High Dielectric Constant Polymer Research Articles

Solution-processed high-k photopatternable polymers for low-voltage electronics.

High dielectric constant (k) polymers have been widely explored for flexible, low-power-consumption electronic devices. In this work, solution-processable high-k polymers were designed and synthesized by ultraviolet (UV) triggered crosslinking at a low temperature (60 °C). The highly crosslinked network allows for high resistance to organic solvents and high breakdown strength over 2 MV cm-1. The UV-crosslinking capability of the polymers enables them to achieve a high-resolution pattern with a feature size down to 1 μm. Further investigation suggests that the polar cyano pendants in side chains are responsible for increasing the dielectric constant up to 10 in a large-area device array, thereby contributing to a low driving voltage of 5 V and high field-effect mobility exceeding 20 cm2 V-1 s-1 in indium gallium zinc oxide (IGZO) thin-film transistors (TFTs). In addition, the solution-processable high-k dielectric polymers were utilized to fabricate flexible low-voltage organic TFTs, which show highly reliable and reproducible mechanical stability at a bending radius of 5 mm after 1000 cycles. And also, the high radiation stability of the dielectric polymers was observed in a UV-sensitive TFT device, thereby achieving highly reproducible pattern recognition, which is promising for artificial optic nerve circuits.

Dielectric nanocomposites with superb high-temperature capacitive performance based on high intrinsic dielectric constant polymer

Dielectric nanocomposites with superb high-temperature capacitive performance based on high intrinsic dielectric constant polymer

Self-Assembled MXene@Fluorographene Hybrid for High Dielectric Constant and Low Loss Ferroelectric Polymer Composite Films.

Modern electrical applications urgently need flexible polymer films with a high dielectric constant (εr) and low loss. Recently, the MXene-filled percolative composite has emerged as a potential material choice because of the promised high εr. Nevertheless, the typically accompanied high dielectric loss hinders its applications. Herein, a facile and effective surface modification strategy of cladding Ti3C2Tx MXene (T = F or O; FMX) with fluorographene (FG) via self-assembly is proposed. The obtained FMX@FG hybrid yields high εr (up to 108 @1 kHz) and low loss (loss tangent tan δ = 1.16 @ 1 kHz) in a ferroelectric polymer composite at a low loading level (the equivalent of 1.5 wt % FMX), which is superior to its counterparts in our work (e.g., FMX: εr = 104, tan δ = 10.71) and other studies. It is found that the FG layer outside FMX plays a critical role in both the high dielectric constant and low loss from experimental characterizations and finite element simulations. For one thing, FG with a high F/C ratio would induce a favorable structure of high β-phase crystallinity, extensive microcapacitor networks, and abundant interfacial dipoles in polymer composites that account for the high εr. For another, FG, as a highly insulating layer, can inhibit the formation of conductive networks and inter-FMX electron tunneling, which is responsible for conduction loss. The results demonstrate the potential of a self-assembled FMX@FG hybrid for high εr and low loss polymer composite films and offer a new strategy for designing advanced polymer composite dielectrics.

Polyarylene ether nitrile dielectric composites with good formability and processability

High dielectric constant polymer matrix composites are widely used in the domain of dielectric energy storage and electric field regulation depending on their high energy density, easy processing and light weight. Nevertheless, high dielectric constants are often achieved by adding fillers to the polymer, which increase the viscosity of the resin and make processing difficult. In this work, a novel filler GO coated with silicone powder (GO-silicone) was designed and prepared. The silicone powder on the surface of GO acts as a lubricant and improves the dispersion of GO in the polyarylene ether nitrile (PEN) resin, thus enhancing the dielectric properties of the PEN-based composite. The dielectric constant of the PEN/GO-silicone composite film with 4 wt% filler loading reaches 15.9 at 1 kHz, which is 4.3 times greater than that of the pure PEN film and 1.1 times greater than that of PEN composite simply filled with GO and silicone powder. Besides, the incorporation of GO-silicone declines the viscosity, which is very favorable for the processing and shaping of high dielectric composites. This work provides a novel technical route for the large-scale production of high dielectric composites.

High dielectric transparent polymer composite with well-organized carboxymethyl cellulose microfibers in silicon elastomer fabricated under direct current electric field

The combination of transparency, high dielectric permittivity, biocompatibility and flexibility is highly desired in the embedded capacitors. Herein, we show that assembling biodegradable sodium carboxymethyl cellulose (CMC) microfibers in biocompatible silicon elastomer (PDMS) under direct current (DC) electric field enables the production of high dielectric constant composite film with above desired properties. This process leads to the formation of columns of CMC microfibers spanning across the thickness direction, thus generating microfiber depleted regions in between fibers and polymer matrix. The as-prepared composite film with CMC (15 wt%) aligned exhibits a remarkable and an almost sevenfold higher dielectric permittivity as compared to that of the film with CMC randomly dispersed (72 vs 11.4, at 100 Hz). This high CMC loading does not compromise the flexibility and optical transmittance. Interestingly, the compression modulus along the thickness direction increases by >20 times from 16.4 MPa (CMC unaligned) to 339.9 MPa (CMC aligned). We demonstrate a facile strategy of fabricating high dielectric materials combining transparency, biocompatibility, flexibility and compression resistant, making the dielectric materials more versatile. This work shows that biomass derived CMC is a promising filler for high dielectric constant polymer composites benefiting from electric field driven construction of ordered micromorphology.

Effect of Glass Transition Temperature on Enhanced Dielectric Breakdown Strength and Lifetime of Multilayer Polymer Films.

High temperature, high energy density, and low loss dielectric films are promising candidates for miniaturized capacitors in electric vehicles and high-speed trains. However, single-component polymers could not achieve these desired properties simultaneously. Polymer multilayer films (MLFs), which combine a high dielectric constant polymer [e.g., poly(vinylidene fluoride) (PVDF)] and a high breakdown/low loss polymer [e.g., polycarbonate (PC)] in a unique layered structure, have the potential achieve them at the same time. In this work, the effects of PC glass transition temperature (Tg) on the dielectric insulation properties (breakdown strength and lifetime) were investigated at high temperatures of 100-150 °C. Three PC materials had Tg values of 145 (PC1), 165 (PC2), and 185 °C (PC3), respectively. It is observed that MLF-PC3 with the highest Tg of PC exhibited the highest Weibull direct/alternating current (DC/AC) breakdown strength and the longest DC/AC lifetime, whereas MLF-PC1 with the lowest Tg showed the lowest Weibull DC/AC breakdown strength and the shortest DC/AC lifetime. A high-temperature high-volage leakage current study revealed that MLF-PC3 exhibited the lowest bulk conductivity at all temperatures under different electric fields. The knowledge obtained from this study will help us design better MLFs with high performance for next-generation miniaturized capacitors.

Solid polymer electrolytes based on a high dielectric polymer and ionic liquids for lithium batteries

Solid-state batteries were produced using new solid polymer electrolytes (SPEs) based on the high dielectric constant polymer poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene), P(VDF-TrFE-CFE) and 40 wt% of different ionic liquids (IL) sharing the same bis(trifluoromethylsulfonyl)imide [TFSI] anion and different cations. The morphological, thermal, mechanical and electrochemical properties of the SPEs were investigated, as a function of the interaction between IL and polymer matrix. The addition of IL increased the amorphous phase of the polymer with respect to the neat polymer, leading to room temperature ionic conductivity values between 2.3 × 10−5 and 1.4 × 10−4 S cm−1, depending on the specific IL. Further, the highest lithium transference number of 0.71 was obtained for the [PMPyrr][TFSI] sample. Li/LiFePO4 half batteries using these SPEs show excellent and stable battery performance at room temperature at different C-rates. The highest discharge capacity value is achieved for the [PMPyrr][TFSI] sample, reaching 137 mAh.g−1 and 117 mAh.g−1 at C/10 and C/2 rates, respectively, with high coulombic efficiency (∼100%) and low capacity fade after 100 cycles. The use of P(VDF-TrFE-CFE) allows the development of room temperature solid-state lithium-ion batteries and the improved results are associated to the high polymer dielectric constant which facilitates IL ions dissociation, improving SPE ionic mobility.

High Performance Ternary Solid Polymer Electrolytes Based on High Dielectric Poly(vinylidene fluoride) Copolymers for Solid State Lithium-Ion Batteries.

Renewable energy sources require efficient energy storage systems. Lithium-ion batteries stand out among those systems, but safety and cycling stability problems still need to be improved. This can be achieved by the implementation of solid polymer electrolytes (SPE) instead of the typically used separator/electrolyte system. Thus, ternary SPEs have been developed based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene), P(VDF-TrFE-CFE) as host polymers, clinoptilolite (CPT) zeolite added to stabilize the battery cycling performance, and ionic liquids (ILs) (1-butyl-3-methylimidazolium thiocyanate ([BMIM][SCN])), 1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([PMPyr][TFSI]) or lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), incorporated to increase the ionic conductivity. The samples were processed by doctor blade with solvent evaporation at 160 °C. The nature of the polymer matrix and fillers affect the morphology and mechanical properties of the samples and play an important role in electrochemical parameters such as ionic conductivity value, electrochemical window stability, and lithium-transference number. The best ionic conductivity (4.2 × 10-5 S cm-1) and lithium transference number (0.59) were obtained for the PVDF-HFP-CPT-[PMPyr][TFSI] sample. Charge-discharge battery tests at C/10 showed excellent battery performance with values of 150 mAh g-1 after 50 cycles, regardless of the polymer matrix and IL used. In the rate performance tests, the best SPE was the one based on the P(VDF-TrFE-CFE) host polymer, with a discharge value at C-rate of 98.7 mAh g-1, as it promoted ionic dissociation. This study proves for the first time the suitability of P(VDF-TrFE-CFE) as SPE in lithium-ion batteries, showing the relevance of the proper selection of the polymer matrix, IL type, and lithium salt in the formulation of the ternary SPE, in order to optimize solid-state battery performance. In particular, the enhancement of the ionic conductivity provided by the IL and the effect of the high dielectric constant polymer P(VDF-TrFE-CFE) in improving battery cyclability in a wide range of discharge rates must be highlighted.

Tailoring the properties of epoxy/silicone blends for high-voltage capacitor applications

In recent decades, high dielectric constant (k) polymer nanocomposites have proved excellent potential in dielectric and energy storage applications. Epoxy/silicon rubber composite materials have shown promising properties in applications such as high-voltage insulation. Three types of nanomaterials (SiO2, TiO2, and TiO2@SiO2) with distinct intrinsic properties are carefully chosen to build high-k epoxy/silicone polymer nanocomposites in this study. To raise the value of K, this work tailored the polarizing ability or permittivity of dielectric material by inserting different weight ratios of nano-fillers (SiO2, TiO2, TiO2@SiO2) in the base matrix of dielectric material in epoxy and silicon rubber blends. With a base matrix containing 75% epoxy and 25% liquid silicone rubber concentration, the maximum value of K obtained is K = 158 for 5% TiO2 and there is an increase in the dielectric strength to 398 kV/mm. The obtained results indicate that, among the three different kinds of epoxy/silicone, TiO2@SiO2 has the most potential in enhancing the energy storage capabilities of the proposed nanocomposites, owing to the largest increase in k while maintaining low dielectric loss and leakage current.

Temperature-Resistant Intrinsic High Dielectric Constant Polyimides: More Flexibility of the Dipoles, Larger Permittivity of the Materials.

High dielectric constant polymers have been widely studied and concerned in modern industry, and the induction of polar groups has been confirmed to be effective for high permittivity. However, the way of connection of polar groups with the polymer backbone and the mechanism of their effect on the dielectric properties are unclear and rarely reported. In this study, three polyimides (C0-SPI, C1-SPI, and C2-SPI) with the same rigid backbone and different linking groups to the dipoles were designed and synthesized. With their rigid structure, all of the polyimides show excellent thermal stability. With the increase in the flexibility of linking groups, the dielectric constant of C0-SPI, C1-SPI, and C2-SPI enhanced in turn, showing values of 5.6, 6.0, and 6.5 at 100 Hz, respectively. Further studies have shown that the flexibility of polar groups affected the dipole polarization, which was positively related to the dielectric constant. Based on their high permittivity and high temperature resistance, the polyimides exhibited outstanding energy storage capacity even at 200 °C. This discovery reveals the behavior of the dipoles in polymers, providing an effective strategy for the design of high dielectric constant materials.

Enhancement of the Dielectric Properties of Polyvinyl Alcohol by Adding TiO2Nanoparticles

High dielectric constant nanocomposite polymer films based polyvinyl alcohol (PVA) with different weight ratios of nanoparticles (NPs) TiO2(1.0, 2.5, 5.0, and 10) are prepared by the casting method. The structure of TiO2NPs is studied using TEM and XRD spectra, where the FTIR spectra show a strong interaction between PVA and TiO2NPs. The addition of TiO2NPs to the composites improves their mechanical properties. The dielectric parameters and AC conductivity are explored in the 10 Hz to 107 Hz frequency range at different temperatures. PVA composite films filled with 5.0 wt% TiO2NPs exhibit the highest dielectric constant (ε′) reaching up to 26 at 25 °C and 100 Hz. The origins of the enhanced dielectric properties are investigated using theoretical predictions of the effectiveε′of composites. The activation energy of a dielectric relaxation process is computed. As the temperature rises, the relaxation time lengthens slightly. A conduction mechanism is described based on thermally activated electron hops at the Fermi edge.

Core@double-shell structured fillers for increasing dielectric constant and suppressing dielectric loss of PVDF-based composite films

High dielectric constant polymer dielectrics have attracted a great deal of attention in flexible electronics. However, it appears to be a paradox for polymer dielectrics that the enhancement of their dielectric constant often comes along with the increase of dielectric loss. Hence, we reported core@double shell structured filler/poly(vinylidene fluoride) (PVDF) composites to overcome this paradox. The hybrid filler with BaTiO3 (BT) as the core, conductive carbon as the inner shell, and insulating polydopamine (PDA) as the outer shell was synthesized. As a result, the BT@C@PDA/PVDF composites at the filler content of 11 vol% exhibit an outstanding dielectric performance with a dielectric constant of 45 and a dielectric loss of 0.053 at 103 Hz. This phenomenon can be attributed to the increased interfacial polarization induced by the inner carbon shell and the conductive paths blockade caused by the outside PDA shell inside the BT@C@PDA/PVDF composites. This work reveals that rational design of core@double shell structured hybrid fillers maybe a promising way to optimize the overall dielectric performance of the PVDF-based composites.

P-nitrophenol-terminated alkyl side chain substituted polymer as high dielectric constant polymer additive enables efficient organic solar cells

Herein, we introduced p-nitrophenol-terminated alkyl side chain into the benzotriazole unit and synthesized a high dielectric constant polymer PBTA-NO2 (εr = 7.1). The properties as absorption spectra, energy levels, aggregation, dielectric constant, photovoltaic performance, etc. of PBTA-NO2 were analyzed and compared with its controlled polymer PBTA-C10H21. It is found that the PBTA-NO2 exhibits a similar absorption spectrum, lower highest occupied molecular orbital (HOMO) energy level, stronger aggregation characteristic and higher dielectric constant at 1 kHz in contrast to that of PBTA-C10H21. Beyond that, the PBTA-NO2 was adopted as a high dielectric constant polymer additive into the active layer of the PM6:Y6 based polymer solar cells (PSCs). The incorporation of 5 wt% PBTA-NO2 slightly increased the relative dielectric constant (εr) of the blend film from 4.4 to 4.8 and simultaneously improved the morphology of the active layer, which promoted the exciton dissociation and carrier transport, inhibited bimolecular recombination, and eventually increased the power conversion efficiency (PCE) by 6% as compared to the original device.

Largely improved dielectric properties of polyimide composites by tuning content and formation of CsPbBr3 nanocrystals

High dielectric constant polymer composites have considerable potentials in energy storage and dielectric applications because of simple fabrication process, facile processability, light-weight, excellent thermal stability and mechanical properties. Perovskite (CsPbBr3)/polyimide (PI) composites were successfully prepared via an in-situ polymerization from CsPbBr3 precursor in polyamic acid, followed by thermal imidization. The dielectric properties of polyimide composites were controlled by adjusting the content of CsPbBr3 nanocrystals. The obtained CsPbBr3/PI composites not only possess a high dielectric constant of up to 25.5 but also exhibit low dielectric loss below 0.25. The maximal discharging energy density reached up to 3.10 J cm−3 with 10% CsPbBr3, which is almost 3 times greater than pure PI under the same conditions. In addtiton, outstanding thermal properties of 5% decomposition temperature beyond 530 °C and good mechanical properties. The CsPbBr3/PI composites can be prepared facilely and rapidly on a large scale, which will be a outstanding dielectric material for high temperature polymer film capacitors.

High dielectric constant, flexible and easy-processable calcium copper titanate/thermoplastic polyurethane (CCTO/TPU) composites through simple casting method

In the past few years, there has been a significant demand for the development of high dielectric constant polymer composites for flexible electronic applications. However, the development of these flexible and stretchable dielectrics through simple and economical processing methods still remains challenging. In the present work, we have addressed this problem by developing high dielectric constant, flexible, calcium copper titanate (CCTO)/ thermoplastic polyurethane (TPU) composites through a simple and cost-effective casting method. At room temperature, 40 vol% CCTO/TPU composite exhibited a dielectric constant of 56 (1 kHz) along with an elongation at break of 202%, making it a promising dielectric material for flexible electronics. To our knowledge this is the best among the reported works in ceramic/ polyurethane composites, exhibiting a remarkable combination of high dielectric constant, excellent elongation at break and good mechanical strength. A prototype embedded capacitor was fabricated on copper cladded printed circuit board (PCB) by spin coating and a specific capacitance of 1.05 nF/cm2 was achieved at 1 kHz.

Getting self-healing ability and ultra-low dielectric loss for high-k epoxy resin composites through building networks based on Li0.3Ti0.02Ni0.68O grafted carbon nanotube bundles with unique surface architecture

Getting self-healing ability and ultra-low dielectric loss is effective to achieve high service reliability and sustainable development for high dielectric constant (high-k) polymer composites. Herein, new functional fillers with special surface architecture (sLTNO@mAC) were synthesized by grafting Li0.3Ti0.02Ni0.68O particles (sLTNO) on surfaces of carbon nanotube bundles (mAC), which was then embedded in epoxy resin (EP) with disulfide bonds to develop new composites (sLTNO@mAC/EP). Compared with composites based on mAC (mAC/EP) or a blend of sLTNO and mAC (sLTNO/mAC/EP) with the same filler loading, sLTNO@mAC/EP composites have much higher dielectric constant and self-healing efficiency as well as much lower dielectric loss at the same frequency. For the composite based on sLTNO@mAC with 8.2 wt% of sLTNO, coded as sLTNO1@mAC/EP, its dielectric loss is only 0.02, about 1.1 × 10 -3 and 9.4 × 10 -3 times of that of mAC/EP and sLTNO/mAC/EP, respectively; meanwhile its dielectric constant (216.1, 100 Hz) is the highest value among self-healable dielectric composites reported so far, and sLTNO1@mAC/EP has higher self-healing efficiency (97.7%) than mAC/EP and sLTNO/mAC/EP. The mechanism behind these attractive properties reveals that dielectric properties of sLTNO@mAC/EP mainly depend on interface polarization, while those of mAC/EP and sLTNO/mAC/EP are mainly related to the integrity of conductive networks.

Graphene derivative based high dielectric constant polymer composite electrodes for supercapacitors

Abstract Graphene oxide (GO) and reduced graphene oxide (rGO) based polyvinylidene fluoride (PVDF) flexible composites were prepared using GO and rGO fillers in PVDF matrix by solution casting method. These composites were characterized with X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Impedance analyzer (dielectric constant) and Field emission electron microscopy (FE-SEM). The dielectric constants at 1 MHz frequency for PVDF, 5%GO/PVDF and 5% rGO/PVDF composites were obtained 3.68, 12.20 & 30.32 respectively, ascribed to Maxwell-Wagner-Sillars (MWS) polarization mechanism and the exchange coupling at the surface and interface. According to MWS polarization charges could be accumulated at the interface when an external field was acted on composites due to heterogeneous response of GO, rGO and PVDF attributed alternate of electrode materials for superacapacitors.

Modulation and mechanism of spatial structure for multi-layer cyanate ester resin composites to achieve remarkably increased energy storage density and decreased dielectric loss

Overcoming sticky problems of large dielectric loss and poor breakdown strength ( Eb) is prerequisite of actual applications for high dielectric constant polymer composites. Herein, three kinds of multi-layer structure composites with different spatial structures (2MP-CE/CNT, CE/CNT-2MP-CE/CNT, MP-CE/CNT-MP) were prepared based on carbon nanotubes (CNTs), cyanate ester (CE) resin and mica paper (MP). Compared with traditional single-layer CE/CNT composite, multi-layer CE/CNT-2MP-CE/CNT composites, of which the middle layer is two pieces of MPs with a thickness of 60 µm, while both bottom and top layers are CE/CNT composite, simultaneously achieve 105 reduction in dielectric loss and 18.1 times increase in energy storage density ( Ue). Through modulating two sheets of MPs and CE/CNT as top and bottom layer, respectively, 2MP-CE/CNT composite with 60 μm MPs has the largest breakdown strength ( Eb), its Eb and Ue are severally about 7.1 and 19.5 times of those of CE/CNT composite. The relationship and mechanism between spatial structure and integrated performance such as dielectric properties, Eb and Ue of composites were systematically investigated. The attractive integrated performances of CE/CNT-2MP-CE/CNT and 2MP-CE/CNT composites are attributed to their unique composition and spatial structures, which bring special micro-capacitance and interfacial polarization, and thus leading to outstanding performances. Therefore, this investigation provides a strategy for getting desirable performances through building composites with specific spatial structure.

A Chip-First Microwave Package Using Multimaterial Aerosol Jet Printing

We show in this article two fully additively manufactured microwave packages with integrated active and passive components. Packages were constructed using a chip-first approach where package substrates (dielectrics) and interconnects (conductors) are built up around power amplifier bare die attached to carriers. Bypass capacitor dielectrics were printed using multimaterial aerosol jet printing, where aerosols of barium titanate and polyimide inks are mixed in place to fabricate a high dielectric constant polymer matrix nanocomposite film. The material properties of the film are characterized using three printed capacitors. We present S-parameter measurements to characterize small-signal performance, as well as load-pull measurements at the saturated output power. Finally, we demonstrate package performance after power cycling and temperature cycling to show the effect of aging on the part and the robustness of this packaging strategy. We measured a maximum packaged gain of 21.7 dB and a saturated output power of 21.9 dBm for a commercial-off-the-shelf (COTS) medium power amplifier specified to have a gain of 22 dB and a saturated output power of 22 dBm. The printed package-level performance is compared with the published bare die performance and a measured COTS packaged amplifier.

Stereolithography based additive manufacturing of high-k polymer matrix composites facilitated by thermal plasma processed barium titanate microspheres

Stereolithography (SL) is a promising 3D printing method for the fabrication of high dielectric constant polymer matrix composites (high-k PMCs) because of its high geometric accuracy and few manufacturing defects. However, the presence of ceramic filler destroys the fluidity and transparency of high-k PMCs, reducing their 3D printability. In this study, we fabricated barium titanate microspheres (BT-S) to facilitate the SL-based 3D printing of high-k PMCs using radio-frequency thermal plasma spheroidization (RF-TPS) technology. Experimental results showed that the prepared BT-S particles have spherical shape, smooth surface, large particle size, improved mechanical strength and higher purity, which lead to the enhancement in the 3D printability of UV curable high-k composites: i) the employment of BT-S significantly reduces the apparent viscosity and yield stress; and ii) the UV curing depth increased by 542% maximum. As a result, high-k composites were successfully printed using digital light processing (DLP) technique under low UV light energy. Moreover, the increase of dielectric constant was experimentally verified, which is explained by electrostatic energy increment according to finite element method (FEM) simulations. This study provided an effective approach (i.e. RF-TPS technology) to enhance the 3D printability of high-k PMCs, and also promoted the usage of SL-based 3D printing in advanced electrical and electronic components