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Dielectric elastomers, used as driver modules, require high power density to enable fast movement and efficient work of soft robots. Polyacrylate elastomers usually suffer from low power density under low electric fields due to limited response frequency. Here, we propose a bimodal network polyacrylate dielectric elastomer which breaks the intrinsic coupling relationship between dielectric and mechanical properties, featuring relatively high dielectric constant, low Young's modulus, and wide driving frequency bandwidth (~200 Hz) like silicones. Therefore, an ultrahigh power density (154 W kg−1@20 MV m−1, 200 Hz) is realized at low electric field and high resonance frequency, 75 times greater than at 10 Hz. Further, a rotary motor is developed, reaching an impressive speed of 1245 rpm at 19.6 MV m−1 and 125 Hz, surpassing previous acrylate-based motors and entering the high-speed domain of silicone-based motors. These findings offer a versatile strategy to fabricate high-power-density dielectric elastomers for low-electric-field soft actuators. The authors make a bimodal network polyacrylate dielectric elastomer featuring high driving frequency like silicones and thereby a high power density of 154 W kg−1@20 MV m−1, 200 Hz. Their rotary motor realizes a maximum rotating speed of 1245 rpm@ 19.6 MV m−1. [ABSTRACT FROM AUTHOR]

Dielectric elastomer actuators (DEAs) face an acknowledged challenge: On the one hand, the majority of elastomers only achieve small electroactive deformation (<20%) in the absence of prestretch; on the other hand, rare elastomers capable of showing large electroactive deformation require relatively complicated processing and chemistry. This work addresses this challenge by fabricating an elastomer with a network of large side groups, which achieves a very large electroactive deformation (218%) without pre‐stretch. This elastomer can be rapidly and massively fabricated within a few min, by polymerizing a commercial monomer with a large alkyl side group. The large side groups in the polymer network repel each other and extend the load‐bearing strands, which results in a pronounced strain‐hardening behavior. This behavior helps the elastomer to get rid of electromechanical instability during actuation and hence to exhibit a large electro‐active deformation, a high energy density (>> human muscle), and a large output force (≈500 times self‐weight). the elastomer capable of manufacturing a soft electroactive gripper is demonstrated with large deformation, large force, and rapid response, which enables grasping fragile objects of various complex shapes in an agile away. [ABSTRACT FROM AUTHOR]

Polymer‐based dielectrics with fast electrostatic energy storage and release, are crucial for advanced electronics and power systems. However, the deterioration of insulation performance and charge–discharge efficiency of polymer dielectrics at elevated temperatures and high electric fields hinder the applications of capacitors in harsh environments. Herein, a facile and scalable approach is reported to fabricating flexible high‐temperature polymer dielectrics for high‐efficiency energy storage by ultraviolet irradiation. The resultant dielectric films exhibit an augment of 493% in energy density and exceeding 800% in discharge efficiency at 200 °C (3.2 J cm−3 and over 90% discharge efficiency at 480 M V−1m for irradiated polyetherimide (PEI), 0.54 J cm−3, and below 10% discharge efficiency at 400 MV m−1 for pristine PEI) and excellent cycle performance. The injected space charge is found to be the dominant contributor to energy loss during the charge–discharge process. Free radicals introduced by ultraviolet irradiation can act as deep traps to capture injected charge and suppress space charge migration. This work clarifies the contribution of space charge to energy loss and demonstrates the effectiveness of ultraviolet irradiation in improving the capacitive performance of high‐temperature polymer dielectrics. These findings provide a novel paradigm for the rational design of high‐temperature polymer dielectrics for high‐efficiency energy storage. [ABSTRACT FROM AUTHOR]

Dielectric capacitors play a pivotal role in the advancement of electric power systems and emerging energy technologies. However, the deterioration of dielectric performance in energy storage materials at elevated temperatures represents a significant challenge. In this study, organic electron‐scattering agents into polyetherimide (PEI) are introduced, creating a "peaked barrier" to impede charge carrier transport. By doping PEI with an ultralow volume fraction (0.8%) of the organic molecule filler 4‐(dimethylamino)phenylboronic acid (4‐NB), the electron‐repelling nature of 4‐NB is leveraged in order to regulate charge carrier injection and transport in a synergistic manner. Consequently, the discharged energy density of the PEI composite material increases to 7.93 J cm−3 (720 kV mm−1) at 30 °C. At 150 °C, the discharged energy density increases to 5.21 J cm−3 (580 kV mm−1). In both cases, the charge and discharge efficiencies are maintained at 90%. It is noteworthy that the prepared PEI composite material also exhibits excellent charge dissipation characteristics, maintaining stable charge and discharge efficiency even after 50 000 charge–discharge cycles. In summary, the study's design concept systematically optimizes the processes of charge carrier injection, transport, and dissipation. This approach offers a novel perspective for the development of dielectrics that are suitable for long‐term energy storage. [ABSTRACT FROM AUTHOR]

In order to meet the requirements of practical applications, the comprehensive performance of thermally conductive high‐voltage insulating composites is worth evaluating. Guided by the particle packing theory, spherical alumina particles with different particle size distributions were compounded and filled into low‐density polyethylene (LDPE), and the thermal conductivity (TC) and mechanical breakdown of different compound systems were systematically investigated. The results show that the particle grading design of small‐particle filled composites has better comprehensive properties than that of single‐scale or large‐particle filled composites, which proves the superiority and feasibility of particle grading design. The 110–40 wt.% composite has a higher TC (0.47 W/(m K)) compared with LDPE, while maintaining excellent insulation properties (227 kV/mm) and mechanical properties (tensile strength of 10 MPa and elongation at break of 720%). Finally, studies on the application of composite materials in the field of thermal management and ice melting of steel‐core aluminum insulated wires were applied, and both studies show good prospects for the applications of Al2O3/LDPE thermal conductive high‐voltage insulation composites. [ABSTRACT FROM AUTHOR]

Machine learning has shown its great potential in the accelerated discovery of advanced materials in the field of computational molecular design. High-temperature polymer dielectrics are urgently required with the emerging applications of energy-storage dielectric film capacitors under high-temperature conditions. Here, we demonstrate the successful prediction of polymers with a high dielectric constant (ɛ) and high glass transition temperature (Tg) using a Bayesian molecular design model. The model is trained on a joint data set containing 382 computed ɛ values using density functional perturbation theory and experimentally measured Tg values of ∼7000 polymers to build relative quantitative structure–property relationships and identify the promising polymers with specific desired range of dielectric constant and glass transition temperature. From the hypothetical polymer candidates, ten promising polymers are proposed based on their predicted properties and synthetic accessibility score for high-temperature dielectric film capacitors' application. Moreover, 250k novel polymer structures are generated with the model to support future polymer informatics research. This work contributes to the successful prediction of high-temperature polymer dielectrics using machine learning models. [ABSTRACT FROM AUTHOR]

Dielectric elastomer actuator (DEA) is considered as an ideal artificial muscle with soft and light in nature, widespread application in soft robotics and sensors. Dielectric elastomer (DE), the core component of DEA, with high output force and large actuation strain under relatively low driving electric field is critical for high‐performance DEA. However, the widely used VHB series (3M) DE suffered from very large pre‐strain and high driving voltage to get their high actuation performance, limiting their scope of application. In this work, the DEs with good mechanical and dielectric properties were prepared via UV curing method consisting of acrylic acid (AA) with strong polar groups as functional monomer, n‐butyl acrylate (BA) as soft monomer and urethane acrylate as cross‐linker (c‐p(BA‐AA)). The c‐p(BA‐AA) DE films obtained the simultaneous increasing of dielectric constant and breakdown strength with the increasing content of AA, which guaranteed the good actuation performance. The c‐p(BA‐AA) film exhibited excellent actuating performance (44.11% actuation strain at 45 kV/mm) without pre‐strain. Besides, a simple linear actuator based on the c‐p(BA‐AA) film could easily output weight that is tens of times of its own active weight (654.1 mN/g at 30 kV/mm). [ABSTRACT FROM AUTHOR]

The performance and stability of perovskite solar cells (PSCs) are dominated by the electron and hole transport dynamics, which are highly desired to be characterized in the working devices. Nevertheless, for the opaque PSCs, the hole transport layer (HTL) in n–i–p devices or the electron transport layer (ETL) in p–i–n devices are typically buried beneath the metal electrode, which makes it difficult to simultaneously characterize the charge transport dynamics from both sides of the working devices. In this work, for the first time, the charge transport dynamics of the working devices from both the front and rear side of semitransparent PSCs (ST‐PSCs) is characterized via femtosecond transient reflection spectroscopy (FS‐TRS). A significant enhancement of the hole transport and negligible change of the electron transport is observed when the perovskite/HTL interface is treated by 2‐chloro‐phenethylammonium iodide (2‐Cl‐PEAI). A champion power conversion efficiency (PCE) of 23.3% (certified 22.3%) is achieved, which is the highest certified PCE for ST‐PSCs up to date. The ST‐PSCs maintained more than 90% of its initial efficiency after 2000 h of maximum power point tracking (MPPT). Additionally, the ST‐PSCs are implemented in 4‐terminal (4‐T) perovskite/passivated emitter rear silicon cell (PERC), reaching a simulated output power of 30.8 mW cm−2. [ABSTRACT FROM AUTHOR]

Polymer composites with high energy density have been of great interest to scientists for a long time, and this accounts for a great wealth of experimental data that are available for interpretation. One of the important phenomena is the variation rate of the permittivity of composites, which always deviates from the linear increase and rises steeply toward the high concentration. Interestingly, the critical transition concentration is always located in the range of 20 vol. %–25 vol. %, but still far less than the common percolation threshold of composites. Through the analysis of the local electric field distribution and surface polarized charges distribution, the phenomenon is successfully interpreted as the effect of the electrostatic interactions between the adjacent polarized particles. Two specified composite configurations (BCC and FCC) are designed, and their dielectric properties have been systematically studied with the help of the finite element method and the phase field method. The simulation results indicate that the strength of the particles' interaction is short-range effective and depends closely on the gap distance between adjacent particles. When the gap distance is smaller than 0.8 times the radius of the particles, which is tantamount to the concentration larger than 20 vol. % and 25 vol. % for BCC and FCC, respectively, the electrostatic interaction of the particles is rather significant, resulting in an additional contribution on the variation of the dielectric properties of composites and vice versa. The synchronous variation tendency between the simulation results and experimental measurements demonstrates the effect of electrostatic interaction on the dielectric properties of composites. [ABSTRACT FROM AUTHOR]

Large deformability and high sensitivity is difficult to be realized simultaneously in flexible sensors. Herein, taking advantage of the high permittivity and highly active surfaces of the ultrasmall barium titanate nanoparticles (BT NPs) and the high stretchability of the p(BA‐GMA) elastomer matrix, we propose a high‐performance soft stretchable sensor. The addition of the ultrasmall BT NPs can not only increase the permittivity and capacitance of polyacrylate‐matrix composite dielectric material to obtain a high sensitivity, but also basically maintains the excellent mechanical properties of the polymer matrix. The dielectric constants of the composite films increase from 5.68 to 13.13 at 10 kHz with the increase of BT NPs content from 0 to 15 vol.%, which results in a high capacitance of 236.16 pF for 15 vol.% BT/p(BA‐GMA) sensor. Combining the high permittivity and the large deformability (a maximal deformation of 87.2%), the 15 vol.% BT/p(BA‐GMA) sensor has high sensitivity and shows high linearity and stable output even if under dynamic measurement. The dual‐mode sensor that utilizes the orthogonality of capacitance‐resistance is designed, which shows excellent performance in monitoring human body movements and noncontact measurement. The results present that the BT/p(BA‐GMA)‐based sensor has high stability and reliability not exceed 65°C, which can meet the application requirements in dynamic monitoring. [ABSTRACT FROM AUTHOR]

Highlights: A bilayer dielectric film is prepared via coating boron nitride nanosheets (BNNSs) by solution casting on the surface of polyethylene terephthalate (PET) film. The BNNS layer acts as the efficient barrier layer to suppress the charge injection, thereby making the surface-modified PET films exhibit excellent breakdown strength and electrostatic energy storage performance. The surface coating methods are accessible and suitable for large-scale roll-to-roll process production of dielectric films. The further electrification of various fields in production and daily life makes it a topic worthy of exploration to improve the performance of capacitors for a long time, including thin-film capacitors. The discharge energy density of thin-film capacitors that serves as one of the important types directly depends on electric field strength and the dielectric constant of the insulation material. However, it has long been a great challenge to improve the breakdown strength and dielectric constant simultaneously. Considering that boron nitride nanosheets (BNNS) possess superior insulation and thermal conductivity owing to wide band gap and 2-dimensional structure, a bilayer polymer film is prepared via coating BNNS by solution casting on surface of polyethylene terephthalate (PET) films. By revealing the bandgap and insulating behavior with UV absorption spectrum, leakage current, and finite element calculation, it is manifested that nanocoating contributes to enhance the bandgap of polymer films, thereby suppressing the charge injection by redirecting their transport from electrodes. Worthy to note that an ultrahigh breakdown field strength (~ 736 MV m−1), an excellent discharge energy density (~ 8.77 J cm−3) and a prominent charge–discharge efficiency (~ 96.51%) are achieved concurrently, which is ascribed to the contribution of BNNS ultrathin layer. In addition, the modified PET films also have superior comprehensive performance at high temperatures (~ 120 °C). The materials and methods here selected are easily accessible and facile, which are suitable for large-scale roll-to-roll process production, and are of certain significance to explore the methods about film modification suitable for commercial promotion. [ABSTRACT FROM AUTHOR]

Dielectric capacitors are fundamental energy storage components in electronics and electric power systems due to their unique ultrahigh power density. However, their relatively low energy storage density is a long‐standing challenge which greatly limits their practical application range. Chitosan (CS) and montmorillonite (MMT) are two kinds of materials that exist abundantly on the earth with natural surface charges. The positively charged CS and negatively charged MMT can be self‐assembled into the typical sandwich‐structured CS/MMT/CS 2D structure through an electrostatic attraction. Loading these surface‐charged sandwich‐structured nanosheets into poly(vinylidene fluoride)‐based composite with a weight fraction as tiny as 0.3 wt.%, an ultrahigh energy storage density of 32.5 J cm−3 accompanied with a high efficiency of 64% are concurrently achieved with a very low cost and scalable process. Guided by finite element simulation, it is revealed that a number of electric potential wells that exist in the charged sandwich nanosheets impede the acceleration of internal charges and hinder the growth of electrical trees. The results offer a novel paradigm for exploring ultrahigh energy storage density capacitors in an economical way. [ABSTRACT FROM AUTHOR]

Polymer dielectrics with high energy density are of urgent demand in electric and electronic devices, but the tradeoff between dielectric constant and breakdown strength is still unsolved. Herein, the synthesis and molar mass control of three alternating [1.1.1]propellane‐(meth)acrylate copolymers, denoted as P‐MA, P‐MMA, and P‐EA, respectively, are reported. These copolymers exhibit high thermal stability and are semi‐crystalline with varied glass transition temperatures and melting temperatures. The rigid bicyclo[1.1.1]pentane units in the polymer backbone promote the orientational polarization of the polar ester groups, thus enhancing the dielectric constants of these polymers, which are 4.50 for P‐EA, 4.55 for P‐MA, and 5.11 for P‐MMA at 10 Hz and room temperature, respectively. Moreover, the high breakdown strength is ensured by the non‐conjugated nature of bicyclo[1.1.1]pentane unit. As a result, these copolymers show extraordinary energy storage performance; P‐MA exhibits a discharge energy density of 9.73 J cm–3 at 750 MV m–1 and ambient temperature. This work provides a new type of promising candidates as polymer dielectrics for film capacitors, and offers an efficient strategy to improve the dielectric and energy storage properties by introducing rigid non‐conjugated bicyclo[1.1.1]pentane unit into the polymer backbone. [ABSTRACT FROM AUTHOR]

In this work, a small amount of ionic liquids (ILs, 1-vinyl-3-ethylimidazolium tetrafluoroborate) was used to modify tungsten disulfide (WS2), and then, the modified WS2 was mixed with ethylene propylene diene monomer (EPDM) to obtain IL-WS2/EPDM composites with different IL contents. The content of WS2 in composites was determined from the result of our previous work. The nonlinear electrical conductivity of composites at 25 °C, 50 °C, and 80 °C was measured and analyzed subsequently. A small amount of ILs has an influence on the nonlinear property of composites, and the inflection point of the ternary composite can be controlled by changing IL contents. The direct current (DC) breakdown strength and thermal conductivity of composites were also measured and researched. Addition of ILs would decrease the breakdown strength of IL-WS2/EPDM composites. [ABSTRACT FROM AUTHOR]

Polymer dielectrics are insulators or energy storage materials widely used in electrical and electronic devices. Polymer dielectrics are needed with outstanding dielectric characteristics than current technologies. In this study, the self-assembly of boron nitride nanosheets (BNNSs) was applied to form an inorganic–organic nanocoating on various common polymer dielectrics. It is inexpensive and easy to fabricate this thin coating on a large scale. The coating has a wide bandgap and thus can significantly improve the breakdown strength of polymer dielectrics. The charge characteristics and trapping parameters of nano-domains on the surfaces of polymer dielectrics were measured, and the coating had shallow trap levels. This facilitated the dissipation of surface charges and thus greatly increased the flashover voltage. The coating also effectively improved the temperature stability and dielectric constant of the polymer dielectric. This nanocoating shows potential as a method to effectively improve the dielectric characteristics of polymer dielectrics and outperform existing composite polymer dielectrics, which are crucial for large-scale applications in energy storage and power and electronic devices. [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]

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]

In order to improve the dielectric properties and the thermal conductivity of the PVDF-based composites, the BaTiO3@super-short MWCNT (BT@SSCNT) particles were modulated by a SSCNT shell fabricated by MWCNT with the different types (S-MWCNT-1020, S-MWCNT-2040). The average size of these particles is about 300 nm. With the increase in the external diameter of MWCNT, the SSCNT content of the BT@SSCNT particles decreases. However, the sum proportions of which the diameter of the particles is not less than 295 nm have a distinct growth leading to that the distance between the neighboring particles shortens. The dielectric constants of the composites are more than 355 and 1500 (103 Hz) at 10 wt% and 60 wt% filler loading, respectively. Compared with the BT@SSCNT/PVDF-1020 composites, the dielectric constants of the BT@SSCNT/PVDF-2040 composites have a more stable frequency dependency in the range of 102 to 106 Hz. The value of the composite with 10 wt% BT@SSCNT loading maintains more than 250 at 106 Hz. The introduction of the shell of SSCNT with larger external diameter can offer the composites a more desirable combined action of dielectric mechanisms, including interfacial polarization and micro-capacitor effect. In addition, the varying SSCNT shells also have evident influence on dielectric loss, breakdown strength, and thermal conductivity. It is worth mentioning that the values of the BT@SSCNT/PVDF-2040 composites are 334 and 0.16 (104 Hz), 229 kV mm−1, and 1.13 W (m K)−1 at 10 wt% filler loading, respectively. This work could extend the strategies for building the core–shell particles to develop dielectric nanocomposites. [ABSTRACT FROM AUTHOR]

Increasing the actuation characteristics of dielectric elastomer actuators (DEAs) under low electric field strength without compromising the elasticity and breakdown strength is still one of the great challenges in application field. Herein, we propose a simple, efficient, and controllable strategy to prepare dielectric elastomers with intrinsically good integrated properties by introducing styrene ethylene butylene styrene (SEBS) in thermoplastic polyurethane (TPU). Combined with experiments and molecular dynamics simulation, we find that the SEBS is uniformly dispersed in TPU matrix and a good interface structure is formed by pi–pi interaction and entanglement. The above characteristics lead to the destruction of the hydrogen bond network of TPU and the formation of single aggregation structure. Consequently, much decreased Young's modulus (Y) and enhanced breakdown field (Ebr) are achieved. Especially, when the content of SEBS is 4.76 wt%, the blend shows a desirable Y of 2.4 MPa and a much improved Ebr (118 kV mm−1), which is about 59% lower and 42% higher than those of TPU, respectively. As a result, the maximum electrical strain area of the dielectric blend elastomer reaches 4.7%, which is 250% higher than that of pure TPU under the same electric field strength. [ABSTRACT FROM AUTHOR]

A new generation of high-temperature dielectric materials toward capacitive energy storage is highly demanded, as power electronics are always exposed to elevated temperatures in high-power applications. Polymer dielectric materials, as ideal candidates for capacitors, suffer from deteriorated energy density because of their depressed dielectric constant and decreased breakdown strength at high temperatures, which become major barriers for their application in harsh environments. Here, sandwich-structured dielectric polymer nanocomposites with superior high-temperature capacitive performances are reported. Very different from the conventional single-layer designs, such sandwich-structured configurations can integrate the complementary properties of multiple spatially organized components in a synergistic manner, simultaneously raising the dielectric constant and breakdown strength, and subsequently greatly increasing the discharged energy density at elevated temperatures. Further analysis by simulation shows the evolution process of electrical tree channels in the experimental breakdown and dissipation of Joule heating. Consequently, the sandwich-structured polymer nanocomposites deliver an outstanding Ud value of 4.14 J cm−3, with a η value of above 90% at 150 °C, outperforming the current high-temperature dielectric polymers and composites. This work provides a new design paradigm for high-temperature electrical energy storage applications. [ABSTRACT FROM AUTHOR]

To suppress the high dielectric loss of graphene oxide (GO)/poly(vinylidene fluoride) (PVDF) while still maintaining a high dielectric constant (k) near the filler percolation threshold, herein, GO nanosheets coated with polyvinyl pyrrolidone (PVP), poly(dopamine) (PDA) and tannic and Fe coordination complexes (TA-Fe), respectively, were incorporated into PVDF to investigate the effects of the three kinds of insulating interlayers on the dielectric properties of the nanocomposites. The results indicate that compared with pristine GO, all surface modified GO exhibit homogeneous dispersion in the matrix owing to the enhanced interface between fillers and matrix, and that the dielectric loss of the nanocomposites are significantly suppressed to rather low levels thanks to the presence of various insulating interlayers between GO nanosheets, which prevent them from direct contact, thereby remarkably reducing the leakage current and conductivity. Moreover, Activation energies for the pristine and modified GO/PVDF nanocomposites are calculated, respectively, and the introduction of insulating interlayers significantly reduces the relaxation activation energy of the nanocomposites. [ABSTRACT FROM AUTHOR]

Dielectric elastomer actuators (DEAs) with large electrically-actuated strain can build light-weight and flexible non-magnetic motors. However, dielectric elastomers commonly used in the field of soft actuation suffer from high stiffness, low strength, and high driving field, severely limiting the DEA's actuating performance. Here we design a new polyacrylate dielectric elastomer with optimized crosslinking network by rationally employing the difunctional macromolecular crosslinking agent. The proposed elastomer simultaneously possesses desirable modulus (~0.073 MPa), high toughness (elongation ~2400%), low mechanical loss (tan δm = 0.21@1 Hz, 20 °C), and satisfactory dielectric properties ( ε r = 5.75, tan δe = 0.0019 @1 kHz), and accordingly, large actuation strain (118% @ 70 MV m−1), high energy density (0.24 MJ m−3 @ 70 MV m−1), and rapid response (bandwidth above 100 Hz). Compared with VHBTM 4910, the non-magnetic motor made of our elastomer presents 15 times higher rotation speed. These findings offer a strategy to fabricate high-performance dielectric elastomers for soft actuators. Dielectric elastomer actuators (DEAs) with large electrically actuated strain can be used in non-magnetic motors, but high stiffness, poor strength and slow response currently limit the application of DEAs. Here, the authors optimize the crosslinking network in a polyacrylate elastomer to enable a DEA with high toughness and actuation strain and use the polyacrylate to build a motor which can be driven under low electric field. [ABSTRACT FROM AUTHOR]

Polymer-based dielectrics are widely applied in the fields of electronics and electrical power systems due to the high breakdown strength, excellent flexibility, and unique self-healing capability. However, the low stored energy density and unsatisfactory heat management of polymer dielectrics hinder the development of polymer-based film capacitors. In this research, artificial composites with improved capacitive energy storage and thermal conductivity are fabricated by blending the two-dimensional semiconductive MXene sheets with a polyimide (PI) matrix. Remarkably, a PI based composite with 1 wt. % MXene sheets increases its dielectric permittivity from ≈3.27 to ≈3.53 and enhances its discharged energy density from ≈1.93 to ≈2.38 J/cm3 while maintaining its low dielectric loss of <0.02 and relatively high charge–discharge efficiency of >80%. Meanwhile, a high in-plane thermal conductivity of 0.418 W m−1 K−1 is achieved for PI/MXene composites with 5 wt. % MXene. In addition, the distribution of temperature field inside the composites has been investigated by a finite element method. These results represent a strategy in polymer dielectrics to achieve simultaneous high energy density and thermal conductivity, which may also have potential for applications in high temperature environments. [ABSTRACT FROM AUTHOR]

Polymer‐based film capacitors with high breakdown strength and excellent flexibility are crucial in the field of advanced electronic devices and electric power systems. Although massive works are carried to enhance the energy storage performances, it is still a great challenge to improve the energy density of polymer composites under the premise of large‐scale industrial production. Herein, a general strategy is proposed to improve the intrinsic breakdown strength and energy storage performances by blending core‐shell structured methyl methacrylate‐butadiene‐styrene (MBS) rubber particles into a polymer matrix. Good compatibility and uniform dispersion state of MBS particles are observed in the matrix. Polarizing microscopy images show that blended films exhibit clear reduction of crystalline grains with the addition of MBS particles. Accordingly, an increased breakdown strength of 515 MV m−1 and discharged energy density of 12.33 J cm−3 are observed in poly(vinylidene fluoride‐co‐hexafluoropropylene)‐based composite films. Through comprehensive characterizations, it is believed that the superior energy storage performance of composite films is attributed to decreased crystalline grains, improved mechanical properties, and restriction on carrier motion. These results provide a novel design of dielectric polymers for high breakdown strength and discharged energy density applications. [ABSTRACT FROM AUTHOR]

Polymer dielectrics with super dielectric constant (ε'), low loss as well as high thermal conductivity (TC) are gaining tremendous momentum owing to the ever-increasing demands on microelectronic devices. Introduction core–shell fillers into polymers has been demonstrated as a promising strategy for high-ε' but low loss. Herein, nickel (Ni) particles were encapsulated by an insulating layer of NiO with various thicknesses via controlling calcination times at 550 °C under air, and the as-prepared core–shell Ni@NiO was incorporated into poly(vinyli-dene fluoride) (PVDF). The results verify the formation of a NiO shell outside of the Ni, and manifest that the PVDF with Ni@NiO particles exhibit a high ε', a signally suppressive loss and conductivity, as well as a high-TC compared with raw Ni. The reason can be ascribed to multiple effects of NiO interlayer including the enhancement of interface compatibility and interface polarizations and the blocking of leakage current. Furthermore, the thickness of NiO shell exerts different influences on long-range and short-range charge migration, and it should be rationally tuned to optimize the dielectric properties and TC. This study provides an effective idea to regulate and control the dielectric properties and TC of polymer composites. [ABSTRACT FROM AUTHOR]

Flaky Cu (f-Cu) particles with surface modification by polystyrene (PS) coating layer were incorporated into poly(vinylidene fluoride) (PVDF), to obtain high dielectric constant (k) and thermal conductivity (TC) but low dielectric loss polymer composites. The results confirm the formation of a layer PS shell outside of the f-Cu, and indicate that the PVDF composites with f-Cu@PS particles exhibit superior dielectric properties compared with pristine f-Cu/PVDF. The improved dielectric performance can be attributed to the insulating PS interlayer preventing the f-Cu from direct contact with each other and meanwhile hindering the long-range electron migration. The dielectric properties of composites can be tuned through finely tailoring the PS shell' thickness. Additionally, the f-Cu@PS/PVDF composites display slightly higher TC than the raw f-Cu/PVDF, owing to the suppressed thermal interfacial resistance and improved interfacial compatibility between the fillers and matrix. The obtained f-Cu@PS/PVDF composites with enhanced high-k and TC but low loss are promising materials for potential applications in microelectronic and electrical industries. [ABSTRACT FROM AUTHOR]

Developing a high dielectric constant (εr) polymer dielectrics with low dielectric loss and high thermal conductivity (TC) is still continuous demands for advanced electrical power systems. Herein, nickel (Ni) particles were encapsulated by silica (SiO2) via a sol–gel process using sodium silicate as a precursor, and the obtained core–shell Ni@SiO2 powders were blended into poly(vinylidene fluoride) (PVDF) to investigate the effects of SiO2 insulating layer and its thickness on dielectric properties and TC of composites. Compared with pristine Ni, the Ni@SiO2/PVDF composites exhibit a superior εr, and remarkably suppressed loss and conductivity, attributable to the SiO2 interlayer between the core Ni particles which effectively prevents them from direct contacts and significantly reduces the leakage loss. Moreover, the Ni@SiO2/PVDF composites still possess a high TC owing to the restrained thermal interfacial resistance and enhanced interfacial compatibility between the fillers and the matrix. The developed Ni@SiO2/PVDF composites with high k and TC but low loss are potential for microelectronic industry. [ABSTRACT FROM AUTHOR]