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This paper presents novel soluble (co)poly(hydroxyimide)s ((co)PIOH) based on 4,4′-oxydiphthalic anhydride (ODPA), 3,3′-dihydroxybenzidine (HAB), and 3,6-diaminodurene (D) with the 3/1, 1/1, and 1/3 HAB/D ratios. This chemical structure of the compounds provides the possibility of their future modification through the thermal rearrangement (polybenzoxazoles) or functionalization via Mitsunobu reaction (azo side-chain polyimides), i.e., obtaining new materials with interesting properties and therefore with expanded applications. Copolymers were characterized via FTIR, NMR, XRD, and GPC methods to confirm their structure, composition, and molar masses. The effect of copolymer composition on the thermal, mechanical, optical, and permeation properties studied for He, O[sub.2], N[sub.2], and CO[sub.2], as well as hydrophobicity, was investigated. They exhibited a large interval between the glass transition temperature and the decomposition temperature, making them promising for the thermoforming technique. Transmittance above 90% was noted in the visible range for all (co)PIOH films deposited on a glass substrate. Young’s modulus of fabricated membranes was in the range of 2.37 to 3.38 GPa. The highest permeability coefficients were recorded for (co)PIOH with a 1:3 HAB-to D-ratio.

The development of humidity sensors with simple transduction principles attracts considerable interest by both scientific researchers and industrial companies. Capacitive humidity sensors, based on polyimide sensing material with different thickness and surface morphologies, are prepared. The surface morphology of the sensing layer is varied from flat to rough and then to nanostructure called nanograss by using an oxygen plasma etch process. The relative humidity (RH) sensor selectively responds to the presence of water vapor by a capacitance change. The interaction between polyimide and water molecules is studied by FTIR spectroscopy. The complete characterization of the prepared capacitive humidity sensor performance is realized using a gas mixing setup and an evaluation kit. A linear correlation is found between the measured capacitance and the RH level in the range of 5 to 85%. The morphology of the humidity sensing layer is revealed as an important parameter influencing the sensor performance. It is proved that a nanograss-like structure is the most effective for detecting RH, due to its rapid response and recovery times, which are comparable to or even better than the ones of commercial polymer-based sensors. This work demonstrates the readiness of the developed RH sensor technology for industrialization.

With the demand for healthy life and the great advancement of flexible electronics, flexible sensors are playing an irreplaceably important role in healthcare monitoring, wearable devices, clinic treatment, and so on. In particular, the design and application of polyimide (PI)-based sensors are emerging swiftly. However, the tremendous potential of PI in sensors is not deeply understood. This review focuses on recent studies in advanced applications of PI in flexible sensors, including PI nanofibers prepared by electrospinning as flexible substrates, PI aerogels as friction layers in triboelectric nanogenerator (TENG), PI films as sensitive layers based on fiber Bragg grating (FBG) in relative humidity (RH) sensors, photosensitive PI (PSPI) as sacrificial layers, and more. The simple laser-induced graphene (LIG) technique is also introduced in the application of PI graphitization to graphene. Finally, the prospect of PIs in the field of electronics is proposed in the review.

Polyimides (PIs) represent a benchmark for high-performance polymers on the basis of a remarkable collection of valuable traits and accessible production pathways and therefore have incited serious attention from the ever-demanding medical field. Their characteristics make them suitable for service in hostile environments and purification or sterilization by robust methods, as requested by most biomedical applications. Even if PIs are generally regarded as “biocompatible”, proper analysis and understanding of their biocompatibility and safe use in biological systems deeply needed. This mini-review is designed to encompass some of the most robust available research on the biocompatibility of various commercial or noncommercial PIs and to comprehend their potential in the biomedical area. Therefore, it considers (i) the newest concepts in the field, (ii) the chemical, (iii) physical, or (iv) manufacturing elements of PIs that could affect the subsequent biocompatibility, and, last but not least, (v) in vitro and in vivo biocompatibility assessment and (vi) reachable clinical trials involving defined polyimide structures. The main conclusion is that various PIs have the capacity to accommodate in vivo conditions in which they are able to function for a long time and can be judiciously certified as biocompatible.

A new unsymmetrical diamine, 4-(2-aminophenoxy)-4′-aminostilbene was successfully synthesized and used to synthesize stilbene-containing sulfonated polyimides. 2,2′-Benzidine-disulfonic acid, 1,4,5,8-naphthalene tetracarboxylic dianhydride and different mole ratios of 4-(2-aminophenoxy)-4′-aminostilbene and 2-bis(4-(4-aminophenoxy)phenyl) hexafluoropropane were used for the synthesis of stilbene-containing polyimides with sulfonic acid groups. The synthesized polymers were characterized using various physicochemical characterization techniques such as nuclear magnetic resonance spectroscopy, infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis and electrochemical impedance spectroscopy. Furthermore, the viscosity, water uptake, ion exchange capacity, swelling ratio, hydrolytic stability, oxidative stability, mechanical properties and proton conductivity of the synthesized membranes were also analyzed. Sulfonated polyimide membranes showed a water uptake capacity of 18.93–28.89%, proton conductivity of 0.028–0.039 S cm −1 at 30 °C, ion exchange capacity of 1.469 meq g −1 and hydrolytic stability of 40–44 h at 80 °C. The solubility of the sulfonated polyimide membranes was improved when unsymmetrical diamine was used to prepare sulfonated polyimides.

In order to improve the properties of melamine foam (MF), a new polyimide–melamine composite foam (PI–MF) was prepared by microwave irradiation foaming with polyimide microspheres (PI) as a modifier and melamine resin as matrix. The micromorphology, temperature resistance, flame retardant and smoke suppression properties and mechanical properties of the foam were characterized and tested. It was observed by SEM that PI microspheres were closely connected to the skeleton of the MF, FT-IR characterization proved the existence of polyimide in the PI–MF. When the amount of PI microspheres is 30%, the overall performance of PI–MF is better. The temperature of 5% weight loss ( T 5% ) is 326.02°C, the limit oxygen index is 35.48%, the maximum smoke density is 9.21%, the smoke density rank is 5.43, the formaldehyde content is 46.65 mg kg −1 , and the elongation at break of the foam is 35.89%. The introduction of PI microspheres has a good effect on the modification of the thermal stability, flame retardant and smoke suppression properties, and mechanical properties of the MF, and has broadened the application range of polyimide. It also provides a new method for the modification of MF.

HighlightsPolyimides (PIs) as coatings, separators, binders, solid-state electrolytes, and active storage materials help toward safe, high-performance, and long-life lithium-ion batteries (LIBs).Strategies to design and utilize PI materials have been discussed, and the future development trends of PIs in LIBs are outlooked.Lithium-ion batteries (LIBs) have helped revolutionize the modern world and are now advancing the alternative energy field. Several technical challenges are associated with LIBs, such as increasing their energy density, improving their safety, and prolonging their lifespan. Pressed by these issues, researchers are striving to find effective solutions and new materials for next-generation LIBs. Polymers play a more and more important role in satisfying the ever-increasing requirements for LIBs. Polyimides (PIs), a special functional polymer, possess unparalleled advantages, such as excellent mechanical strength, extremely high thermal stability, and excellent chemical inertness; they are a promising material for LIBs. Herein, we discuss the current applications of PIs in LIBs, including coatings, separators, binders, solid-state polymer electrolytes, and active storage materials, to improve high-voltage performance, safety, cyclability, flexibility, and sustainability. Existing technical challenges are described, and strategies for solving current issues are proposed. Finally, potential directions for implementing PIs in LIBs are outlined.

Polyimides, high-performance polymers with superior properties such as high temperature stability, resistance to solvents and high strength, can be used in high-tech applications of the aerospace and aviation, medical or electronics industry in different forms (film, fiber, nanofiber, membrane, foam, adhesive or coating). Among these applications, coating has a special place and is used to develop advanced structures having high temperature resistance, flame retardancy and etc. for high tech industries via an economical and feasible way. Therefore, in this review, we aimed to report the broad application status of polyimide coatings by reviewing publications, patents and commercial products. Thus, this study can assist in selecting suitable polyimide types and production methods for polyimide coating applications and in understanding their applicability for future products.

Aromatic polyimides have excellent thermal stability, mechanical strength and toughness, high electric insulating properties, low dielectric constants and dissipation factors, and high radiation and wear resistance, among other properties, and can be processed into a variety of materials, including films, fibers, carbon fiber composites, engineering plastics, foams, porous membranes, coatings, etc. Aromatic polyimide materials have found widespread use in a variety of high-tech domains, including electric insulating, microelectronics and optoelectronics, aerospace and aviation industries, and so on, due to their superior combination characteristics and variable processability. In recent years, there have been many publications on aromatic polyimide materials, including several books available to readers. In this review, the representative progress in aromatic polyimide films for electronic applications, especially in our laboratory, will be described.

With the rapid development of wireless communication technology and electronic devices, the issue of electromagnetic interference (EMI) is becoming increasingly severe. Developing a new and flexible electromagnetic interference shielding material has become a challenging task. Here, a sandwich-structured EMI shielding composite film was prepared using electrospinning and vacuum filtration methods. In this process, a porous MXene was synthesized through a reaction with cobalt acetate and served as the intermediate layer in the composite film to shield electromagnetic waves. The electrospun polyimide (PI) fibers were used as the top and bottom layers of the composite film, which can protect the porous MXene from oxidation. This lightweight and flexible composite film integrates electromagnetic interference shielding and thermal insulation capabilities, showing excellent comprehensive performance. The composite film achieves an EMI shielding effectiveness of 48.8 dB in X-band (8.2–12.4 GHz), and absolute shielding effectiveness of the composite film reached a satisfying 4142.43 (dB·cm 2 )/g. Owing to the design of a multi-layer porous structure, the density of the composite film is 0.65 g/cm 3 . Furthermore, the thermal conductivity of the film is 0.042 W/(m·K) due to the clamping of electrospun PI fibers, showing excellent thermal insulation performance. Additionally, the composite film exhibits excellent high and low-temperature resistance. In summary, this work provides a feasible strategy for preparing a lightweight polymer-based EMI shielding film.