Towards Flexible Dielectric Materials with High Dielectric Constant and Low Loss: PVDF Nanocomposites with both Homogenously Dispersed CNTs and Ionic Liquids Nanodomains

Electrospun Poly(vinylidene fluoride) Nanocomposites with Ionic Liquid Functionalized Graphene Nanoplatelets by a Noncovalent Method for Piezoresistive Pressure Sensor Applications

Piezoresistive pressure sensors have been prepared by the electrospinning of poly(vinylidene fluoride) (PVDF) containing graphene nanoplatelets (GNP) functionalized using 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIM(OTf)) ionic liquid (IL). Optical microscopy demonstrated that the functionalized GNP powder presented particles with a smaller lateral size. The obtained mats were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, differential scanning calorimetry, electrical resistivity using two and four probes, and electromechanical testing with up to 32 load-unload cycles. Functionalization with BMIM(OTf) resulted in a higher PVDF electroactive phase. Electrospun mats obtained without the IL displayed a signal comparable to noise, while mats obtained with the BMIM(OTf) functionalized GNP displayed a clear signal, indicating that the IL helped with the dispersion of GNP on the PVDF matrix. Electrospun mats containing 1.0%m functionalized GNP presented the best performance among the evaluated samples, presenting low hysteresis and a lower distribution of the read values especially in the working range of 0 to 250 kPa. The piezoresistive behavior of the sample was tested under 32 load-unload cycles, remaining stable. Higher ranges of axial load resulted in the rupture of the fibers and swift degradation of the piezoresistive signal under a high number of cycles. A simple load cell was assembled to demonstrate the capacity of the membranes to act as piezoresistive compressive sensors capable of detecting the pressing of a human finger and differentiating between applied weights.

A High-Methanol-Permeation Resistivity Polyamide-Based Proton Exchange Membrane Fabricated via a Hyperbranching Design

Four non-fluorinated sulfonimide polyamides (s-PAs) were successfully synthesized and a series of membranes were prepared by blending s-PA with polyvinylidene fluoride (PVDF) to achieve high-methanol-permeation resistivity for direct methanol fuel cell (DMFC) applications. Four membranes were fabricated by blending 50 wt% PVDF with s-PA, named BPD-101, BPD-102, BPD-111 and BPD-211, respectively. The s-PA/PVDF membranes exhibit high methanol resistivity, especially for the BPD-111 membrane with methanol resistivity of 8.13 × 10-7 cm2/s, which is one order of magnitude smaller than that of the Nafion 117 membrane. The tensile strength of the BPD-111 membrane is 15 MPa, comparable to that of the Nafion 117 membrane. Moreover, the four membranes also show good thermal stability up to 230 °C. The BPD-x membrane exhibits good oxidative stability, and the measured residual weights of the BPD-111 membrane are 97% and 93% after treating in Fenton's reagent (80 °C) for 1 h and 24 h, respectively. By considering the mechanical, thermal and dimensional properties, the polyamide proton-exchange membrane exhibits promising application potential for direct methanol fuel cells.

Fabrication of a Capacitive 3D Spacer Fabric Pressure Sensor with a Dielectric Constant Change for High Sensitivity

Smart wearable sensors are increasingly integrated into everyday life, interfacing with the human body to enable real-time monitoring of biological signals. This study focuses on creating high-sensitivity capacitive-type sensors by impregnating polyester-based 3D spacer fabric with a Carbon Nanotube (CNT) dispersion. The unique properties of conductive particles lead to nonlinear variations in the dielectric constant when pressure is applied, consequently affecting the gauge factor. The results reveal that while the fabric without CNT particles had a gauge factor of 1.967, the inclusion of 0.04 wt% CNT increased it significantly to 5.210. As sensor sensitivity requirements vary according to the application, identifying the necessary CNT wt% is crucial. Artificial intelligence, particularly the Multilayer Perception (MLP) model, enables nonlinear regression analysis for this purpose. The MLP model created and validated in this research showed a high correlation coefficient of 0.99564 between the model predictions and actual target values, indicating its effectiveness and reliability.

Impedance and Dielectric Properties of PVC:NH4I Solid Polymer Electrolytes (SPEs): Steps toward the Fabrication of SPEs with High Resistivity

In the present article, a simple technique is provided for the fabrication of a polymer electrolyte system composed of polyvinyl chloride (PVC) and doped with varying content of ammonium iodide (NH4I) salt using solution-casting methodology. The influences of NH4I on the structural, electrochemical, and electrical properties of PVC have been investigated using X-ray diffraction, electrochemical impedance spectroscopy (EIS), and dielectric properties. The X-ray study reveals the amorphous nature of the polymer-salt complex. The EIS measurement revealed an ionic conductivity of 5.57 × 10-10 S/cm for the electrolyte containing 10 wt.% of salt. Our hypothesis is provided, which demonstrated the likelihood of designing highly resistive solid electrolytes using the concept of a polymer electrolyte. Here, the results showed that the resistivity of the studied samples is not dramatically decreased with increasing NH4I. Bode plots distinguish the decrease in resistance or impedance with increasing salt contents. Dielectric measurements revealed a decrease in the dielectric constant with the increase of NH4I content in the PVC polymer. The relaxation time and dielectric properties of the electrolytes confirmed their non-Debye type behavior. This pattern has been validated by the existence of an incomplete semicircle in the Argand plot. Insulation materials with low εr have found widespread applications in electronic devices due to the reduction in delay, power dissipation, and crosstalk. In addition, an investigation of real and imaginary parts of electric modulus leads to the minimized electrode polarization being reached.

A Succinct Review on the PVDF/Imidazolium-Based Ionic Liquid Blends and Composites: Preparations, Properties, and Applications

Poly(vinylidene fluoride) (PVDF) is a versatile thermoplastic fluoropolymer with intriguing characteristics, which is receiving considerable attention from researchers in many areas. Recently, PVDF and its copolymer, such as poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) have been blended with ionic liquids to produce blend and composite materials for target applications. In this succinct review, two types of ionic liquids that are utilized for the preparation of PVDF and PVDF-HFP blends and composites, namely, hydrophilic and hydrophobic imidazolium-based ionic liquids, are reviewed. In addition, the effect of the ionic liquids on the physicochemical properties of the PVDF and PVDF-HFP blends and composites, is described as well. On top of that, a multitude of applications of the blends and composites are also succinctly reviewed. This review may give inspirations to the polymer blend and composite researchers in diversifying the applications of thermoplastic fluoropolymers through the utilization of ionic liquids.

Improvement of the electromechanical properties of thermoplastic polyurethane composite by ionic liquid modified multiwall carbon nanotubes

Carbon nanotubes (CNTs) were non-covalently modified by two categories of ionic liquids (ILs), including 1-vinyl-3-ethylimidazole bromide (VEIMBr) and 1-vinyl-3-hexylimidazole bromide (VHIMBr) in the ratio of 1:1 and 1:4, respectively. The surface interaction between CNTs and ILs was well-characterized by FTIR, Raman spectra, XPS, etc. Thermoplastic polyurethane (TPU) containing different amounts of CNTs/ILs was fabricated by melting blending method. TPU-CNTs/ILs composites exhibited simultaneously enhanced electromechanical properties with improved dielectric constant and lowered elastic modulus. The electromechanical sensitivity of sample TPU-3CNT/12VHIMBr increased by approximately 45 times in comparison with that of pure TPU at 200 Hz. Besides, improved dispersion of CNTs/ILs in the TPU matrix was also exhibited.

High-k Polymer Nanocomposite Materials for Technological Applications

Understanding the properties of small molecules or monomers is decidedly important. The efforts of synthetic chemists and material engineers must be appreciated because of their knowledge of how utilize the properties of synthetic fragments in constructing long-chain macromolecules. Scientists active in this area of macromolecular science have shared their knowledge of catalysts, monomers and a variety of designed nanoparticles in synthetic techniques that create all sorts of nanocomposite polymer stuffs. Such materials are now an integral part of the contemporary world. Polymer nanocomposites with high dielectric constant (high-k) properties are widely applicable in the technological sectors including gate dielectrics, actuators, infrared detectors, tunable capacitors, electro optic devices, organic field-effect transistors (OFETs), and sensors. In this short colloquy, we provided an overview of a few remarkable high-k polymer nanocomposites of material science interest from recent decades.

Enhanced Dielectric Performance of P(VDF-HFP) Composites with Satellite-Core-Structured Fe2O3@BaTiO3 Nanofillers

Polymer dielectric materials are extensively used in electronic devices. To enhance the dielectric constant, ceramic fillers with high dielectric constant have been widely introduced into polymer matrices. However, to obtain high permittivity, a large added amount (>50 vol%) is usually needed. With the aim of improving dielectric properties with low filler content, satellite–core-structured Fe₂O₃@BaTiO₃ (Fe₂O₃@BT) nanoparticles were fabricated as fillers for a poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) matrix. The interfacial polarization effect is increased by Fe₂O₃ nanoparticles, and thus, composite permittivity is enhanced. Besides, the satellite–core structure prevents Fe₂O₃ particles from directly contacting each other, so that the dielectric loss remains relatively low. Typically, with 20 vol% Fe₂O₃@BT nanoparticle fillers, the permittivity of the composite is 31.7 (1 kHz), nearly 1.8 and 3.0 times that of 20 vol% BT composites and pure polymers, respectively. Nanocomposites also achieve high breakdown strength (>150 KV/mm) and low loss tangent (~0.05). Moreover, the composites exhibited excellent flexibility and maintained good dielectric properties after bending. These results demonstrate that composite films possess broad application prospects in flexible electronics.

Development of Polymer Blends Based on PVA:POZ with Low Dielectric Constant for Microelectronic Applications

There is a huge request for the development of low dielectric constant polymeric materials for microelectronic applications. In thisstudy, polymer blends based on PVA:POZ with low dielectric constant has been fabricated. The results of XRD indicate that crystalline domain is enhanced at higher POZ concentration. Brilliant phases between spherulitesare attributed to the enhanced crystalline domains at high POZ content. White portions are appeared in SEM images on the surface of PVA:POZ blends. From EDX analysis, these leaked portions are referred to the POZ material. The number and sizes of the white portions were also found to increase with increasing the POZ content. Using electrical equivalent circuits (EEC), electrical impedance plots (Z″ vs Z') are fitted for all the samples. The results of impedance study illustrated that the resistivity of the samples increases with increasing POZ concentration. From dielectric measurements, dielectric constant was found to decrease with the introduction of more POZ into the PVA polymer. It is found to be about 1.68 at 40 wt.% POZ. Insulating materials with low dielectric constant (ε' < 2) are found to be important in the electronics manufacturing, owing to decrease in crosstalk, resistance-capacitance time delay and power dissipation in high-density circuits. Therefore, further investigations concerning the dielectric constant and impedance for all the samples are also carried out. The real and imaginary parts of electric modulus are studied, where minimizing of electrode polarization can be achieved.

Design and Optimization of a Hyper-Branched Polyimide Proton Exchange Membrane with Ultra-High Methanol-Permeation Resistivity for Direct Methanol Fuel Cells Applications

A hyper-branched sulfonated polyimide (s-PI) was synthesized successfully and composited with polyvinylidene fluoride (PVDF) to achieve ultra-high methanol-permeation resistive for direct methanol fuel cell application. The optimized s-PI-PVDF composite membrane exhibited methanol resistivity low to 1.80 × 10-8 cm²/s, two orders of magnitude lower than the value of the commercial Nafion 117 membrane (60 × 10-7 cm²/s). At the same time, the tensile strength of the composite membrane is 22 MPa, which is comparable to the value of the Nafion 117 membrane. Therefore, the composite membrane is promising for application in direct methanol fuel cell.