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Flexible polymer dielectrics tolerant to electric field and temperature extremes are urgently needed for a spectrum of electrical and electronic applications. Given the complexity of the dielectric breakdown mechanism and the vast chemical space of polymers, the discovery of suitable candidates is nontrivial. We have laid the foundation for a systematic search of the polymer chemical space, which starts with "gold-standard" experimental measurements and data on the temperature-dependent breakdown strength (Ebd) for a benchmark set of commercial dielectric polymer films. Phenomenological guidelines are derived from this data set on easily accessible properties (or "proxies") that are correlated with Ebd. Screening criteria based on these proxy properties (e.g., band gap, charge injection barrier, and cohesive energy density) and other necessary characteristics (e.g., a high glass transition temperature to maintain the thermal stability and a high dielectric constant for high energy density) were then setup. These criteria, along with machine learning models of these properties, were used to screen polymers candidates from a candidate list of more than 13 000 previously synthesized polymers, followed by experimental validation of some of the screened candidates. These efforts have led to the creation of a consistent and high-quality data set of temperature-dependent Ebd, and the identification of screening criteria, chemical design rules, and a list of optimal polymer candidates for high-temperature and high-energy-density capacitor applications, thus demonstrating the power of an integrated and informatics-based philosophy for rational materials design.

Polymer dielectrics essentially revolutionized the electrical power system, pervasively used in nearly all the key electronic and electrical devices, due mainly to their suitably large bandgaps. However, insufficient attention has been paid to the bandgap in the design of new polymer dielectrics for high temperatures. In this paper, we present a unified principle for the design of flexible, high temperature polymer dielectrics. As exemplified by our recently discovered poly(oxa)norbornenes (POFNB), saturated bicyclics with varying carbonyl and ether groups in the bicyclic repeat units, connected by unconjugated alkenes and freely rotatable single bonds in conjunction with freely rotating fluorinated benzene ring side-groups, can impart flexibility yet retain thermal stability while providing large bandgaps to olefinic polymers. The results indicate that POFNB has stably low conduction current under concurrent high electric field and elevated temperatures beneficial from its large band gap of ∼5 eV and high glass transition temperature of 186 °C.

Next-generation wearable systems call for flexible, breathable, and skin-friendly wireless transmitters for realizing body area networks and the internet of things. This work presents the first fully functional, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) screen-printed fabric patch antenna for next-generation wearable antennas. This is an unparalleled milestone as prior conductive polymer based fabrics all demonstrated insufficient RF radiation due to skin effect loss, whereas here, an all-organic fabric RF transmitter is realized with the help of nanotemplate-assisted PEDOT:PSS conductive phase segregation on the surface of fabric fibers, forming a continuum coaxial structure with a conductive shell. This multi-strand wire structure endows the conductive fibers with a high surface area that is similar to high frequency Litz-wire, resulting in an extremely high RF conductivity. The fabricated patch antenna based on this conductive fabric shows an extremely low return loss of −50 dB and a satisfactory radiation efficiency of 28% at its resonant frequency of 2.35 GHz, and preserves its performance characteristics when bent over a representative phantom. In addition, the Doppler radar system based on the fabric patch antennas demonstrates satisfactory speed and distance detection with high precision, well suited for future application as a short-range sensing device for blind assistance. This development paves a new way to fabricate all-organic flexible RF devices for wireless communication with profound implications for the field of integrated wearable electronic networks.

Flexible large bandgap dielectric materials exhibiting ultra-fast charging-discharging rates are key components for electrification under extremely high electric fields. A polyoxafluoronorbornene (m-POFNB) with fused five-membered rings separated by alkenes and flexible single bonds as the backbone, rather than conjugated aromatic structure typically for conventional high-temperature polymers, is designed to achieve simultaneously high thermal stability and large bandgap. In addition, an asymmetrically fluorinated aromatic pendant group extended from the fused bicyclic structure of the backbone imparts m-POFNB with enhanced dipolar relaxation and thus high dielectric constant without sacrificing the bandgap. m-POFNB thereby exhibits an unprecedentedly high discharged energy density of 7.44 J/cm(3) and high efficiency at 150 °C. This work points to a strategy to break the paradox of mutually exclusive constraints between bandgap, dielectric constant, and thermal stability in the design of all-organic polymer dielectrics for harsh condition electrifications.

Ultrafast infrared vibrational spectroscopy is widely used for the investigation of dynamics in systems from water to model membranes. Because the experimental observation window is limited to a few times the probe's vibrational lifetime, a frequent obstacle for the measurement of a broad time range is short molecular vibrational lifetimes (typically a few to tens of picoseconds). Five new long-lifetime aromatic selenocyanate vibrational probes have been synthesized and their vibrational properties characterized. These probes are compared to commercial phenyl selenocyanate. The vibrational lifetimes range between ∼400 and 500 ps in complex solvents, which are some of the longest room-temperature vibrational lifetimes reported to date. In contrast to vibrations that are long-lived in simple solvents such as CCl4, but become much shorter in complex solvents, the probes discussed here have ∼400 ps lifetimes in complex solvents and even longer in simple solvents. One of them has a remarkable lifetime of 1235 ps in CCl4. These probes have a range of molecular sizes and geometries that can make them useful for placement into different complex materials due to steric reasons, and some of them have functionalities that enable their synthetic incorporation into larger molecules, such as industrial polymers. We investigated the effect of a range of electron-donating and electron-withdrawing para-substituents on the vibrational properties of the CN stretch. The probes have a solvent-independent linear relationship to the Hammett substituent parameter when evaluated with respect to the CN vibrational frequency and the ipso 13C NMR chemical shift.

Advanced polymers with high energy density and high efficiency are urgently needed in pulse power capacitor applications. Here, we present a practical design approach towards all-organic polymers with high energy density and high efficiency by enhancing dipolar polarization at the molecular level. Flexible segments were introduced into the backbones of rigid polar aromatic polymers to increase the flexibility of dipoles. Dielectric spectroscopy measurements of designed polymers revealed multiple strong sub-glass transition (sub-Tg) relaxation peaks with low activation energies, which indicated the enhanced movement freedom of dipoles below the glass transition temperature. As a result, dielectric constants were increased up to 46% when compared with their base polymers and D–E loop measurements showed that all these designed polymers had high energy densities above 11 J cm−3 with efficiencies above 90%. These results unveiled a novel approach towards high dielectric constant organic polymers for electrical energy storage.

Polymer dielectrics are key materials for capacitive energy storage in electrical and electronic systems owning to their ultra-high power density and high breakdown strength. However, the dramatically increased electrical conduction leads to poor energy storage performance under high electric fields, especially at elevated temperatures. Here we introduce structural defects into Polyetherimide (PEI) to modify the high-temperature dielectric properties. The polarization and conduction properties are investigated to reveal the effect of the structural defect. The modified PEI exhibits largely improved charge-discharge efficiency at elevated temperatures due to the suppressed electrical conduction, e.g., 91 % under ~400 MV/m at 200°C. The modification of PEI through a high-throughput facile process exhibited an enormous potential in capacitive energy storage under harsh conditions. The strategy demonstrated here unveils an unexplored space for modifying established polymers by introducing local structural defects.

Piezoelectric nanogenerators used for energy harvesting in wearable electronics require flexibility, durability, and skin compatibility. Previous work has identified expanded polytetrafluoroethylene (ePTFE) as a potential candidate. A ferroelectret film was prepared by laminating ePTFE membranes and two fluorinated ethylene propylene (FEP) films using hot pressing, and injecting charges through corona discharge process. Using conductive fabric containing poly(3,4- ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as electrodes, an all-organic nanogenerator was obtained. The open- circuit voltage and short-circuit current were measured to characterize the piezoelectric response. The short-circuit current was found to be approximately 50 nA for one layer of ePTFE membrane (15 × 15 mm2) under light pressure from one finger, and no increase in current and voltage was found from additional ePTFE layers. The polarizability and charges stability of the FEP/ePTFE/FEP film were also evaluated. The flexible ferroelectret nanogenerator can be embedded into clothes or insole and is expected to power continuously future wearable electronics system.

Nanoscale fibers and non-woven meshes composed of DNA complexed with a cationic surfactant (cetyltrimethylammonium chloride, or CTMA) have been fabricated through electrospinning. The DNA–CTMA complex can be electrospun far more easily than DNA alone. Incorporation of a hemicyanine chromophore resulted in materials that demonstrated amplified emission as compared to thin films of identical composition. The enhanced fluorescence resulted from both the fiber morphology (5–6-fold amplification) and specific interactions (groove-binding) between the chromophore and DNA (18–21-fold amplification). The mechanical properties of freestanding electrospun non-woven fiber meshes were evaluated, and revealed stress-induced alignment of DNA strands within the DNA–CTMA fibers. These fiber-based materials are easily processable into a variety of morphologies, and have promise for applications in molecular electronics, filtration, sensors, and the medical industry.

The dielectric constant (ϵ) is a critical parameter utilized in the design of polymeric dielectrics for energy storage capacitors, microelectronic devices, and high-voltage insulations. However, agile discovery of polymer dielectrics with desirable ϵ remains a challenge, especially for high-energy, high-temperature applications. To aid accelerated polymer dielectrics discovery, we have developed a machine-learning (ML)-based model to instantly and accurately predict the frequency-dependent ϵ of polymers with the frequency range spanning 15 orders of magnitude. Our model is trained using a dataset of 1210 experimentally measured ϵ values at different frequencies, an advanced polymer fingerprinting scheme and the Gaussian process regression algorithm. The developed ML model is utilized to predict the ϵ of synthesizable 11,000 candidate polymers across the frequency range 60–1015 Hz, with the correct inverse ϵ vs. frequency trend recovered throughout. Furthermore, using ϵ and another previously studied key design property (glass transition temperature, Tg) as screening criteria, we propose five representative polymers with desired ϵ and Tg for capacitors and microelectronic applications. This work demonstrates the use of surrogate ML models to successfully and rapidly discover polymers satisfying single or multiple property requirements for specific applications.

Advances in materials can be achieved once we understand their property well. In this study, a series of zinc and cadmium aliphatic polyesters with varying numbers of methylene spacer(s), 1 to 8, are synthesized and characterized to understand their features, which control their dielectric properties. The rational co-design of these materials is adopted by Density Functional Theory (DFT) computations of local structural features, and physical properties as dielectric constant and band gap energies. Synthesized polyesters of zinc and cadmium exhibit high band gap energies, > 5 eV, with the dielectric constant from ca. 4.69-3.61 and ca. 6.61-4.01, respectively; with metal volume fractions ca. 3–12% experimentally, which supports the DFT computations strongly to behave as a good dielectric material. These initial studies give insight into the potential advantages and expansion of the chemical design space for developing new dielectrics and provide valuable validation and feedback to enrich Material Genome Initiative.

The electronic structure of polymers contains signatures that correlate with their short-term and long-term integrity when subjected to large electric stresses. A detailed picture of the electronic structure of realistic models of polymers has been difficult to obtain, mainly due to the chemical and morphological complexity encountered in polymers. In this work, we have undertaken a comprehensive analysis of the electronic structure of six model polymers displaying chemical and morphological diversity, namely, polyethylene (PE), polypropylene (PP), polystyrene (PS), poly(methyl methacrylate) (PMMA), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT), using first-principles density functional theory computations and classical molecular dynamics simulations. In particular, we have studied the role of monomer chemistry, tacticity, and large-scale morphological disorders in shaping the electronic structure of these polymers. We find that monomer chemistry and morphological disorder coopera...

The real-time mechano-optical behavior of Polyimide 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) 1,6-diaminohexane (DAH) [PI(BTDA-DAH)] films during uniaxial deformation was investigated in the glassy and rubbery states as a function of temperature and stretch rate to understand the stretching characteristics of the polymer and elucidate the structural evolution. The study combined real-time spectral birefringence with true stress and true strain measurements and the data were further augmented by offline DSC and WAXD measurements. During deformation near glass transition temperature, initial photoelastic regime exhibiting very small slope is followed by regimes II and III. As the deformation temperature increases, the initial photoelastic regime disappears and gives way to temperature-independent regime I following classic stress-optical behavior. Regime I is followed by either a negative deviation from SOR into regime IIIa at lower deformation temperatures, or a positive deviation from SOR into regime II at higher deformation temperatures which eventually transitions into regime IIIc at large strains. The polymer was essentially amorphous in regime I. As the deformation increased, strain-induced crystallization occurred in regime II where crystallinity as high as 24% was achieved. The strain-induced crystals enhanced network connectivity and increased the rate of polymer chain orientation before transitioning to regime IIIc. Under conditions where regime II was not observed, a linear mechano-optical response in regime I extended to higher deformations before transitioning into regime IIIa where the highly oriented chains exhibited a “nematic-like” order with translational disorder along the chain directions. Based on the above observations a schematic for the structural evolution of PI(BTDA-DAH) during uniaxial deformation was proposed.

Due to their electrically polarized air-filled internal pores, optimized ferroelectrets exhibit a remarkable piezoelectric response, making them suitable for energy harvesting. Expanded polytetrafluoroethylene (ePTFE) ferroelectret films are laminated with two fluorinated-ethylene-propylene (FEP) copolymer films and internally polarized by corona discharge. Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)-coated spandex fabric is employed for the electrodes to assemble an all-organic ferroelectret nanogenerator (FENG). The outer electret-plus-electrode double layers form active device layers with deformable electric dipoles that strongly contribute to the overall piezoelectric response in the proposed concept of wearable nanogenerators. Thus, the FENG with spandex electrodes generates a short-circuit current which is twice as high as that with aluminum electrodes. The stacking sequence spandex/FEP/ePTFE/FEP/ePTFE/FEP/spandex with an average pore size of 3 µm in the ePTFE films yields the best overall performance, which is also demonstrated by the displacement-versus-electric-field loop results. The all-organic FENGs are stable up to 90 °C and still perform well 9 months after being polarized. An optimized FENG makes three light emitting diodes (LEDs) blink twice with the energy generated during a single footstep. The new all-organic FENG can thus continuously power wearable electronic devices and is easily integrated, for example, with clothing, other textiles, or shoe insoles.

Electrocardiography (ECG) is an essential technique for analyzing and monitoring cardiovascular physiological conditions such as arrhythmia. This article demonstrates the integration of screen-printed ECG circuitry from a commercially available conducting polymer, PEDOT:PSS, onto commercially available finished textiles. ECG signals were recorded in dry skin conditions due to the ability of PEDOT:PSS to function as both ionic and electronic conductors. The signal amplifies when the skin transpires water vapor or by applying a common lotion on the skin. Finally, PEDOT:PSS wires connected to PEDOT:PSS electrodes have been shown to record ECG signals comparable to Ag/AgCl connected to copper wires.

In order to interface power sources with any electrical load, energy storage and conversion are important components. The ability to store electrical energy is essential in many applications. Dielectric materials with high electric energy density are essential components in modern power electronics such as pulsed power systems and switched mode power supplies. The current state-of-the-art film capacitor is biaxially oriented polypropylene that has a breakdown strength of >730 MV/m and low dielectric loss of

The next generation electrical-power and electronic systems with wide band gap semiconductors require thin dielectric films operating under the extreme electric field at elevated temperatures. Here we investigated the conduction properties under high electric field up to 450 MV/m for biaxially oriented polypropylene (BOPP), which is the state-of-the-art commercially available polymer for capacitive applications, as well as three high-temperature polymers poly(ether ether ketone)(PEEK), poly(etherimide)(Ultem) and polyimide(Kapton). Further analysis was performed based on the hopping conduction mechanism. At elevated temperature, the increased thermally-assisted excitation energy gave rise to an increase of the hopping distance. It is argued that the large band gap provided a higher energy barrier to the charge hopping. If the band gap is large enough, the tunneling process dominated the charge transport, i.e., the case of BOPP. For high-temperature applications, both the thermal stability and large band gap are required in order to suppress the temperature and electric field dependent conduction.

Highly conductive, metal-like poly(ethylene terephthalate) (PET) nonwoven fabric was prepared by coating poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) containing dimethyl sulfoxide (DMSO) onto PET nonwoven fabric previously coated with graphene/graphite. The sheet resistance of the original nonwoven fabric decreases from80 MΩ□

Recently, there has been a growing interest in developing wide band gap dielectric materials as the next generation insulators for capacitors, photovoltaic devices, and transistors. Organotin polyesters have shown promise as high dielectric constant, low loss, and high band gap materials. Guided by first-principles calculations from density functional theory (DFT), in line with the emerging codesign concept, the polymer poly(dimethyltin 3,3-dimethylglutarate), p(DMTDMG), was identified as a promising candidate for dielectric applications. Blends and copolymers of poly(dimethyltin suberate), p(DMTSub), and p(DMTDMG) were compared using increasing amounts of p(DMTSub) from 10% to 50% to find a balance between electronic properties and film morphology. DFT calculations were used to gain further insight into the structural and electronic differences between p(DMTSub) and p(DMTDMG). Both blend and copolymer systems showed improved results over the homopolymers with the films having dielectric constants of 6.8 and 6.7 at 10 kHz with losses of 1% and 2% for the blend and copolymer systems, respectively. The energy density of the film measured as a D-E hysteresis loop was 6 J/cc for the copolymer, showing an improvement compared to 4 J/cc for the blend. This improvement is hypothesized to come from a more uniform distribution of diacid repeat units in the copolymer compared to the blend, leading toward improved film quality and subsequently higher energy density.

Although traditional materials discovery has historically benefited from intuition-driven experimental approaches and serendipity, computational strategies have risen in prominence and proven to be a powerful complement to experiments in the modern materials research environment. It is illustrated here how one may harness a rational co-design approach-involving synergies between high-throughput computational screening and experimental synthesis and testing-with the example of polymer dielectrics design for electrostatic energy storage applications. Recent co-design efforts that can potentially enable going beyond present-day "standard" polymer dielectrics (such as biaxially oriented polypropylene) are highlighted. These efforts have led to the identification of several new organic polymer dielectrics within known generic polymer subclasses (e.g., polyurea, polythiourea, polyimide), and the recognition of the untapped potential inherent in entirely new and unanticipated chemical subspaces offered by organometallic polymers. The challenges that remain and the need for additional methodological developments necessary to further strengthen the co-design concept are then presented.

Herein, we present a facile method for color-tuning an electrochromic device that switched between two neutral colors through simple color mixing of a conjugated polymer, poly(2,2-dimethyl-3,4-propylenedioxythiophene) and an electrochromic small molecule aromatic diester, diethyl-4,4′-biphenyldicarboxylate. The resulting device had a photopic contrast of ca. 57% across the visible spectrum. In addition, the device exhibited color uniformity and stability over 2,000 switches. Using these mixed coloring materials, a large area electrochromic device of 140 cm2 was fabricated, exceeding the size of ophthalmic lenses and small displays.

Herein, screen printed electrodes prepared from commercially available conducting polymer poly(3,4-ethylenedioxythiophene):polystyrene sulfonate have been shown to record simultaneous electromyogram (EMG), electrocardiogram (ECG), and electrodermal activity (EDA) from a spandex t-shirt sleeve in dry state. Secondly, electrodes printed on an arm sleeve recorded EMG during muscle contraction and were compared to commercial Ag/AgCl electrodes that use hydrogel. Thirdly, the printed electrodes have been shown to be stable to ten washes with detergent and ten dry cycles upon treatment with commercially sold fabric protectors with ECG signals being recorded in underwater conditions from wrist. Lastly, EDA was measured from fingers by recording changes in skin conductance brought about by cognitive stress. This use of integrated sensors on a t-shirt provides a tool for continuous and simultaneous measurement of vital signals in at-risk patients.

Flexible dielectrics operable under simultaneous electric and thermal extremes are critical to advanced electronics for ultrahigh densities and/or harsh conditions. However, conventional high-performance polymer dielectrics generally have conjugated aromatic backbones, leading to limited bandgaps and hence high conduction loss and poor energy densities, especially at elevated temperatures. A polyoxafluoronorbornene is reported, which has a key design feature in that it is a polyolefin consisting of repeating units of fairly rigid fused bicyclic structures and alkenes separated by freely rotating single bonds, endowing it with a large bandgap of ≈5 eV and flexibility, while being temperature-invariantly stable over -160 to 160 °C. At 150 °C, the polyoxafluoronorbornene exhibits an electrical conductivity two orders of magnitude lower than the best commercial high-temperature polymers, and features an unprecedented discharged energy density of 5.7 J cm-3 far outperforming the best reported flexible dielectrics. The design strategy uncovered in this work reveals a hitherto unexplored space for the design of scalable and efficient polymer dielectrics for electrical power and electronic systems under concurrent harsh electrical and thermal conditions.

Dielectric flexible film with high dielectric permittivity and low dielectric loss has received increased demands over the past decade due to its wide range of applicability in modern electronics like flexible circuits, hybrid vehicles, pulsed power systems. Novel Sn-polyester based organometalllic pDMTDMG polymer is processed with organic polyimide based pBTDA-HDA polymer to form a flexible free-standing film with tunable dielectric properties. Its dielectric properties were characterized by frequency domain dielectric spectroscopy and high voltage DC breakdown test. In addition, films were characterized by using Differential Scanning Calorimetry for their thermal behavior and by Wide Angle X Ray diffraction for microstructural analysis. Hybrid film with 60% pDMTDMG and 40% PI was found to have improved dielectric properties over previously synthesized and processed organic polyimide and organometallic Sn-polyester homopolymers.

Flexible films having high dielectric constants with low dielectric loss have promising application in the emerging area of high-energy-density materials. Here, for the first time, an organometallic, Sn-polyester-containing hybrid free-standing film in polyimide matrix is reported. Polyimide, pBTDA-HDA, is used with poly(dimethyltin glutarate) and poly(dimethyltin-3,3-dimethyglutarate) (pDMTDMG) for having a processable film with tunable dielectric properties. Hybrid film with 60% pDMTDMG and 40% PI (HB2) is found to have improved dielectric features over previously synthesized organic polyimide and organometallic Sn-polyester homopolymers. These novel organometallic-organic hybrid systems expanded a new area of dielectrics for next-generation electronics with superior overall electrical performance.

Large dielectric constant and band gap are essential for insulating materials used in applications such as capacitors, transistors and photovoltaics. Of the most common polymers utilized for these applications, polyvinyldiene fluoride (PVDF) offers a good balance between dielectric constant, >10, and band gap, 6 eV, but suffers from being a ferroelectric material. Herein, we investigate a series of aliphatic organotin polymers, p[DMT(CH2)n], to increase the dipolar and ionic part of the dielectric constant while maintaining a large band gap. We model these polymers by performing first-principles calculations based on density functional theory (DFT), to predict their structures, electronic and total dielectric constants and energy band gaps. The modeling and experimental values show strong correlation, in which the polymers exhibit both high dielectric constant, ≥5.3, and large band gap, ≥4.7 eV with one polymer displaying a dielectric constant of 6.6 and band gap of 6.7 eV. From our work, we can identify ...

We examine the influence of confining gold nanoparticles on the overall nanoscale morphology, mechanical and electrochemical properties of nanocomposite ion gels. Stimuli-responsive ion gels are generated via the synthesis of gold nanoparticles (AuNPs) within a thiol-functionalized liquid crystalline brush-like block copolymer (LCBBC) and subsequent gelation in ionic liquids. AuNPs are prepared by in situ reduction of the gold ions and stabilized by direct anchoring through coordination bonds with the thiol-functionalized LCBBC. The resulting LCBBC/AuNP nanocomposite comprises a hierarchical structure in which polymer-coated AuNPs are dispersed in a microsegregated LCBBC matrix that further contains both liquid crystalline (LC) and block copolymer ordering. More importantly, this LCBBC/AuNP nanocomposite is solubilized in an ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate, to form a nanocomposite ion gel. At 5 wt% concentration, LCBBC/AuNP nanocomposite ion-gel exhibits interesting characteristics including excellent mechanical strength (∼103 Pa), good optical properties with higher ionic conductivity (∼10−2 S cm−1) and long-term electrochemical stability over a larger potential range compared to the plain LCBBC ion gel. Thus, nanocomposite ion gels present tunable optical, thermal and mechanical properties by virtue of their polymer architecture, morphology and functionality. These are versatile and modular hybrid materials to design nanocomposite ion gels with multiple functionalities for applications in electrochemical devices, photonics, and opto-electronics.

Conductive fabrics are central to smart textiles, a concept that has been gaining attention for applications such as wearable electronics or biosensors. However, current approaches for creating electrically conductive fabrics struggle with issues ranging from low conductivity to skin irritation. The use of graphitic carbon has been investigated as a possible way to impart conductivity to fabrics, yet low loadings, required post-infusion reductions, or the need to remove additives, has limited the application of these materials. In this paper, we introduce an approach that infuses fabric with pristine few layer graphene (FLG)/graphite from natural bulk graphite using an interfacial trapping method. No additives or chemical modification of the graphite is required, and electrical conductivities an order of magnitude higher than previous approaches are achieved.

Rational strategies combining computational and experimental procedures accelerate the process of designing and predicting properties of new materials for a specific application. Here, a systematic study is presented on polythioureas for high energy density capacitor applications combining a newly developed modelling strategy with synthesis and processing. Synthesis was guided by implementation of a high throughput hierarchical modelling with combinatorial exploration and successive screening, followed by an evolutionary structure search based on density functional theory (DFT). Crystalline structures of polymer films were found to be in agreement with DFT predicted results. Dielectric constants of ∼4.5 and energy densities of ∼10 J cm−3 were achieved in accordance with Weibull characteristic breakdown fields of ∼700 MV m−1. The variation of polymer backbone using aromatic, aliphatic and oligoether segments allowed for tuning dielectric properties through introduction of additional permanent dipoles, conjugation, and better control of morphology.

Herein, we present a versatile way to increase the photopic contrast of electrochromic devices (ECDs), approximately 14%, through the use of binary mixtures of propylene carbonate, diethyl carbonate, and ethylene carbonate that serve the role as plasticizers in the gel electrolyte. The binary plasticizer mixture changed the physical properties of the gel electrolyte medium, including the viscosity and dielectric constant, and also facilitates the diffusion of ions and monomer in the medium leading to an increase in ionic conductivity and the photopic contrast. ECDs were fabricated using a one-step lamination procedure, based on poly(2,2-dimethyl-3,4-propylenedioxythiophene) (PProDOT-Me2) with different polymer gel electrolyte compositions where the electrochromic polymer was electrochemically obtained in situ. Gel electrolytes based on unary or binary plasticizer systems and poly(ethylene glycol) diacrylate (PEG-DA) with varying lithium trifluoromethanesulfonate (LiTrif) loading were investigated for the effect of solvent on ionic conductivity and the resulting photopic contrast of the ECD. This study demonstrates a relationship between photopic contrast and ionic conductivity, where the system reaches a maximum in photopic contrast the system is also at the maximum ionic conductivity.

Utilizing the in situ method, we report the fabrication of flexible electrochromic (EC) devices in a one-step lamination procedure. In this study, electrochromic device performance was enhanced via the use of new gel polymer electrolyte (GPE) materials based on poly(ethylene glycol) (PEG) derivatives. PEG serves as the polymer matrix in electrochromic devices (ECDs) that provides not only mechanical stability, but also a wide potential window and compatibility with a variety of salts. Poly(ethylene glycol) dimethacrylate (PEGDMA) in conjunction with poly(ethylene glycol) methyl ether acrylate (PEGMA), containing lithium trifluoromethanesulfonate (LiTRIF) as the salt and propylene carbonate (PC) as a plasticizer; we investigated various electrolyte parameters, including salt loading, the mono/di-functional PEG ratio, and the plasticizer to PEG ratio. Optimized gel systems exceed the mechanical flexibility of indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates in their sustainable minimum bending radius of curvature, exhibit an ionic conductivity up to 1.36 × 10−3 S cm−1, and yield electrochromic devices (ECDs) with photopic contrasts as high as 53% (without background correction) using poly(2,2-dimethyl-3,4-propylenedioxythiophene) (PProDOT-Me2) as the standard electrochromic material. In addition to ionic conductivity, the crosslink density of the GPEs was found to have an important effect on the photopic contrast of the resultant ECDs. Using these results, 110 cm2 flexible patterned EC displays were assembled as a demonstration of their potential in real world applications.

Herein, we describe the synthesis and characterization of polymers formed by the Diels–Alder (DA) reaction between various difurans and divinylsulfone, and evaluate their dielectric properties. These syntheses were planned with computational support a priori in the form of HOMO/LUMO calculations for the dienes and dienophiles, with the calculated ΔE for the DA reactions ranging between 9.33 and 9.42 eV. We describe the structure–property relationship observed when changing an atom in the linking unit between two furan rings (–CH2–, –O-, –S-, –NH–) with respect to the dielectric constant and loss tangent. Dielectric constants for the polymers range between 4.96 and 5.98, with dielectric loss tangents ranging from 0.4 to 0.9% at 1 kHz and room temperature. Bandgaps of the polymers are elucidated with UV/Visible spectroscopy, and range from 2.15 to 2.61 eV. The retro DA onset is determined using three analytical methods: thermogravimetric analysis, dynamic scanning calorimetry, and gas chromatography/mass spectrometry polymer desorption spectroscopy, and is determined to be over 125 °C in all cases.

Herein, a study on varying salts and their composition used in the gel electrolyte for a one-step lamination assembly procedure for electrochromic devices was carried out to explore their effects on various electrochromic performance parameters, such as color uniformity, photopic contrast, switching speed, and optical memory. Electrochromic polymers formed in different gel electrolyte compositions are highly dependent on the type, amount, and composition of salt used. The following groups of salts were investigated: ionic liquids, ammonium salts, and lithium salts. The lithium salts yielded devices with the best color uniformity, photopic contrast as high as 48%, and switching response speeds as low as 1 s for 5.5 cm2 devices using the electroactive monomer 2,2-dimethyl-3,4-propylenedioxythiophene (ProDOT-Me2) to generate the electrochromic polymer. Hermetically sealed electrochromic devices exhibited optical memory of 27 h for a 2% photopic transmittance loss under normal laboratory conditions, and a 171 cm2 electrochromic device was demonstrated.

Electrochromic fabric devices represent a further extension to the plethora of available literature on conductive fabrics. This article contains a brief overview of electrochromic devices, electrochromic polymers, conductive materials, conductive fabrics, and electrochromic fabric devices. A tabulated list of the perceived colour of a number of electrochromic polymers that is contained herein is designed to serve as an aide to colour mixing studies. The challenges of optimisation and commercialisatiion of electrochromic fabric devices and their mitigating factors are conjectured, along with some future potential applications for electrochromic fabric device technologies.

The use of the fluorinated alcohol, 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as a processing solvent for orthogonal alignment of a DNA–surfactant complex is reported herein. 1-butanol (BuOH) was used as the control. At low frequencies, films of DNA–CTMA cast from HFIP exhibited a higher, more consistent dielectric constant and a lower dissipation factor compared to films cast from BuOH.

Enhancing dipole polarization has been demonstrated as an effective approach to increase the dielectric constant of polymer dielectrics and thus to improve their discharged energy density for energy storage applications in electrical power and electronic systems. However, further optimization to get a higher dielectric constant and lower polarization loss hinges upon a more insightful understanding of the dynamics of dipole relaxation. Here, we demonstrate an approach, based on the Dissado-Hill dielectric response model, to probe the dynamics of dipole polarization in an all organic polythiourea (PDTC-HK511) composed of p-phenylene diisothiocyanate (PDTC) as rigid segments and Jeffamine® HK511 as flexible segments. Our results reveal that PDTC-HK511 possesses strong subglass transition β and γ relaxation processes in conjunction with the quasi-DC diffusion process at relatively high temperature and a low frequency range. The γ relaxation enhances the dielectric constant by 20%–25% but causes no apparent loss at the operating temperature and frequency conditions due to the high flexibility and short relaxation time of the dipole orientation. In comparison to β relaxation, the weak interactions and much shorter relaxation time of dipoles in γ relaxation evidenced the large flexibility of dipole movement. This work provides deeper insight into the dipole movement and aids future rational designs of polymers for dielectric energy storage.

Conductive poly(3,4-ethylenedioxythiophene):sulfonated polyimide (PEDOT:SPI) films were successfully developed by decreasing the particle size along with the addition of anionic surfactant leading to potential applications in electronic devices. By varying the mixing system (magnetic bar at 1000rpm, mechanical at 1000rpm and mechanical at 4000rpm), we observed significant conductivity and thermal stability enhancement of the obtained PEDOT-SPI films by using designed stir shaft with high-speed mechanical mixing systems allowing for smaller particle sizes of PEDOT:SPI about 43nm averaging. In addition, the further conductivity enhancement and thermal stability of PEDOT:SPI was achieved by adding various amounts of anionic surfactant into the aqueous polymer suspension because of the resulting conformational changes. The highest conductivity, 9.5Scm^-^1, was achieved at 1wt% SDS in PEDOT:SPI (6FDA) film which increased by a factor of 5 from the PEDOT:SPI without addition of SDS. Moreover, using a high-speed mechanical mixing system and addition of anionic surfactant also improved the thermal stability of conductive films, which was verified by TGA analysis. Due to the combination of using high-speed mechanical mixing and adding of anionic surfactant, superior dispersion stability, high conductivity and good thermal stability PEDOT:SPI films were achieved.

Conductive poly(3,4-ethylenedioxythiophene):sulfonated polyimide (PEDOT: SPI) nanoscale thin films were successfully developed by addition of anionic surfactant and poly(vinyl alcohol) (PVA) for potential application in electronic devices. In this work, sodium dodecyl sulfate (SDS) surfactant was introduced into PEDOT:SPI aqueous suspensions to improve the dispersion stability of the particles in water, leading to high transparency and low contact angle of PEDOT:SPI thin films. All of the conducting polymer thin films showed high transparency of more than 85% transmission. Conductivity enhancement and good film-formation properties of PEDOT:SPI were achieved by adding various amounts of PVA to each polymer aqueous suspension because of the resulting conformational changes. The highest conductivity of 0.134 S/cm was achieved at 0.08 wt.% PVA in PEDOT:SPI2/SDS/PVA film, increased by a factor of 3.5 compared with the original material. In addition, PVA also improved the thermal stability of the conductive films, as verified by thermogravimetric analysis (TGA). The interactions between conducting polymers, PVA, and SDS surfactant affecting nano-thin film properties were revealed and investigated. Moreover, the interactions between SDS and SPI were proven to be different from those between SDS and poly(styrenesulfonate) (PSS) in conventional PEDOT:PSS solutions.

Herein, the addition of an anionic surfactant, sodium dodecyl sulfonate (SDS), during the template polymerization of conducting polymers to improve the nano-thin films properties was investigated. In order to compare the effects, three methods of addition SDS were demonstrated: addition of SDS during template polymerization, addition after template polymerization, and addition of both during and after template polymerization. Sodium dodecyl sulfonate (SDS) was utilized as a stabilizer and a dopant for the polymerization of 3,4-ethylenedioxythiophene (EDOT) with two different templates, sulfonated poly(imide) (SPI) and polystyrene sulfonate (PSS). The addition of SDS during polymerization of both PEDOT-SPI and PEDOT-PSS was more effective in stabilizing particles against coagulation, significantly reducing the sizes of conducting particles, forming stable spherical particles, and enhancing thermal stability and conductivity. Evidence from FTIR measurements indicated that molecular interactions between SDS and PEDOT chains resulted in the decrease in distortion of the structures and in the effectiveness of doping of the PEDOT chains. TEM and TGA analyses further showed that SDS molecules were intercalated in conducting particles when they were added during polymerization. The addition of SDS during template polymerization of PEDOT demonstrated a greater effect on colloid stability and intercalation doping than that of the addition of SDS after polymerization, resulting in significant conductivity improvements of PEDOT-SPI and PEDOT-PSS films.

Herein we report the synthesis of a new class of processable siloxane precursor polymers consisting of aromatic groups and flexible siloxane linkages and their conversions to green and blue electrochromic polymers in the solid state. 3,4-Ethylenedioxythiophene (EDOT), 2,2′-bis(3,4-ethylenedioxythiophene) (BiEDOT), and a donor–acceptor moiety 4,7-bis(EDOT)-2,1,3-benzothiadiazole (BEBTD) were incorporated as aromatic groups to demonstrate the versatility of the precursor method to different aromatic systems. The utilization of a siloxane linkage allows for a precursor polymer exhibiting improved solubility in common organic solvents and accessible glass transition temperatures (−1 to 132 °C) as compared to a previously reported silane precursor. A simple method to control the thermal properties of the precursor was also demonstrated by incorporation of both siloxane and silane functionalities into the precursor backbone. The oxidatively converted product from the precursors showed electronic and optoelectro...

When designing polymeric capacitors, it is important to understand the structure–property relationship between chemical functionalities and dielectric properties to tailor materials for specific applications in terms of dielectric constant, dielectric loss, band gap, breakdown strength, etc. Herein, we report a clear structure–property relationship with dielectric constant and dielectric loss in a series of polyurea and polyurethane thin films. We demonstrate that the dielectric constant systematically increases and the dielectric loss decreases as the number of carbons between polarizable functional groups decreases. Our syntheses are guided with data obtained from high-throughput density functional theory calculations. By modeling 382 polymer systems, we have determined that a dielectric constant >4 is achieved with at least one aromatic group and at least one of the following moieties: –NH–, –C( O)–, or –O–.

Most polyolefins that are used for dielectric materials exhibit a low dielectric constant and operating temperatures up to 70 � C. Polyimides offer a means to a higher dielectric constant material by the introduction of a polar group in the polymer backbone and are thermally stable at temperatures exceeding 250 � C. A common dianhydride, pyromellitic dianhydride (PMDA), is reacted with various short-chain diamines to produce polymers with high imide density. Homopolymers and copolymers synthesized had dielectric constants ranging from 3.96 to 6.57. These materials exhibit a dielectric constant twice that of biaxially oriented polypropylene and therefore a twofold increase in capacitance as well as maintaining low dissipation factors that are acceptable for this application. The experimental dielectric constants of these materials are also compared to density functional theory calculations and exhibit a close relationship. V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 000: 000-000, 2013