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Polyimide (PI) is an indispensable material in the field of electrical insulation devices owing to its high mechanical strength, high insulating properties and excellent thermal stability. However, the rigid structure not only gives PI these excellent properties but also makes it difficult for PI to self-heal, be recycled, and reused. Herein, a self-healable PI (SHPI) film is developed by the synergistic combination of dynamic disulfide bonds and flexible polysiloxane molecules (PDMS). Two functional monomers are introduced into the PI matrix through simple copolymerization, which confers excellent self-healing and recycling abilities. Furthermore, the SHPI retains high thermal stability with thermal decomposition temperature at 5 wt% weight reduction (Td5%) = 427 °C and good breakdown strength (E0 ∼ 318 MV m−1). Moreover, carbon fiber (CF) reinforced composite films (CFRCs) by combining SHPI with CFs are also produced, and they exhibit excellent mechanical strength and load-bearing capacity. The CFs can be reused multiple times with a recycling efficiency of nearly 100%. The SHPI is expected to have widespread use and popularity in the field of electrical insulation as an excellent recyclable insulation material. [ABSTRACT FROM AUTHOR]

With the rapid development of high-temperature energy storage devices, polyimide films with excellent thermal stability have become candidates for capacitor materials. However, the energy density (Ue) and efficiency (η) of the most commonly used polyimide (common PI) decrease exponentially at high temperatures. In this work, the "isomer-like" of common PI (i-PI) is prepared by optimizing the structure of the repeating unit of common PI. Compared with the common PI film (Ue of 0.59 J cm−3 and η of 24% at 150 °C), the i-PI film obtains a high Ue of 3.48 J cm−3 with an η of 54% at 150 °C. The adjustment of the position of the ether bond reduces the interchain space of the polymer, which decreases the free volume for electron acceleration resulting in a better insulation performance. Then, flexible thermoplastic polyurethane (TPU) with high dielectric permittivity is introduced into i-PI, which further reduces the interchain space. The obtained TPU/i-PI film achieves a synergistic improvement in dielectric permittivity and breakdown strength. At 150 °C, the high Ue of 4.23 J cm−3 with η of 73% is achieved. Compared with those of common PI, Ue and η of TPU/i-PI film are improved by 617% and 204%, respectively. Therefore, reducing the interchain space by optimizing the polymer chains is a feasible method to enhance the high-temperature capacitive performance. [ABSTRACT FROM AUTHOR]

Self-healing of damage is a common phenomenon in organisms but is hardly ever encountered in rigid polymer materials. For next-generation electricals and electronics, it is crucial to accurately mimic organisms to detect and heal mechanical/electrical damage. Herein, disulfide bond exchange is designed to introduce the self-healing ability in a copolymerized polyimide (copolyimide). A copolyimide insulation film with two diamine monomers is successfully prepared, which also possesses good self-healing ability after being mechanical/electrical damaged. Furthermore, the self-healing copolyimide film still maintains its good Young's modulus (E) >4 GPa, high thermal stability with glass transition temperature (Tg) >190 °C, and excellent insulation property with breakdown strength (Eb) >300 kV mm−1. The combination of the simple copolymerization and unique self-healing ability is suitable for high Tg polyimide to make this an ideal method for insulation field. [ABSTRACT FROM AUTHOR]

Polymer dielectrics have been widely used in electrical energy storage devices. However, the relatively low operating temperature hinders their applications in harsh environments. Herein, the molecular structure of polyimide (PI) is optimized by adjusting the reaction kinetics of polyamic acid, which improves the energy storage performance of PI at elevated temperature. The PI film with an optimal imidization degree achieves a simultaneous increase in dielectric permittivity (εr) and breakdown strength (Eb), resulting in a maximum discharged energy density (Ue) of 6.9 J cm−3 with a charge–discharge efficiency of 90.0% at room temperature and a high Ue of 3.9 J cm−3 at 150 °C. The introduced –COOH/–CN–OH– polar groups increase the εr through the enhancement of dipole polarization. Moreover, an appropriate number of –COOH/–CN–OH– groups as deep traps reduce the mobility of carriers, thereby increasing the Eb. Finite element simulation reveals that PI with an appropriate imidization degree exhibits suppressed space charge accumulation and improved electric field distortion. This method reduces the PI processing temperature, which effectively reduces the production energy consumption. For verifying the universality of the design strategy, two other PIs prepared from different monomers are also demonstrated to have simultaneous improvement in εr and Eb.Finally, this production process of only reducing the preparation temperature without adjusting the original commercial PI production equipment is crucial for the practical application of capacitor films in the future. [ABSTRACT FROM AUTHOR]

Solid polymer electrolytes (SPEs) have drawn considerable attention owing to their reliable safety performance, electrochemical stability and exceptional flexibility, which make them superior to conventional liquid electrolytes. Here, we report a novel composite electrolyte which is composed of homogeneously dispersed Li ion-conducting Li0.33La0.557TiO3 (LLTO) nanowires in a poly(ethylene oxide) (PEO)/LiClO4 matrix. It is demonstrated that only 3 wt% LLTO nanofibers are needed for the optimal performance of SPEs. The PEO-based composite electrolyte shows an excellent Li ion conductivity of 4.01 × 10−4 S cm−1 at 60 °C. In addition, it is worth mentioning that the all-solid-state lithium battery based on this composite electrolyte exhibits a specific capacity of 140 mA h g−1 and an excellent capacity retention of 92.4% after running 100 cycles at a rate of 1C and 60 °C. The study offers a superior alternative for the design of PEO-based solid composite electrolytes. [ABSTRACT FROM AUTHOR]

Epoxy resin is widely used for electrical and electronics packaging in various forms due to its excellent adhesion, low cure shrinkage and good electrical insulation. However, the low thermal conductivity and mismatched dielectric properties limit its application in highly integrated circuits. In this work, alumina fibers (AFs) were firstly prepared via electrospinning with sol–gel precursor. Epoxy (EP) composites with graphene nanoplatelets (GNPs) and AFs were fabricated using a hot-pressing process. Microstructures, thermal conductivity and dielectric properties of EP hybrid composites were studied. Scanning electron microscopy images reveal that the modified AFs and GNPs were uniformly dispersed in the epoxy matrix and the thermal conductive reticular structures were formed. The AFs can not only link the GNPs and epoxy but also reduce the interfacial thermal resistance so that a high thermal conductivity of 1.62 W m−1 K−1 is realized in the EP–GNP–AF composite, which is about 8 times higher than pure EP. The decomposition temperature of the epoxy composites with 2 vol% GNP and 50 vol% AF loading was enhanced by about 100 degrees. Dielectric properties of EP composites have a strong dependence on frequency and a weak dependence on temperature, which gives rise to the potential in different electronic/electrical field applications. [ABSTRACT FROM AUTHOR]

Herein we report a novel and efficient approach to fabricate dielectric elastomers with enhanced dielectric constant and high dielectric strength. Azobenzenes with strong permanent dipole moments were synthesized to co-crosslink with hydroxyl-terminated polydimethylsiloxane through a simple one-step process, which realized a type of robust, molecularly homogenous silicone rubber (SR). The chemical structure, dielectric and mechanical properties of the resultant azo-g-PDMS elastomers with azobenzne contents ranging from 0 to 13.2 wt% were carefully characterized. The dielectric constant of azo-g-PDMS films at 1 kHz increased from 2.72 to 4.88 with the increase of azobenzene contents. By grafting with 4.0 wt% of azobenzene, the breakdown strength of azo-g-PDMS reached 89.4 V μm−1, which is 36% higher than that of pristine SR. The electric field induced deformation of silicone rubber could be enhanced by grafting with azobenzenes. The azo-g-PDMS film with 7.1 wt% of azobenzenes displayed a maximum area strain of 17%. Meanwhile, the azo-g-PDMS films exhibited a short response time (about 0.5 s) to the change in the electric field. Some prototype electromechanical actuators based on this type of azo-g-PDMS films were fabricated, demonstrating that the azo-g-PDMS dielectric elastomer is a very promising candidate for artificial muscle applications. [ABSTRACT FROM AUTHOR]

Polydimethylsiloxane (PDMS) elastomers with high mechanical and healing properties are developed as smart materials for electrical power systems and electronic devices to address electrical or mechanical damage. However, the challenge is to reconcile the conflicting molecular mechanisms of mechanical and healing properties in the development of PDMS elastomers. This study adopts the "rigid-while-flexible" mutual network structure by copolymerizing the rigid polyimide (PI) with flexible segments with dynamic reversible crosslinking designed on the PDMS backbones. This elastomer (designated PSiPI) exhibits high toughness, tensile strength and elongation at break, as well as excellent healing efficiency and recyclability. Moreover, the PSiPI elastomer also exhibits good insulation and corona damage healing properties. Taking advantage of the recyclability and healing properties of PSiPI elastomers, healable superhydrophobic coatings with contact angles greater than 150° have been prepared by compositing PSiPI elastomers with SiO 2 . Likewise, combining the elastomer with conductive materials can create a healing flexible conductor. This "rigid-while-flexible" design approach provides important inspiration for the development of high-performance, sustainable and environmentally friendly PDMS elastomers for electrical and electronic applications.

Solid polymer electrolytes (SPEs) have drawn considerable attention owing to their reliable safety performance, electrochemical stability and exceptional flexibility, which make them superior to conventional liquid electrolytes. Here, we report a novel composite electrolyte which is composed of homogeneously dispersed Li ion-conducting Li 0.33 La 0.557 TiO 3 (LLTO) nanowires in a poly(ethylene oxide) (PEO)/LiClO 4 matrix. It is demonstrated that only 3 wt% LLTO nanofibers are needed for the optimal performance of SPEs. The PEO-based composite electrolyte shows an excellent Li ion conductivity of 4.01 × 10 -4 S cm -1 at 60 °C. In addition, it is worth mentioning that the all-solid-state lithium battery based on this composite electrolyte exhibits a specific capacity of 140 mA h g -1 and an excellent capacity retention of 92.4% after running 100 cycles at a rate of 1C and 60 °C. The study offers a superior alternative for the design of PEO-based solid composite electrolytes.