 24.2 min and is compatible with various analytes. 10 benchmark redox compounds were shown as electrocatalytic examples. The performance of each analyte was investigated by voltammetry. As proof of concept, 96 L-MGE-MP was connected to a 96× connector for multichannel detection. The RSD of the 96 L-MGE-MPwas below 5.3%, which demonstrated good fabrication reproducibility. [Display omitted] • A novel array of 96 laser-induced graphene electrochemical cells is presented. • Each cell comprises working, auxiliary, and reference electrodes, along with a PMMA well. • Laser-induced graphene electrodes (L-GE) are fabricated by ablation on PI adhesive tape. • L-GrE had the best electrochemical properties when the laser power-to-speed ratio was 0.008–0.02 W s mm-1. • 10 benchmark redox compounds were tested using L-GE to demonstrate their applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Responses of organic and inorganic materials to vertical and oblique incidence of AO. • The method and force field presented here are suitable for studying the tensile mechanical properties of polyimide-based materials. • The erosion of AO results in a reduction of the Young's modulus of the material in relation to the Yield stress and Yield strain. This is primarily due to the formation of defects at the boundaries. KAPTON and UPILEX-S have commonly used polyimide polymers in various types of spacecraft due to their exceptional properties. However, when spacecraft equipped with these polymers travel in low Earth orbit, they become vulnerable to atomic oxygen (AO) erosion, which reduces their mechanical properties. Covering polymer surfaces with protective coatings is an effective means of preventing AO erosion. In this study, we utilized the molecular dynamics (MD) method based on reactive force field (ReaxFF) to investigate changes in KAPTON, UPILEX-S, KAPTON-PDMS coated composites, and KATPON-SiO 2 coated composites exposed to AO erosion at various incidence angles. It has been discovered that the polymers with polymer chains are susceptible to shear, resulting in the breakdown of molecular chains when subjected to oblique incidence AO, and the erosion of materials without polymer chains is mainly affected by the velocity of vertical incidence of AO. Then, we conducted uniaxial tensile simulations of KAPTON, UPILEX-S, and KAPTON-PDMS before AO erosion, and at 5 ps intervals during the erosion process. We discovered the precise mechanism by which AO erosion leads to the advancement of the material's Yield point and strain hardening stage. This paper presents a preliminary theory on AO erosion damage, which evaluates the alterations in the mechanical properties of materials following erosion. [ABSTRACT FROM AUTHOR]

Wear is the primary cause of damage to the bushing area of the Variable Stator Vane (VSV) mechanism. This paper presents an approach for predicting the wear-damage behavior of the bushing region to enhance the long-term effectiveness and safety of the VSV mechanism. The approach is based on an energy dissipation model and innovatively combines the FRIC COEF and UMESHMTION subroutines embedded in finite element software to perform wear simulations. The new approach takes into account the variation of the friction coefficient with normal load and sliding velocity and applies it to the wear simulation. The friction and wear models used in the simulations are based on the fitting of real experimental data. The simulation results are then compared with the wear results based on the Archard model. The results demonstrate that the new approach is more effective in simulating the wear of the bushing material. The study revealed that the contact stress between the upper and lower specimens decreases as wear behavior develops. Additionally, the wear on the surface disperses the distribution of the contact stress. [ABSTRACT FROM AUTHOR]

As one single membrane material could not fulfill the requests of chemical stability, mechanical strength, and resistance to pollution in practical applications. Modifications of the membrane to improve its separation performance were of great significance. In this study, UV irradiation grafting modification was employed and butyl acrylate was selected as a modification monomer for polyimide membrane to improve its lipophilicity and separation efficiency in lubricant solvent recovery. And effects of monomer concentration, irradiation distance, and grafting time on the grafting results and separation properties of modified polyimide membranes were investigated. The results exhibited that modified polyimide membranes obtained an enhanced lubricant retention rate compared with raw membranes, which increased from 66.5% to 93.1%. The industrial test for 40 days proved the great stability of modified polyimide membranes. Overall, this work confirmed the good industrial utilization potential of modified polyimide membranes and offered an effective way for lubricant solvent recovery. [ABSTRACT FROM AUTHOR]