Polydimethylsiloxane Nanocomposites Research Articles

High Quasi-Isotropic Thermal Conductivity of Polydimethylsiloxane Nanocomposites with Hexagonal-Boron Nitride Microspheres and Flakes

High Quasi-Isotropic Thermal Conductivity of Polydimethylsiloxane Nanocomposites with Hexagonal-Boron Nitride Microspheres and Flakes

Strain cartography of bilayer graphene‐PDMS nanocomposites using Raman spectroscopy

AbstractEffective transmission of stress between fillers and the host matrix is instrumental in enhancing the properties of nanocomposites and optimizing filler reinforcement. This study delves into understanding stress transfer in materials, exploring the impact of synthesis methods and matrix materials through a comprehensive examination of a bilayer graphene (BLG)‐polydimethylsiloxane (PDMS) nanocomposite. BLG was synthesized via chemical exfoliation and subjected to various strain conditions within a PDMS matrix. A precisely controlled strain, ranging from 0% to 0.19%, was applied using a meticulous 4‐point bending method, monitored with a standard strain gauge. The study unveiled significant shifts in the Raman spectra's 2D band, indicating a direct linear relationship with applied strain. Utilizing contour mapping techniques on well‐defined Raman spectra and stress‐induced band shifts, we mapped strain distribution within the BLG layer. The results revealed a gradual increase in strain from the lower to the upper end of the BLG structure, resembling strain behaviors observed in differently shaped fibers. These compelling findings advance our understanding of strain dynamics within BLG‐PDMS nanocomposites, highlighting the crucial role of strain mapping methodologies in scrutinizing the material's structural response to deformation.Highlights The study reports successful synthesis of high‐quality bilayer graphene (BLG) using a chemical exfoliation method, as evidenced by the sharp 2D and G Raman peaks. Significant shifts in 2D band exhibited linear correlation between applied strain; observed within precise strain levels of 0% to 0.19%. Contour maps revealed a gradual increase in strain from the lower to the upper end of the BLG structure, akin to strain behaviors observed in differently shaped fibers.

Dielectric and Ultrasonic Properties of PDMS/TiO2 Nanocomposites.

This work presents the dielectric and ultrasonic properties of polydimethylsiloxane (PDMS) nanocomposites filled with titanium dioxide nanoparticles. The dielectric study was performed over a very broad range of frequencies (20 Hz-3 THz). The dielectric permittivity was almost frequency-independent in all the composites at room temperature over the whole range of measurement frequencies, and the dielectric losses were very low under these conditions (less than 2). The dielectric permittivity strongly increases with the nanoparticle concentration according to the Maxwell-Garnet model. Therefore, the investigated composites are suitable for various flexible electronic applications, particularly in the microwave and terahertz frequency ranges. Dielectric dispersion and increased attenuation of ultrasonic waves were observed at lower temperatures (below 280 K) due to the relaxation of polymer molecules at the PDMS/TiO2 interface and in the polymer matrix. The relaxation time followed the Vogel-Vulcher law, while the freezing temperature increased with the titanium dioxide concentration due to interactions between the polymer molecules and nanoparticles. The significant hysteresis in the ultrasonic properties indicated that titanium dioxide acts as a crystallization center. This is confirmed by the correlation between the hysteresis in the ultrasonic properties and the structure of the composites. The small difference in the activation energy values obtained from the ultrasonic and dielectric investigations is related to the fact that the dielectric dispersion is slightly broader than the Debye-type dielectric dispersion.

Flexible carbon-coated FeNi alloy/PDMS nanocomposites toward a multifunctional high-performance electromagnetic absorber

The increasing prevalence of electromagnetic wave technology has raised concerns regarding electromagnetic pollution and its potential hazards. Microwave absorbing materials (MAMs) have emerged as an effective solution for capturing and dissipating electromagnetic waves. This study presents a novel approach for developing flexible microwave absorbers by dispersing carbon-coated FeNi alloy nanoparticles (FeNi@C NPs) into a polydimethylsiloxane (PDMS) matrix. The unique contributions lie in the mass production of (FeNi)@C NPs through the arc plasma and controlled making of (FeNi)@C/PDMS nanocomposites for practical electromagnetic wave (EMW) absorption/shielding application. Simultaneously, the formation mechanism of (FeNi)@C NPs is illustrated in detail by real-time optical emission spectroscopy. The obtained (FeNi)@C/PDMS nanocomposites show multifunctionality such as hydrophobicity and mechanical performance, rendering them suitable for applications in lightweight flexible electronics, wearable devices, and stealth technology. Through adjustments in the contents of (FeNi)@C fillers, the (FeNi)@C/PDMS nanocomposites exhibit excellent microwave absorption capacity. At a mass ratio of 15% of (FeNi)@C NPs, the minimum reflection loss is −33.51 dB at a thickness of 2.3 mm with an effective absorption band of 4.96 GHz. This enhanced performance is attributed to the synergistic effects of magnetic and dielectric loss, multiple reflection/scattering, conduction loss, and suitable impedance matching. Furthermore, the (FeNi)@C/PDMS nanocomposites demonstrate remarkable corrosion resistance, exhibiting a positive shift in corrosion potential to −0.18 V compared to bare aluminum (−0.83 V), along with a corresponding protection efficiency of 98.78%. In conclusion, this study provides a validated strategy for the fabrication of EMW absorption nanocomposites consisting of magnetic nanoparticle fillers and polymer matrix, highlighting their potential for application in intricate environments.

Tailoring mechanical and electrical properties of polydimethylsiloxane nanocomposites With graphene and carbon nanotubes for wearable electronics

We explored the use of soft and flexible graphene (Gr)-reinforced polydimethylsiloxane (PDMS; Gr-PDMS) and Gr-carbon nanotube (CNT)-reinforced PDMS (Gr-CNT-PDMS) as nanocomposites (NCPs) in wearable electronic applications and investigated their mechanical and electrical properties. Specifically, we evaluated the mechanical reinforcement of the NCPs by performing Shore scleroscope hardness and machine-washing tests and evaluated their electrical properties by using a four-point probe. The results revealed that as the Gr or CNT concentrations increased, the NCPs’ hardness and surface resistance increased and decreased, respectively. Scanning electron microscopy revealed the formation of layered polymeric structures in the Gr-PDMS NCPs, contributing to the increase in hardness and decrease in surface resistance. Furthermore, bending tests revealed that changes in resistance were positively correlated with the Gr concentration. PDMS with low Gr concentrations exhibited no substantial changes in surface resistance after bending tests. However, for PDMS, as the Gr concentration increased (>5 wt.%), the cross-sectional morphology observed after 500 bending cycles differed substantially from that before observed bending tests. Additionally, the influence of one-dimensional (CNT) and two-dimensional (Gr) nanomaterials on the mechanical and electrical properties of the flexible PDMS samples was investigated. The aim of this study is to highlight the importance of considering the properties of different nanomaterials in developing high-performance NCPs for wearable electronics.

Dynamics Responses of Graphene Nanoplatelets‐Reinforced Polydimethylsiloxane Nanocomposites: A Molecular Dynamics Study

AbstractMolecular dynamics method is employed to characterize the mechanical properties of polydimethylsiloxane (PDMS) materials reinforced by graphene nanoplatelets (GNPs). Modeling results demonstrate that the addition of GNPs to PDMS significantly improves the damping properties of PDMS at high temperatures. The underlying physical mechanism is further investigated, and it is found that the interfacial interactions between the GNPs and PDMS play a crucial role in the energy dissipation capabilities. At elevated temperatures, a decrease in the interaction energy between the GNPs and PDMS matrix is observed, increasing the interfacial shipment, and improving the energy dissipation. In addition, GNPs will reflect more impact energy at a higher temperature. This study provides valuable insights into the use of GNPs for the improvement of the damping performance of PDMS materials at high temperatures.

Integration of Wireless Power Transfer Technology With Hierarchical Multiwalled Carbon Nanotubes-Polydimethylsiloxane Piezo-Responsive Pressure Sensor for Remote Force Measurement

Integrating sensory devices with wireless power transfer technology for remote sensing (RS) requires the implementation of complex electronic circuitry and communication protocols. To overcome this challenge and remotely monitor mechanical force, we directly integrated piezo-responsive porous multiwalled carbon nanotubes (MWCNTs)/polydimethylsiloxane (PDMS) nanocomposites with a near-field wireless power transfer system. The wireless system transfers power bidirectionally between the transmitter and the sensing receiver at the resonant frequency of 13.56 MHz. The detection principle is based on the mechanical force-induced impedance changes in the receiver circuit. The modulated impedance signal is detected wirelessly at the transmitter circuit via a full-bridge rectifier and a smoothing capacitor. Furthermore, we demonstrate the wireless monitoring of finger bending and applied force using our flexible and disposable sensor without using any energy storage devices. The results suggest a response and recovery time of 400 ± 50 ms, strain sensitivity of 24.73, and pressure sensitivity of 0.98. Our approach adds a new path for disposable haptic-based sensory applications that do not require complex communication protocols in medical, robotics, and other fields.

Enhanced sensing performance of flexible strain sensors prepared from biaxially stretched carbon nanotubes/polydimethylsiloxane nanocomposites

AbstractFlexible strain sensors from biaxially stretched carbon nanotubes (CNTs)/polydimethylsiloxane (PDMS) nanocomposites are fabricated in this study. It is shown that biaxial stretching promotes the homogeneous distribution and alignment of CNTs in the stretching plane, improving the sensing performance of the strain sensors. The optimized stretching ratios (SRs) of CNT/PDMS nanocomposites are determined. Compared to an unstretched CNT/PDMS‐1.0 sensor (gauge factor [GF] value = 0.73, detectable range from 0 to 60%), the 1.5 wt% CNT/PDMS‐1.5 sensor (SR = 1.5) exhibits enhanced strain sensitivity (GF = 2.8), a wider detectable range (0–370%) and better performance stability. The GF values of CNT/PDMS‐2.0 and CNT/PDMS‐2.5 sensors with SRs of 2.0 and 2.5, respectively, were 1.18 and 1.06, respectively, due to more significant conductive network reconstruction in the process of applying strain, leading to a decreasing GF. The possibility of sensors in the application of wearable electronic components is also demonstrated. The sensor shows a clear and stable signal output when different strain modes are applied, such as tensile, compressive, bending, and twisting.

Flexible Graphite Nanoflake/Polydimethylsiloxane Nanocomposites with Promising Solar–Thermal Conversion Performance

Flexible polymer nanocomposites have emerged as promising photothermal materials for various solar energy applications. However, developing photothermal materials meeting low cost, excellent light absorption capability, and facile fabrication processes has remained challenging. Herein, a set of graphite nanoflake (GnF)/polydimethylsiloxane (PDMS) nanocomposites having different concentrations from 1 to 10 wt % GnF are fabricated to find the optimum amount of GnF in a GnF/PDMS nanocomposite for the maximum absorption of solar energy within the entire solar spectrum. The optical and photothermal properties of GnF/PDMS nanocomposite films were found to be optimum at 3 wt % GnF/PDMS. Specifically, the total solar absorption is 94.8 ± 0.20%, outperforming most of the previous flexible carbon-based polymer nanocomposites. As an example of the potential application of optimized GnF/PDMS nanocomposites, a floatable interfacial water evaporator was developed by dip-coating GnF/PDMS on polyurethane (PU) foam. The coated PU at 1 wt % GnF/PDMS yields an evaporation rate of 1.14 Kg/m2·h and solar–vapor conversion efficiency of 68.2% under 1 sun illumination. The advantages of stable coating of GnF/PDMS nanocomposites and their excellent photothermal effect will benefit various solar-powered applications such as desalination, purification, and steam generation.

Optically transparent PDMS nanocomposites with ultrafine electrospun nanofiber reinforcement

Electrospun nanofibers have unique characteristics like high aspect ratio, surface area, easy processability, and scaling-up ability that make them attractive candidates as reinforcements. Here we report on facile in-situ fabrication method of nanofiber-reinforced polydimethylsiloxane (PDMS) nanocomposites. Electrospun nylon six nanofibers are embedded randomly in PDMS matrix to achieve high mechanical properties, optical transparency, and flexibility. The fabricated electrospun nylon nanofiber-reinforced PDMS nanocomposite exhibits improved mechanical strength compared to the reference PDMS, and it can be utilized in soft electronic devices such as electrolytes and separators for batteries and insulating/passivation layers, wearable electronic devices, microfluidic devices, and epidermal electronics.

Bioinspired Graphene Oxide-Magnetite Nanocomposite Coatings as Protective Superhydrophobic Antifouling Surfaces.

Antifouling (AF) nanocoatings made of polydimethylsiloxane (PDMS) are more cost-efficient and eco-friendly substitutes for the already outlawed tributyltin-based coatings. Here, a catalytic hydrosilation approach was used to construct a design inspired by composite mosquito eyes from non-toxic PDMS nanocomposites filled with graphene oxide (GO) nanosheets decorated with magnetite nanospheres (GO-Fe3O4 nanospheres). Various GO-Fe3O4 hybrid nanofillers were dispersed into the PDMS resin through a solution casting method to evaluate the structure-property relationship. A simple coprecipitation procedure was used to fabricate magnetite nanospheres with an average diameter of 30-50 nm, a single crystal structure, and a predominant (311) lattice plane. The uniform bioinspired superhydrophobic PDMS/GO-Fe3O4 nanocomposite surface produced had a micro-/nano-roughness, low surface-free energy (SFE), and high fouling release (FR) efficiency. It exhibited several advantages including simplicity, ease of large-area fabrication, and a simultaneous offering of dual micro-/nano-scale structures simply via a one-step solution casting process for a wide variety of materials. The superhydrophobicity, SFE, and rough topology have been studied as surface properties of the unfilled silicone and the bioinspired PDMS/GO-Fe3O4 nanocomposites. The coatings' physical, mechanical, and anticorrosive features were also taken into account. Several microorganisms were employed to examine the fouling resistance of the coated specimens for 1 month. Good dispersion of GO-Fe3O4 hybrid fillers in the PDMS coating until 1 wt % achieved the highest water contact angle (158° ± 2°), the lowest SFE (12.06 mN/m), micro-/nano-roughness, and improved bulk mechanical and anticorrosion properties. The well-distributed PDMS/GO-Fe3O4 (1 wt % nanofillers) bioinspired nanocoating showed the least biodegradability against all the tested microorganisms [Kocuria rhizophila (2.047%), Pseudomonas aeruginosa (1.961%), and Candida albicans (1.924%)]. We successfully developed non-toxic, low-cost, and economical nanostructured superhydrophobic FR composite coatings for long-term ship hull coatings. This study may expand the applications of bio-inspired functional materials because for multiple AF, durability and hydrophobicity are both important features in several industrial applications.

Microporous vertically aligned CNT nanocomposites with tunable properties for use in flexible heat sinks

Effective thermal management of electronic systems depends on the heat transfer efficiency or the heat dissipation capability, and the thermal conductivity of heat sink components, which has a critical impact on the performance of the devices. The rapidly growing field of microelectronics creates an enormous need for next-generation flexible, lightweight heat sinks. In this work, flexible, microporous nanocomposites are fabricated utilizing a unique yet easily tunable processing method, targeting heat-sink applications. The highly porous and low-density nanohybrid structures were fabricated in a unique processing technique using conformally pyrolytic carbon (PyC) coated vertically aligned carbon nanotube (VACNT) arrays and polydimethylsiloxane (PDMS) infiltration. Simply by varying the concentration of the PDMS in the VACNT structure, the microporosity can be tuned from 50% to 93%, and at the same time, the density of the structure varies from 0.11 g/cm 3 to 0.51 g/cm 3 . The through-thickness thermal conductivity of the VACNT – PDMS nanocomposites did not vary substantially with increasing PDMS concentration, and the highest performance samples exhibited 14.1 W/mK thermal conductivity. The highly flexible nanocomposite structure also showed excellent mechanical resiliency and exhibited complete recovery from 80% compressive strain. The final heat-sink structure with fins was fabricated by a controlled laser etching technique. Analysis of the flexible VACNT array heat sink showed a significant ∼27% reduction in thermal resistance with an air velocity of 1.5 m/s, and about ∼40% improvement in the output performance of a thermoelectric generator (TEG) on which it was mounted. The high thermal conductivity of VACNTs and the large surface area provided by the microporous structure, as well as the laser-etched fins all together contributed to better thermal management performance.

Bismuth Quantum Dot (Bi QD)/Polydimethylsiloxane (PDMS) Nanocomposites with Self-Cleaning and Antibacterial Activity for Dental Applications.

In the oral microenvironment, bacteria colonies are easily aggregated on the tooth-restoration surface, in the manner of a biofilm, which usually consists of heterogeneous structures containing clusters of a variety of bacteria embedded in an extracellular matrix, leading to serious recurrent caries. In this contribution, zero-dimensional (0D) bismuth (Bi) quantum dots (QDs) synthesized by a facile solvothermal method were directly employed to fabricate a Bi QD/polydimethylsiloxane (PDMS)-modified tooth by simple curing treatment. The result demonstrates that the as-fabricated Bi QD/PDMS-modified tooth at 37 °C for 120 min not only showed significantly improved hydrophobic performance with a water contact angle of 103° and 115° on the tooth root and tooth crown, respectively, compared to that (~20° on the tooth root, and ~5° on the tooth crown) of the pristine tooth, but also exhibited excellent antibacterial activity against S. mutans, superior biocompatibility, and biosafety. In addition, due to the highly photothermal effect of Bi QDs, the antibacterial activity of the as-fabricated Bi QD/PDMS-modified tooth could be further enhanced under illumination, even at a very low power density (12 mW cm-2). Due to the facile fabrication, excellent hydrophobicity, superior antibacterial activity, and biocompatibility and biosafety of the Bi QD/PDMS-modified tooth, it is envisioned that the Bi QD/PDMS-modified tooth with a fascinating self-cleaning and antibacterial performance can pave the way to new designs of versatile multifunctional nanocomposites to prevent secondary caries in the application of dental restoration.

Lightweight and flexible bismuth oxide composite with enhanced x‐ray shielding efficiency

AbstractLead‐based shielding materials are commonly used to protect clinical personnel and patients from high energy x‐ray radiations. However, the toxicity and heavy weight of lead can result in serious health concerns and limit its applications. Alternatively, polymer composites are known as one of the potential candidates to shield high energy photons. Herein, polydimethylsiloxane (PDMS) nanocomposites are fabricated using different weight percentages (wt.%) of bismuth oxide (Bi2O3) and multi walled carbon nanotube (MWCNT) nanoparticles. The mechanical strength of nanocomposites is evaluated by Instron 5548 Micro Tester. Also, x‐ray shielding properties are characterized using continuous x‐ray energies from 60 to 90 keV. To study the effect of the nanocomposite structure on mechanical and shielding properties, multilayer nanocomposites in 2 to 5 layers are also fabricated with alternately PDMS/Bi2O3 and PDMS/MWCNT layers and are characterized by the same methods. The 5‐layer nanocomposite improves the mechanical strength from 1.7 MPa in neat PDMS to 4.68 MPa. It is also capable of attenuating 89% of the scattered x‐rays generated at a tube potential of 60 keV, with a weight advantageous in comparison with pure lead.

Enhanced mechanical, thermal and adhesion properties of addition cured polydimethylsiloxane nanocomposite adhesives

The reinforcement of elastomeric polydimethylsiloxanes (PDMS) with carbon-based fillers and silica has gained much attention over the last few decades due to the inherent stability of the fillers which improves the physical and mechanical properties of the polymer nanocomposites. We report herein the preparation of an addition cured V-PDMS (vinyl-terminated PDMS) nanocomposite using CNT (carbon nanotube) and Aerosil COK 84 (mixed silica and alumina) as fillers. The influence of the fillers on the morphology, mechanical properties, thermal stability, thermal conductivity, and adhesive strength of these addition cured PDMS nanocomposites was studied in detail. It was observed that the tensile strength and thermal stability of the nanocomposites were enhanced upon the addition of fillers. The higher thermal conductivity of the CNT reinforced nanocomposites has potential application in heat sealing materials. The adhesive strength was studied by conducting a lap shear test on both mild steel and aluminum substrates and the adhesive strength was found to be higher for the mild steel substrate.

Laser-induced heating of polydimethylsiloxane-magnetite nanocomposites for hyperthermic inhibition of triple-negative breast cancer cell proliferation.

This paper presents the results of an experimental and computational study of the effects of laser-induced heating provided by magnetite nanocomposite structures that are being developed for the localized hyperthermic treatment of triple-negative breast cancer. Magnetite nanoparticle-reinforced polydimethylsiloxane (PDMS) nanocomposites were fabricated with weight percentages of 1%, 5%, and 10% magnetite nanoparticles. The nanocomposites were exposed to incident Near Infrared (NIR) laser beams with well-controlled powers. The laser-induced heating is explored in: (i) heating liquid media (deionized water and cell growth media [Leibovitz L15+]) to characterize the photothermal properties of the nanocomposites, (ii) in vitro experiments that explore the effects of localized heating on triple-negative breast cancer cells, and (iii) experiments in which the laser beams penetrate through chicken tissue to heat up nanocomposite samples embedded at different depths beneath the chicken skin. The resulting plasmonic laser-induced heating is explained using composite theories and heat transport models. The results show that the laser/nanocomposite interactions decrease the viability of triple-negative breast cancer cells (MDA-MB-231) at temperatures in the hyperthermia domain between 41 and 44°C. Laser irradiation did not cause any observed physical damage to the chicken tissue. The potential in vivo performance of the PDMS nanocomposites was also investigated using computational finite element models of the effects of laser/magnetite nanocomposite interactions on the temperatures and thermal doses experienced by tissues that surround the nanocomposite devices. The implications of the results are then discussed for the development of implantable nanocomposite devices for localized treatment of triple-negative breast cancer tissue via hyperthermia.

Thermally stable carbon-coated SiC/polydimethylsiloxane nanocomposites for EMI shielding in the terahertz range

Rapid development of terahertz (THz) technologies makes electromagnetic interference (EMI) shielding increasingly critical for control of electromagnetic (EM) radiation and reduction of EM pollution. In this study, carbon-coated silicon carbide nanoparticles (SiC@C NPs) are synthesized by arc-discharge plasma and dispersed into a polydimethylsiloxane (PDMS) matrix to fabricate SiC@C/PDMS nanocomposites (SiC@C/PDMS NCs). The NCs demonstrate excellent THz shielding/absorption performances in virtue of the SiC@C NP fillers and composite structure in a wide range from 0.5 to 3.0 THz. The maximum shielding efficiency and reflection loss in the range from 0.5 to 3.0 THz reach up to 44.5 and 19.0 dB on average, respectively, for the NC with a loading of 10 wt.% SiC@C NPs and 0.6 mm thickness. The SiC@C/PDMS NCs possess a high thermal stability in air, as well as lightweight and hydrophobicity. This work would provide an insight into the functionalization of the SiC@C NPs as high-performance THz shielding materials.

Functional modification of polydimethylsiloxane nanocomposite with silver nanoparticles-based montmorillonite for antibacterial applications

The functionalization of polydimethylsiloxane (PDMS) nanocomposites with advanced nanostructure materials suggests that tailored control and objective design would create significant stages with improved mechanical properties and antimicrobial properties. This work designs a creative and easy technique for the binding of silver nanoparticles-lecithin modified montmorillonite (AgNPs@LEC-Mt) in PDMS nanocomposite for antibacterial Applications. The PDMS/ AgNPs@LEC-Mt nanocomposite was evaluated by XRD, FTIR, SEM and TEM analyses. PDMS/ AgNPs @LEC-Mt nanocomposites showed better thermal stability than pure PDMS by thermogravimetric analysis. The effect of AgNPs @ LEC-Mt on the mechanical properties of PDMS was studied. The mechanical property was the best among four of them when the content of AgNPs @ LEC-Mt within reaches 1%. PDMS / AgNPs @ LEC-Mt nanocomposites showed high antimicrobial activity against E. coli and S. aureus. In vitro experiments (cell experiments) and in vivo experiments (animal experiments) evaluated that PDMS/ AgNPs @LEC-Mt nanocomposites had excellent biocompatibility. The effortlessness of the procedure, the quick response time and the better antibacterial property is useful for the advancement of antimicrobial PDMS nanocomposites for medical antibacterial devices.

Graphene fibre film/polydimethylsiloxane nanocomposites for high-performance electromagnetic interference shielding.

Exploration of high-performance electromagnetic interference (EMI) shielding materials has become a trend to address the increasing electromagnetic (EM) wave pollution environment. In this paper, oriented graphene fibre film (GFF)/polydimethylsiloxane (PDMS) nanocomposites with one-ply unidirectional, two-ply cross-ply, and two-ply unidirectional configurations were prepared using wet-spinning and hot-pressing techniques in a two-step process. Due to the anisotropic electrical performance of GFF, the one-ply laminate exhibits EMI shielding anisotropy that is affected by fibre orientation relative to the electric field component in EM waves. The maximum shielding difference at 8.8 GHz is up to 32.0 dB between the fibre orientation parallel to and perpendicular to the electric field component. In addition, we found that adding a layer of GFF is an intuitive method to enhance the shielding efficiency (SE) of GFF/PDMS nanocomposites by providing more interfaces to enhance absorption losses. An optimal EMI shielding performance of a two-ply unidirectional laminate is observed with an SE value of 50.6 dB, which shields 99.999% of EM waves. The shielding mechanisms are also discussed and clarified from the results of both experimental and theoretical analyses by adjusting the GFF structural parameters, such as the fibre orientation, areal density, number of plies and stacking sequence.

Interfacial engineering of polydimethylsiloxane based dielectric elastomers with excellent electromechanical properties via incorporating polyphenol encapsulated multiwalled carbon nanotube

AbstractThe paradox of obtaining dielectric elastomers (DEs) with both low modulus and high‐dielectric properties has long been puzzling researchers in this field. To solve this problem, a preliminary attempt is made here by solution compounding polyphenol nanoparticles modified multiwalled carbon nanotube (PNs@MWCNT) with polydimethylsiloxane (PDMS) to obtain PDMS based DEs with excellent electromechanical properties. The PNs layer can improve the interfacial interaction between MWCNT and PDMS probably through interfacial hydrogen bonding, thus improving the dispersion of PNs@MWCNT in PDMS. Compared with pure MWCNT filled PDMS nanocomposites, despite the hardening effect brought by the filler network, a softening effect (i.e., decreased cross‐linking) by the finer filler‐dispersion enhances in PNs@MWCNT/PDMS, resulting in lower moduli. Meanwhile, the as‐prepared PNs@MWCNT/PDMS composites exhibit high permittivity, low‐dielectric loss and high‐breakdown strength. Finally, the PNs@MWCNT/PDMS nanocomposites show excellent electromechanical properties with a largest actuated strain of 7.4% at a breakdown strength of 13.1 kV/mm, which is 2.2 times that (3.3%@13.3 kV/mm) of MWCNT/PDMS and 3.9 times that (1.9%@18.8 kV/mm) of neat PDMS.