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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]

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 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]

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]

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]

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]

Poly(amic acid) (PAA) is prepared by the reaction of dianhydride 4,4′-biphthalic anhydride and diamine bis[4-(3-aminophenoxy)phenyl]sulfone in N,N'-dimethylacetamide. Two types of fillers were dispersed in the as-synthesized PAA via a solution intercalation method; polyimide (PI) hybrid films were synthesized under various heat treatment conditions. Octylamine (C8) was introduced into graphene sheets (C8-GS) and bentonite (C8-BTN), which were then used as nanofillers in the PI hybrid films. The synthesized nanofillers were used in varying amounts of 0.25–1.00 wt% with respect to the matrix PI. The thermal and morphological properties and optical transparency of the hybrid films were investigated and compared for both C8-GS and C8-BTN at varying nanofiller content. The C8-BTN nanocomposite showed superior thermal properties, and optical transparency, and the filler was well dispersed in the PI matrix compared to the C8-GS nanocomposite. The thermal stability of the hybrid films improved upon the addition of small amounts of the nanofiller. However, beyond a certain critical filler concentration, the thermal stability declined. These results were verified through the dispersion of fillers via transmission electron microscopy. [ABSTRACT FROM AUTHOR]

Polyimide films derived from representative PMDA/ODA were prepared with thickness ranging from 5 µm to 25 µm, and the effect of aggregation structure on thermal expansion behavior along different directions was studied. Both in-plane and out-of-plane linear thermal expansion (CTF// and CTF⊥) were respectively characterized by thermal mechanical analysis and FT-near-IR interference method. Volumetric and anisotropic behavior of thermal expansion were also investigated. With increasing film thickness, CTF// gradually increased from 32.2 ppm/°C to 46.1 ppm/°C while CTF⊥ decreased from 149.7 ppm/°C to 128.2 ppm/°C. Volumetric thermal expansion of polyimide films was less sensitive to the varied thickness, but anisotropy of thermal expansion was reduced. Polyimide film of 5 µm thickness showed large birefringence, indicating more considerable in-plane chain orientation anisotropy. Besides, molecular chains were more densely packed along in-plane direction when film thickness increased, while became loosely stacked in the out-of-plane direction. In contrast to the enhanced lateral chain packing for thicker films, higher vertical chain packing order was found in thinner films. The variation of aggregation structure during thermal expansion procedure was analyzed by temperature-dependent WAXD. It is proved that thermal expansion behavior of thinner films could be largely attributed to molecular chain packing, whereas that may be influenced by many factors for thicker films in addition to the effect of chain packing. The results revealed that thermal expansion of films with thickness variation is closely related to molecular chain orientation and packing, which is associated with both chemistry and morphological structure of polyimide. [ABSTRACT FROM AUTHOR]

In this study, mesoporous silica nanoparticles previously prepared from the rice husk ash were utilized as nanofillers to fabricate thin films of polyimide/silica hybrid nanocomposites with different ratios (0, 6, 8, 10, and 12%). Subsequently, all hybrid films were further subjected to comprehensive characterization using XRD, SEM, AFM, and contact angle analyzers. The films exhibited a variety of optoelectronic properties depending on the silica nanoparticles' content. Where the silica nanofillers affected the optical clarity of polyimide films and increasing the silica ratio resulted in decreasing in films transmittance which led to reducing the transparency and enhanced the absorption coefficient of films in the UV range. Besides, the dielectric constant value and free charge carrier concentrations have increased which promoted the optical conductivity of the films. Moreover, increasing silica content resulted in converting the films from hydrophobic to hydrophilic surfaces, and has improved their wettability at all pH values. [ABSTRACT FROM AUTHOR]

The excellent thermal conductivity of graphite films makes it an ideal thermal management material in the field of electronics. Flexibility is an important property for preparing polyimide (PI)-derived graphite films with high thermal conductivity. In the study, hexagonal boron nitride (h-BN) was used as a foaming agent to improve the flexibility of PI-derived graphite films. A series of graphite films were prepared via carbonization and graphitization of self-synthesized polyimide films using h-BN as the foaming agent. The influence of different amounts of h-BN on the structure, flexibility, and thermal conductivity of graphite films was studied in detail. Compared with pure PI-derived graphite film, the flexibilities of h-BN/PI-derived graphite films improved significantly. The flexibility improvement mechanism of graphite film using h-BN as foaming agent was also proposed. The vaporization of BN powders at ultra-high temperature results in the pressure difference between inside and outside of the graphite layers, and then the graphitic "bubbles" were formed on the graphite film. The semicircular "bubbles" created by h-BN sublimation could provide enough adjustment space for the shear slip, and some of the forces around the pores could be partially offset. According to the results, the graphite film derived from the 0.06 wt% h-BN/PI composite film owe the best comprehensive performance, including excellent flexibility, relatively high thermal diffusivity and high in-plane thermal conductivity. This research has important application value in the field of heat dissipation of electronic devices. [ABSTRACT FROM AUTHOR]

The DLC/Kapton structures irradiated with 60Co γ-rays at doses to 1 MGy have been studied by measuring transmission and attenuated total reflection (ATR) spectra. It has been shown that there are significant changes in the spectra in the ranges of vibrations of О–Н, CH2, and CH3 bonds due to radiation-induced processes in the byproducts of polyimide synthesis and residual solvents. Significant differences were found in the radiation-induced processes occurring in the bulk and near-surface region of a polyimide film and DLC/polyimide structures. After irradiation, the bulk of polyimide exhibited bands due to asymmetric and symmetric vibrations of the CH3 group. Bands associated with the vibrations of the CH2 group were additionally observed in the near-surface region. The formation of CH2 groups in the near-surface layer under irradiation was more pronounced in DLC/polyimide structures than in polyimide films; this was due to the additional supply of hydrogen from the DLC film. [ABSTRACT FROM AUTHOR]

A novel method of patterning high precision copper conductive micropatterns on flexible polymer substrate (polyimide) is developed. We utilized the coordination effect between palladium salts and pyridine structures to fix the palladium chloride (PdCl2) on the surface of polymer film while the 2,6-dimethylpyridine structures formed in the specific areas under ultraviolet light guaranteed the resolution of final patterns. Simultaneous thermal reduction of PdCl2 on the surface can be achieved in the process of thermal cyclization of the polymer substrate. As a consequence, the obtained polyimide (PI) film can be patterned with conductive copper micropatterns directly by electroless plating. In particular, we accomplished the deposition of high precision copper pattern with a minimum line width of 50 µm and minimum line spacing of 20 µm on PI thin films (thickness ∼10 µm) by electroless plating. The prepared conductive copper micropatterns exhibit a low resistivity of 1.78 µΩ·cm the same as the pure block copper. And the relationship between the structures of the polymer chains and the physical properties of polymer substrates, such as the dimensional stability, mechanical and dielectric properties were also discussed in detail. This simple and novel method of patterning metal on the polymer surface does not need to achieve the catalytic metal adhesion required for electroless plating at the cost of destroying the substrate surface and avoiding the introduction of unstable interlayers. This patterning method is compatible with the current roll-to-roll production process and can be used to develop high-performance micro-integrated circuits. [ABSTRACT FROM AUTHOR]

The recent development of flexible display technology raised additional requirements for optical and electric properties of polyimides, accelerating the structure and property tunning of transparent polyimides. The unique electronic effect and steric hindrance effect of fluorine substitutions make fluorine-containing polyimides occupy an important position in the transparent polyimide family. In this work, a series of transparent aromatic polyimides were prepared from a fixed 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and biphenyl diamines with different substitute groups at the 2,2′,6,6′-positions. We systematically studied the effects of pendant groups on the thermal, mechanical, optical and dielectric properties of these 6FDA-based polyimides with the aid of density function theory (DFT) calculation. In particular, we paid special attention to the simple but compact fluoro group substitution. The simple fluoro substitution brought the advantages of maintaining the linearity of the backbone and dense polymer chain packing, which would minimize the weakening of polyimides' inherent thermal, dimensional and mechanical properties. Comparing with trifluoromethyl substituted polyimides with the best optical transparency, polyimides containing fluoro substitutes exhibited slightly decreased optical transparency, but increased thermal and dimensional stability and higher mechanical strength. These results could shed light on the ultimate transparent polyimide film development toward the application in extreme working condition, e.g., the colorless polyimide substrate film for the flexible display technology. [ABSTRACT FROM AUTHOR]

Polyimide aerogels are high-performance polymer materials, but they have been restricted by costly drying and low mechanical strength in practical applications. Here, we report a family of porous polyimide (PI) aerogel films prepared through a partial pre-imidization process under ambient pressure drying and freeze-drying. The effect of pre-imidization degree (pre-ID) on the mechanical and dielectric properties of porous films was investigated in detail. The Fourier transform infrared spectra show that the partial pre-imidization process made the molecular chain with coexisted amide acid and imide rings. The porous structure of film was successfully controlled by adjusting the pre-ID, which was confirmed by pore size distributions. These aerogel films with nanoporous structures exhibit better mechanical properties (e.g., 10.61 MPa at 0.433 g cm−3 at room temperature) and lower dielectric constant (minimum of 1.414 at 106 Hz) over the entire bulk density range (0.398–0.5 g cm−3). Their morphology, pore characteristics, and properties were similar, whether by ambient pressure drying or freeze-drying. Moreover, this work will provide a new perspective on the fabrication of porous PI aerogel film via ambient pressure drying with efficient processability. [ABSTRACT FROM AUTHOR]

The combination of continuous-flow microreactors and photoreaction is one of the important researches in flow chemistry. Dimethyl-substituted cyclobutanetetracarboxylic dianhydride (DM-CBDA) was prepared through photodimerization in photomicroreactors and applied in the preparation of polyimide films. It was found that ethyl acetate as the solvent and an appropriate concentration of substrate could benefit this photodimerization process in the capillary photomicroreactor. Higher photonic efficiency and higher DM-CBDA yield were obtained in the photomicroreactor as compared to batch photoreactors. DM-CBDA was applied to prepare the colorless transparent polyimide films, which showed a high polymerization activity for the preparation of poly(amic acid) with high molecular weight. A PI film of DM-CBDA/ODA with the UV cutoff wavelength of 295 nm, the glass transition temperature of 376 °C, and the elongation at break of 11.3% was prepared. This work broadens the application of photomicroreactors for the preparation of polyimide monomers in flow chemistry and its films with good transparent, thermal and mechanical properties. [ABSTRACT FROM AUTHOR]

Highlights: Hierarchically multifunctional polyimide composite films were fabricated by hierarchical design and assembly strategy. Polyimide composite films have three functional layers and integrates high thermal conductivity (95.40 W (m K)−1), excellent EMI shielding (34.0 dB) and good tensile strength (93.6 MPa). Polyimide composite films present broad application prospects in electronics fields according to the test results in the central processing unit. The development of lightweight and integration for electronics requires flexible films with high thermal conductivity and electromagnetic interference (EMI) shielding to overcome heat accumulation and electromagnetic radiation pollution. Herein, the hierarchical design and assembly strategy was adopted to fabricate hierarchically multifunctional polyimide composite films, with graphene oxide/expanded graphite (GO/EG) as the top thermally conductive and EMI shielding layer, Fe3O4/polyimide (Fe3O4/PI) as the middle EMI shielding enhancement layer and electrospun PI fibers as the substrate layer for mechanical improvement. PI composite films with 61.0 wt% of GO/EG and 23.8 wt% of Fe3O4/PI exhibits high in-plane thermal conductivity coefficient (95.40 W (m K)−1), excellent EMI shielding effectiveness (34.0 dB), good tensile strength (93.6 MPa) and fast electric-heating response (5 s). The test in the central processing unit verifies PI composite films present broad application prospects in electronics fields. [ABSTRACT FROM AUTHOR]

Herein, novel isomeric diamines containing semi-N-methyl substituted bisbenzimidazole and derived polyimides (PIs) were successfully synthesized. Experimental data showed that the obtained PIs exhibited outstanding heat resistance and dimensional stability, including 5 % thermal weight loss temperature (Td5 %) of 547 ~ 557 °C, high glass transition temperature (Tg) of 407 ~ 423 °C, and low coefficient of thermal expansion (CTE) of 2.2 ~ 17.6 ppm/°C. The influence of molecular structure of isomeric diamines, including para and ortho substituted N-methyl, on the molecular packing and properties of polymer was discussed. As a result, the novel PIs showed lower CTE than traditional PABZ (5-amino-2-(4-aminobenzene)-benzimidazole) based PIs without bringing high water absorption. These high-performance PI films with matching CTE of copper have potential applications in flexible display substrates and printed circuit boards. [ABSTRACT FROM AUTHOR]

Due to their excellent properties, polymides (PIs) result promising as high-performance materials in different technological fields. In this research, both micron-sized tubular mesoporous silica (mSiO2) and double-tube tubular diatomite particles with cadmium sulfide quantum dots are prepared by chemical deposition method. A cluster of type fluorescent particles is prepared by self-assembling carbon quantum dots (CDs) on the inner surface of the above materials. Then, a fluorescent polyimide film is prepared by uniform dispersion of fluorescent particles. The study of different properties of the film becomes then mandatory to evaluate possible application perspectives. Therefore, after synthesizes, all samples were investigated in term of chemical structure, microstructure and fluorescence properties by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and fluorescence spectrophotometry. Fluorescence performance of diatomite-based fluorescent particles (diatomite@CdS@CDs) results not as good as the mSiO2-based fluorescent particles (mSiO2@CdS@CDs) ones; the mechanical properties of the composite film deteriorate as the content of the inorganic component increases. The performance of PI/mSiO2@CdS@CDs is 7.6 times the PI/diatomite@CdS@CDs ones. [ABSTRACT FROM AUTHOR]

New (co)polyimides possessing good thermal and physicomechanical characteristics, high hydrolytic stability, and transparency at the best world level were synthesized. It was shown that, depending on the natures of diamine and dianhydride used in the synthesis, the optical properties of polymers also change. These properties of (co)polyimide films correlate with the ΔE value, which is defined as the difference between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies of the polyimide repeating unit. It was shown that the use of 1,2-dichlorobenzene makes it possible to obtain high-molecular-weight (co)polyimides with a set of enhanced performance characteristics. [ABSTRACT FROM AUTHOR]

The effect of carbon nanofibers introduced into the polyimide matrix on the mechanical properties of initial nanocomposite films and nanocomposite films oriented by uniaxial drawing at various stages of polyimide synthesis is studied. It is demonstrated that the storage moduli of nanocomposite films are higher compared to initial polyimide films at equal draw ratios. The self-orientation ability of the studied samples drawn at the stage of a prepolymer (poly(amic acid)) during thermal imidization is revealed, and it is shown that this ability increases upon the introduction of carbon nanofibers into the polyimide matrix. It is found that the polyimide films with the highest rigidity of macromolecules among the studied structures exhibit the highest storage moduli owing to their high self-orientation ability. Using X-ray diffraction and electron microscopy, a change in the supramolecular structure of rigid-chain polyimide films upon their orientational drawing at various stages of synthesis is investigated. [ABSTRACT FROM AUTHOR]

An effective design strategy for preparing highly transparent polyimide film with low dielectric constant is presented. The key to the strategy is to simultaneously introduce meta-substituted structure and trifluoromethyl in polymer chains. By using this design strategy, a highly transparent polyimide film with low-k was synthesized from 3,5-diaminobenzotrifluoride (m-TFPDA) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) through a two-step method. The obtained m-TFPDA/6FDA (CPI) film (∼30 µm) possesses high optical transparency (λcutoff=334 nm, T450nm=85.26%, Haze=0.31) and is close to colorless (L*=96.03, a*=−0.34, b*=2.12, yellow index=3.96). The intrinsic k and dielectric loss value of the film are 2.27 and 0.0013 at 10 kHz, respectively. More importantly, such low dielectric performance could remain stable up to 280 °C, and the film shows a low moisture rate (∼0.51%), which helps to maintain the low-k property stability in different humid environments. Meanwhile, the film also shows good thermal stability and mechanical properties, with a glass transition temperature (Tg) of 296 °C and the 5 wt% decomposition temperature (Td,5%) of 522 °C under N2. The tensile strength and tensile modulus of the film are 85.1 MPa and 1.96 GPa, respectively. In addition, the film is soluble in common solvents, which allows simple solution processing and low-cost, continuous roll-to-roll processes. This design strategy is beneficial to improving the transparency, lightening yellow color, lowering the dielectric constant and meanwhile maintaining the comprehensive properties of polyimide films, which is mainly due to the introduced meta-substituted and trifluoromethyl structures effectively inhibiting the transfer of charge transfer complex (CTC) effects and increasing the free volume of film. This design strategy could also be extended to other high-performance polymer systems. [ABSTRACT FROM AUTHOR]

The development of flexible dielectric polymers with robust temperature durability, excellent mechanical properties and high transparency will be of great significance for the soft electronics. In current work, a highly fluorinated polyimide (hF-PI) material was successfully synthesized. By using (3-Aminopropyl) triethoxysilane as "bridge" and controlling the humidity rigidly, transparent polyimide films with smooth surface and tight adhesion to a strong substrate was prepared. As well, the mechanism of non-transparent hF-PI film formation in an ambient atmosphere at a low concentration was clarified. Based on the high temperature resistance of the hF-PI, the indium–zinc oxide (IZO) semiconductor film was successfully prepared on hF-PI film by the simple eco-friendly aqueous route. The IZO thin-film transistor using hF-PI film as insulating layer exhibited highly transparent and excellent electrical performance in the carrier mobility and the on/off current ratio. In addition, the operating voltage was greatly reduced by physically doping with carbon nanotube, while the devices still maintained good transparency. [ABSTRACT FROM AUTHOR]

An effective electrochemical sensor was developed from triaminotriazine-based polyimide (PI) films as selective membrane for the detection of catechin (CT). Firstly, triaminotriazine-based PI films were synthesized from 2,4,6-triamino-1,3,5-triazine (TAT) and pyromellitic dianhydride by thermal imidization method with different monomer ratios. Structural and morphological of synthesized PI films were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. Prepared polyimide films were used as membrane for the preparation of the modified electrodes. Catechin (CT) selectivity behavior of polyimide-modified Pt electrodes was investigated by means of differential pulse voltammetry (DPV). DPV voltammograms showed that peak currents of the modified electrode increased proportionally with increase in CT concentration. TAT-PI-1/1 sensor showed high selectivity, a high regression coefficient (R value = 0.9982), good repeatability (RSD of 2.15%), and limit of detection 0.0152 mM for catechin determination in the presence of multiple interferent species (1 mM coumaric acid, ascorbic acid, gallic acid, lactose, sucrose, fructose, maltose and glucose). Moreover, the TAT-PI-1/1 sensor was employed to determine CT in real sample. [ABSTRACT FROM AUTHOR]

Multigraphene films have been for the first time obtained on the surface of quartz glass via carbonization of polyimide Langmuir–Blodgett films. The Raman spectra of the films show bands G and D and a broad band at 2300–3200 cm–1, which are characteristic of graphite-like films. The transmission electron microscopy demonstrated that the films are constituted by "stacks" of layers spaced by 0.36 nm. The surface resistance of the 5-nm-thick films was 1.2 ± 0.2 kΩ, and the transmittance was 87% at λ = 550 nm. The transmittance was 97% in the IR part of the spectrum and 70–80% in the UV part. [ABSTRACT FROM AUTHOR]

The results of an investigation into the thermoelectric power of thin block Bi1 –xSbx films (0 ≤ x ≤ 0.15) 100–1000 nm in thickness on mica and polyimide substrates in the temperature range of 77–300 K are presented. When measuring the thermoelectric power, a method excluding strain distortion in the film–substrate system is used. The structure, temperature dependences of the thermoelectric power, and resistivity of thin films are analyzed, and the power factor is estimated. A difference in the character of the temperature dependences of the thermoelectric power and resistivity of the films on mica and polyimide substrates is found. This difference is explained by a variation in the band structure parameters under the effect of strain appearing in the film–substrate system due to a difference in the thermal expansion of the film and substrate materials. [ABSTRACT FROM AUTHOR]

The mesoscopic simulation technique was applied to describe the phase separation behavior of polyimide blends and used for design of immiscible polyimide/BN blend films with enhanced thermal conductivity. The simulation equilibrium morphologies of different poly(amic acid) (PAA) blend systems were investigated and compared with optical images of corresponding polyimide blend films obtained by experiment. The immiscible polyimide blend films containing nano-/micro-sized BN with vertical double percolation structure were prepared. The result indicated that the thermal conductivity of polyimide blend film with 25 wt% nano-sized BN reached 1.16 W/(m·K), which was 236% increment compared with that of the homogenous film containing the same BN ratio. The significant enhancement in thermal conductivity was attributed to the good phase separation of polyimide matrix, which made the inorganic fillers selectively localized in one continuous phase with high packing density, consequently, forming the effective thermal conductive pathway. [ABSTRACT FROM AUTHOR]

Thin films of four polyimides of various structures having ether, isopropylidene or hexafluoroisopropylidene groups in their repeating units, which had been synthesized in meta-cresol, were treated with supercritical carbon dioxide and their gas transport properties, were investigated. Transport parameters, (permeability and selectivity coefficients) measured before and after treatment with supercritical carbon dioxide, increased from 16 to 168 % and from 5 to 49 %, respectively. [ABSTRACT FROM AUTHOR]

A new aromatic diamine bearing ether and pendant 9(10H)-anthrone groups, 10,10-bis[4-(4-aminophenoxy)phenyl]-9(10H)-anthrone was reacted with various aromatic dianhydrides to yield the corresponding cardo polyimides via the poly(amic acid) (PAA) precursors and thermal or chemical imidization. The PAAs were produced with moderate to high inherent viscosities of 0.91–1.53 dL/g. All the PAAs could be cast from DMAc solution and thermally converted into transparent, flexible and tough polyimide films with tensile strength of 79.6–115.2 MPa, tensile modulus of 1.97–2.48 GPa, and elongation at break of 10.8–21.7%. These polyimides were predominantly amorphous, and displayed excellent thermal stability with glass-transition temperature of 290–359 °C, 10% weight loss temperature of 522–566 °C, and the residue of 59–65% at 800 °C in nitrogen. Most of the polyimides obtained by chemical cyclodehydration procedure were found to be soluble in NMP, DMF and mcresol at room temperature. [ABSTRACT FROM AUTHOR]

A series of intrinsically black polyimide (PI) films have been designed and synthesized by the copolymerization of pyromellitic dianhydride (PMDA), 4,4′-oxydianiline (ODA) and 4,4′-diaminodiphenylamine (NDA) via a two-step polycondensation procedure, followed by the high temperature imidization reaction of the poly(amic acid) (PAA) intermediates. Incorporation of the electron-rich NDA diamine apparently enhanced the formation of charge transfer complex (CTC) between the electron-donating diamine units and the electron-accepting dianhydride moiety; thus greatly absorbing the visible light and endowing the derived PI films deep colors. PI-5 with the 100% molar ratio of NDA in the diamines exhibited a cutoff wavelength value of 555 nm, which was 127 nm higher than that of PI-1 without NDA component. The PI films were nearly totally opaque at the wavelength of 500 nm when the molar ratio of NDA exceeded 80% in the diamines. PI-5 showed International Commission on Illumination (CIE) lab color parameters of 23.36 for L*, 46.43 for a*, and 40.26 for b*, indicating the essentially black plus red color instead of the yellow plus blue color for PI-1 film (L* = 89.93, a* = −11.09, and b* = 84.23). In addition, introduction of NDA into the copolymer films increased the high temperature dimensional stability of the films. PI-5 exhibited a glass transition temperature (Tg) and coefficient of thermal expansion (CTE) of 431.6 °C and 18.8 × 10−6 /K, respectively, which were superior to those of the PI-1 film (Tg = 418.8 °C, CTE = 29.5 × 10−6 /K). At last, incorporation of NDA components somewhat decreased the tensile properties and thermal decomposition temperatures of the PI films. [ABSTRACT FROM AUTHOR]