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Thermo‐responsive dielectric materials are in urgent demand owing to the rapid development of smart electronic/electrical systems. Although different types and structures of thermally responsive dielectric materials have been continuously reported, their dielectric response behaviors all originate from thermodynamic phase transitions. Herein, it is demonstrated that structural relaxation in poly(vinylidene fluoride) (PVDF), a non‐thermodynamic phase transition, can induce a significant thermal dielectric pulse at room temperature. The dielectric pulse strength of up to 6.3 × 105 at 20 Hz, with a dielectric pulsing temperature of 24 °C, is achieved from polyethylene glycol (PEG)‐PVDF coaxial nanofibrous films (PVDF@PEG), fabricated via a continuous blow spinning method. Moreover, the films exhibit excellent flexibility, adjustable strength and toughness, switchable hydrophilicity/hydrophobicity, and effective thermal management capability. The relaxation‐induced dielectric pulsing effect, outstanding multifunctionality, and simple preparation combine to promote further scalability and prospects of PVDF@PEG. In particular, the work contributes to the discovery of the relaxation‐induced dielectric response mechanism, which provides a new strategy for the generation of thermo‐responsive dielectric materials. [ABSTRACT FROM AUTHOR]

Polymer‐based dielectric capacitors have attracted much attention because of their good flexibility, lightness, and high‐power density. However, the current polymer dielectric capacitors usually have too low energy density and cannot be used in high temperature environments, which limits the further development. Therefore, it has become increasingly important to develop high‐temperature dielectric materials with high energy density and low dielectric loss. In this study, long‐chain functionalized carbon nanotubes (CNTF) were introduced in Polyimide (PI) to obtained CNTF/PI composite film. CNTF have good compatibility with polymer and can solve the dispersion problem. The CNTF/PI composite film exhibits good dielectric property and an ultralow dielectric loss of 0.015. Especially, the discharged energy density of 3.77 J/cm3 of CNTF/PI composite film is the highest discharged energy density of reported polyimide‐based dielectric films at 300 MV/m. Therefore, these polyimide‐based dielectric materials are promising in the high temperature field of novel high‐performance film dielectric capacitor. [ABSTRACT FROM AUTHOR]

The materials with low dielectric constant and low dielectric loss are vital for high integration degree of the circuit board. Although many polymers like epoxy resin exhibit excellent comprehensive performance, their dielectric constant is unable to satisfy high electronic packaging application. In this work, we present a simple grafting strategy via reaction between the hollow glass microsphere and polyhedral oligomeric silsesquioxane followed by blending epoxy resin to fabricate epoxy resin hollow glass microspheres composite materials. The superior heat resistance of hollow glass microspheres (HGM) can improve the thermal performance of composites. Due to the addition of Ge‐POSS, P‐HGM exhibited a good interfacial compatibility with epoxy resin matrix and forms an interfacial adhesion region. With the P‐HGM loading of 20 wt%, the fabricated composite materials exhibited the low dielectric constant of 2.59 and low dielectric loss of 0.0145. At the same time, the tensile strength, impact strength and flexural strength were 42.15 MPa, 24.33 kJ/m2 and 90.82 MPa, respectively, which demonstrated that the epoxy resin hollow glass microspheres composite materials processed superb mechanical behavior. It suggests that this method is a promising potential for fabricating low dielectric composite materials. [ABSTRACT FROM AUTHOR]

Construction of environment‐friendly biomass‐based nanocomposites with high performance is in great demand for developing of a sustainable low‐carbon society. Here, transparent and flexible regenerated cellulose (RC)/layered double hydroxide (LDH) nanocomposite films were prepared from aqueous NaOH/urea solutions. The obtained nanocomposite films were characterized using AFM, SEM, FTIR, XRD, tensile testing, water contact angle, and thermogravimetric analysis. The results show that LDH nanoplatelets were individually dispersed with a thickness of 1 nm and surface diameter of 100 nm after ultrasonic treatment. Strong interaction existed between LDH nanoplatelets and cellulose molecules, leading to the improved thermal stability and mechanical strength of RC together with the original good properties of LDH. In particular, the nanocomposite films with 10 wt% LDH showed a 135% and 234% increase in the tensile strength and Young's modulus than those of the neat RC film. Meanwhile, the nanocomposite films exhibited high transparency. Therefore, these RC/LDH nanocomposites are promising in the fields of high‐performance packaging materials, flexible display panels, and high‐temperature dielectric materials. [ABSTRACT FROM AUTHOR]

Development of advanced dielectric materials with both high‐electric energy density and high‐temperature resistant attributes is highly desirable in modern electronics and electrical systems. Herein, a series of polyimide (PI)‐based sandwich‐structured dielectric nanocomposite films have been attempted to develop the advanced high‐temperature resistant capacitor films, wherein the boron nitride nanosheets/PI nanocomposite acts as the outer layers and the zinc oxide (ZnO)/PI as the middle layer. Benefitting from the merits of both fillers and the unique structure, the resulting nanocomposite films can simultaneously achieve both high‐dielectric constant and high‐breakdown strength, as well as low‐electrical conduction loss, thus leading to improved discharged energy densities (Ue) and charge/discharge efficiency (η) at elevated temperatures. It is found that the sandwich‐structured nanocomposite film with 0.4 vol% ZnO (0.4ZnO/PI‐S) can deliver a maximum Ue of 5.29 J cm−3 at 400 MV m−1 and 150°C, which is about 1.9 times that of the pristine PI film. Moreover, outstanding dielectric stability over 10,000 charge/discharge cycles has been demonstrated in such PI‐based sandwich‐structured nanocomposite films at 150°C and 200 MV m−1. This research may provide a new paradigm to explore polymer nanocomposites having excellent energy storage and efficiency at elevated temperatures. [ABSTRACT FROM AUTHOR]

Flexible dielectric materials with high energy density and remarkable charge–discharge efficiency are currently in great demand for the field of energy storage. On the other hand, it is also urgent to develop renewable, biodegradable and environmentally friendly dielectric materials. In this work, Al2O3 nanoparticles (AO) with a diameter of ~ 10 nm were incorporated into regenerated cellulose matrix (RC) without extra treatment to fabricate environment-friendly RC–AO dielectric nanocomposites via a simple dissolution/regeneration pathway. Effects of Al2O3 nanoparticles on the structure and dielectric properties of RC–AO nanocomposite films were systemically investigated. The results showed that the RC–AO films exhibited excellent comprehensive performance, including increased dielectric constant, reduced dielectric loss, improved breakdown strength and high energy storage density. Particularly, the high energy density of 5.7 J cm−3 was achieved at the breakdown strength of 380 MV m−1 when the Al2O3 content was 5 wt%. Furthermore, the composites possessed excellent thermal conductivity, stability and mechanical property. This work provides a good choice for the development of high-performance and 'green' natural polymer-based dielectric materials. [ABSTRACT FROM AUTHOR]

The development of flexible and high‐performance dielectric materials is of critical importance in energy storage devices. Since energy density of a dielectric capacitor is determined by the dielectric constant and breakdown strength, in this work, a simple and effective way is provided to increase the energy storage density of polymer matrix dielectric film via adding exfoliated mica nanosheets. Few‐layered mica nanosheets were successfully exfoliated by a facile one‐step method and incorporated with Poly(vinylidene fluoride) (PVDF) matrix. The mica nanosheets could act as the insulating barriers, which help to increase the breakdown strength of the PVDF/mica composites. The maximum discharged energy density of the prepared composite film was 7.93 J cm−3 at 450 MV m−1 with only 5 vol% of mica nanosheets, which is about three times higher than pure PVDF. This study introduced an economic and effective approach to get flexible and high energy density polymer composite films and broadened the application of mica. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Dielectric materials with low dielectric loss are highly desirable for future energy storage and management. Relatively high dielectric loss and complex fabrication process with high cost are current major factors limiting percolative dielectric composites for applications. In this study, low dielectric loss has been obtained using multi‐interface silver/epoxy/poly(vinylidene fluoride) (Ag/epoxy/PVDF) percolative composites by simple thermal curing and mechanical crushing, coupled with melt mixing and hot pressing. Isolated Ag/epoxy islands were formed in the PVDF matrix. The dielectric permittivity of the composite near the percolation threshold reached 132 whereas the loss tangent was around 0.1 at 100 Hz. This multi‐interface structure played an important role in suppressing the dielectric loss and achieving the relatively high dielectric permittivity in these composites. Our results suggest that the simple and low‐cost fabrication of the Ag/epoxy/PVDF is a promising approach for the development of low‐loss percolative dielectric composites. POLYM. COMPOS., 39:E2606–E2610, 2018. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The development of advanced dielectric materials with high electric energy densities is of crucial importance in modern electronics and electric power systems. Here, a new class of multilayer-structured polymer nanocomposites with high energy and power densities is presented. The outer layers of the trilayered structure are composed of boron nitride nanosheets dispersed in poly(vinylidene fluoride) (PVDF) matrix to provide high breakdown strength, while PVDF with barium strontium titanate nanowires forms the central layer to offer high dielectric constant of the resulting composites. The influence of the filler contents on the electrical polarization, breakdown strength, and energy density is examined. Simulations are carried out to model the electrical tree formation in the layered nanocomposites and to verify the experimental breakdown results. The trilayered polymer nanocomposite with an optimized filler content displays a discharged energy density of 20.5 J cm−3 at Weibull breakdown strength of 588 MV m−1, which is among the highest discharged energy densities reported so far. Moreover, the nanocomposite exhibits a superior power density of 0.91 MW cm−3, more than nine times that of the commercially available biaxially oriented polypropylene. The findings of this research provide a new design paradigm for high-performance dielectric polymer nanocomposites. [ABSTRACT FROM AUTHOR]

Flexible dielectric materials with high electric energy density and high‐temperature resistant characteristic are of great importance for modern electronics and electrical systems. Herein, two‐dimensional molybdenum disulfide (MoS2) nanosheets were efficiently produced via liquid‐phase exfoliation and then incorporated into polyimide (PI) to prepare MoS2/PI dielectric nanocomposites. Compared to the pristine PI, MoS2/PI nanocomposite films exhibited much larger dielectric permittivity while their dielectric losses still maintained relatively low levels. On the other hand, the Weibull breakdown strength of these nanocomposite films initially increased and then decreased with the increase in the MoS2 content and gave rise to a maximum value of 395 MV m−1 at 1 vol % loading. Combination of the improved dielectric permittivity and breakdown strength makes the MoS2/PI nanocomposite film with 1 vol % MoS2 possess an elevated energy density of about 3.35 J cm−3. Moreover, good tensile and thermal properties of the nanocomposite films hold great promise for their applications in high‐temperature and harsh conditions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47991. [ABSTRACT FROM AUTHOR]

Multilayered polymer nanocomposites with high energy and power densities are described by Chuanxi Xiong, Hong Wang, Qing Wang, and co‐workers in article number 1606292. Boron nitride nanosheets dispersed in poly(vinylidene fluoride) (PVDF) matrix provide high breakdown strength for the outer layer, while PVDF with barium strontium titanate nanowires forms a central layer ensuring high dielectric constant of the resulting composites. [ABSTRACT FROM AUTHOR]

Abstract It is of crucial importance to develop novel dielectric materials with high discharge energy densities to meet the urgent requirements in the rapid advances in modern electronics and electrical power systems. In this work, we describe a new class of sandwich-structured ceramic-polymer nanocomposites base on poly(vinylidene fluoride- co -hexafluoropropylene) exhibiting outstanding energy storage performance. The central layer of the composite consists of MgO nanowires to offer high breakdown strength, whereas the outer layers contain BaTiO 3 nanofibers to provide improved dielectric constant of the composites. The systematic investigation gave the composites with 2 wt% MgO in the central layer and 20 wt% BaTiO 3 in the outer layers to yield the best energy density of 15.55 J cm−3 with a charge-discharge efficiency of 68% at the Weibull breakdown strength of 416 MV m−1. It is found that the trilayered nanocomposite exhibits superior energy storage performance as compared to the corresponding single-layered composite films. The result demonstrates the uniqueness of the layered structure to incorporate multiple inorganic components into polymer with enhanced collective properties for energy applications. [ABSTRACT FROM AUTHOR]

Dielectric materials with ultrahigh energy densities are of importance in modern electric industry. However, for dielectric nanocomposites, their ultrahigh energy densities were typically achieved at the expense of low charge-discharge efficiencies (η) of 60%–70% at high electric fields, which is not desirable for practical applications. In this study, a class of newly designed sandwiched polymer nanocomposites based on poly(methyl methacrylate) (PMMA) as the central layer to enhance the breakdown strength and charge-discharge efficiency and poly(vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP) loaded BaTiO 3 nanoparticles (BT NPs) as the outer layers to boost the polarization. It is found that the sandwiched nanocomposite with 10 wt% BT NPs in the outer layers possesses a largely enhanced energy density of 17.1 J cm−3 with a high η of 82% at the Weibull breakdown strength of 559 MV m−1. To our knowledge, this is one of the highest η achieved at high electric fields among the dielectric nanocomposites reported so far. This work demonstrates the uniqueness of the trilayered structure to incorporate multiple components and display much enhanced collective properties for energy applications. Image 1 [ABSTRACT FROM AUTHOR]

• PDA modification improved interaction between BaTiO 3 nanofiber and cellulose. • RC/PDA@BTNF films possessed improved dielectric constant and breakdown strength. • The composite films exhibited high energy density, cycle stability and efficiency. • The composite films maintained good dielectric properties for a long time. Flexible electrostatic capacitors have many potential applications in modern electric power systems. In this study, flexible cellulose-based dielectric films were prepared by compositing regenerated cellulose (RC) and one-dimensional BaTiO 3 nanofiber (BTNF) via a simple and environmentally friendly process. To improve compatibility and distributional homogeneity of the fillers/matrix, BTNF was surface modified by dopamine to prepare the poly(dopamine) modified BTNF (PDA@BTNF). The obtained RC/PDA@BTNF composite films (RC-PDA@BTNF) possessed higher dielectric constant and breakdown strength than those of the RC and RC/BTNF composite films. In particular, RC/PDA@BTNF composite films with 2 vol% PDA@BTNF (RC-2PDA@BTNF) exhibited a high discharged energy density of 17.1 J/cm3 at 520 MV/m, which exceeded 40 % compared with that of RC-2BTNF at 460 MV/m. Meanwhile, RC-2PDA@BTNF could continuously work for more than 10,000 times with a high efficiency of 91 %. Furthermore, the composite films could maintain good dielectric properties for a long time when stored in vacuum condition (under 0.3 atm). Therefore, these flexible cellulose-based dielectric materials are promising in the field of novel high-performance film dielectric capacitors. [ABSTRACT FROM AUTHOR]

• Chitin was investigated for the first time as dielectric film capacitors. • Chitin/BNNS composites were fabricated through dissolution/regeneration process. • The dielectric properties of composites were improved by the incorporation of BNNS. • The composites also showed enhanced mechanical properties and thermal stability. Polymer-based film capacitors have attracted considerable attention owing to their important applications in both electronics and electrical systems. However, ever-growing environmental challenges stimulate a great demand for exploring renewable dielectric materials. Herein, flexible film dielectrics based on regenerated chitin and boron nitride nanosheets (BNNSs) were fabricated, for the first time, through a straightforward low-temperature dissolution/regeneration process, in which a "green" KOH/urea aqueous system was chosen as both the solvent of chitin and the exfoliation agent of BNNSs. Benefit from the excellent intrinsic properties of embedded BNNS, substantially elevated dielectric performances were achieved, including much suppressed dielectric loss along with significantly enhanced breakdown strength. Particularly, an ultrahigh charge-discharge efficiency of above 90% could be well-maintained in composites with only 6 wt% BN loading, even the applied electric field up to 400 MV m−1, therefore resulting in a marvelous discharge energy density of 8.67 J cm−3. Furthermore, aside targeted excellent dielectric properties, the resultant composites also possessed improved mechanical and thermal properties. This strategy developed here not only broadens the application of chitin, but also opens a new window for the establishment of next-generation environment-friendly dielectrics with superb dielectric properties. [ABSTRACT FROM AUTHOR]

Temperature responsive dielectrics provide the opportunity to obtain permittivity tunable materials, which is particularly useful in modern electrical and electronic devices. However, the applications of the tunable dielectric materials are largely limited owing to the low dielectric transition temperature and/or insufficient shape stability during phase transition. Herein we present the first example of poly(vinylidene fluoride)/polyethylene glycol/graphene oxide (PVDF/PEG/GO) composites with tunable dielectric permittivity based on temperature-dependent phase transition of PEG. The permittivity switching of shape-stabilized PVDF/PEG/GO composites can be triggered above room temperature. This report may provide a roadmap of fabricating new tunable or switchable dielectrics with relatively high dielectric transition temperatures based on polar organic phase change materials. [ABSTRACT FROM AUTHOR]