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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]

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]

Polyethylene oxide composite electrolytes are widely used in lithium‐ion batteries because of their excellent moldability, good flexibility, and favorable chemical compatibility. However, they still suffer from low ionic conductivity and weak mechanical strength. Herein, a 3D nanofiber‐reinforced dual‐salt composite solid electrolyte (PI@PCB) is synthesized. Benefiting from the support of the porous polyimide films and the addition of lithium bis(oxalate)borate, the obtained PI@PCB electrolyte exhibits high mechanical strength, good thermal stability, excellent electrochemical stability, and a high lithium ion transference number (0.70). In addition, the assembled Li/PI@PCB/Li cell shows the lowest overpotential of 200 mV at the initial cycling stage and increases to 246 mV slightly after 1500 h. The capacity retention rate of Li/PI@PCB/LFP battery is about 88.3% after 500 cycles at 60 °C. [ABSTRACT FROM AUTHOR]

Polyimide (PI) films equipped on the surface of spacecraft are susceptible to ultraviolet damage. Herein, the performance of two kinds of polyimide films i.e. 3,3′,4,4′-biphenyl dianhydride-p-phenylenediamine (BPDA-PDA) and pyromellitic dianhydride-4,4′-oxydianiline (PMDA-ODA) under vacuum ultraviolet (VUV, 172 nm) irradiation was studied. The failure behavior of the PI films was studied by tensile tests, thermogravimetry (TGA), thermomechanical analysis (TMA), electric breakdown, UV–visible transmittance and scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to analyze the molecular structure. The results indicated that the tensile strength of BPDA-PDA PI and PMDA-ODA PI films decreased by 10.4 and 7.4% under VUV irradiation, respectively; the breakdown strength and UV-transmittance also deteriorated. Besides, the surface morphology of the PI films showed a large number of microcracks after VUV irradiation, which we ascribe to the breakage of imide rings (C-N-C) and ether bonds (C-O-C) of the PI films. However, the thermal stability (residual weight) of both PI films remained constant compared to the initial level; this can be explained by the combined effect of bond breaking and cross-linking of the polyimide films. [ABSTRACT FROM AUTHOR]

NASA seeks to develop technologies to mitigate dust accumulation from planetary surfaces on robotic and human systems hardware during planned space exploration missions. With a return to the Lunar surface, lunar dust threatens the durability and reusability of components and vehicles due to its fine, jagged morphology and highly abrasive nature. Lunar dust consists of particles less than 60 μm in size that are chemically reactive, electrostatically and sometimes magnetically charged. Unique materials and technologies that reduce or mitigate lunar dust adhesion will be critical to support long duration missions and eventual sustained presence on the lunar surface. The goal of this work was to prepare dust resistant, space durable polymer films to satisfy dust accumulation mitigation needs for future NASA missions. In this regard, several graphene coated polyimide thin films have been developed with surface resistivity properties in the range of 103 Ω/sq to 1011 Ω/sq and evaluated for their dust adhesion performance. Raman spectroscopy was used to characterize and assess the quality of graphene ink coated sheets while surface resistivity measurements were used to assess electrical conductivity. Scratch testing and abrasion resistance measurements were used to evaluate overall abrasion performance. Water contact angle and optical microscopy were used to evaluate changes in surface topography and chemistry. Graphene coated polyimide surfaces with charge dissipative resistivity (106 Ω/sq) demonstrated a minimum in residual particle areal coverage compared to conductive and insulating surfaces. Graphene ink/polymer thin film coated polyimide sheets (15 cm X 15 cm area, 75 μm thickness) are shown in order of decreasing sheet surface resistivities ranging from 103 Ω/sq, 104 Ω/sq, 106 Ω/sq, 108 Ω/sq, 1010 Ω/sq, and 1011 Ω/sq. Uncoated Kapton®, with sheet surface resistivity 1014 Ω/sq, is shown for comparison. [Display omitted] • Graphene ink coated polyimide sheets with surface resistivities in the range of 102 Ω/sq to 1012 Ω/sq have been prepared. • A significant improvement in scratch hardness (∼2 times) was observed for the coated substrates compared to the uncoated. • A minimum in residual particle areal coverage was observed for surfaces that exhibited intermediate surface resistivity values. • Dust resistant polymer films have been demonstrated for graphene coated polyimide sheets. [ABSTRACT FROM AUTHOR]

Despite the remarkable progress of perovskite solar cells (PSCs), challenges remain in terms of finding effective and viable strategies to enhance their long‐term stability while maintaining high efficiency. In this study, a new insulating and hydrophobic fluorinated polyimide (FPI: 6FDA‐6FAPB) was used as the interface layer between the perovskite layer and the hole transport layer (HTL) in PSCs. The functional groups of FPI play a pivotal role in passivating interface defects within the device. Due to its high work function, FPI demonstrates field‐effect passivation (FEP) capabilities as an interface layer, effectively mitigating non‐radiative recombination at the interface. Notably, the FPI insulating interface layer does not impede carrier transmission at the interface, which is attributed to the presence of hole tunneling effects. The optimized PSCs achieve an outstanding power conversion efficiency (PCE) of 24.61 % and demonstrate excellent stability, showcasing the efficacy of FPI in enhancing device performance and reliability. [ABSTRACT FROM AUTHOR]

Despite the remarkable progress of perovskite solar cells (PSCs), challenges remain in terms of finding effective and viable strategies to enhance their long‐term stability while maintaining high efficiency. In this study, a new insulating and hydrophobic fluorinated polyimide (FPI: 6FDA‐6FAPB) was used as the interface layer between the perovskite layer and the hole transport layer (HTL) in PSCs. The functional groups of FPI play a pivotal role in passivating interface defects within the device. Due to its high work function, FPI demonstrates field‐effect passivation (FEP) capabilities as an interface layer, effectively mitigating non‐radiative recombination at the interface. Notably, the FPI insulating interface layer does not impede carrier transmission at the interface, which is attributed to the presence of hole tunneling effects. The optimized PSCs achieve an outstanding power conversion efficiency (PCE) of 24.61 % and demonstrate excellent stability, showcasing the efficacy of FPI in enhancing device performance and reliability. [ABSTRACT FROM AUTHOR]

Attenuated total internal reflection (ATR) spectra of polyimide PI-2610 films deposited on single-crystal silicon wafers by centrifugation were studied after irradiation with 5-MeV electrons in a linear accelerator at doses of 1∙1014–2∙1015 cm–2. The strongest bands in the spectrum of the PI-2610 polyimide films were attributed to vibrations of the imide ring C–N–Cst (1349 cm–1) and aromatic ring (1517 cm–1), stretching vibrations of the imide ring C=Ostr (1700 cm–1) and CO–Cst-group C–C bonds (1074 cm-1), and bending vibrations of C–H bonds with maxima at 734 and 828 cm–1. The spectral shape and intensities of bands with maxima at 1700 and 1349 cm–1 due to C=O and C=N–Cstr vibrations were observed to change at an initial dose of 1∙1014 cm–2. It was assumed that this was due to relaxation of metastable states of these groups. The intensities of bands corresponding to asymmetric and symmetric stretching vibrations of C–H2 bonds decreased at a dose of 2∙1015 cm–2. The intensities of ATR bands due to vibrations of C=O and C–N bonds and aromatic and imide rings practically did not change. [ABSTRACT FROM AUTHOR]

Polymer materials with a low dielectric constant and low dielectric loss have the potential to be applied to high-frequency signal transmissions, such as mobile phone antennas and millimeter wave radars. Two types of diamines, 4,4′-diamino-p-tetraphenyl (DPT) and crown ether diamine (CED), were prepared for ternary copolymerization with BPDA in this study. Cross-links with molecular chains were formed, increasing molecular chain distance by utilizing rings of CED. The MPI films exhibit a good thermal performance with the increase in CED addition, with Tg > 380 °C and CTE from −4 × 10−6 K−1 to 5 × 10−6 K−1. The Young's modulus can reach 8.6 GPa, and the tensile strength is above 200 MPa when 5% and 7% CED are introduced. These MPI films exhibit good mechanical performances. The dielectric constant of PI−10% film can go as low as 3.17. Meanwhile, the relationship between dielectric properties and molecular structure has been demonstrated by Molecular Simulation (MS). PI molecules are separated by low dielectric groups, resulting in a decrease in the dielectric constant. [ABSTRACT FROM AUTHOR]

In order to prepare polymer dielectric materials with high energy storage density, a series of polyimide (PI) based Janus composite films were prepared by metal–organic frameworks (MOFs) material (UiO‐66) with high dielectric constant (ɛr) and boron nitride nanosheets (BNNSs) with high breakdown strength (Eb). As reported, the UiO‐66 can significantly improve the ɛr of the composites. The ɛr of 20 wt% UiO‐66/PI film is 10.51 at 103 Hz, which is 3.1 times that of pure PI film (3.39 at 103 Hz). However, the Eb of 20 wt% UiO‐66/PI is only 58 MV m−1, which is only 16.51% of pure PI (352 MV m−1). The sharp decline in Eb reduces the energy storage capacity of the composites. To solve this problem, first, BNNSs with an average diameter of 2 μm and a thickness of 1.36 nm (about 4–5 layer) were obtained by hydrothermal reflux stripping. BNNSs/PI//UiO‐66/PI Janus composite films with double‐layer structure were prepared by directly casting BNNSs/PI on the surface of UiO‐66/PI. For 0.3 wt% BNNSs/PI//10 wt% UiO‐66/PI, the calculated energy storage density (Ue) is 5.75 J cm−3 at 140 MV m−1, which is 3.57 times that of pure PI film (1.61 J cm−3 at 140 MV m−1). Meanwhile, the charge discharge efficiency is 82.55% (at 140 MV m−1). Highlights: BNNSs prepared by hydrothermal reflux stripping have fewer layers.BNNSs/PI composites improve the Eb of UiO‐66/PI composites by Janus structure.The Ue of BP‐0.3//UP‐10 composites with Janus structure was 5.75 J cm−3. [ABSTRACT FROM AUTHOR]

Polyimide films with molecular imprints of erythrosine and indigocarmine have been obtained. The structure and morphology of the film surfaces have been studied by scanning probe microscopy and IR spectroscopy. It has been found that the surface roughness of molecularly imprinted polymers (MIPs) increases, while the relief height amounts to 3–4 nm. The removal of template molecules leads to a redistribution of pores over sizes in the polymers with molecular imprints. The adsorption of dyes by MIP films has been carried out under static conditions. The degrees of extraction and the imprinting factors have been calculated for polymers with molecular imprints of the dyes. The high values of these parameters indicate the selectivity of MIPs to the target template molecules. [ABSTRACT FROM AUTHOR]

A versatile strategy of preparing colored polyimide (PI) films is developed by embedding colored monomers on the backbones of colorless substrate polymers. Intrinsically colored PI films of four colors—red, yellow, blue, and purple—are prepared by introducing relative chromophores to the substrate PI that are synthesized from 2,2′‐bis(trifluoromethyl)benzidine (TFMB) and 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride (6FDA)—two widely used monomers for colorless and transparent PI films. In addition, a series of orange and green PI films are prepared by simple mixing of the red, yellow, or blue PIs. The properties of these colored PI films are characterized, exhibiting good mechanical, thermal, and solubility properties, as well as different color and brightness depending on the amounts and types of chromophores. The optical properties of these films are determined by UV–vis spectroscopy and Commission Internationale de I'Eclairage (CIE) Lab. It is demonstrated that the introduction of even small amounts of chromophores can afford spectrally colored films while maintaining the original benign properties of the substrate PIs. [ABSTRACT FROM AUTHOR]

The design of high-performance polyimide (PI) films and understanding the relationship of the structure–dielectric property are of great significance in the field of the microelectronics industry, but are challenging. Herein, we describe the first work to construct a series of novel tert-butyl PI films (denoted as PI-1, PI-2, PI-3, and PI-4) based on a low-temperature polymerization strategy, which employed tetracarboxylic dianhydride (pyromellitic anhydride, 3,3′,4,4′-biphenyl tetracarboxylic anhydride, 4,4′-diphenyl ether dianhydride, and 3,3′,4,4′-benzophenone tetracarboxylic anhydride) and 4,4′-diamino-3,5-ditert butyl biphenyl ether as monomers. The results indicate that introducing tert-butyl branches in the main chain of PIs can enhance the free volume of the molecular chain and reduce the interaction between molecular chains of PI, resulting in a low dielectric constant. Particularly, the optimized PI-4 exhibits an excellent comprehensive performance with a high (5) wt% loss temperature (454 °C), tensile strength (117.40 MPa), and maximum hydrophobic angle (80.16°), and a low dielectric constant (2.90), which outperforms most of the results reported to date. [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]

Although polyimide films have a low dielectric constant, with the advent of the 5G era, the dielectric properties of the material are required to be further improved. Therein, we prepared controlled hollow mesoporous SiO2 nanomicrospheres by the hard template method to make mesoporous low dielectric polyimide films. The composite membrane exhibits better thermal stability, mechanical properties, and hydrophobicity compared to the pure membrane. Hollow mesoporous SiO2 dispersed in polyimide can reduce the inhomogeneity of charge distribution between molecules and reduce the interaction between polar chemical bonds and aromatic rings, thus improving the dielectric properties of the whole film. The minimum dielectric constant of the composite films was 2.80 when the hollow mesoporous SiO2 was added at 1.0%. These results fully indicate that the addition of hollow mesoporous SiO2 is beneficial to the multifaceted performance of the polyimide films. Highlights: Preparation of hollow mesoporous SiO2 microspheres by using different polystyrene microsphere solutions and TEOS ratios.Synthesis of composite films with different contents of hollow mesoporous SiO2 as functional fillers.The effect of hollow mesoporous SiO2 content on the mechanical properties and thermal stability of PI composite films was investigated.Addition of hollow mesoporous SiO2 reduces the dielectric constant of polyimide composite films. [ABSTRACT FROM AUTHOR]

Since compact high temperature superconducting (HTS) transformer has a small size and high efficiency, it can meet the requirements of high‐voltage transformers for vehicle‐mounted mobile substation. However, due to the small internal insulation size of the compact HTS transformers, it is necessary to improve the insulation strength to ensure the insulation safety of the transformer. Reasonable main insulation structure can greatly improve the insulation level of transformer. Based on the design theory of main insulation structure, this paper designs a main insulation structure model "small liquid nitrogen gap—barrier" suitable for compact HTS transformer. The insulation withstand voltage experiment of the main insulation structure shows that when the liquid nitrogen gap distance is less than 8 mm, the insulation strength of liquid nitrogen in the structure is improved. When the liquid nitrogen gap distance is too small, the size and thickness of the barrier will affect the insulation strength of the structure. According to the insulation strength of main insulation structures with different liquid nitrogen gaps, the feasibility of "small liquid nitrogen gap—barrier" main insulation structure is verified. The small liquid nitrogen gap structure can be adopted for the main insulation of compact HTS transformer. [ABSTRACT FROM AUTHOR]

Polyimide (PI) has been widely used in cable insulation, thermal insulation, wind power protection, and other fields due to its high chemical stability and excellent electrical insulation and mechanical properties. In this research, a modified PI composite film (MoS2@PDA/PI) was obtained by using polydopamine (PDA)-coated molybdenum disulfide (MoS2) as a filler. The low interlayer friction characteristics and high elastic modulus of MoS2 provide a theoretical basis for enhancing the flexible mechanical properties of the PI matrix. The formation of a cross-linking structure between a large number of active sites on the surface of the PDA and the PI molecular chain can effectively enhance the breakdown field strength of the film. Consequently, the tensile strength of the final sample MoS2@PDA/PI film increased by 44.7% in comparison with pure PI film, and the breakdown voltage strength reached 1.23 times that of the original film. It can be seen that the strategy of utilizing two-dimensional (2D) MoS2@PDA nanosheets filled with PI provides a new modification idea to enhance the mechanical and electrical insulation properties of PI films. [ABSTRACT FROM AUTHOR]

The development of soft photoactuators with multifunctionality and improved performance is highly important for their broad applications. Herein, we report on a facile and efficient strategy for fabricating such photoactuators with UV‐NIR dual light‐responsivity, room‐temperature 3D shape reprogrammability and reprocessability, and photothermal healability by doping polydopamine (PDA) nanoparticles into a main‐chain azobenzene semi‐crystalline poly(ester‐amide) (PEA). The PEA/PDA nanoparticle composite was readily processed into free‐standing films with enhanced mechanical and photomechanical properties compared with the blank PEA films. Its physically crosslinked uniaxially oriented films showed rapid and highly reversible photochemically induced bending/unbending under the UV/visible light irradiation at room temperature in both the air atmosphere and water. When exposed to the NIR light, they (and their bilayer films formed with a polyimide film) exhibited photothermally induced bending even at a temperature much lower than their crystalline‐to‐isotropic phase transition temperature based on a unique mechanism (involving photothermally induced polymer chain relaxation due to the disruption of their hydrogen bonds). The room‐temperature 3D shape reprogrammability and reprocessability and photothermal healability of the composite polymer films were also demonstrated. Such multifunctional dual light‐responsive photoactuators with well‐balanced mechanical robustness, actuation stability, 3D shape reprogrammability/reprocessability and photothermal healability hold much promise in various photoactuating applications. [ABSTRACT FROM AUTHOR]

Polyimide (PI) film with hydrophilic greatly limits their application in the field of microelectronic device packaging. A novel hydrophobic PI film with sag structure and improved mechanical properties is prepared relying on the reaction between anhydride‐terminated isocyanate‐based polyimide (PIY) containing a seven‐membered ring structure and the amino‐terminated polyamide acid (PAA) via multi‐hybrid strategy, this work named it as hybrid PI film and marked it as PI‐PIY‐X. PI‐PIY‐30 showed excellent hydrophobic properties, and the water contact angle could reach to 102°, which is 20% and 55% higher than simply PI film and PIY film, respectively. The water absorption is only 1.02%, with a decrease of 49% and 53% compared with PI and PIY. Due to that the degradation of seven‐membered ring and generation of carbon dioxide led to the formation of sag structure, the size of sag structures is ≈16.84 and 534.55 nm for in‐plane and out‐plane direction, which are observed on surface of PI‐PIY‐30. Meanwhile, PI‐PIY‐30 possessed improved mechanical properties, and the tensile strength is 109.08 MPa, with 5% and more than 56% higher than that of pure PI and PIY film, showing greatly application prospects in the field of integrated circuit. [ABSTRACT FROM AUTHOR]

Colorless and transparent polyimide (CPI) films with good atomic oxygen (AO) resistance and high thermal endurance are highly required in low earth orbit (LEO) space exploration. Conventional CPI films based on fluoro-containing 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) have been widely used in space applications. However, the AO erosion yields and glass transition temperatures (Tg) of the 6FDA-based CPI films have to be modified in order to meet the severe serving environments. In the current work, novel CPI films based on a multi-ring fluoro-containing 9,9-bis(trifluoromethyl)xanthene-2,3,6,7-tetracarboxylicdianhydride (6FCDA) monomer were developed. In order to enhance the AO resistance of the derived CPI film, a phosphorus-containing aromatic diamine, 2,5-bis[(4-aminophenoxy)phenyl]diphenylphosphine oxide (BADPO) was used to polymerize with the dianhydride to create the organo-soluble resin. Then, two phosphorus-containing CPI films (PPI), including PPI-1 (6FDA-BADPO) and PPI-2 (6FCDA-BADPO) were prepared by thermally curing of the PPI solutions at elevated temperatures. The PPI films maintained good optical transparency with transmittance values over 80% at a wavelength of 450 nm. PPI-2 exhibited a Tg value of 311.0 °C by differential scanning calorimetry (DSC) measurement, which was 46.7 °C higher than that of the PPI-1 counterpart (Tg = 264.3 °C). In addition, the PPI-2 film showed a coefficient of linear thermal expansion (CTE) value of 41.7 × 10−6/K in the range of 50~250 °C, which was apparently lower than that of the PPI-1 sample (CTE = 49.2 × 10−6/K). Lastly, both of the two PPI films exhibited good AO resistance with the erosion yields (Ey) of 6.99 × 10−25 cm3/atom for PPI-1 and 7.23 × 10−25 cm3/atom for PPI-2 at an exposure flux of 5.0 × 1020 atoms/cm2. The Ey values of the current PPI films were obviously lower than that of the standard polyimide (PI) film based on pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA) (Ey = 3.0 × 10−24 cm3/atom). [ABSTRACT FROM AUTHOR]

A series of uniaxially oriented polyimide (PI) films were fabricated via hot drawing at varying temperatures and draw ratios, and their orientation structure and thermal dimensional stability were investigated in detail. The infrared dichroism based on C = O symmetrical stretching was employed to effectively determine the orientation of chain segments. Other characteristic peaks, such as C = O asymmetric and C-N stretching, were highly sensitive to the geometric structure of chain segments, thereby providing a valuable means for comprehending their morphology. It has been observed that lower thermal expansion coefficient (CTE) can be achieved through low-temperature stretching, while high-temperature stretching is more effective in suppressing thermal shrinkage of the film. By quantitatively analyzing the orientation structure of infrared groups, the minimum structural unit highly associated with CTE was determined. These findings help to deepen our understanding of PI film performance and provide new ideas for studying thermal dimensional stability and draw processing. [ABSTRACT FROM AUTHOR]

This study developed a novel approach to ammonia borane (AB) and silica assembly for all-solid-state thermal dehydrogenation, which can be integrated into current hydrogen generation systems. The AB/silica assembly apparatus is created by attaching pelletized AB specimens to both sides of a polyimide film heater, thus facilitating direct heat supply. The temperature, pressure, and power consumption data of the heater demonstrate that the dehydrogenation reaction is completed within 2 min from the initiation of the electric heating signal. Notably, the temperature and pressure of the generated hydrogen gas reach 39.5 °C and 1.95 barg, respectively, and the maximum hydrogen yield reached 11.46 wt% during the experiment. The infrared spectroscopy analysis indicates that all AB/silica samples inside the assembly undergoes complete reaction. This direct heating method significantly reduces the energy required for AB thermal decomposition and it increases the amount of AB that can be used at once. • All-solid-state thermal decomposition enables generation of large amounts of H 2. • Ammonia borane (AB) and silica were used for thermal dehydrogenation. • AB/silica pellets were attached to a polyimide film heater to create the assembly. • The AB/silica assembly made it possible to facilitating direct heat supply. • The direct heating reduced the energy required for thermal dehydrogenation. [ABSTRACT FROM AUTHOR]

Polyimide films of thickness 7.5 µm are irradiated by a wide range of ions (1H to 197Au) with energies between 1.05 and 48 MeV. Irradiated samples are then chemically etched in sodium hypochlorite solution to investigate nanopore formation due to ion track etching. A threshold in terms of electronic stopping power, Set, needs to be surpassed to preferentially etch the ion tracks. Close to Set, intermittent tracks are formed where only part of the track is etchable. The fraction of these etchable parts increases as we move away from Set, toward higher stopping powers, eventually yielding continuous etchable tracks. Both intermittent and continuous track formation thresholds are observed to be velocity‐dependent, yielding a decrease of the thresholds in the present work compared to previously reported thresholds for swift heavy ions. This finding leads the authors to suggest that electrostatic ion accelerators with terminal voltages of several MV are applicable for the production of ion track membranes up to ≈10–20 µm in thickness. Suitable ions for nanopores in 7.5 µm polyimide films include 42 MeV 59Co and 48 MeV 197Au. The growth mechanism for the pores during etching is discussed, relating it to the properties of the original ion track. [ABSTRACT FROM AUTHOR]

Polyimide belongs to the class of high performance polymers containing imide functionalities in the backbone. Polyimide has wide ranging properties of optical transparency, heat stability, mechanical strength, dimensional stability, thermal conductivity, dielectric properties, etc. Fullerene is a zero dimensional hollow symmetrical nanocarbon, frequently employed as nanofiller in the polymers. Fullerene has been reinforced in the polyimide films to further augment the exclusive features and performance. This state-of-the-art review basically emphases the fundamentals, structure, properties, and applications of polyimide films, especially the films reinforced with fullerene nanofiller. The polyimide/fullerene nanocomposite films have been prepared using facile routes such as solution casting, spin casting, in situ method, and other film forming methods. Fullerene nanofiller has been filled in numerous designed polyimides. Number of experimental and theoretical studies have been performed on the high performance polymer/fullerene nanocomposite films. The structural diversity of the polymer/fullerene nanocomposite films and inimitable characteristics have led to significant applications in the optoelectronic devices, photodetectors, and sensors. [ABSTRACT FROM AUTHOR]

Neat polyimide films are known to be dense and rigid. They are therefore not suitable for use in membranes, sensors and sustainable energy storage applications. In this study, a novel technique has been used to simultaneously improve the porosity, rigidity, damping ability and impact resistance of polyimide membranes. It is demonstrated that dispersion of a small amount of polyaniline copolymer-modified clay of about 0.25–0.5 wt.% into the polyimide matrix resulted in an enhanced storage modulus while maintaining high damping ability and glass transition temperature, Tg. Novel polyimide/substituted polyaniline-copolymer-clay nanocomposite membranes containing poly(N-ethyl-aniline-co-aniline-2-sulfonic-acid)-modified-clay (SPNEAC) was successfully prepared and incorporated into the polyimide matrix to form modified clay/polyimide nanocomposites. UV-Vis analysis of the nanocomposite films shows that the optical transparency of the SPNEAC-PI nanocomposite membranes decreased with increasing SPNEAC concentration due to the high UV-Vis absorption of SPNEAC. Transmittance of about 3% was observed in the nanocomposite membrane containing 5 wt.% modified clay at 500 nm wavelength, which is significantly lower than that for the neat PI membrane of about 36%. The dispersion of SPNEAC containing a high concentration of clay (≥40 wt.% clay), in polyimide matrix, resulted in the attainment of a higher degree of imidization than was possible for the organoclay/polyimide nanocomposite. This behavior is believed to be due to the synergistic interaction between PI and SPNEAC. A correlation of the morphology and elastic modulus of the SPNEAC2/PI nanocomposites shows that at low loading of SPNEAC 2 ≤ 0.5 wt.%, the cross-sectional morphology of the composite is an open, spiky, weblike structure with a storage modulus of about 1 GPa, but it progressively evolves into densely packed microspheroids with storage moduli of ≥2 GPa at 10 wt.% SPNEAC2. The impact energy of SPNEAC/PI composites, calculated from the α-transition peak area, increased with increasing SPNEAC loading and were about 4 times that of neat PI at 10 wt.% SPNEAC. [ABSTRACT FROM AUTHOR]

An ordered micron-sized honeycombed macroporous polyimide (PI) film was efficiently fabricated from polyamic acid-b-polystyrene (PAA-b-PS) copolymer. The synergistic effect of the hydrogen bonding and π–π interaction contributes to the generation of this distinct morphology of PAA-b-PS. [ABSTRACT FROM AUTHOR]

In this work, a new diamine was designed by connecting flexible structures such as ether bond and aliphatic carbon chain between benzene rings, and was synthesized and purified through simple reactions such as Suzuki reaction. Finally, a series of polyimide (PI) films were synthesized by copolymerization with 4.4'-diaminodiphenyl ether (ODA)\pyromellitic dianhydride (PMDA) in different proportions. We prepared polyimide films with new monomer copolymerization ratios of 1% (PI-1), 5% (PI-2), 10% (PI-3), and 20% (PI-4). The polyimide films showed excellent glass transition temperatures, which were attributed to their unique bent architectures. The mechanical and thermal properties of the thermosets were studied using tensile testing, static thermomechanical analysis (TMA), and thermogravimetric analysis (TGA). As the results, the films exhibited the optimal glass transition temperatures (317.56°C–381.91°C), and the component with the highest copolymerization ratio has a 15% decrease in glass transition temperature compared to the component without copolymerization. Moreover, PI-1-PI-4 showed good heat resistance in the N2 atmosphere. The temperatures corresponding to a 5% heat loss in the films (T5%) were 458.12 °C–548.75°C, respectively. [ABSTRACT FROM AUTHOR]

The influence of the exposure time in the initial state at room temperature, which is comparable to the time of operation in orbit (5, 8, and 10 years), on the mechanical properties of polyimide films of the kapton H type of different thicknesses and manufacturers under tensile conditions at room temperature was studied. A change in all studied characteristics (forced elasticity limit, fracture stress, total deformation before fracture, contributions of individual strain components to it, modules of elasticity, and forced elasticity at individual stages of deformation) was revealed. The changes were different for amorphous and partially crystalline films, as well as for amorphous films of the same thickness, but obtained by different manufacturers. [ABSTRACT FROM AUTHOR]

Stretching has been extensively applied for decades in the production of polyimide (PI) materials with improved mechanical, electrical, and thermal properties. Meanwhile, a detailed understanding of the molecular motions during stretching is still limited. Herein, the thermomechanical behaviors of uniaxially stretched PI films prepared from 3,3′,4,4′‐biphenyl tetracarboxylic dianhydride (BPDA) and 2,2′‐bis (trifluoromethyl) benzidine (TFDB) are studied, and the possible molecular motions responsible for the sub‐glass transition temperature (Tg) stretchability and retraction after stretching are systematically investigated. Based on X‐ray diffraction and dynamic mechanical analysis, it is revealed that both the sub‐Tg stretchability and retraction correlates with β2 relaxation, which originates from the highly cooperative molecular motions of conformational rotations involving segmented BPDA units. A thermodynamic model is established and applied for the analysis of the retraction behaviors of stretched BPDA‐TFDB PI films. It is found that the increase of entropy under stretching plays a significant role in most retraction cases. However, as the stretching temperature increases, the α relaxation‐correlated large‐scale molecular motions emerge. Such motions partially counterbalance the conformational rotations of BPDA segments, leading to an enhanced contribution of enthalpy decrease during the retraction of BPDA‐TFDB PI films. [ABSTRACT FROM AUTHOR]

The molecular orientation of steroidal side chains at rubbed polyimide (PI) surfaces is studied by sum frequency generation (SFG) vibrational spectroscopy. The main objective is to find a correlation between the molecular structure of the PI film and the liquid crystal alignment on the polymer. Analysis of the SFG spectra shows that rubbing of the polymer film appears to cause conformational changes in the methyl group of the polymer side chain near the steroidal structure. However, rubbing does not significantly influence the orientation of the isopropyl group at the end of the polymer side chain. This shows that the liquid crystal alignment is not correlated with the orientation of the isopropyl group. [ABSTRACT FROM AUTHOR]

Polyimides are a group of polymers with excellent thermal and mechanical properties. However, generally, they exhibit brown coloration due to charge transfer interactions between diamine donor and dianhydride acceptor moieties. In this study, semi-alicyclic polyimides derived from cyclohexane tetracarboxylic dianhydride and 4,4′-oxydianiline were prepared using a two-step method, where the imidization step proceeded via a chemical route. The effects of the catalyst type (quinoline, triethylamine, and 1,4-diazabicyclo(2.2.2)octane (DABCO)) and reaction temperature (120, 140, and 160 °C) on the imidization process were evaluated using infrared spectroscopy and nuclear magnetic resonance spectroscopy. The prepared polyimides' thermal, mechanical, and optical properties were compared with those synthesized via standard thermal imidization. Polyimide films possessing favorable mechanical properties, thermal stability, and good optical transparency were prepared via a simple preparation route based on chemical imidization using the triethylamine catalyst at the reaction temperature of 160 °C, which was shown to be a promising way for the PI preparation on an industrial scale. [ABSTRACT FROM AUTHOR]

Herein a one-step, cost-effective, chemical-free, and versatile graphene fabrication by employing a CO2 laser is presented. A cost-effective desktop laser, compared to expensive and bulky lasers reported in the literature, is utilized for the conversion of polyimide films to graphene. Optimization of the fabrication is enabled by the examination of laser parameters such as laser power and scanning speed. Also, various 2D pattern drawings and in-situ fabrication were realized by the Laser Draw software. Furthermore, characterization experiments such as Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Raman Spectroscopy, and X-Ray Photon Spectroscopy (XPS) were performed to prove the successive graphene fabrication. [ABSTRACT FROM AUTHOR]

Proton exchange membrane (PEM) plays a relatively significant part in PEM fuel cells (PEMFCs). In this study, ionic liquid were grafted onto boron nitride (ILs@BN) were prepared by wet ball milling, and the polyimide (PI) composite films with different contents (1, 2, 3, 4, and 5 wt%) of ILs@BN were fabricated by solution‐casting method. Results showed that compared with the original polyimide films, the performance of the obtained composite films has been significantly improved. Tensile strength of film containing 4 wt% ILs@BN was enormously enhanced by 93.62% (from 47 to 91.8 MPa), respectively, in contrast to pure PI film. Compared with pure PI film, film containing with 4 wt% ILs@BN was reduced from 71.2° to 63.2°, which indicated the better hydrophilicity of the film and potential proton transport channels. The composite film exhibited excellent proton conductivity, which was tremendously elevated by 58.35% (from 0.1215 S cm−1 for pure PI to 0.1924 S cm−1 for film containing with 4 wt% ILs@BN). Comprehensively, the film containing with 4 wt% ILs@BN presenting excellent mechanical properties (91.8 MPa), contact angle (63.2°) and proton conductivity (0.1924 S cm−1) demonstrating strong potential applications in fuel cells. [ABSTRACT FROM AUTHOR]

Highlights: Flash-induced porous graphene (FPG) was synthesized via a broad-spectrum flash lamp that induced synergistic photo-effects between ultraviolet and visible-near-infrared wavelengths, resulting in large-area synthesis in just a few milliseconds. A hollow pillar graphene with low sheet resistance of 18 Ω sq−1 was produced, exhibiting low density (0.0354 g cm−3) and outstanding absolute electromagnetic interference shielding effectiveness of 1.12 × 105 dB cm2 g−1. A lightweight, flexible, and high-throughput FPG is applied for electromagnetic interference shielding of a drone radar system and the human body. Porous 2D materials with high conductivity and large surface area have been proposed for potential electromagnetic interference (EMI) shielding materials in future mobility and wearable applications to prevent signal noise, transmission inaccuracy, system malfunction, and health hazards. Here, we report on the synthesis of lightweight and flexible flash-induced porous graphene (FPG) with excellent EMI shielding performance. The broad spectrum of pulsed flashlight induces photo-chemical and photo-thermal reactions in polyimide films, forming 5 × 10 cm2-size porous graphene with a hollow pillar structure in a few milliseconds. The resulting material demonstrated low density (0.0354 g cm−3) and outstanding absolute EMI shielding effectiveness of 1.12 × 105 dB cm2 g−1. The FPG was characterized via thorough material analyses, and its mechanical durability and flexibility were confirmed by a bending cycle test. Finally, the FPG was utilized in drone and wearable applications, showing effective EMI shielding performance for internal/external EMI in a drone radar system and reducing the specific absorption rate in the human body. [ABSTRACT FROM AUTHOR]

Thin films of polyimide (PI) and graphene oxide (GO) were exposed to the accelerated Cu-ions with an energy of 1500 keV at different ion fluences (3.75 × 1012; 3.75 × 1014; 1 × 1016) cm−2. The reason for Cu-ion irradiation lies in the modification of thin PI and GO layers and their subsequent use in electronics, photo-catalysis and humidity sensing. It was expected that three ways would primarily carry out modification: i) interaction of the accelerated ions with atoms and electrons of the irradiated films, ii) implantation of Cu ions inside the matrices and their attachment to the structures in the form of CuO, and iii) formation of C and Cu aggregates and Cu nanoparticles in the subsurface layer to form an electrically conductive network. The effects of the interactions of energetic Cu-ions on the PI and GO matrices, including the prediction of the depth of Cu ion penetration, were simulated by SRIM software. Elemental changes, including the depth profiles of implanted Cu-ions, were investigated by Rutherford backscattering spectrometry (RBS) and Elastic recoil detection analysis (ERDA). Changes in the chemical bonding on the PI and GO surfaces were studied by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The effect of energetic Cu-ions on the surface morphology was analyzed by Atomic force microscopy (AFM). For the possible application of PI and GO composites in electronics and sensory, the sheet resistivity were measured by the two- point method and the effect of air humidity on electrical properties was studied. Furthermore, the degradation of Rhodamine B solution in the presence of prepared composites under UV-light irradiation was measured for possible use in photo-catalysis. It was found that the interaction of Cu- ions with the matrix leads to the release of oxygen and hydrogen, resulting in an increase in carbon concentration. The increase in carbon concentration leads to an increase in the electrical conductivity of both materials. The irradiation with Cu ion fluence of 1 × 1016 cm−2 probably formed in PI a subsurface conducting network that reduced the sheet resistivity by almost eleven orders of magnitude. The ion irradiation by Cu ion with fluences below 1 × 1016 cm−2 enhances the photo- catalytic properties of both used materials and the best result was achieved in the case of PI irradiated by the ion fluence of 3.75 × 1014 cm−2. [ABSTRACT FROM AUTHOR]

The effect of the thickness of the amorphous polymerized films of poly-4,4'-diphenylene oxide pyromellitimide on the structure after deformation by stretching at 293 K and 77 K was studied. The evolution of the macromolecular structure was concluded based on the results of the redistribution of the intensity diffraction peaks. It was established that the structure of films with a thickness of 75 μm is homogeneous and does not cardinal changes after deformation. Deformation of polymer films with a thickness of 125 μm leads to the appearance of regions with long-range order in the sample. [ABSTRACT FROM AUTHOR]

The rapid development of communication networks (5G and 6G) that rely on high-speed devices requiring fast and high-quality intra- and inter-terminal signal transmission media has led to a steady increase in the need for high-performance, low-dielectric-constant (Dk) (<2.5) materials. Consequently, low-dielectric polymeric materials, particularly polyimides (PIs), are very attractive materials that are capable of meeting the requirements of high-performance terminal devices that transmit broadband high-frequency signals. However, such a PI needs to be properly designed with appropriate properties, including a low Dk, low dielectric loss (Df), and low water absorptivity. PI materials are broadly used in various fields owing to their superior property/processibility combinations. This review summarizes the structural designs of PIs with low Dk and Df values, low water-absorbing capacity, and high optical transparency intended for communication applications. Furthermore, we characterize structure–property relationships for various PI types and finally propose structural modifications required to obtain useful values of the abovementioned parameters. [ABSTRACT FROM AUTHOR]

The ever increasing demand for high‐speed communication at high frequency promotes the rapid development of low‐dielectric polymer films. Aromatic polyimide (PI) has been widely used as the main dielectrics in the flexible circuit board due to its excellent dielectric, mechanical, and thermal properties. Nevertheless, the dielectric constant of PI films at a high frequency range (several GHz) is relatively high and cannot satisfy the requirement of high‐frequency communication. On this basis, a hyper‐crosslinked polymer (HCP) and fabricated all‐organic HCP/PI composite films through a physical blending method is synthesized. The porous structure of HCP is helpful to reduce the dielectric constant of PI matrix. The effects of HCP loadings on the dielectric, mechanical, and thermal properties of HCP/PI composite films are systematically investigated. The dielectric constants of the composite films can be reduced to 1.6–1.8 in the frequency range of 8.2–9.6 GHz when the HCP content reached 10 wt.%. The proposed method in this work is simple and effective to reduce the dielectric constant of PI and can be easily extended to other organic component‐filled PI systems. [ABSTRACT FROM AUTHOR]

With the acceleration of industrialization, the removal of refractory organic dyes from water and how to promote its practical application remains a challenge. Herein, we synthesized an FeCo-LDH/LI-NDG composite electrode material by a simple laser-induced technique on polyimide films, which could electrocatalytically activate peroxymonosulfate (PMS) to completely degrade MB in about 6 min. The reaction rate constant (kobs) was 0.461 min−1. It was faster than most of the currently reported electrocatalysts. The reaction system demonstrated good interference resistance and catalytic effectiveness in the pH range of 3 to 9. According to the chemical quenching and electron paramagnetic resonance (EPR) experiments, the non-radical pathway of 1O2 and the radical pathways of SO4·−, ·OH and O2·− were involved in the reaction synergistically, with 1O2 playing the dominant role. 1O2 was produced through the dual pathway of PMS electron loss at the anode and O2·− intermediate transformation at the cathode. The two activation methods of electro-activation and catalytic activation of PMS had synergistic effects to achieve high efficiency in the whole process of production, reaction and recovery, providing new ideas to advance practical applications. [ABSTRACT FROM AUTHOR]

In this paper, we report on novel polyimide (PI) nanocomposites filled with binary mixtures of metal oxide (either TiO2 or ZrO2) nanoparticles and nanocarbon (either carbon nanofibers (CNFs) or functionalized carbon nanotubes (CNTfs)). The structure and morphology of the materials obtained were comprehensively studied. An exhaustive investigation of their thermal and mechanical properties was performed. We revealed a synergistic effect of the nanoconstituents with regard to a number of functional characteristics of the PIs compared with single-filler nanocomposites, including thermal stability, stiffness (below and above glass transition temperature), yield point, and temperature of flowing. Moreover, the possibility of manipulating the properties of the materials by choosing a proper combination of the nanofillers was demonstrated. The results obtained can become a platform in the design of PI-based engineering materials with tailored characteristics capable of operating in extreme conditions. [ABSTRACT FROM AUTHOR]

New polymeric materials formation by controlling their properties is the primary and most challenging problem in developing a methodology for synthesizing a chosen technology and its use. The combined effect of high-energy electron radiation and tensile stress will cause a decrease in crystallinity and the breakage of chemical bonds in polyimide film macromolecules and is a new approach in their production technology. The effect of uniaxial tension and electron irradiation on the modification of polyimide film at room temperature was studied. Irradiation of the films caused an increase in the intensity of the IR spectrum by ~2–6 times and an increase in the width of the bands. The intensity in the range of 1700–3500 cm−1 increased, indicating an increase in the content of radicals as a result of irradiation. The amplitudes of the electron paramagnetic resonance signal from non-irradiated films increased from 3 × 103 to 5 × 103 as a result of uniaxial tension to fracture, indicating an increase in radicals in the material. The lines of the electron paramagnetic resonance spectrum shifted from 3475.0 cm−1 to 3512.5 cm−1, with a simultaneous decrease in the signal's amplitude from 6 ×103 to 4 × 103, as a result of the electron irradiation of the films, followed by their subjection to tension. This was due to a decrease in the concentration of the radicals of the =N-H and –N-H2 groups until their disappearance and the formation of new ones. [ABSTRACT FROM AUTHOR]

High-quality and free-standing polyimide (PI) film with desirable mechanical properties and uniformity is in high demand due to its widespread applications in highly precise flexible and chip-integrated sensors. In this study, a free-standing PI film with high toughness was successfully prepared using a diamine monomer with ether linkages. The prepared PI films exhibited significantly superior mechanical properties compared to PI films of the same molecular structure, which can be attributed to the systematic exploration of the film-forming process. The exploration of the film-forming process includes the curing procedures, film-forming substrates, and annealing treatments. Additionally, the thickness uniformity and surface homogeneity of free-standing films were crucial for toughness. Increasing the crystallinity of the PI films by eliminating residual stress also contributed to their high strength. The results demonstrate that by adjusting the above-mentioned factors, the prepared PI films possess excellent mechanical properties, with tensile strength and elongation at break of 194.71 MPa and 130.13%, respectively. [ABSTRACT FROM AUTHOR]

In this study, thermal and argon (Ar) plasma/wetting treatments were combined to enhance the bonding strength of polyimide (PI) films. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) was used to analyze the changes in the PI imidization degrees. The contact angles of the PI films were also measured. The results show that the contact angles of the fully cured PI films markedly decreased from 78.54° to 26.05° after the Ar plasma treatments. X-ray photoelectron spectroscopy (XPS) analysis was also conducted on the PI surfaces. We found that the intensities of the C-OH and C-N-H bonds increased from 0% to 13% and 29% to 57%, respectively, after Ar plasma activation. Such increases in the C-OH and C-N-H intensities could be attributed to the generation of dangling bonds and the breakage of the imide ring or polymer long chains. Shear tests were also conducted to characterize the bonding strength of the PI films, which, after being treated with the appropriate parameters of temperature, plasma power, and wetting droplets, was found to be excellent at greater than 35.3 MPa. [ABSTRACT FROM AUTHOR]

Firstly, the BaTiO3 nanoparticles were coated with a layer of paraffin, forming a core shell structure. Then, as‐prepared paraffin@BaTiO3 nanofillers were directly blended with polyimide (PI) prepolymer to fabricate paraffin@BaTiO3/PI composite films. The microstructure, thermal, and dielectric properties were investigated in detail. The surface‐modified paraffin@BaTiO3 nanoparticles exhibited a typical core shell structure with uniform and complete coverage. The char yield of the composite film with 10 wt% paraffin@BaTiO3 increased from 56.40% to 70.73%. It is obvious that the paraffin@BaTiO3 nanofillers have a positive effect on ablative performance of the composite film. Compared with pure PI, the εr of paraffin@BaTiO3/PI composites with 40% mass fraction increased from 3.41 to 9.35 (1 kHz). The tanδ of paraffin@BaTiO3/PI composites was just 0.0065 (1 kHz) when the filler loading was 40 wt%. Temperature dependency of the permittivity of the composites reveals a zero‐temperature‐coefficient from 80°C to 180°C. [ABSTRACT FROM AUTHOR]

Boron nitride nanosheet (BNNS) is widely used in electronic thermal management due to its excellent planar thermal conductivity and insulating properties. However, it is challenging to improve the out-of-plane thermal conductivity of BNNS-doped composites due to the anisotropy of the thermal conductivity of BNNS. Therefore, the BNNS in the matrix must be oriented to obtain composites with high out-of-plane thermal conductivity. In this study, BNNS powders with directional structures were synthesized directly using sodium chloride templates. The as-obtained BNNS powders have a unique hollow cube-like structure with an ultra-low density of 2.67 × 10−2 g/cm3 and nearly 8 times the volume of the same mass of two-dimensional (2D) BNNS, making it easy to form the out-of-plane thermal conductivity paths in the polymer matrix. In addition, the high out-of-plane thermal conductivity of 4.93 W m−1 K−1 at 23.3 wt% loadings was obtained by doping it into a polyimide (PI) matrix. This value is 9.7 times higher than that of 2D BNNS-doped PI at the same loadings, 17.6 times higher than pure PI, and 6.1 times higher than the thermally conductive PI film sold by DuPont. Therefore, the prepared composite film has great potential for application in electronic thermal management. [ABSTRACT FROM AUTHOR]

Polyimide (PI) films are wildly used in the field of electrical equipment and electronic devices due to their excellent thermal, electrical, and mechanical properties. The various mechanisms of sample thickness on the electrical breakdown of polyimide have been proposed. The purpose of this study is to apply the state of macromolecular aggregation to analyze the breakdown strength of PI film with different thickness. In this paper, the direct current (dc) electrical breakdown properties of PI films as a function of thickness were investigated employing water absorption, mechanical properties, thermal properties, and thermally stimulated depolarization current (TSDC). These experimental results exhibit a good coincidence with the breakdown measurement. On the condition of the structure of the polymeric molecules to the same case, the congregating state of the polymer might be the fundamental reason causing the dc electrical breakdown field of PI film with different thickness. [ABSTRACT FROM AUTHOR]

The hydrolytic stability of polyimide films (PI) in a 0.9% sodium chloride solution in the temperature range of existing biological objects was studied. The kinetic parameters of hydrolysis of PI films were calculated. It was established that the hydrolysis rate constant of an adamantane-containing film was significantly lower than that of an industrial Kapton film. The dielectric constant after hydrolysis was determined. It was shown that the dielectric properties of the adamantane-containing polymer remained unchanged under the hydrolysis conditions. [ABSTRACT FROM AUTHOR]

Two novel electrochromic aromatic polyimides (named as TPA-BIA-PI and TPA-BIB-PI, respectively) with pendent benzimidazole group were synthesized from 1,2-Diphenyl-N,N′-di-4-aminophenyl-5-amino-benzimidazole and 4-Amino-4′-aminophenyl-4″-1-phenyl-benzimidazolyl-phenyl-aniline with 4,4′-(hexafluoroisopropane) phthalic anhydride (6FDA) via two-step polymerization process, respectively. Then, polyimide films were prepared on ITO-conductive glass by electrostatic spraying, and their electrochromic properties were studied. The results showed that due to the π-π* transitions, the maximum UV–Vis absorption bands of TPA-BIA-PI and TPA-BIB-PI films were located at about 314 nm and 346 nm, respectively. A pair of reversible redox peaks of TPA-BIA-PI and TPA-BIB-PI films that were associated with noticeable color changed from original yellow to dark blue and green were observed in the cyclic voltammetry (CV) test. With increasing voltage, new absorption peaks of TPA-BIA-PI and TPA-BIB-PI films emerged at 755 nm and 762 nm, respectively. The switching/bleaching times of TPA-BIA-PI and TPA-BIB-PI films were 13 s/16 s and 13.9 s/9.5 s, respectively, showing that these polyimides can be used as novel electrochromic materials. [ABSTRACT FROM AUTHOR]

The development of novel polymer dielectrics with enhanced dielectric performance is a great challenge for application of film capacitors in modern electronics and electrical systems. Herein, an innovative approach of chemical vapor deposition polymerization technology is proposed to prepare the all‐organic sandwich structured parylene/polyimide/parylene (Py/PI/Py) composite films by employing poly(chloro‐para‐xylylene) (parylene C) as the outer layers and polyimide (PI) as the inner layer. The Py/PI/Py composites exhibit superior thermal resistance and outstanding mechanical properties. Moreover, thanks to the interfacial effect which contributes to reinforcing the dielectric response and the thickness effect which facilitates improving the breakdown strength, the dielectric performance of Py/PI/Py composites has been enhanced significantly. Accordingly, dielectric constant of 4.52–5.09, dissipation factor of 0.21–1.01%, and breakdown strength of 307–460 MV m−1 are achieved. Besides, notable energy storage performance is also obtained in Py/PI/Py composite dielectrics. Consequently, this novel application of chemical vapor deposition polymerization method in preparing all‐organic multilayered polymer composite films with sandwich structure shows promising potential in film capacitor applications in harsh conditions. [ABSTRACT FROM AUTHOR]