Dielectric Properties Of Polymers Research Articles

Study on the Effect of Electron/Hole Injection on the Energy-Storage Properties of Polymer Dielectrics

As a critical component of electrostatic capacitors, the polymer dielectric directly affects the performance of the capacitor. In this work, Polycarbonate (PC)/Polyvinylidene fluoride (PVDF) asymmetric bilayer polymer dielectrics were prepared, and the influence of different polymer materials’ barrier characteristics on various electrical properties of composite dielectrics was studied by changing the direction of applied electric fields. Research has found that the dielectric constant of a composite dielectric is between PVDF and PC (approximately 4.8 at 10 Hz) and is independent of the relative position of PVDF and PC in the dielectric. However, the relative position of PC and PVDF has a significant impact on the energy-storage characteristics of composite dielectrics. When PVDF comes into contact with the negative electrode, even though PC has a higher hole barrier, the composite dielectric can only withstand a maximum electric-field strength of 400 MV/m, which is much lower than the maximum electric-field strength that pure PC can withstand (520 MV/m), and it only achieves an energy-storage density of 3.7 J/cm3. When the PC comes into contact with the negative electrode, the high electron barrier of the PC effectively suppresses the injection of electrons at the electrode. It can withstand the same electric-field strength as PC (520 MV/m), achieving an energy-storage density of 5.48 J/cm3, which is 1.46 times that of pure PC and 1.64 times that of PVDF. This experiment effectively combined the advantages of PC and PVDF by utilizing the electron/hole barrier of polymer materials to obtain a fully organic dielectric with excellent energy-storage performance.

Understanding microwave interactions with polymers to enable advanced plastic chemical recycling

The widespread adoption of plastics has led to substantial production and waste generation, raising environmental concerns. Chemical recycling offers a promising solution to enhance recycling rates, with microwave heating emerging as an attractive technology for polymer breakdown. This paper investigates the dielectric properties of various polymers and their temperature dependencies, providing insight into the effectiveness of microwave heating. Results indicate that while polymers may show low dielectric loss at room temperature, those with polar segments exhibit increasing loss at high temperatures, indicating that additional susceptors may not always necessary for effective microwave heating. Three key transitions are identified with respect to their significant impact on the dielectric properties of polymers at elevated temperatures: the glass transition temperature, the decomposition temperature, and the point where the dispersion/displacement peak exceeds the measurement frequency. Additionally, this paper introduces a new approach for utilising microwave heating for the selective, multistage recycling of mixed plastics.

Research progress and prospect of polymer dielectrics

With the increasing demand for energy, how to store and release energy efficiently and stably has become an urgent research topic. Polymer dielectrics have become a kind of ideal dielectric materials in electrostatic capacitors for energy storage due to their advantages of light weight, easy fabrication, low cost, and high breakdown strength. It has a wide application prospect in smart power grids, new energy vehicles, pulse power weapons, electromagnetic guns, and lasers. However, existing polymer dielectrics cannot simultaneously possess the characteristics of high energy density, high breakdown field intensity, high charge and discharge efficiency, and low dielectric loss, thus limiting the development of compact, efficient, and reliable electronic power technology. In addition, the inherent thermal/field charge injection, excitation, and transport phenomena of polymer dielectrics make the resistivity and dielectric energy storage properties of polymer dielectrics decrease sharply under the combined action of high temperature and high electric field. In order to optimize the energy storage performance of polymer dielectrics (including room temperature and high temperature dielectrics), it has been obtained excellent dielectric breakdown strength, energy storage density, energy storage charge, and discharge efficiency from polymer nanocomposites, polymer/small molecule composites, polymer/polymer blends, new synthetic polymers, multilayer polymers, and other material systems. Based on these material systems, this review summarizes and compares these material systems, points out their advantages and disadvantages including the key problems, and puts forward suggestions for the future research.

Physical passivation of deep-level defect states in polymer dielectrics for outstanding dielectric properties

The limited dielectric strength of polymer dielectrics hampers their reliable use in highly integrated electrical systems and high-energy storage film capacitors. This constraint is closely associated with the presence of deep-level defect states in polymer dielectrics. Here, we present an efficient and stable approach for the physical passivation of deep-level defect states aimed at enhancing the dielectric properties of polymer dielectrics. Employing inductively coupled plasma technology with argon as the carrier gas, the polymer undergoes substantial decreased deep-level defect states, as evidenced by nano-micro-region defect measurements. Consequently, the localized charge accumulation in the treated polymer dielectric is significantly reduced, resulting in a remarkable 62% increase in flashover voltage. The breakdown strength is also enhanced, and the treated material exhibits long-term stability. Moreover, materials featuring passivated deep-level defect states can boost discharge energy density without compromising efficiency. For instance, PTFE with passivated deep-level defect states maintains a discharge energy density of 1.18 J/cm3 and a charge-discharge efficiency of 95.06% at 200 °C and 300 MV/m. By focusing on deep-level defect states passivation, we introduce a strategy for receiving polymers with exceptional performance and stability.

Enhancing the dielectric properties of polyimide-based composites with donor-doped SiO2

It is important that the dielectric material in the electrical system be able to handle the increasing applied electric strength owing to the rising demands for power supply reliability. Based on this, in this work, Nb2O5 donor doped SiO2 (NSO) particles were synthesized by high-temperature sintering method and successfully doped into the PI matrix. The maximum Eb of the composite material is 527.3 kV/mm, which is 64.2% higher than that of pure PI (321.1 kV/mm) and 34.8% higher than that of the SiO2/PI composite material (392.5 kV/mm) owning to the effect of donor doping on the carrier transport of the composite material. At the same time, it maintains excellent dielectric stability and lower dielectric loss even at 100 ℃. These consequences offer a new strategy for enhancing the integrated dielectric properties of polymer dielectrics in insulation fields.

The application of organic graphene-based electrodes for studies of electrophysical properties of polymer dielectrics and ferroelectrics

Dielectric properties of a linear polymer dielectric polypropylene and a ferroelectric copolymer vinylidene fluoride – tetrafluoroethylene VDF/TFE 94/6 using a graphene-based carbon material as electrodes were measured in wide frequency and temperature range. An additional dispersion region in the frequency dependencies of dielectric properties is observed above 105 Hz as compared to the same materials with evaporated Ag electrodes. It is suggested that this additional dispersion appears because of the reduced conductivity of an organic electrode. It is concluded that ferroelectric VDF/TFE copolymer with graphene electrodes can be used in low-frequency energy converters.

Study of dielectric properties of meta-aramid fibers by molecular dynamics methods using modified OPLSAA force field

The dielectric properties of materials have been a prevalent subject in dielectric physics research. However, the theoretical calculation of the dielectric properties of polymer insulating materials remains challenging. Taking meta-aramid fiber (PMIA) as the research object, the micro-dielectric relaxation process of the PMIA system was studied by molecular dynamics and the polarization frequency response theory. The OPLSAA force field was optimized based on the density functional theory B3LYP/6-31G. Using calculations of the spatial structure, chain motion, basic physical and chemical properties, and dielectric properties of PMIA, it was found that the optimized OPLSAA force field accurately indicated the dielectric properties of PMIA. The frequency-dependent dielectric properties of PMIA calculated by the optimized OPLSAA force field were consistent with the polarization frequency response theory, and the simulation results agreed with the Debye model theory. The theoretical calculation process of polymer dielectric properties based on molecular dynamics presented in this paper provides a new avenue to improve the prediction accuracy of polymer dielectric properties. • The optimized OPLSAA can accurately indicated the dielectric properties of PMIA. • Intermolecular hydrogen bonds obstruct the dielectric relaxation of PMIA molecules. • The minimum degree of polymerization to build a PMIA model is 10.

Enhanced dielectric properties of polyvinyl alcohol doped with ZrC Nanoparticles

In this paper, effect of ZrC nanoparticles on dielectric properties of polyvinyl alcohol has been investigated. The polymer nanocomposites films were fabricated by using casting method. The dielectric properties of prepared nanocomposites were recorded at frequency(f) ranged from100Hz to 5MHz. Results showed that the dielectric properties of polymer were enhanced with increase in the ZrC NPs ratio. The ε' and ε" were reduced while the σAC was rise with rise in the frequency.

Controllable synthesis and structural design of novel all-organic polymers toward high energy storage dielectrics.

As the core unit of energy storage equipment, high voltage pulse capacitor plays an indispensable role in the field of electric power system and electromagnetic energy related equipment. The mostly utilized polymer materials are metallized polymer thin films, which are represented by biaxially oriented polypropylene (BOPP) films, possessing the advantages including low cost, high breakdown strength, excellent processing ability, and self-healing performance. However, the low dielectric constant (ε r < 3) of traditional BOPP films makes it impossible to meet the demand for increased high energy density. Controlled/living radical polymerization (CRP) and related techniques have become a powerful approach to tailor the chemical and physical properties of materials and have given rise to great advances in tuning the properties of polymer dielectrics. Although organic-inorganic composite dielectrics have received much attention in previous studies, all-organic polymer dielectrics have been proven to be the most promising choice because of its light weight and easy large-scale continuous processing. In this short review, we begin with some basic theory of polymer dielectrics and some theoretical considerations for the rational design of dielectric polymers with high performance. In the guidance of these theoretical considerations, we review recent progress toward all-organic polymer dielectrics based on two major approaches, one is to control the polymer chain structure, containing microscopic main-chain and side-chain structures, by the method of CRP and the other is macroscopic structure design of all-organic polymer dielectric films. And various chemistry and compositions are discussed within each approach.

Exploring dielectric spectra of polymer through molecular dynamics simulations

ABSTRACT In this work, poly(N-isopropylacrylamide) (PNIPAM) was used as a research object to explore the feasibility of molecular dynamics (MD) simulations to study the dielectric properties of polymers. A comparison of the static dielectric constants for two different calculation schemes, the applied electric field method and the dipole moment fluctuation method, has been conducted. The dielectric properties of PNIPAM aqueous solutions with different concentrations were studied as a function of temperature. The static dielectric constants derived from dipole moment fluctuation method at different temperatures can accurately describe the phase transition process. The concentration does not affect the lower critical solution temperature, but significantly affects the relaxation process of the system. According to the frequency-dependent dielectric constants, two relaxation processes are observed, namely, the dielectric relaxation process in the region of frequency less than 30 terahertz (THz) determined by the synergistic interaction of PNIPAM and water molecules, and that in the region of frequency higher than 30 THz mainly determined by water molecules beyond the solvation shell of the polymer. The calculation results suggest that the dielectric behaviour is concentration and temperature independent, similar to Debye behaviour of bulk water. This method of calculating dielectric properties using MD simulations can be used in detecting the dynamic processes of soft condensed matter and in aiding the design of materials with excellent dielectric properties.

Functional Groups Assisted Tunable Dielectric Permittivity of Guest-Free Zn-Based Coordination Polymers for Gate Dielectrics.

The dielectric properties of coordination polymers has been a topic of recent interest, but the role of different functional groups on the dielectric properties of these polymers has not yet been fully addressed. Herein, the effects of electron-donating (R=NH2 ) and electron-withdrawing (R=NO2 ) groups on the dielectric behavior of such materials were investigated for two thermally stable and guest-free Zn-based coordination polymers, [Zn(L1 )(L2 )]n (1) and [Zn(L1 )(L3 )]n (2) [L1 =2-(2-pyridyl) benzimidazole (Pbim), L2 =5-aminoisophthalate (Aip), and L3 =5-nitroisophthalate (Nip)]. The results of dielectric studies of 1 revealed that it possesses a high dielectric constant (κ=65.5 at 1 kHz), while compound 2 displayed an even higher dielectric constant (κ=110.3 at 1 kHz). The electron donating and withdrawing effects of the NH2 and NO2 substituents induce changes in the polarity of the polymers, which is due to the inductive effect from the aryl ring for both NO2 and NH2 . Theoretical results from density functional theory (DFT) calculations, which also support the experimental findings, show that both compounds have a distinct electronic behavior with diverse wide bandgaps. The significance of the current work is to provide information about the structure-dielectric property relationships. So, this study promises to pave the way for further research on the effects of different functional groups on coordination polymers on their dielectric properties.

Flexible polyolefin dielectric by strategic design of organic modules for harsh condition electrification

A paradigm-shifting design strategy is demonstrated that unifies the treatment of electronic and conformational properties of polymer dielectrics for concurrent high electric field and elevated temperature harsh conditions.

Determination of dielectric properties of natural fiber reinforced polymer composite using adaptive neuro fuzzy inference system

AbstractIn this study, the dielectric properties of polylactic acid reinforced with natural fibers are objectified by using adaptive neuro fuzzy inference system (ANFIS). This method is considered to be economically feasible as compared to fabricating dielectric samples and measuring dielectric properties with apt operating conditions and advanced equipment. Also, past research has focused primarily on polymer dielectric properties which does not involve any natural fiber inclusion, such that this research will focus on producing ANFIS models for natural fibers which will then be used to calculate dielectric permittivity ( ), dielectric loss ( ) with respect to frequency dependencies. Furthermore, experimental results of dielectric constants and losses of polylactic acid (PLA) based composites will be analyzed from past research which used physical techniques to fabricate composites and will be compared with the results from ANFIS models. It was found that error computation of both the properties are found to be low and the percentage difference in output data is considered less. In addition, the ANFIS neural network had predicted most of the data that was trained, and the crisp output values were found to correlate with the experimental dielectric properties which makes this prediction model possible to use as an alternative approach to fabricating composites and testing.

Dielectric and energy storage performance of polymers bearing terpyridyl group and metal ion complex by ring-opening metathesis polymerization

Block copolymers with terpyridyl-metal ion pendant were prepared by ring-opening metathesis polymerization, and self-assembled into nanostructure in the selective solvent. The dielectric properties of polymers could be well regulated by adjusting the content of metal ions. The dielectric constant of Ru(II)-contained block copolymer reached high value of 32.5, the dielectric loss was lowered to 0.01 in the frequency range of 100 Hz to 1 MHz, and the energy storage density was up to 5.2 J·cm−3 at the electric field strength of 325 mV·m−1 accompanied with the charge-discharge efficiency of 83.3%, which was attributed to the electronic polarization and interface polarization from the metal ions and nanostructure. Therefore, the introduction of metal ion into the side chain was an effective way to enhance the dielectric and energy storage properties of polymers.

Miscibility, microstructure, and dielectric properties of the polymer blends of cyanoethyl pullulan and fluoroterpolymer

The blending of two polymers is often used as a strategy to improve the dielectric properties of polymers. In this work, the blends of cyanoethyl pullulan (CEP) and poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)], both of which have high dielectric properties, are systematically studied. We show that although there exists a certain level of interaction between the two polymers, the blends are not completely miscible. The CEP-rich phase forms a particulate phase in the terpolymer matrix. Evidence indicates that the addition of CEP impedes the inclusion of bulky CTFE monomer units into the crystalline phase of the terpolymer, leading to a more polar crystalline structure of the terpolymer. Furthermore, a high-temperature thermal treatment (HTT) was conducted on the blended films to study the relationship between microstructure and dielectric properties. Experimental results suggest that the HTT process favors the incorporation of CTFE units into the crystalline phase and induces a less polar crystal structure of the terpolymer, resulting in a more relaxor ferroelectric–dielectric behavior, a higher dielectric constant, and a lower dielectric loss. By optimizing the composition of the blends and heat treatment, the dielectric energy storage performance of the blends can be improved in comparison with that of the terpolymer.

High temperature stable conjugated polyazomethines containing naphthalene moiety: Synthesis, characterization, optical, electrical and thermal properties.

A series of azomethine diol monomers containing naphthalene moiety were synthesized and oxidatively polymerized in aqueous alkaline medium using NaOCl as oxidant. The structure of the monomers and polymers was characterized by using various spectroscopic techniques. PL spectra of polymers are exhibiting good emission with high Stokes shift values than the monomers due to their polyconjugated structure. The electrical conductivity of polymers was measured by a two-point probe technique, and it increases with an increase in iodine vapour contact time up to 144h. The electrical conductivity values were correlated with the charge density on azomethine nitrogen obtained from the Hückel calculation method. The dielectric properties of polymers were studied at different temperatures in the frequency range from 50Hz to 5MHz. The synthesized polyazomethines have recorded high thermal stability and are shown by carbon residue of around 50% at 800°C in the thermogravimetric analysis.

Patterning and process parameter effects in 3D suspension near-field electrospinning of nanoarrays

The extracellular matrix (ECM) contains nanofibrous proteins and proteoglycans. Nanofabrication methods have received growing interest in recent years as a means of recapitulating these elements within the ECM. Near-field electrospinning (NFES) is a versatile fibre deposition method, capable of layer-by-layer nano-fabrication. The maximum layer height is generally limited in layer-by-layer NFES as a consequence of electrostatic effects of the polymer at the surface, due to residual charge and polymer dielectric properties. This restricts the total volume achievable by layer-by-layer techniques. Surpassing this restriction presents a complex challenge, leading to research innovations aimed at increasing patterning precision, and achieving a translation from 2D to 3D additive nanofabrication. Here we investigated a means of achieving this translation through the use of 3D electrode substrates. This was addressed by in-house developed technology in which selective laser melt manufactured standing pillar electrodes were combined with a direct suspension near-field electrospinning (SNFES) technique, which implements an automated platform to manoeuvre the pillar electrodes around the emitter in order to suspend fibres in the free space between the electrode support structures. In this study SNFES was used in multiple operation modes, investigating the effects of varying process parameters, as well as pattern variations on the suspended nanoarrays. Image analysis of the nanoarrays allowed for the assessment of fibre directionality, isotropy, and diameter; identifying optimal settings to generate fibres for tissue engineering applications.

Recent Progress on High‐Capacitance Polymer Gate Dielectrics for Flexible Low‐Voltage Transistors

AbstractThe gate dielectric layer is an essential element of field‐effect transistors (FETs), large area integrated circuits, and various application electronics. Beyond basic insulation between the semiconductor layer and gate electrode, FET performance largely depends on the capacitance of the chosen insulator layer properties. Recent functional devices developments require new functionalities, such as high mechanical flexibility and stretchability in addition to basic insulating and physical properties. This review focuses on recent developments of high‐capacitance polymer gate dielectric materials and their application for low‐voltage flexible FETs. The fundamental principles and components of transistors are discussed briefly, then the underlying concepts for gate dielectrics and the mechanisms for polymer dielectric properties, such as capacitance control, leakage current formation in dielectric polymer films, and patternability, are described. Strategic approaches to achieve high capacitance based on low‐k dielectric materials, and the development and use of high‐capacitance polymers and hybrid polymer gate dielectrics in the context of emerging transistors on flexible substrates are also discussed.

Highly Contrasting Static Charging and Bias Stress Effects in Pentacene Transistors with Polystyrene Heterostructures Incorporating Oxidizable N,N'-Bis(4-methoxyphenyl)aniline Side Chains as Gate Dielectrics.

Charge storage and trapping properties of polymer dielectrics govern the charge densities of adjacent semiconductors and greatly influence the on-off switching voltage (threshold voltage, ) of organic field-effect transistors (OFETs) when the polymers are used as gate insulators. Intentional charging of polymer dielectrics in OFETs can change and affect the bias stress. We describe a chemical design and fabrication protocol to construct multilayer-stack dielectrics for pentacene-based OFETs using different polystyrene (PS)-based polymers in each layer, with oxidizable N,N-bis(4-methoxyphenyl)anilino (TPAOMe)-substituted styrene copolymers in arbitrary vertical positions in the stacks. Thermal, byproduct-free cross-linking of benzocyclobutene subunits provides integrity to the multilayer structure by preventing dissolution of the previous deposited layer. Neutron reflectivity data verified the multilayer morphology. We compared the shift before and after charging the stacks by application of ±100 V across 0.5-1 μm total film thicknesses. Bias stress was the dominant effect in bilayer devices with a TPAOMe layer in contact with the pentacene, indicated by the direction of shift associated with either polarity of external electric field. In structures with no TPAOMe subunit in contact with the pentacene, when charging with -100 V on top of the source and drain electrodes, electron injection from pentacene to dielectric was the major charging mechanism, again consistent with the bias stress direction. When charging with +100 V, bilayer devices without TPAOMe showed little change in , suggesting there was no bias stress effect or charge injection in these devices for this charging polarity. For the bilayer devices with the TPAOMe layer in the bottom, and the trilayer devices with TPOMe in the middle, when +100 V was applied, the shifts were opposite those expected from bias stress. Dipole formation or partial ionization of chargeable groups at the interface between the dielectric layers are likely polarization mechanisms in these cases. A simple analytical model levelports the plausibility of these mechanisms. This work provides examples of both stabilization and shifting of , and therefore controlling charge carrier density, in semiconductors overlying the dielectric multilayers.

Methacrylate based side chain liquid crystalline polymers with pendant cholesterol group: Preparation and investigation of electrical conductivity mechanism

ABSTRACTMethacrylate based side‐chain liquid crystalline polymers (SCLCP) bearing cholesterol pendant moieties with various lengths of aliphatic spacer were synthesized and their electrical conductivity mechanism was studied for their possible applications in elastic microelectronic devices. All the polymers exhibited liquid crystalline behavior of broken focal‐conic fan texture of smectic phase. The dielectric properties of polymers were investigated by impedance spectroscopic technique in the frequency range of 100 Hz to 15 MHz at room temperature. Alternating current (AC) conductivity ( ) of the liquid crystalline polymeric films was observed to vary with angular frequency, ω as ωS with s &lt; 2. Detailed conductivity analysis revealed that the conductivity of the polymeric films follows quantum mechanical tunneling and correlated barrier hoping conductivity mechanisms at low frequency regime, whereas it obeys super linear power law and direct current conductivity mechanisms at high frequency region. The investigation of the SCLC polymeric films helped to propose a model system for their possible potential applications. In the light of this study, the SCLC polymers will be employed as the gate insulator for organic field effect transistor applications, such as large area flexible arrays or as other advanced microelectronic devices that have superior performance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45207.