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The organic electronic ion pump (OEIP) is an on-demand electrophoretic drug delivery device, that via electronic to ionic signal conversion enables drug delivery without additional pressure or volume changes. The fundamental component of OEIPs is their polyelectrolyte membranes which are shaped into ionic channels that conduct and deliver ionic drugs, with high spatiotemporal resolution. The patterning of these membranes is essential in OEIP devices and is typically achieved using laborious micro processing techniques. Here, we report the development of an inkjet printable formulation of polyelectrolyte, based on a custom anionically functionalized hyperbranched polyglycerol (i-AHPG). This polyelectrolyte ink greatly simplifies the fabrication process, and is used in the production of free standing, OEIPs on flexible polyimide substrates. Both i-AHPG and the OEIP devices are characterized, exhibiting favorable iontronic characteristics of charge selectivity and ability to transport aromatic compounds. Further, the applicability of these technologies is demonstrated by transport and delivery of the pharmaceutical compound bupivacaine to dorsal root ganglion cells with high spatial precision and effective nerve-blocking, highlighting the applicability of these technologies for biomedical scenarios. Funding: Swedish Foundation for Strategic Research; Knut and Alice Wallenberg Foundation; Swedish Research Council; European Research Council [834677]; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Vinnova

The materials with thermal insulating and fire-retardant properties are highly demanded for architectures to improve the energy efficiency. The applications of conventional inorganic insulating materials such as silica aerogels are restricted by their mechanical fragility and organic insulating materials are either easily ignitable or exhibit unsatisfactory thermal insulation performance. Here, we report an organic/inorganic composite aerogel with integrated double network structure, in which silica constituent homogeneously distribute in the anisotropic polyimide nanofiber aerogel matrix and strong interfacial effect is formed between two components. The integrated binary network endows the polyimide/silica composite aerogels with outstanding compressibility and flexibility even with a high inorganic content of 60%, which can withstand 500 cyclic fatigue tests at a compressive strain of 50% in the radial direction. The resulting composite aerogel exhibits a combination of outstanding insulating performance with a low thermal conductivity (21.2 mW m−1 K−1) and excellent resistance to a 1200°C flame without disintegration. The high-performance polyimide/silica aerogels can decrease the risk brought by the collapse of reinforced concrete structures in a fire, demonstrating great potential as efficient building materials.

Layered structure MoS2 nanosheets have shown great potential for energy storage applications. However, the methodology for elaborately controllable growth of MoS2 onto carbonaceous matrix for promoting the electrochemical performance is highly desirable. Herein, a high-effective, all-in-one in-situ conversion growth strategy has been proposed to construct a stable sandwich-type nanostructure. The formation of the optimized C-MoS2/NCNTs product undergoes a dissolution-recrystallization process, in which ultrathin carbon layer-coated MoS2 nanosheets densely assembled onto the surface of polyimide (PI) derived N-doped carbon nanotubes (CNTs). Theoretical simulation reveals that MoS2 nanosheets possessing an expanded interlayer spacing of 0.92 nm can greatly reduce the barrier energy of Na ions mitigation. Accordingly, the as-made C-MoS2/NCNTs anode delivers superior cycling stability (82% capacity retention after 400 cycles at 1 A g−1) and rate performance (348 mAh g−1 at 2 A g−1). The results demonstrate that the expanded MoS2 interlayer distance, ultrathin outer carbon coating, and N-doped CNTs matrix together accounts for the outstanding sodium storage capability for the C-MoS2/NCNTs electrode.

Lithium (Li) metal batteries have received extensive research focusing on the dendrite growth issue on account of the high chemical activity of Li anode. While, thermal safety, as one of the important security concerns facing the further application, gets little attention. Here, the high-performance polyimide film is successfully developed to enhance the safety margin based on the excellent mechanical strength and heat resistance corresponding to the traditional separator. And, the polyimide film with the MoS2 coating made by spraying method as the composite separator can not only improve the wettability to the electrolyte, but also in-situ form an artificial layer with the low nucleation barrier for the Li ions. When used in both the coin cell and the pouch cell, all achieve the outstanding cycling stability and the coulombic efficiency. Specially, the in-situ Li ions nucleation behaviors are investigated by optical microscopy in the capillary cell. The electric field intensity at the Li anode surface is also simulated by COMSOL Multiphysics to further elucidate the effect of the coating.

A novel imide compound (DH-MC) and polyimides (DH-PIs) that form multiple intramolecular hydrogen bonds (H-bonds) were synthesised from 2,2′-dihydroxybenzophenone-3,3′,4,4′-tetracarboxylic dianhydride (DHBA) to investigate the effects of distinct H-bond structures on the photoluminescence properties of these compounds. The DHBA moiety, which contains two proton donors and three proton acceptors, can form three types of H-bond structures (MC-0, MC-1, and MC-2). DFT calculations have predicted that the most energetically stable conformation is MC-1, forming an asymmetric H-bond structure, which is consistent with the FT-IR spectroscopy and single-crystal XRD analysis results. A colourless toluene solution of DH-MC exhibited orange fluorescence with a large Stokes shift (ν = 11 905 cm−1), and DH-MC and the DH-PIs exhibited yellow fluorescence with a large ν of >10 000 cm−1 in the solid state, with both originating from excited-state intramolecular proton transfer (ESIPT). In addition, these compounds exhibit small-Stokes-shifted fluorescence from the anionic form of the DHBA moiety, resulting in yellow coloration of the DH-PI film and the DH-MC powder. To reduce coloration, a polyimide copolymer (CoPI) film was prepared using DHBA and 4,4′-oxydiphthalic anhydride (ODPA) in which the molar ratio of DHBA was set at 3%. Owing to the dilution effect and efficient energy transfer from the blue-fluorescent ODPA to the DHBA moiety in the excited state, the colourless and transparent CoPI film exhibited prominent yellow fluorescence with a quantum yield of 0.14. The wavelength-converting spectrum demonstrated that the CoPI film absorbs a wide range of UV radiation from a xenon light source and significantly enhances the yellowish light component via ESIPT emission. The CoPI film is a promising candidate for solar spectral conversion applications.

There is a great demand for low dielectric materials as insulating interlayers in large-scale integrated circuit development. However, it is still a huge challenge to reduce the dielectric permittivity of polymers while maintaining excellent thermal stability and mechanical properties. In this work, the fluorinated polyimides (PIs) in combination with a micro-branched crosslinking structure were prepared successfully by introducing different amounts of 1,3,5-tris(4-aminophenyl) benzene (TAPB) to obtain ultra-low dielectric permittivity. The results revealed that PI film containing 2 mmol TAPB had the lowest dielectric permittivity (2.47) and dielectric loss (0.008) at 1 MHz due to the fluorine atoms and the micro-branched crosslink structure, which not only decreased the molecular polarizability but also increased the free fractional volume. In addition, PI film containing 2 mmol TAPB had the highest tensile strength of 106.02 MPa with an elongation at a break of 15.1% because the presence of TAPB effectively promoted the connection between PI molecular chains, resulting in the inhibition of the molecular mobility. The incorporation of TAPB also enhanced the thermal stability and ultraviolet light-shielding performance of PI films. This method paves the way for the development of PIs with ultra-low dielectric permittivity for the electronic industry.

In this paper, the nanofiller consisting of graphene oxide (GO) and organically modified hydrotalcite (HT) was fabricated via the electrostatic self-assembly and further reduced and incorporated into the polyimide (PI) matrix to prepare superior nanocomposite films with high energy storage density. It was observed by transmission electron microscopy (TEM) that the insulating HT facesheets were attached well onto the GO film to form a stable sandwich structure. The synthesized ternary nanocomposite film (1.0 rGO@HT/PI) showed high breakdown strength of 175.9 kV/mm and ultra-high dielectric constant at 10 kHz (er = 35.4), about 10 folds more than pure PI (er = 3.4), resulting in a maximum energy storage density of 4.84 J/cm3. On account of electrostatic self-assembly, HT nanosheets can efficiently reduce the contact area between graphene oxides and inhibit the formation of conductive networks, thus maintaining a high level of breakdown strength and increasing the energy storage density of the nanocomposite films.

In this paper, a flexible liquid crystal display (LCD) is developed by applying hybrid alignment layers made of vanadium dioxide (VO2) nanoparticles and homeotropic-polyimide (h-PI) onto colorless ...

Wireless communication technology plays a crucial role in the development of aviation and aerospace owing to the increasing demand for high performance, lightweight, environmentally adaptability, and structural stability. With these advantages, three-dimensional woven spacer structure becomes a potential platform for microstrip antennas, which is a significant candidate in wireless technology. In this study, we proposed an ultra-light-weight Kevlar/polyimide 3D woven spacer microstrip antenna (3DWS-MA-T) by embedding the conductive copper threads into the fabric to form an integrated structure. The fabricated 3D woven spacer composites (3DWSCs) overcome the conflict between lightweight and strong mechanical properties, exhibiting ultra-low volume density of 0.34 g/cm3 and compressive strength of 3.8 MPa. The resulting all-textile multifunctional 3DWS-MA-T achieved superb electromagnetic performance (gain value > 5 dB) with a good impedance matching (S11 value 5 dB) for aerospace applications

The effective means to solve material wear is to develop self-lubricating composite materials with excellent tribological, thermal, and mechanical properties. Herein, the composites of reduced graphene oxide (r-GO) nanosheet decorated with Silicon Carbide (SiC) were facilely prepared with employing a silane coupling agent, and the corresponding r-GO/SiC/thermosetting polyimide (r-GO/SiC/TPI) nanocomposite films were obtained by in situ polymerization method. The mechanical, tribological, and thermal properties of these nanocomposite films were investigated. When the content of r-GO/SiC was at 1.0 wt%, the compression strength and compression modulus of the composite increased by 37.7% and 47.3%, respectively, which were much higher than that of TPI composites addition of r-GO or SiC alone. Furthermore, r-GO/SiC/TPI composites also exhibited the lowest wear rate and friction coefficient in these reinforced TPI nanocomposites. When the content of r-GO/SiC was 0.8 wt%, particularly, the friction coefficient and wear rate of r-GO/SiC/TPI decreased by 22.8% and 79.8% compared to pure TPI, respectively. Additionally, trace amount r-GO/SiC hybrids also significantly enhance the thermal stability of TPI matrix. Compared to the polyimide composites reinforced by common nano-scale inorganic fillers, the outstanding mechanical and tribological properties of this r-GO/SiC/PI composites could be attributed to the ball on plane structure of GO/SiC, which lead to crack reflection, strength increment. These r-GO/SiC/TPI composites demonstrate the promising potential to be used as high-performance tribological materials in industry applications.

Organic carbonyl compounds have been widely investigated as a promising candidate for graphite anodes in lithium-ion batteries (LIBs) because of their high capacity, low cost, and diverse structure...

Colorless and transparent polymer films and sheets with good high-temperature resistance and low dielectric constant (low-Dk) and low dissipation factors (low-Df) features are highly desired in advanced optoelectronic integrated circuits (OEIC) fabrications. In the current work, a series of semi-alicyclic polyimide (PI) powders were first prepared by the onestep high-temperature polycondensation of an alicyclic dianhydride, hydrogenated 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (HBPDA) and aromatic diamines which were beneficial for endowing the derived PI films with low-Dk features, including 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) for PI-1, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (BDAF) for PI-2, and 9,9-bis[4-(4-aminophenoxy)phenyl]fluorene (BAOFL) for PI-3. Then, the derived PI powders were fabricated into colorless films and light-colored sheets, respectively. The freestanding flexible and tough PI films showed excellent optical transparency with the ultraviolet (UV) cutoff wavelength (λcut) lower than 300 nm, the optical transmittance higher than 85% at the wavelength of 400 nm, yellow indices (b*) lower than 1.0, and haze values lower than 1.2%. The hot-processed PI sheets also exhibited light colors. The PI films and sheets showed good thermal stability with the glass transition temperatures (Tg) higher than 220 °C. More importantly, the derived semi-alicyclic PI sheets showed Dk and Df values as low as 2.56 and 0.008 at 1 MHz, respectively.

Several polyimides were prepared via two-step polycondensation from novel 2,5-furandicarboxylic acid–based diamine, 2,5-bis[4-(4-aminophenoxy)benzoyl]furan, with commercial dianhydrides. The chemical structures of the monomers and polymers were characterized by FT-IR and NMR in detail, respectively. The polyimides exhibited high performances with 5 wt% weight loss temperatures of over 410 oC, glass transition temperatures of over 214 oC, and tensile strengths and Young’s moduli of up to 130 MPa and 3.2 GPa, respectively. The thermal crosslinking mechanism was studied by FT-IR, Raman spectroscopy, and model reaction analysis, which showed the Diels–Alder reaction between the furan group and diphenylethylene group was the main reaction. The crosslinked polyimide films showed improved solvent resistance, and thermal and mechanical properties.

To prepare soluble polyimides with high temperature resistance, two new diamine monomers, namely, 2,2′-(4,4′-oxybisphenylene)-bis(1-phenyl-5-aminobenzimidazole) (5a), and 2,2′-(4,4′-hexafluoroisopropylidene)-bis(1-phenyl-5- aminobenzimidazole) (5b), were synthesized and exploited to prepare three series of poly(benzimidazole imides)s (PBIIs) by a conventional two-stage synthesis. The resulting PI films were flexible and tough, possessing high glass-transition temperatures (Tgs = 311°C–390°C), improved optical transparency, and excellent solubility. Moreover, the effect of different configuration on performance was revealed, and these data provided a feasible method to enhance both Tg and solubility of PIs by incorporating N-phenyl benzimidazole and corresponding functional moieties.

Polyimide-block-poly(dimethyl siloxane) copolymer was synthesized by a two-step process, initiated by coupling anhydride terminated poly(amic acid), AT-PAA with amino terminated poly(dimethyl siloxane), (NH2)2-PDMS to form poly(amic acid)-block-poly(dimethyl siloxane). The resulting copolymer is then thermally treated to produce polyimide-block-poly(dimethyl siloxane), PI-PDMS. Because of the high glass transition temperature, Tg of polyimide, it is usually cured at a high temperature of about 300°C for over 2.5 h. Copolymerization of polyimide with polysiloxane, reduces the imidization temperature while maintaining high thermomechanical properties. A series of instruments were used to monitor the progress of copolymerization. The time-based analysis of the product of copolymerization enables the optimization of the structure and properties of the copolymers. The chemical structure and composition of the copolymer were studied by Fourier Transform Infrared Spectroscopy, (FT-IR). The incorporation of PDMS blocks into the copolymer and the degree of imidization of the polyimide block increased with increasing reaction time. The change in the viscosity of the copolymerizing solution was monitored by simple shear viscometry conducted with the Brookfield Viscometer. The reported increase in solution viscosity with increasing copolymerization time is associated with increasing molecular weight of the copolymer. The intrinsic viscosity of the copolymer solution was measured as a function of copolymerization time and it was found that the intrinsic viscosity of the copolymer solution increased with increasing reaction time. The glass transition temperature (Tg) and the thermal stability of the copolymer were determined by differential scanning calorimetry, DSC and thermogravimetric analysis, and TGA, respectively. Between 25°C and 420°C, the copolymers synthesized in this study show two glass transition temperatures due to the polyimide, PI block at around 380°C and another peak associated with PDMS plasticized polyimide at about 290–300°C. The two Tg peaks observed in the DSC thermogram are believed to be indicative of the structure of a block copolymer. TGA analysis shows that the thermoxidative stability of the copolymers increased with increasing reaction time, due to the incorporation of increased amount of PDMS unit into the copolymer. The combination of increasing molecular weight of copolymer, higher degree of imidization of polyimide blocks and enhanced thermoxidative stability may translate into improved flame retardancy of copolymers. This suggested enhancement in flame retardancy in air atmosphere, is believed to be due the incorporated PDMS blocks, which can be converted into silica, SiO2, a recognized thermally stable material.

The fatigue damage behavior of the nanocrystalline Au films on polyimide substrates was investigated. It was found that the very high-cycle fatigue damage resistance of the Au film was significantly enhanced by at least a factor of ∼2 in supported loading through adding an ultrathin Ti interlayer at the Au film/polyimide interface. Such a better fatigue damage resistance is mainly ascribed to the effective suppression of voiding at the Au film/polyimide interface through modulation of the Au/Ti interface, and thus the propensity of the cyclic strain localization and grain boundary cracking is reduced. The finding may provide a potential strategy for the design of flexible devices with ultra-long fatigue life.

This paper reports the preparation of a novel polyimide (PI)-based hole-transporting material comprising carbazole and arylamine moieties as the backbone of the polymer. A diamine monomer named 4,4′-(9H,9′H-[3,3′-bicarbazole]-9,9′-diyl)dianiline is an electron-rich molecule which is suitable for achieving electrochromic materials. It is used to prepare an electrochromic carbazole-based PI via chemical imidization. The carbazole-based PI shows excellent thermal stability with a high decomposition temperature up to 500 °C, refractive index of 1.74, and reasonable transparency of 85%. In addition, the PI exhibits characteristics similar to those of electrochromic materials such as violet-green emissions in the visible range when in solution form, highest occupied molecular orbital (HOMO) energy levels of ∼5.4 eV, and a hole mobility of 7.44 × 10−4 cm2 V−1s−1. The excellent performance of the PI makes it a potential candidate for hole-transporting material in optoelectronic devices.

A major issue limiting the thermal conductivity (TC) of polymer-based composites is the inevitable vacancy among thermal conductive fillers; the fabrication of continuous thermal conductivity network is significant. In this work, we successfully constructed interpenetrating carbon nanotube (CNT) @carbonized polyvinyl alcohol (αPVA) network in polyimide (PI)/boron nitride nanosheets (BNNS) membranes through co-electrostatic spinning of polyamide acid (PAA)/BNNS precursor fibers and PVA/CNT precursor fibers and subsequent high-temperature treatment. The CNT @αPVA network works as a continuous thermal conductivity network in the membrane, which could also bridge BNNS to remove the vacancies among BNNS fillers. Due to the formation of dual thermal conductive networks, the TC of PI/BNNS with 30 wt% BNNS reached an increasement of 100% with the addition of only 0.3 wt% CNT. In addition, the composites present electrical insulating properties with volume resistivity of about 1015 Ω·cm, as well as excellent flexibility, pretty good acid–alkali tolerance, and self-extinguishing. This work provides an effective way to develop continuous thermal conductive networks in polymer-based composites for scalable thermal management applications in microelectronics devices.

Highly oriented graphitized films demonstrate outstanding thermal conductivity in recent telecommunication applications. In this work, polyimide films were prepared with catalyst pyridine. High orientated and high thermal conductive graphite films were successfully prepared by pure polyimide (PI) films without any other carbon source inducing growth. The result showed that pyridine could promote the imidization of PI. Suitable dosages of pyridine can improve the crystallinity, promote the orderly arrangement of molecular chains, and facilitate the growth of the crystal lattice after graphitization. After graphitization, graphitized PI films exhibited highly oriented layers. The graphitized film coming from a pyridine concentration of 3.5 wt% provided the best thermal conductivity (1092 W / ( m . K ) ), which was 49 times more than those from the thermally imidized films. The average crystalline size of it was 62.16 nm and its degree of graphitization was 90%. Therefore, the graphite film prepared by polyimide formed with catalyst pyridine has the potential of thermal management and is a highly prospective candidate as heat dissipation substrates for miniaturization electronic devices.

As an important power storage device, the demand for capacitors for high-temperature applications has gradually increased in recent years. However, drastically degraded energy storage performance due to the critical conduction loss severely restricted the utility of dielectric polymers at high temperatures. Hence, we propose a facile preparation method to suppress the conductivity loss of polyimide (PI) films by inserting boron nitride interlayer. The experimental results and computational simulations indicate that consecutive boron nitride interlayer has better effect on suppressing leakage current density of the entire material compared with uniform dispersed boron nitride nanosheet (BNNS) composite films. The experimental results show that the leakage current density of PI films is reduced by an order of magnitude and a classy energy density of 2.58 J/cm3 at a charge–discharge efficiency of 90% has been achieved at 150 °C, far better than pristine PI (0.75 J/cm3 of energy density and 65% of efficiency under 275 kV/mm and at 150 °C). The method we reported in this work is applicable to a variety of polymer dielectric films produced by solution casting for elevated temperature energy storage application. Aiming at the main problem of drastically degraded of energy storage performance caused by the sharp increase of leakage current of polymer dielectric film at high temperature, the energy storage performance of PI at 150 °C is improved by embedding boron nitride intermediate layer in PI.

The adoption of polymer nanocomposites in the design/manufacturing of parts for engineering and technological applications showcases their outstanding properties. Among the polymer nanocomposites, polyimide (PI) nanocomposites have attracted much attention as a composite material capable of withstanding mechanical, thermal and electrical stresses, hence engineered for use in harsh environments. However, the nanocomposites are limited to the application area that demands conduction polymer and polymer composites due to the low electrical conductivity of PI. Although, there has been advancement in improving the mechanical, thermal and electrical properties of PI nanocomposites. Thus, the review focuses on recent progress on improving the mechanical, thermal and electrical conductivity properties of PI nanocomposites via the incorporation of carbon nanotubes (CNTs), graphene and graphene oxide (GO) fillers into the PI matrix. The review summarises the influence of CNTs, graphene and GO on the mechanical and conductivity properties of PI nanocomposites. The authors ended the review with advancement, challenges and recommendations for future improvement of PI reinforced conductive nanofillers composites. Therefore, the review study proffers an understanding of the improvement and selection of PI nanocomposites material for mechanical, thermal and electrical conductivity applications. Additionally, in the area of conductive polymer nanocomposites, this review will also pave way for future study.

Polyimide composites (PETI-340M) were fabricated and subjected to high-temperature aging and thermal cycling to evaluate resistance to degradation. Mechanical-degradation mechanisms and kinetics depended on aging temperature. Aging at 232°C resulted in strength loss due to polymer degradation, while intra-tow cracking was the dominant mechanism during aging at 288°C. Composite panels subjected to thermal-cycling fatigue (−54°C to 232°C) retained mechanical properties without microcracking. However, in regions containing pre-existing fabrication-induced defects (primarily voids), intra-tow microcracks were observed after thermal cycling. Unlike some polyimide composites (PMR-15), oxidative aging effects during thermal cycling were negligible. The thermo-oxidative stability and the retention of mechanical performance after thermal cycling indicates potential for long-term, high-temperature structural applications.

Purpose Phenolic epoxy vinyl ester resin (PEVER) is an advanced resin matrix, which has excellent heat resistance, electrical insulation. However, the brittleness and poor toughness of its curing product limited its application, so this paper aims to modify the PEVER with hyperbranched polyimide (HBPI), so as to enhance the toughness, heat resistance and dielectric properties of PEVER. Design/methodology/approach Hexamethylene diisocyanate trimer was used as the central reactant. Methyl tetrahydrophthalic anhydride was used as the branching unit, stannous octoate was used as the catalyst and hydroquinone was prepared as the inhibitor. Then, the hyperbranched structure of HBPI was characterized by Fourier transform infrared spectrometer and 13C-NMR. Next, PEVER was mixed with different contents of HBPI, and then the authors tested its curing product. Findings It is found that with the addition of HBPI, the free volume of the system was increased and the content of polar groups was decreased in each unit space, so the dielectric constant (ε) and the dielectric loss (tanδ) were decreased. In addition, PEVER could be well toughened by HBPI and the thermal stability of PEVER was improved. Originality/value HBPI has excellent heat resistance. The addition of hyperbranched polymer increases the free volume of the system so it can slow down the transfer of stress and its nearly circular structure can absorb the impact energy from all directions. Moreover, an appropriate amount of free volume can decrease the dielectric constant of PEVER by reducing the content of polar groups.

Polyimide/silica dust composites (PI/SD) were prepared with different SD NPs content (0,2,4,6 and 8) wt.% by using in situ polymerization and solution mixing methods. The prepared PI/SD was characterized by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The FT-IR results showed that the characteristic absorption bands of C = O stretching of the imide group are clearly visible near 1740 cm−1. The strongest characteristic vibration bands of Si–O–Si hydrolyzed from silica were also observed in the range (689–1156) cm−1. The TGA results indicated that the thermal stability of prepared PI/SD was increased with an increase in SD content, this effect is clearly seen in the samples prepared by in situ polymerization method, and the glass transition temperature of the PI/SD NPs composites was in the range of (276–334) °C, i.e., higher than the pure PI 221 °C. The thermal conductivity and hardness for PI/8 wt.% SD composites prepared by in situ polymerization were increased from (0.5 to 1.025) W/m.K and from (100 to 412) MPa when compared with pure PI.

Electromagnetic shielding performance has been achieved for a polyimide (PI)-matrix composite by the strategy of self-metallization of its thermosetting PI matrix. Self-metallization of the thermosetting PI was realized by silver ion/poly(amic acid) (PAA) precursor ion exchange and thermal reduction. The factors influencing the self-metallization were investigated. The electrical conductivity and integrity for the surface of the PI were achieved by optimization of ion exchange/thermal reduction parameters. The fabricated PI-matrix composite exhibits a maximum electromagnetic interference shielding effectiveness value of 81 dB. Importantly, the electromagnetic shielding performance can be maintained even after heat condition of 300°C. Meanwhile, the surface-metallized PI composite exhibits mechanical property equivalent to the pristine composite, and an Ag/matrix interfacial strength higher than 19.6 MPa. Besides, self-metallization mechanism of the thermosetting PI was investigated.

A series of biobased polyimides bearing a structure derived from a predetermined tetracarboxylic dianhydride was synthesized. By ionizing the COOH group of the side chain with potassium hydroxide, four kinds of polyimides were solubilized in water, and the water-soluble polyimides were cast onto films over an aqueous solution, leading to higher optical transparency than that of non-water-soluble polyimides. 1H nuclear magnetic resonance measurements of the polyimides revealed no residual reactants from the polymerization process or side-chain modification. Partial crosslinking of the water-soluble polyimide chains by condensation of the carboxylate side chain with an amino acid-based diamine such as 4-aminophenylalanine or 4,4′-diamino-α-truxillic acid induced the formation of polyimide hydrogels. The remaining COOK groups of the obtained hydrogel were protonated/deprotonated by changing the pH, accompanied by reversible shrinking and swelling. In this study, novel water-soluble polyimides and hydrogels were synthesized and evaluated. The water-soluble polyimides were synthesized from biobased 4-aminocinnamic acid dimer and appropriate tetracarboxylic dianhydrides by reaction with aqueous potassium hydroxide. A polyimide hydrogel was prepared using a crosslinking agent with 4-aminophenylalanine or 4-aminocinnamic acid dimer, which are also biobased amino acids, resulted in a fully biobased polyimide hydrogel. This hydrogel exhibits stimulus responsiveness, accompanied by a pH-dependent volume change because of the effect of carboxylate group derived from the polyimide side chain and crosslinking agent.

Efficient purification technology is crucial to fully utilize hydrogen (H2) as the next generation fuel source. Polyimide (PI) membranes have been intensively applied for H2 purification but its current separation performance of neat PI membranes is insufficient to fulfill industrial demand. This study employs blending and crosslinking modification simultaneously to enhance the separation efficiency of a membrane. Polyethersulfone (PES) and Co-PI (P84) blend asymmetric membranes have been prepared via dry–wet phase inversion with three different ratios. Pure H2 and carbon dioxide (CO2) gas permeation are conducted on the polymer blends to find the best formulation for membrane composition for effective H2 purification. Next, the membrane with the best blending ratio is chemically modified using 1,3-diaminopropane (PDA) with variable reaction time. Physical and chemical characterization of all membranes was evaluated using field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR). Upon 15 min modification, the polymer membrane achieved an improvement on H2/CO2 selectivity by 88.9%. Moreover, similar membrane has demonstrated the best performance as it has surpassed Robeson’s upper bound curve for H2/CO2 gas pair performance. Therefore, this finding is significant towards the development of H2-selective membranes with improved performance.

In this study, modified sericite is used to improve the bonding performance of polyimide(PI) adhesives which owe to its high temperature resistance, corrosion resistance and low cost. In order to f...

A series of semi-alicyclic poly(amic acid) varnishes designed for potential applications as the alignment layers for thin-film transistor driven liquid crystal display devices (TFT-LCDs) were prepared from an alicyclic dianhydride, norbornane-2-spiro-α- cyclopentanone-α′-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride (CpODA) and aromatic diamines. Then, the liquid crystal (LC) minicells were fabricated by using the polyimide (PI) as the alignment layers, which were prepared by thermally dehydrating the PAA varnishes at elevated temperatures. The derived PI alignment layers exhibited good thermal stability with the 5% weight loss temperatures higher than 470 °C. In addition, the PI layers showed excellent optical transparency with the transmittances higher than 94.0% at the wavelength of 550 nm with a thickness around 100 nm. The LC cells fabricated with the CpODA-PI alignment layers exhibited good optoelectronic features. The rubbing PI layers could induce the effective alignment of the LC molecules with the pretilt angles in the range of 1.62–2.14°. The voltage holding ratios of the LC cells were higher than 92.00%, and the residual direct voltage values were all lower than 300 mV.

This work reports the synthesis of a series of shape memory polyimides by polycondensation of 2,2′-bis[4-(3-aminophenoxy)phenyl]hexafluoropropane (m-6FBAPP), 4,4′-(hexafluoroisopropylidene) (6FDA) and PA-terminated OAPS. The influence upon shape memory properties by the introduction of PA-terminated OAPS was investigated systematically in both experiments and simulations. PA-terminated OAPS acted as both a plasticizer and a rigid cage structure, preventing excessive movement of the polymer chain. Thus, both strain and shape recovery values of the resulting polyimide composites strongly depended on the content of PA-terminated OAPS. The shape memory polyimide composites showed high strain and recovery values equal to 247 and 94.3%, respectively. Additionally, these polyimide composites showed multiple shape memory effects and excellent shape memory cycle stability.

Conventionally, interface effects between polymers and fillers are essential for determining the breakdown strength and energy storage density of polymer-based dielectric composites. In this study, we found that interface effects between different fillers have similar behavior. BN and BaTiO3 fiber composite fillers with three different interface bonding strengths were successfully achieved by controlling composite processes (BT-fiber/BN