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Upgrading the available dielectric materials is the most effective approach to solve the poor quality of signal transmission and heat buildup caused by high density integration. In this work, a design strategy for multilayer 3D porous composite networks is proposed, relying on the self‐assembly effect of “crystal‐like phase” to achieve the synergistic optimization of low permittivity and high thermal conductivity of polyimide. The obtained three‐layer porous polyimide composite film (PSLS) features an ultralow permittivity of 1.89, an in‐plane thermal conductivity as high as 13.58 W m−1 K−1, and maintains well electrical insulating property. Inspiringly, the first digital thermoacoustic generator with wide frequency response has been designed based on PSLS film. It achieves sound pressure levels up to 60.1 dB in the 20–100 kHz range and integrates the efficient sound generation of an ultrasonic generator with real‐time display. This work will provide a novel concept material for the smart electronics and electrical fields. [ABSTRACT FROM AUTHOR]

Highlights The Stirling engine is a high‐efficiency externally heating piston engine. The self‐lubricating properties of polytetrafluoroethylene (PTFE) are crucial for the operation of Stirling engines. Three PTFE composites filled with different contents of carbon fiber (CF), polyimide (PI) and nano‐zirconia (nano‐ZrO2) were prepared and their mechanical, friction and wear properties were investigated. The results showed that the density of CF‐containing PTFE composites was significantly reduced by 1.46% to 6.9% compared to neat PTFE. Meanwhile, the incorporation of fillers greatly enhanced the hardness by more than 21.4% over the hardness of neat PTFE. In addition, the friction coefficients of three PTFE composites were lower than those of neat PTFE, and the wear rate of these composites was three orders of magnitude lower than that of neat PTFE. In particular, the wear rate of PTFE filled with CF and PI at high pressure (2 MPa) and high velocity (4 m/s) was only 1.24 × 10–6 mm3/Nm. The wear morphology was also analyzed by scanning electron microscopy and energy‐dispersive x‐ray spectroscopy. It was found that the addition of CF and PI in PTFE has the most pronounced improvement on tribological performances. The synergistic effect of CF's mechanical reinforcement and PI's adhesive properties reduces the wear of the matrix, resulting in excellent wear resistance of PTFE composites. The compressive strength of PTFE was reinforced by CF and nano‐ZrO2. CF can lower the density and significantly enhance hardness of PTFE. Synergistic CF and PI enhance PTFE composites' friction & wear performance. Adhesive fillers & debris size key to forming uniform continuous transfer films. [ABSTRACT FROM AUTHOR]

Polyimide (PI) aerogels have attracted attention in thermal management due to their low thermal conductivity, high porosity, and robust mechanical properties. However, building PI aerogels with elaborately tailored micro‐ and macro‐ structures for optimized thermal insulation performance in specific scenarios remains a challenge. Here, a scalable approach is reported to prepare PI aerogels with controllable micro‐ and macro‐ structures by freezing‐assisted direct ink writing (FADIW) of poly(amic acid) (PAA) inks. This FADIW strategy can enable continuous ink deposition and transient low‐temperature‐induced gelation, contributing to the facile construction of spatially free geometries with structural complexity and shape fidelity. Importantly, controllable construction of microstructures of the aerogels is achieved by controlling the extrusion substrate temperature. The resulting customized PI aerogels show good thermal insulation owing to the porous microstructure and customized macrostructure, enabling good thermal management for portable electronics. In addition, this FADIW strategy is universal and allows for multi‐material integration, broadening the functionality of PI aerogels. Significantly, such FADIW approach can be promisingly applied to realize on‐demand design of PI aerogels and other polymer aerogels with targeted micro‐ and macro‐structures, offering an alternative avenue for the manufacture of customized aerogels toward widespread applications. [ABSTRACT FROM AUTHOR]

The interaction properties can be significantly improved by using conjugated polymers with aromatic rings for carbon nanotube (CNT)‐reinforced composites. In this study, we investigated the influence of the molecular structure of the polyimide (PI) conjugated polymer on the mechanical properties and interfacial characteristics of CNT/PI composites. To that end, nanocomposites composed of aligned multi‐walled carbon nanotubes (MWNTs) and PI with three different molecular structures were examined. Tensile tests, small‐angle x‐ray scattering (SAXS), and molecular dynamics (MD) simulations were conducted, which revealed significant variations in the tensile properties among the three aligned MWNT/PI nanocomposites. The SAXS analyses indicated that MWNT/BPDA‐PDA had the largest interfacial specific surface area, as corroborated by the MD simulation results, which further demonstrated that the rigidity of the molecular structure influenced the extent of wrapping the PI chains around MWNTs. A highly rigid molecular chain hindered the intrachain folding of the PI chain, facilitating better wrapping of the MWNTs and a larger interfacial area. The MWNTs induced conformational changes in the PI chain owing to π–π stacking. Hermans orientation factor revealed that BPDA‐PDA exhibited the highest degree of orientation with MWNTs, whereas BTDA‐MPD displayed the greatest extent of MWNT‐induced conformational changes. The calculated interaction energy confirmed that MWNT/BTDA‐MPD exhibited the strongest interface strength (−41.50 Kcal/mol/nm2), which was 36.32% and 43.03% higher than that of MWNT/BPDA‐ODA and MWNT/BPDA‐PDA, demonstrating its superior tensile properties. This study provides insights into the interfacial characteristics between conjugated polymers and CNTs, which are essential for designing interfaces and developing high‐performance nanocomposites. Highlights: Interfacial interaction between polyimide and aligned carbon nanotubes was investigated.Modulation by polyimide structures on the mechanical property of composite was revealed.The rigidity of the polyimide hinders the folding and facilitates the wrapping.The interfacial interaction induces molecular orientation in polyimide can be observed by molecular dynamic simulation. [ABSTRACT FROM AUTHOR]

Polyimide (PI) is widely used in high-frequency communication technology due to its exceptional comprehensive properties. However, traditional PI has a relatively elevated dielectric constant and dielectric loss. Herein, the different cross-linked structures were introduced in PI matrix and conducted a detailed discussion on the influence of cross-linking agent content and cross-linking structure type on the overall performance of PI films. In comparison to the dielectric constant of 2.9 of neat PI, PI with an interchain cross-linking structure containing 2 wt% 1,3,5-tris(4-aminophenyl)benzene (TAPB) (interchain-PI-2) exhibited the reduced dielectric constant of 2.55 at 1 MHz. The PI films with intrachain cross-linking structure containing 2 wt% TAPB (intrachain-PI-2) exhibited the lowest dielectric constant of 2.35 and the minimum dielectric loss of 0.0075 at 1 MHz. It was due to the more entanglement junctions of intrachain-PI resulting in decreased carrier transport. The thermal expansion coefficients of both interchain-PI and intrachain-PI films were effectively reduced. Moreover, in contrast to interchain-PI films, the intrachain-PI films maintained colorlessness and transparency as the cross-linking agent content increased. This work compared the effects of two different cross-linked structures on the performance of PI films and provided a feasible way to obtain low-k PI films with excellent comprehensive performance for 5G applications. [ABSTRACT FROM AUTHOR]

Electrospun nanofibrous separators, despite lacking superior mechanical strength, have gained widespread attention with high porosity and facile processing. Herein, utilizing the fact that thermal imidization temperature of poly(amic acid) (PAA) into polyimide (PI) coincides with the pre-oxidation temperature of polyacrylonitrile (PAN) into carbon fiber, we proposed a new cross-electrospinning strategy to obtain a composite nanofibrous separator (PI/oPAN) randomly interwoven by PI and pre-oxidized PAN (oPAN) nanofibers, via synchronously electrospinning the PAA and PAN onto the same collector and then heat-treating for 2 h at 300 °C. The resultant PI/oPAN separator was able to preserve high porosity (71.7%), electrolyte wettability and thermal stability of PI nanofibrous membrane, and surprisingly exhibited high mechanical strength, being 3 times of PI, which mainly because of the numerous adhesion points generated by the melting of PAN in the pre-oxidation process. Meanwhile, the polar groups of oPAN and 3D fibrous network enhanced the PI/oPAN separator's ionic conductivity and Li+ transference number, rendering the corresponding cell with more stable cycling performance than cells assembled with pure PI, PAN or commercial PP separator. Therefore, this work might provide a new avenue for the ongoing design and further development of LIB separators capable of high safety and high performance. [ABSTRACT FROM AUTHOR]

Sepsis is a life-threatening organ dysfunction caused by a disorder in the regulation of a body's response to infection. If sepsis is not recognized at an early stage and treatment is not started, it can lead to septic shock, multiple organ failure, and death. Sepsis diagnostics, traditionally based on the clinical picture and the detection of etiologically significant microorganisms in the blood and foci, has been improved in recent years through the search for and the implementation of various biomarkers. One of promising sepsis biomarkers is 3-(4-hydroxyphenyl)lactic acid (4-HPLA). In this work, an amperometric sensor modified with a molecularly imprinted polymer (MIP) of hydroxyphenyllactic acid is developed, and a fundamental possibility of determining 4-HPLA in model aqueous solutions using this sensor is demonstrated. Molecularly imprinted polymers are widely used in substance separation processes and in the fabrication of selective sensors. Among a variety of selective materials, polyimides are of particular interest. In this regard, MIP sensors with imprints of 4-hydroxyphenyllactic acid were developed based on a copolymer of 1,2,4,5-benzenetracarboxylic acid with 4,4'-diaminodiphenyl oxide. The sensors are obtained in two stages (stage I at 80°C, stage II at 180°C) using the non-covalent imprinting method. The high selectivity of the MIP sensors with respect to the target molecules was established. The analytical range of the acid is 0.0002−0.2 mg/L. The experimentally established limit of detection for 4-hydroxyphenyllactic acid is 4.5 × 10–5 mg/L. [ABSTRACT FROM AUTHOR]

Aqueous ammonium ion batteries (AIBs) have emerged as a promising next‐generation rechargeable battery due to their safety, sustainability, abundant resources, and superior electrochemical performance. However, organic anode materials, particularly polyimide anode materials, suffer from low specific capacity caused by limited active sites. Herein, the study has developed a micro‐granular‐structured π‐conjugated enhanced polyimide (PTPD) as the anode material for AIBs. The large π‐conjugated enhanced structure enables long‐range electron delocalization, decreased bandgap, and reduced spatial steric hindrance, resulting in increased active sites capable of storing NH4+ ions. PTPD exhibits reversible oxidation and reduction reaction in (NH4)2SO4 solution, delivering a high specific capacity of 206.67 mAh g−1 at a current density of 0.5 A g−1, exceptional rate capability, and excellent cycling stability with a capacity retention of 74.28% after 2500 cycles at a current density of 10 A g−1. Furthermore, theoretical simulations and materials analysis demonstrate that PTPD undergoes enol‐keto transformation of carbonyl groups, effectively capturing NH4+ to store charges. This study provides an effective strategy for designing polymer‐based AIBs anodes with high specific capacity and cycling stability. [ABSTRACT FROM AUTHOR]

The preparation of polyimide matrix composites with low curing temperature and high mechanical properties is of great importance. In this study, a low‐cost and multi‐functional nanofiller, 5‐aminobenzimidazole grafted graphene oxide (5‐ABZ@GO) has been designed. By nucleophilic attack on 5‐aminobenzimidazole basic groups and doping of GO, the above requirements of polyimide composites were skillfully realized. The results show that when the addition of 5‐ABZ@GO is 1%, the 5‐ABZ@GO/PI nanocomposites can achieve complete imidized at 200°C. Moreover, the nanocomposite prepared by imidization at 200°C has good mechanical and thermal properties (tensile strength is 141.64 MPa, modulus is 6.05 GPa, T5% is as high as 543.5°C), which is better than the PI composites prepared at 320°C. This study provides an innovative approach to preparing polyimide composites that meet mechanical performance requirements while utilizing comparatively lower curing temperatures, low curing temperature polyimide resins provide a new path for integrated composites with structure–function integration. [ABSTRACT FROM AUTHOR]

Highlights This research involved the modification of carbon fiber (CF) through electrochemical anodizing under different conditions and focused on analyzing the impact of modifying CF surface and examining the interfacial characteristics of thermoset polyimide (PI) composites. The process of electrochemically oxidizing CF consists of two distinct stages. The oxidation stage mainly occurs under the conditions of low current intensity and low electrolyte concentration, at the graphite boundary defects on CF surface. The etching effect stage intensifies on CF surface under high current intensity and electrolyte concentration, resulting in the fracture and detachment of the carbon rings. Electrochemical oxidation improves CF roughness and the quantity of active functional groups, which enhances mechanical interlocking and chemical bonding between CF and PI. Furthermore, the introduction of reactive hydrogen groups can contribute to the PI curing process, significantly improving the weak interface bonding problem between CF and PI. The interfacial shear strength (IFSS) of the composites increased from 82.08 to 104.33 MPa and 114.08 MPa in acidic and alkaline electrolyte environments, respectively. Improved interfacial compatibility between CF and polyimide resin through electrochemical oxidation The relationship between the physical morphology and chemical composition of the surface of CF and their interfacial properties was investigated. The interfacial shear strength of CF/PI was increased by 38.99% without any loss in mechanical properties of the CF. The electrochemical oxidation mechanism of CF under different electrolytes was revealed. [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]

Highlights A novel organic coating was created by dispersing solvent‐free covalent graphene oxide nanofluids (GO NFs) into a polyimide (PI) matrix. The tribological properties of GO NFs/PI composite coatings was tested against ball‐on‐disk tribometer. Even a low loading of GO NFs significantly improve the tribological properties of PI. MD simulation and nanoindentation tests reveal that GO NFs adsorbs the PI molecular chains, enhancing the composites' mechanical properties. Moreover, a stable tribofilm develops on the steel ball surface lubricated with the GO NFs/PI composite coating, with analyses indicating that the GO NFs promote its growth. The enhancement of mechanical properties and the formation of this tribofilm are essential for the improved tribological performance of the composite. This research aims to contribute to the development of novel PI composite coatings with superior anti‐friction and wear‐resistant properties. The GO NFs exhibited excellent dispersion stability and tribological properties. Novel GO NFs/PI composite coating with significantly enhanced tribological properties. A carbon‐based tribofilm forms on the steel ball. The strengthening mechanisms of composites were revealed by MD simulation. [ABSTRACT FROM AUTHOR]

Radiative cooling films (RCFs) are crucial for spacecraft thermal management, but their optical performance is currently limited by their structures and intrinsic high absorption at short wavelengths. In this study, a novel RCF using electrospun polyimide nanofibers optimized at both the molecular and microscale levels is developed. The newly designed polyimide molecules significantly decrease visible and ultraviolet (UV) light absorption while maintaining excellent thermal radiation properties in the infrared spectrum. By optimizing the diameter and orientation of the nanofibers using Monte Carlo simulations, the resulting film achieves a solar reflectivity of 99.6% and a mid‐infrared emissivity of 0.93. Its physical structures and optical properties remain stable under exposure to UV light, atomic oxygen, and extreme temperature changes. Further vacuum radiative cooling tests reveal that the thermal equilibrium temperature of this film is approximately 28 °C lower than that of Kapton‐based RCFs currently used in spacecraft. These results provide a new approach for creating efficient thermal management materials for space applications, with potential for broader use in architecture, electronic devices, and outdoor equipment. [ABSTRACT FROM AUTHOR]

Polyimide films with low dielectric loss (Df) at high frequencies are urgently needed owing to the rapid development of high‐frequency communication technologies. Herein, various polyimide films with rigid mesogenic units are prepared to address this issue. Improving molecular flexibility has been found to promote crystallization during thermal imidization and, consequently, the formation of liquid‐crystal‐like polyimide (LCPI) films. The optimal LCPI film exhibits an ultralow Df value of 0.00178 at 10 GHz owing to the limited intermolecular friction. Furthermore, this LCPI film absorbs significantly less water (0.59%), which endows it with favorable durability of low Df value in a humid environment. The Df value of the LCPI film at 10 GHz is only 0.00288 after 24 h of exposure to 60% relative humidity. In addition, the LCPI film exhibits a glass transition temperature, coefficient of thermal expansion, and tensile strength of 371 °C, 21.8 ppm K−1, and 240 MPa respectively, and is therefore a suitable low‐dielectric‐material candidate. [ABSTRACT FROM AUTHOR]

Polymer composites with heat resistance, good thermal conductivity, and insulation properties can meet the special needs of electronics and electrical appliances. In this work, graphene oxide (GO) and carbon nanotubes (CNTs) are coated by polydopamine (PDA). 4,4′‐diaminodiphenyl ether (ODA), pyromellitic dianhydride (PMDA), and 4,4′‐oxydiphthalic anhydride (ODPA) in‐situ polymerize to prepare poly(amide acid) (PAA) containing thermally conductive yet insulating fillers (PDA@GO, PDA@CNTs). As the concentration of fillers in PI composites increases, the thermal conductivity rises, but the insulation property decreases. Keeping the filler content constant and varying the ratio of PDA@GO and PDA@CNTs, the thermal conductivity increases and then decreases. When PDA@GO and PDA@CNTs have a mass ratio of 10:1, the significant synergistic effect affects the thermal conductivity. The PI/PG10C1–25 sample has a thermal conductivity of 1.46 W/(m·K), which is 6.9 times greater than the pure PI. Additionally, the volume resistivity, dielectric permittivity, and dielectric loss (100 kHz) of PI/PG10C1–25 are 2.8 × 1013 Ω cm, 5.4 and 0.28, respectively. The heat resistance of PI composites is almost the same as that of pure PI. Given these outstanding attributes, the developed PI composites offer vast applications in many fields. Highlights: Synergistic PDA@GO and PDA@CNTs (10:1) optimize thermal conductivity.PI/PG10C1–25 achieves 6.9 times higher thermal conductivity than pure PI.Volume resistivity of PI/PG10C1–25 reaches 2.8 × 1013 Ω·cm.Dielectric permittivity of PI/PG10C1–25 reaches 5.4 at 100 kHz.Developed PI composites maintain excellent heat resistance. [ABSTRACT FROM AUTHOR]

Chiral catalysts for asymmetric catalysis represent a crucial research focus in chemistry and materials science. However, a few cases about chiral‐dependent photocatalysts primarily focus on plasmonic noble metals. Particularly, developing chiral nano‐catalysts that can be driven by mechanical energy remains in the blank stage. Herein, organic polymer‐based enantiomers, chiral polar polyimide (PI) microspheric nano‐assembly are synthesized as novel bifunctional catalysts for asymmetric photocatalysis and piezocatalysis. The PI catalyst enantiomers present enantioselectivity towards left‐ and right‐circularly polarized light, demonstrating chiral‐dependent H2O2 photoproduction. Interestingly, enantioselectivity of the catalyst reverses under irradiation of different bands, presenting tunability in the interaction between chiral catalysts and circularly polarized light. For the first time, enantioselective piezocatalytic behavior is demonstrated by the chiral polar PI catalysts. They show remarkable chiral preference for asymmetric Diels–Alder reaction and enantioselective conversion of tyrosine substrates under ultrasonic vibration. The findings provide a new perspective into exploring metal‐free chiral catalysts and their asymmetric catalysis applications across multiple energy forms. [ABSTRACT FROM AUTHOR]

Biogas is a type of biomass energy source, primarily composed of methane and carbon dioxide. It is generated through the controlled anaerobic digestion of manure or other organic residues. As a cleaner alternative to conventional fuels, fully purified biogas can produce approximately 36.68 MJ/m3 of en.ergy. As the separation of CO2/CH4 in biogas became an important part of the energy industry, we used membrane separation technique to study its separation methods. At first, 3,3′‐dihydroxy‐4,4′‐diamino‐biphenyl (HAB) and 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) were polymerized by open‐loop as polyamide acid macromolecules. Then it was divided into two research routes. One was condensation to polyimide (PI) membranes directly and then thermal rearrangement (TR); the other one was ionic liquid (IL) added before condensation and thermal rearrangement. Through adjusting the thermal rearrangement temperature, different modified polyimide membranes were obtained and tested their separation performance of CO2/CH4. For the result of the test, the best one, membrane HAB‐6FDA‐IL‐TR400, could reach a good separation performance as PCO2 = 403.80 Barrer, αCO2/CH4 = 82.35. It was beyond the Robeson's 2019 upper limit and proved that the modification by IL and thermal rearrangement was benefit for the separation performance of polyimide membranes. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive experimental project in polymer chemistry, centered on polyimide aerogels. The project encompasses the synthesis, structural characterization, mechanical property evaluation, and molecular dynamics simulations of aerogels. Emphasis is placed on the application of interdisciplinary knowledge and innovative experimental design. The educational framework adheres to an "Inspiration-Design-Experiment-Insight" research exploration model. This model begins by igniting students' interest in research, progresses through the design of experimental plans, proceeds to the execution of experimental procedures, and culminates in the analysis of results and the derivation of insights. The objective is to incrementally deepen students' understanding of chemistry and polymer science, foster innovation and research interest, and develop scientific thinking and literacy. [ABSTRACT FROM AUTHOR]

3, 3 5, 4, 4 5 -Biphenyltetracarboxylic dianhydride is a precursor of high・per£ormance material polyimide. This article adopts the method of Grignard reagent coupling to study the synthesis of 3, 3 ', 4, 4 J -biphenyl tetracarb oxy lie dianhydride ・ Firstly, 4 ・brom o・o-xylene reacted w 让h magnesium metal to prepare Grignard reagent・ Secondly, under the action of ferric trifluoromethanesulfonate, the Grignard reagent self-coupled to produce 3, 3 ', 4, 4' -tetramethyl biphenyl, which was oxidized and then dehydrated to ob・ tain 3, 3 '-biphenyl tetracarboxylic dianhydride・ The effects of key factors of the experiments were examined, the optimal reaction conditions of coupling were determined・ The reaction mechanism has been analyzed ・ The results showed that the coupling reaction temperature was 60 °C and the reaction time was 8 h, the yield of 3, 3 ', 4, 4 '・tetramethylbiphenyl reached 83% ・ The yield of 3, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride was 78% ・ Mechanism analysis shows that Grignard reagent undergoes self coupling reaction with iron catalyst and 1, 2-dichloroethane to prepare 3, 3', 4, 4' -tetramethylbiphenyl. [ABSTRACT FROM AUTHOR]

Inspired by nepenthes pitcher plants, the slippery liquid-infused porous surfaces have received extensive attention. In its practical application, good oil storage and oil-locking ability are important guarantee for the surface to maintain the interface performance for a long time. In this paper, mesoporous silica (KCC-1) was obtained by cetyltrimethylammonium bromide (CTAB) as template agent, urea as a hydrolyzing agent, and TEOS as silicon source reagent, then modified with (3-Aminopropyl) trimethoxysilane. Then combined with the breath figures, amino-modified mesoporous silica, 3,3'-4,4'-biphenyltetracarboxylic dianhydride (S-BPDA), 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP) were used as raw materials to prepare polyimide SLIPS with good stability by a two-step method. The wettability and stability of SLIPS were investigated, and the results show that the introduction of mesoporous silica inorganic nanoparticles enhanced the performance of SLIPS. Among them, the sliding angle of polyimide SLIPS with a nanoparticle content of 10% is 2°, which has good self-cleaning performance, antifouling performance, and stability. [ABSTRACT FROM AUTHOR]

Transparent and light films with high electrical conductivity are preferred for flexible electronic applications. Here, a film exhibiting high transparency, electrical conductivity, and flexibility is produced using a polyimide (PI) substrate and multiwalled carbon nanotubes (MWCNTs) through spray coating. Cost‐effective MWCNTs are used instead of other electrically conductive materials, including silver nanowire ink, single‐walled carbon nanotubes (SWCNTs), and other carbon materials. The average sheet resistance of the prepared MWCNT–PI film is 520.2 Ω □−1 (infinite for the bare PI film), which is lower than the sheet resistances of the SWCNT–PI film reported by another group. This can be attributed to the increase in electrical conductivity of the highly transparent PI film due to the use of MWCNTs. The transparency of the MWCNT–PI film is 71.834% at 550 nm. When MWCNTs and PI are combined, MWCNTs protrude from the surface of the PI film, creating networks and increasing electrical conductivity. Atomic force microscopy analysis reveals that MWCNT networks form on the surface of the MWCNT–PI film. This study suggests the possibility that MWCNTs can also be used as carbon materials for flexible and highly transparent films. [ABSTRACT FROM AUTHOR]

Optically transparent polyimide (PI) films with good atomic oxygen (AO) resistance have been paid extensive attention as thermal controls, optical substrates for solar cells or other components for low Earth orbit (LEO) space applications. However, for common PI films, it is usually quite difficult to achieve both high optical transparency and AO resistance and maintain the intrinsic thermal stability of the PI films at the same time. In the current work, we aimed to achieve the target by using the copolymerization methodology using the fluorinated dianhydride 9,9-bis(trifluoromethyl)xanthene-2,3,6,7-tetracarboxylic dianhydride (6FCDA), the fluorinated diamine 2,2-bis [4-(4-aminophenoxy)phenyl]hexafluoropropane (BDAF) and the polyhedral oligomeric silsesquioxane (POSS)-containing diamine N-[(heptaisobutyl-POSS)propyl]-3,5-diaminobenzamide (DABA-POSS) as the starting materials. The fluoro-containing monomers were used to endow the PI films with good optical and thermal properties, while the silicon-containing monomer was used to improve the AO resistance of the afforded PI films. Thus, the 6FCDA-based PI copolymers, including 6FCPI-1, 6FCPI-2 and 6FCPI-3, were prepared using a two-step chemical imidization procedure, respectively. For comparison, the analogous PIs, including 6FPI-1, 6FPI-2 and 6FPI-3, were correspondingly developed according to the same procedure except that 6FCDA was replaced by 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA). Two referenced PI homopolymers were prepared from BDAF and 6FDA (PI-ref1) and 6FCDA (PI-ref2), respectively. The experimental results indicated that a good balance among thermal stability, optical transparency, and AO resistance was achieved by the 6FCDA-PI films. For example, the 6FCDA-PI films exhibited good thermal stability with glass transition temperatures (Tg) up to 297.3 °C, good optical transparency with an optical transmittance at a wavelength of 450 nm (T450) higher than 62% and good AO resistance with the erosion yield (Ey) as low as 1.7 × 10−25 cm3/atom at an AO irradiation fluence of 5.0 × 1020 atoms/cm2. The developed 6FCDA-PI films might find various applications in aerospace as solar sails, thermal control blankets, optical components and other functional materials. [ABSTRACT FROM AUTHOR]

Vitrimers, possessing associative covalent adaptable networks, are cross‐linked polymers exhibiting malleable (glass‐like) feature and recyclable and reprocessable (thermoplastics‐like) properties. The dynamic behaviors of vitrimer are dependent on both chain/molecular mobility (glass transition temperature, Tg) and dynamic bond‐exchanging reaction rate (topology freezing transition temperature, Tv). This work aims on probing the effect of high Tg on the stress relaxation and physical recyclability of vitrimers, employing a polyimide cross‐linked with dynamic ester bonds (Tg: 310 °C) as the example. Due to its high Tg and chain rigidity, the cross‐linked polyimide does not exhibit a high extent of stress relaxation behavior at 320 °C (10 °C above its Tg), even though the temperature is much higher than the hypothetical Tv. While raising the processing temperature to 345 °C, the cross‐linked polyimide exhibits a stress relaxation time of about 3300 s and physical malleability. Nevertheless, side reactions may occur in the recycling and reprocessing process under the harsh condition (high temperature and high pressure) to alter the thermal properties of the recycled sample. The diffusion control plays a critical role on the topography transition of a vitrimer having a high Tg. The Tg ceiling is noticeable for developments of vitrimers. [ABSTRACT FROM AUTHOR]

The performance of triboelectric polymers relies on their molecular structure. Therefore, investigating how to construct high‐performance molecular structures of triboelectric polymers becomes imperative, yet the relationship between microscopic structural parameters and triboelectric performance remains unclear. In this study, the relationship is studied between dihedral angles of adjacent conjugated planes and triboelectric performance. Various polyimide monomers are synthesized to manipulate the conjugated dihedral angles within the molecular chains. Introducing larger dihedral angles in polyimides (PIs) reduces the conjugation between molecular chains, suppressing the formation of charge transfer complexes (CTCs), and widening the energy gap between molecular orbitals. With the increase in dihedral angles, the output performance improved by 100%. The surface charge density of 335 µC·m−2 is achieved through the synergistic effect of the high charge retention capability of the PI film and the high triboelectric properties of the corona‐polarized fluorinated ethylene propylene (FEP). A large dihedral angle can form numerous deep traps and effectively prevent charge escaping while ensuring stable output. This study provides a feasible strategy for investigating the construction of high triboelectric performance molecular structures, enriching the understanding of how molecular structures influence the triboelectric properties of polymer materials and promote high‐performance fluorine‐free and environmentally friendly polymers. [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]

Hard carbon, characterized by high ion storage capacity, low operating voltage, and excellent cycling stability, is considered an ideal negative electrode material for sodium‐ion batteries. However, the high cost and low carbon yield of thermosetting precursors limit their practical application in SIBs, while low‐cost and high‐yield raw materials exhibit highly ordered carbon structures and narrow interlayer spacing under high‐temperature carbonization. Discarded polyimide materials are inexpensive, which offer a high carbon yield and possess good thermal stability and thermoplasticity, with functional groups of imide rings (−CO−N−CO−) on their main chains. This study recycled and converted polyimide materials into hard carbon materials from discarded engineering plastics, investigating the influence of carbonization temperature on the degree of graphitization, interlayer spacing, and pore structure of the materials to achieve high reversible sodium storage capacity. After carbonization at 1300 °C, the polyimide material exhibited 319 mAh g−1 reversible capacity and excellent electrochemical performance (with a capacity retention of 91.92 % after 100 cycles at a 0.5 C current rate) and rate performance (up to 242.5 mAh g−1 at 2 C). This study provided a simple, high‐yield, and effective method for the reuse of discarded organic polymers, promoting the sustainable utilization of resources. [ABSTRACT FROM AUTHOR]

The growing demand for electronic devices has induced a significant requirement for high energy density capacitors. In this investigation, we introduced small groups of cyanoethyl cellulose (CEC) into a polyimide (PI) substrate to create all organic CEC/PI composite films for high energy density capacitor applications. Due to the large dipole moment in C–CN dipoles in CEC groups, the dielectric constant of the CEC/PI-5 (5% CEC) composite increased by 26.3% to 4.31. Compared to the pristine PI film at room temperature, the breakdown field of the CEC/PI-0.5 increased by 4.7% from 502.29 to 526.1 MV m−1 and the energy storage density increased by 95% to 11.70 J cm−3. Furthermore, the CEC/PI-0.5 film exhibited an energy density of 6.39 J cm−3 with the breakdown field of 400 MV m−1 at 150 °C, which is 93.05% higher in energy densities than that of the pristine PI film. Furthermore, simulation results indicate that CEC groups can introduce deep traps in the CEC/PI composite, which can inhibit charge movement in the composite and increase the breakdown field of it. In this study, it was found that by adding small amount of CEC polar group in PI film, the high temperature energy density of CEC/PI composite materials was significantly improved. This study not only makes a significant contribution to the development of high-temperature energy-density capacitors, but also pave a way by using small molecule polar polymers to improve the energy density of dielectric materials at high temperature. [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]

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]

To enhance the performance of polyimides, novel polyimides (P1, P2, P3) were synthesized through the reaction of isophthalic dianhydride with a series of furan-based diamines. The structures and properties of these polyimides (P1, P2, P3) were analyzed through molecular dynamics and quantum chemical simulation methods, including glass transition temperature, dielectric properties, free volume, and cohesive energy density. Compared with traditional polyimides, the results showed that P1, P2, and P3 exhibited a significant increase in glass transition temperature and cohesive energy density, while their dielectric properties decreased compared to traditional PI (3.4–3.6), all falling within the range of (2.5-3.0). The free volume also decreased. However, there was no significant impact on the materials' radial distribution functions at the atomic level. [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]

The thermal aging process of polyimide is simulated by reactive molecular dynamics method to simulate the property changes of plasma-modified polyimide materials after thermal cracking. By studying the generation of gas during aging, it was found that as the temperature increases, the interaction forces between molecular chains weaken, resulting in a decrease in the denseness of the material, a decrease in the modulus of elasticity, and a decrease in the ability of the material to resist external stress. At the same time, the relative dielectric constant of the polyimide material increases due to the increase of temperature, and the insulation property of the material decreases and the breakdown strength is also weakened. [ABSTRACT FROM AUTHOR]

To enhance PI films' triboelectric nanogenerator(TENG) performance , we synthesized amino-functionalized reduced graphene oxide (FRGO)/polyimide (PI) composite films via in-situ polymerization. As a charge capturer, FRGO significantly increases the film's charge density and storage capacity, offering a novel method to boost the TENG performance of PI films. [Display omitted] As a promising sustainable power source in intelligent electronics, Triboelectric Nanogenerators (TENGs) have garnered widespread interest, with various strategies explored to enhance their output performance. However, most optimization methods for triboelectric materials have focused solely on tuning chemical compositions or fabricating surface microstructures. Here, we have prepared amino-functionalized reduced graphene oxide (FRGO)/polyimide (PI) composite films (PI-FRGO) via in-situ polymerization, aimed at enhancing PI materials' nanotribological power generation performance. By varying the doping levels of amino groups and controlling the FRGO proportion during synthesis, we can explore the optimal FRGO/PI composite film ratio. At a p-Phenylenediamine: reduced Graphene Oxide (PPDA: RGO) ratio of 1:1 and an FRGO addition of 0.1 %, the output electrical performance peaks with a voltage of 58 V, a charge of 33 nC and a current of 12 μA, nearly 2 times that of a pure PI film. We have fabricated a TENG with an optimally formulated PI-FRGO composite to explore its application potential. Under a 10 MΩ external load resistance, the TENG can deliver a power density of 3.5 mW/m2 and can be powering small devices. This work presents new effective strategies to significantly enhance TENG output performance and promote their widespread application. [ABSTRACT FROM AUTHOR]

Aluminum‐doped ZnO (AZO) were successfully prepared on polyimide (PI) film using electrochemical deposition. Field emission scanning electron microscopy (FESEM) analysis revealed that as the aluminum concentration increased, the morphology of AZO nanostructures changed from pellets to nanorods. X‐ray photoelectron spectrometry (XPS) was employed to study the chemical states of undoped and Al‐doped ZnO on a polyimide substrate. The X‐ray diffraction (XRD) patterns of the PI/AZO nanostructures showed a polycrystalline wurtzite structure with a crystallographic orientation along the (002) plane. The XRD analysis also indicated that the average crystallite size decreased from 50.5 nm to 31.0 nm with increasing aluminum concentration (from 0.05 mM to 10 mM). Transmittance analysis revealed that with increasing aluminum concentration, the average optical transmittance in the visible region decreased from 90 % to 75 %. The aluminum concentration has a significant effect on the electrical properties of the samples, as shown by current‐voltage (I–V) and Hall measurements. Among the samples, the AZO/PI film prepared with 5 mM aluminum concentration exhibited the minimum electrical resistivity (4.14×10−2 Ω.cm), the highest carrier density (1.10×1021 cm−3) and the Hall mobility (5.40 cm2 V−1 s−1). We also discuss the possible mechanisms underlying these results compared to undoped ZnO films. This study contributes to the potential applications in flexible electronics and optoelectronics by demonstrating the tunability of AZO nanostructures on a flexible polyimide substrate through controlled aluminum doping. [ABSTRACT FROM AUTHOR]

The continuous upgrading of electronic technology has facilitated the integration and miniaturization of electronic and electrical equipment, as well as putting great pressure on the multifunctional demand for internal materials. Developing insulating materials with both low permittivity and high thermal conductivity has become imperative. This perspective focuses on polyimide (PI), which is the top material of the polymer material pyramid, discusses the characteristic parameters that affect its dielectric property and thermal conductivity. A series of basic schemes to regulate the dielectric/thermal properties of PI are summarized, revealing the bottlenecks and drawbacks of the current research. Future development trends of PIs featured low permittivity-high thermal conductivity are anticipated, and novel ideas are proposed for the development of new generation of multifunctional PIs. [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]

Highlights A fluorinated polyimide (PI‐FTD) was synthesized for preparing a thermally conductive PI matrix and composites. Additionally, surface‐treated boron nitride (BN) was incorporated into the PI‐FTD via the solution casting method to form efficient heat paths along the through‐plane direction. The resultant composite demonstrated remarkable characteristics, including an impressive through‐plane thermal conductivity of 3.6 W mK−1, a substantial tensile strength of 69.4 MPa, and excellent thermal stability. When this composite was applied to light‐emitting diodes, it effectively managed heat, reducing the operating temperature by 29°C. The PI‐FTD/BN‐OH composites can potentially improve thermal management in electronic devices. A novel fluorinated polyimide (PI‐FTD) was fabricated. Introducing CF3 functionalities in the PI‐FTD provides high thermal stability. BN‐OH reinforced the thermal and mechanical properties of the composites. The PI‐FTD/BN‐OH composites achieved excellent thermal management. [ABSTRACT FROM AUTHOR]

Metalized plastic current collectors (MPCCs) have shown potential in improving the energy density and safety of lithium‐ion batteries (LIBs). However, the poor mechanical strength, weak interfacial adhesion force, and surface metal corrosion have impeded the practical application of MPCCs. Here, an innovative engineering of MPCCs is proposed by incorporating halloysite nanotubes (HNTs) as fillers into polyimide (PI) polymer layer, which is further coated with two thin copper (Cu) layers. Because of the strong bonding between HNTs surface and the PI precursor, HNTs improve the mechanical strength of PI‐HNTs composite film, reinforce the interfacial adhesion force between the PI‐HNTs film and the coated Cu layer, and suppress the Cu corrosion by electrolyte. The prepared MPCCs exhibit a low mass density and only account about one‐fifth of the density of commercial Cu CCs. Furthermore, the PI‐HNTs‐Cu composite demonstrates significantly enhanced interfacial adhesion force doubled to 4 N cm−1 along with prolonged stability under electrolyte immersion and electrochemical reaction conditions, and delivers a high fracture strength of 125 MPa. LIBs assembled with MPCCs deliver a twice higher discharge capacity compared to battery with Cu CCs and reach a long‐term cycle capacity retention as high as 92.9% at 0.5 C after 500 cycles. [ABSTRACT FROM AUTHOR]

A novel fluorinated diamine monomer (FPMDA ) was synthesized from p-fluorobenzaldehyde and 2, 6-dimethylaniline, and then reacted with pyromellitic anhydride to obtain a fluorinated polyimide (FPI). The structures of the synthesized FPMDA diamine monomer and polyimide were characterized by FTIR, nuclear magnetic hydrogen spectroscopy, and mass spectrometry (MS) ;the thermal properties of the polyimide film were characterized using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results showed that FPI has excellent solubility in solvents such as DMF, NMP, and THF. FPI also shows good thermal stability, under nitrogen environment, with thermal decomposition temperature Td5% of 550 °C, Td10% of 580 °C, and char yield of 58.7% at 1 000 °C, its glass transition temperature is greater than 400 °C . [ABSTRACT FROM AUTHOR]

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 °C, 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 molecular 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 complicating factors, greatly different from polyimide films prepared by high temperature method. To investigate aggregation structures of films, the effect of chain rigidity and catalyst on the stacking or orientation of molecular chains was further elaborated. This work 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. [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]

In this study, 4-biphenyl-3,5-diaminobenzoate (E- m -PDA) was synthesized by three steps using 3,5-dinitrobenzoic acid as a starting material. Two series of colorless polyimides (CPIs) PI-(1a-1d) and PI-(2a-2d) were prepared by traditional two-step polycondensation of m -phenylenediamine (m -PDA) based diamines with different pendant groups (-H, CF3, COOH and biphenyl ester) with aromatic dianhydrides BPADA and 6FDA, respectively. All of the prepared CPIs exhibited high thermal stability with 5% weight loss at temperatures ranging from 428 to 539°C in nitrogen, and glass transition temperatures (T gs) ranging from 228 to 332°C. These PI films displayed a UV-vis absorption cut-off wavelength at 338–376 nm and transparency of 76%–89% at a wavelength of 450 nm. Both series of colorless PI films also showed low birefringence values of 0.0021–0.0100. In addition, the optical retardations of these CPIs were extremely low (48–220 nm), indicating low optical anisotropy of these CPI films. Colorless PI film PI-2d prepared based on E- m -PDA and 6FDA had good comprehensive properties of low birefringence (∆ n of 0.0064), high T g (319°C) and excellent transparency (T 450 of 88%). [ABSTRACT FROM AUTHOR]

2D conjugated metal–organic frameworks (2D c‐MOFs) with large pore sizes and high surface areas are advantageous for adsorbing iodine species to enhance the electrochemical performance of aqueous dual‐ion batteries (ADIBs). However, most of the reported 2D c‐MOFs feature microporous structures, with few examples exhibiting mesoporous characteristics. Herein, we developed two mesoporous 2D c‐MOFs, namely PA‐TAPA−Cu‐MOF and PA‐PyTTA−Cu‐MOF, using newly designed arylimide based multitopic catechol ligands (6OH‐PA‐TAPA and 8OH‐PA‐PyTTA). Notably, PA‐TAPA−Cu‐MOF exhibits the largest pore sizes (3.9 nm) among all reported 2D c‐MOFs. Furthermore, we demonstrated that these 2D c‐MOFs can serve as promising cathode host materials for polyiodides in ADIBs for the first time. The incorporation of triphenylamine moieties in PA‐TAPA−Cu‐MOF resulted in a higher specific capacity (423.4 mAh g−1 after 100 cycles at 1.0 A g−1) and superior cycling performance, retaining 96 % capacity over 1000 cycles at 10 A g−1 compared to PA‐PyTTA−Cu‐MOF. Our comparative analysis revealed that the increased number of N anchoring sites and larger pore size in PA‐TAPA−Cu‐MOF facilitate efficient anchoring and conversion of I3−, as supported by spectroscopic electrochemistry and density functional theory calculations. [ABSTRACT FROM AUTHOR]

2D conjugated metal–organic frameworks (2D c‐MOFs) with large pore sizes and high surface areas are advantageous for adsorbing iodine species to enhance the electrochemical performance of aqueous dual‐ion batteries (ADIBs). However, most of the reported 2D c‐MOFs feature microporous structures, with few examples exhibiting mesoporous characteristics. Herein, we developed two mesoporous 2D c‐MOFs, namely PA‐TAPA−Cu‐MOF and PA‐PyTTA−Cu‐MOF, using newly designed arylimide based multitopic catechol ligands (6OH‐PA‐TAPA and 8OH‐PA‐PyTTA). Notably, PA‐TAPA−Cu‐MOF exhibits the largest pore sizes (3.9 nm) among all reported 2D c‐MOFs. Furthermore, we demonstrated that these 2D c‐MOFs can serve as promising cathode host materials for polyiodides in ADIBs for the first time. The incorporation of triphenylamine moieties in PA‐TAPA−Cu‐MOF resulted in a higher specific capacity (423.4 mAh g−1 after 100 cycles at 1.0 A g−1) and superior cycling performance, retaining 96 % capacity over 1000 cycles at 10 A g−1 compared to PA‐PyTTA−Cu‐MOF. Our comparative analysis revealed that the increased number of N anchoring sites and larger pore size in PA‐TAPA−Cu‐MOF facilitate efficient anchoring and conversion of I3−, as supported by spectroscopic electrochemistry and density functional theory calculations. [ABSTRACT FROM AUTHOR]

Air pollution containing microorganisms poses a major hazard to human health. It is critical to develop air filters that are both highly efficient for indoor use and suitable for use in industrial settings. Developing long‐lasting electrostatic force‐assisted filtration while keeping high‐temperature resistance and antibacterial qualities is still challenging. Here, centrifugal spinning is used to fabricate fiber mats consisting of polyimide with silver incorporation (PI/Ag). The electrostatic force remained over –700 V after 330 days. The strong electrostatic effect improves the filtration efficiency, resulting in a high PM0.3 removal efficiency of 99.1% with a low‐pressure drop of 103.67 Pa. The high filtration efficiency remains above 91.3% for PM0.3 after placing it for 330 days and heating it at 280 °C. The PI/Ag fiber mats also show antimicrobial properties against the E. coli (Gram‐negative) and S. aureus (Gram‐positive) with prominent bacteriostatic zones >1.2 mm. The PI/Ag fiber mat filters are expected to have great potential for multi‐scenario air filtration. [ABSTRACT FROM AUTHOR]

Aerogels are widely used as thermal insulation materials because of their high porosity and low bulk density. However, the insulation performance of aerogels is limited to a narrow temperature range. Besides, the preparation of aerogel materials with precisely controlled and complex architectures is still challenging. Here, we report 3D printed polyimide/silica aerogel particle (PI/SAP) composite aerogels for thermal insulation in a wide range of temperature with customized applications. The printability and shape fidelity of 3D printed composite aerogels is improved by adding hydrophilic SAP as a rheology modifier. The resulting PI/SAP composite aerogel exhibits excellent flame-retardant properties and thermal insulation from −50 °C to 1300 °C. Moreover, the PI/SAP composite aerogel with customized shape can be applied for battery insulation at subzero temperatures, promising to be used as customizable and stable insulating materials in a variety of complex and extreme applications. [ABSTRACT FROM AUTHOR]

Recently, PI as high-performance polymer with high glass transition temperature have been regarded as promising matrix for high-temperature dielectric nanocomposites. As such, the review aimed to summarize the influence of nanoceramic fillers on the characteristics of polyimide-based nanocomposites for high-temperature energy storage. Herein, it is worth noting that SiO2, TiO2, AlN, and BN remain favorable reinforcement materials for improving thermal stability, breakdown strength, and energy density of PI-matrix for high-temperature energy storage. Thus, as they depict the potential properties needed in high-temperature dielectrics, the authors concluded the study with challenges/recommendations for further enhancement of PI-based nanocomposites for high-temperature energy storage. [ABSTRACT FROM AUTHOR]

Proton exchange membranes (PEMs) are the core components of fuel cells, and research has long focused on how to balance their proton conductivity and durability. In this work, a series of homogeneous blend of sulfonated polyimide (SPI) and sulfonated polyether ether ketone (SPEEK) hybrid membranes with were constructed refined with sulfonated MoS 2 (H–MoS 2) and sodium lignosulfonate (SLS). The results showed that the tensile strength of the films was enhanced by 39.4% (67.84 MPa) compared to the base film. The composite films incorporating 1 wt% H-MoS 2 and 2 wt% SLS has excellent proton conductivity, which can reach 50.24 mS/cm at 80°C and 100% humidity. The embed hybrid structure constructed by H–MoS 2 and SLS, which not only effectively solves the limitations of the proton transport channel of traditional polymer materials, but also provides abundant proton transport sites, which provides a new strategy for preparing high-performance PEM. [Display omitted] • The stability of composite films was improved by organic/inorganic co-modification • H–MoS 2 and SLS together construct a continuous proton transport channel • The tensile strength of the best composite film is up to 67.84 MPa [ABSTRACT FROM AUTHOR]

Titanium oxide (TiO2) coated polyimide has broad application prospects under extreme conditions. In order to obtain a high-quality ultra-thin TiO2 coating on polyimide by atomic layer deposition (ALD), the polyimide was activated by in situ oxygen plasma. It was found that a large number of polar oxygen functional groups, such as carboxyl, were generated on the surface of the activated polyimide, which can significantly promote the preparation of TiO2 coating by ALD. The nucleation and growth of TiO2 were studied by x-ray photoelectron spectroscopy monitoring and scanning electron microscopy observation. On the polyimide activated by oxygen plasma, the size of TiO2 nuclei decreased and the quantity of TiO2 nuclei increased, resulting in the growth of a highly uniform and dense TiO2 coating. This coating exhibited excellent resistance to atomic oxygen. When exposed to 3.5 × 1021 atom cm−2 atomic oxygen flux, the erosion yield of the polyimide coated with 100 ALD cycles of TiO2 was as low as 3.0 × 10−25 cm3/atom, which is one order less than that of the standard POLYIMIDE-ref Kapton® film. [ABSTRACT FROM AUTHOR]

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]