Electroactive Nanocomposites Research Articles

Flexible piezoelectric nanocomposites based on PVDF-HFP/PLA blend doped PZT

In the present work, we studied the effect of adding PZT nanoparticles to PVDF-HFP/PLA matrix on piezoelectric properties of blend-based nanocomposites. Polyvinylidene fluoride hexafluoro-propylene /Polylactic acid /Lead titanate zirconate (PVdF-HFP/PLA/PZT) films nanocomposites were prepared by solvent casting technique using different percentages of PZT Nano fillers. The different samples were characterized by Polarized optical microscope (POM), Fourier transformed infrared (FTIR) and Thermogravimetric analysis (TGA).POM images indicate uniform distribution of PZT Nano fillers in the PVdF-HFP/PLA matrix. FTIR analysis reveals the appearance of β-phase in nanocomposites and the enhancement of their piezoelectric properties. These electroactive nanocomposites thin films are a potential candidate for the piezoelectric Nano generators, energy storage devices and energy harvesting applications.

Development of electroactive nanocomposites based on poly(vinylidene fluoride-hexafluoropropylene)/polycarbonate blends with improved dielectric, thermal, and mechanical properties

Development of electroactive nanocomposites based on poly(vinylidene fluoride-hexafluoropropylene)/polycarbonate blends with improved dielectric, thermal, and mechanical properties

Synthesis, characterization and electro active properties of poly (MT-co-4-Fluoro aniline) Ag dispersed polymer nano composites

A series of electroactive nanocomposites was prepared by in-situ polymerization method. The silver nanoparticles dispersed in poly (metatoluidine-co-4-fluoroaniline) copolymer. The solubility characteristic of these materials are tested in various polar and polar solvents. The m-toluidine-co-4-fluoroaniline silver doped polymer nanocomposites is more soluble in organic solvents. These polymer nanocomposites possess better soluble nature than that of its homopolymer. From the UV–visible spectra absorption band obtained at 382 nm is attributed to the π-π* transition of the benzenoid moiety. The charge transfer process from benzenoid to quinoid, the band at 659 nm. The shifting of bands from 1596, 1488 cm−1 to 1598, 1495 cm−1 in the m-toluidine-co-4-fluoroaniline silver doped polymer nanocomposites observed in FTIR spectra. X-ray diffraction confirms the non-crystallinity of the m-toluidine-co-4-fluoroaniline silver doped polymer nanocomposites at a band around 25°. The crystalline peaks observed at 2θ around 32, 46, 64 and 73°is due to the lattice planes of face-centered cubic (FCC) (111), (200), (220) and (311) silver nanoparticles in poly (m-toluidine-co-4-fluoroaniline). SEM analysis shows the composites exhibits spherical granular sponge structure. They are microclustured in nature having porosity too. The conductivity value of m-toluidine-co-4-fluoroaniline silver doped polymer nanocomposites is decreased from 1.1 × 10-8 S/cm to 0.2524 × 10-8 S/cm.

Exploring electroactive microenvironments in polymer-based nanocomposites to sensitize bacterial cells to low-dose embedded silver nanoparticles

The search for alternative antimicrobial strategies capable of avoiding resistance mechanisms in bacteria are highly needed due to the alarming emergence of antimicrobial resistance. The application of physical stimuli as a mean of sensitizing bacteria for the action of antimicrobials on otherwise resistant bacteria or by allowing the action of low quantity of antimicrobials may be seen as a breakthrough for such purpose. This work proposes the development of antibacterial nanocomposites using the synergy between the electrically active microenvironments, created by a piezoelectric polymer (poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE)), with green-synthesized silver nanoparticles (AgNPs). The electrical microenvironment is generated via mechanical stimulation of piezoelectric PVDF-TrFE/AgNPs films using a lab-made mechanical bioreactor. The generated material's electrical response further translates to bacterial cells, namely Escherichia coli and Staphylococcus epidermidis which in combination with AgNPs and the specific morphological features of the material induce important antibacterial and antibiofilm activity. Both porous and non-porous PVDF composites have shown antibacterial characteristics when stimulated at a mechanical frequency of 4 Hz being the effect boosted when AgNPs were incorporated in the nanocomposite, reducing in more than 80% the S. epidermidis bacterial growth in planktonic and biofilm form. The electroactive environments sensitize the bacteria allowing the action of a low dose of AgNPs (1.69% (w/w)). Importantly, the material did not compromise the viability of mammalian cells, thus being considered biocompatible. The piezoelectric stimulation of PVDF-based polymeric films may represent a breakthrough in the development of antibacterial coatings for devices used at hospital setting, taking advantage on the use of mechanical stimuli (pressure/touch) to exert antibacterial and antibiofilm activity. Statement of significanceThe application of physical methods in alternative to the common chemical ones is seen as a breakthrough for avoiding the emergence of antimicrobial resistance. Antimicrobial strategies that take advantage on the capability of bacteria to sense physical stimuli such as mechanical and electrical cues are scarce. Electroactive nanocomposites comprised of poly(vinylidene fluoride-co-trifluoroethylene (PVDF-TrFE) and green-synthesized silver nanoparticles (AgNPs) were developed to obtain material able to inhibit the colonization of microorganisms. By applying a mechanical stimuli to the nanocomposite, which ultimately mimics movements such as walking or touching, an antimicrobial effect is obtained, resulting from the synergy between the electroactive microenvironments created on the surface of the material and the AgNPs. Such environments sensitize the bacteria to low doses of antimicrobials.

Fabrication of MnS/GO/PANI nanocomposites on a highly conducting graphite electrode for supercapacitor application

We demonstrate a high surface area of manganese sulfide (MnS) nanoparticles via a simple solution method and investigated its morphology, physicochemical, and electrochemical studies. For the first time, we attempted to exploit the polymerization of aniline without adding HCl, as it is corrosive to the metal sulfide. Instead, the acidic group present on the graphene oxide surface plays a significant role to some extent as an acidic dopant in the polymerization process. This in-situ polymerization results in the uniform coverage of granular PANI on the entire MnS/GO nanocomposite, which enhances the interfacial interactions between PANI and MnS/GO nanoparticles. The introduction of graphene oxide (GO) to pristine MnS improved the specific capacitance, surface area, and average pore size. And incorporating PANI to MnS/GO leads to an increase in the interfacial interaction between the different pore sized nanoparticles giving enhanced specific capacitance. The specific capacitance for MnS/GO/PANI nanocomposite as measured by galvanostatic charge-discharge measurements was found to be 773 F/g at 1 A/g current density, and even at higher current density, it showed a specific capacitance of 484 F/g at 3.8 A/g. The specific capacitance obtained for MnS/GO/PANI nanocomposite from CV shows 822 F/g at 10 mV/s and 315 F/g at 200 mV/s. The combinatorial effects without destroying the metal sulfide nanostructure can provide an alternate route to design, promising electroactive nanocomposites is an ideal choice as a cost-effective, next-generation high-performance supercapacitor application.

Octakis(phenyl)‐T8‐silsesquioxane‐filled silicone elastomers with enhanced electromechanical capability

AbstractThe first dielectric elastomer actuators based on electroactive nanocomposites with octakis(phenyl)‐T8‐silsesquioxane (phenyl‐T8), obtained ex‐situ, used as voltage stabilizer filler for silicone elastomers are reported. The incorporation and homogeneous dispersion of crystalline phenyl‐T8 in percentages of 2.5, 3.5, 5, and 10 into the amorphous matrix consisting in a polydimethylsiloxane‐α,ω‐diol with Mn = 240,000 g/mol was successfully achieved by solution mixing and crosslinking. For the sample with the best actuation performance (that containing 3.5 wt.% filler), an optimized filled elastomer was obtained by dispersing 3.6 wt. % phenyl‐T8 in the matrix using a suitable surfactant (Pluronic L81), thus gaining an increased electrical breakdown of 30% compared with the pristine sample. Beside dielectric strength, the matured films were characterized in terms of morphology, mechanical, dielectric and actuation tests. In spite of structural incompatibility between the filler and the matrix, the obtained materials are soft elastomers showing high strain (~800%) and low Young's modulus of 50–100 kPa. The use of phenyl‐T8 in a silicone matrix lead to electroactive films with slightly increased lateral actuation strain and electric breakdown strength.

Electroactive polypyrrole-molybdenum disulfide nanocomposite for ultrasensitive detection of berberine in rat plasma

Electroactive polypyrrole-molybdenum disulfide (MoP) nanocomposites were synthesized and used for modifying screen-printed carbon electrodes (SPCEs) for ultrasensitive detection of berberine, an anticancer drug, in rat plasma. The electroactive nanocomposites were fabricated by exfoliating MoS2 followed by pyrrole polymerization. The effect of polypyrrole in the MoP nanocomposite was evaluated by varying the pyrrole concentration during polymerization, and the resulting nanocomposites prepared with pyrrole concentrations of 10, 20, 30 μL were named as MoP-1, MoP-2, and MoP-3, respectively. The electrochemical characterization of the three MoP nanocomposite sensors revealed that MoP-2/SPCE exhibited the highest electroactivity. The detection of berberine by the three MoP-coated SPCEs revealed that MoP-2/SPCE exhibited the highest activity against berberine due to a two-electron transfer mechanism on the MoP-2/SPCE electrode surface. The detection limit of berberine using the MoP-2/SPCE sensor was found to be about 0.05 μM, which is remarkably lower than the reported detection limits. The interference study proved the selectivity of the MoP-2/SPCE sensor toward berberine in the presence of other bioactive molecules and metal ions. The designed MoP-2/SPCE sensor retained 92% of its initial activity after 15 days of storage at room temperature, with RSD values of about 2.95% and 3.68% for the repeatability and reproducibility studies. Finally, the detection limit of berberine in a rat plasma sample determined using the MoP-2/SPCE sensor was found to be about 5 μM.

Probing the local piezoelectric behavior in stretched barium titanate/poly(vinylidene fluoride) nanocomposites

The nanoscale piezoelectric and ferroelectric behavior of barium titanate/poly(vinylidene fluoride) (BT/PVDF) nanocomposite films has been investigated by means of atomic force microscopy (AFM). An uniaxial stretching step was first carried out to promote the polar β crystal phase of the PVDF matrix, as confirmed by infrared spectroscopy and piezoelectric force microscopy (PFM) analysis. Fragmentation of the original polymer crystalline structure upon drawing, as evidenced by the presence of nanometric crystalline blocks did not damage the composite film, thanks to the strong interfacial cohesion between ceramic and polymer brought by nitrodopamine functionalization of the BT inclusions. By scanning the composite surface using PFM, highly piezo-active regions were evidenced and attributed to the BT nanoparticles that could not be identified on the AFM topography images. The precise manipulation of the ferroelectric polarization states in these individual BT grains embedded into the PVDF matrix has been successfully achieved, confirmed by the local electromechanical deformation simultaneously detected. Reversible switching of the out-of-plane polarization orientation spatially confined into the particles was evidenced. The ability of the contact PFM tool to both directly visualize individual piezoelectric nanofillers dispersed into a polymer matrix and monitor the polarization states is demonstrated, thus highlighting the versatility of PFM for the advanced characterization of electroactive nanocomposites.

Electroactive Nanocomposite Porous Scaffolds of PAPn/op-HA/PLGA Enhance Osteogenesis in Vivo.

The three-dimensional (3D) porous nanocomposite biomimic scaffolds with electroactivity and bioactivity were prepared as bone implants by a freeze-drying method using 1,4-dioxane as a solvent. The multiblock copolymer (PAPn) was synthesized by the condensation polymerization of hydroxyl-capped poly(lactide)(PLA) and carboxyl-capped aniline pentamer (AP), which were introduced as electroactive functional polymers. A bioactive component, hydroxyapatite (HA) grafting l-lactic acid oligomer (op-HA), showed a better interface compatibility with PAPn and poly(lactide-co-glycolide) (PLGA). Honeycomb-like and interconnected porous structures could be obtained as displayed by scanning electron microscopy (SEM). The intramuscular implants showed a good biocompatibility and higher osteogenetic activity by promoting cell ingrowth and collagen fibers forming as indicated by SEM, hematoxylin-eosin (H&E) staining, and Masson's trichrome staining. Implantation for the repair of rabbit radius defects under 5 V at 100 Hz with a 50% duty cycle for 30 min every other day was evaluated, and sheep tibia defects were also carried out. The composite scaffold with 1 wt % PAPn exhibited better behaviors, such as a distinct bone callus, bridging growth, vague borderlines between newly formed bone at the two defect ends, and increased bone density as indicated by radiographic images and micro-computed tomography (Micro-CT) images. Electricity stimulation could significantly accelerate the healing of a fracture. All in all, the stimuli-responsive electroactive nanocomposites showed a potential application in bone tissue engineering.

Novel electroactive polyamide 12 based nanocomposites filled with reduced graphene oxide

Novel electroactive nanocomposites were prepared by adding to a polyamide 12 (PA12) matrix different amounts (from 1 to 8 wt%) of reduced graphene oxide (rGO), and the thermo‐electrical behavior of the prepared bulk materials was compared with that of the corresponding fibers. FESEM micrographs on bulk materials highlighted an evident aggregation of the rGO lamellae, proportional to the filler concentration. The presence of rGO stacks was responsible of a heavy embrittlement of the samples, with a strong reduction of the elongation at break, and of the limited electrical conductivity of the samples (about 105 Ω·cm with a rGO amount of 4 wt%). Moreover, nanofiller addition determined an improvement of the thermal degradation resistance, associated to a slight drop of the glass transition temperature (about 7°C with a nanofiller concentration of 4 wt%) and of the crystallinity degree (up to 9% for an rGO loading of 4 wt%). The extrusion process adopted to prepare nanocomposite fibers caused a partial breakage of rGO aggregates and their progressive alignment along the drawing direction, determining thus an electrical resistivity increase with respect to the bulk samples. Therefore, the surface heating of the prepared fibers through Joule effect was possible only at elevated rGO amounts (i.e., 8 wt%). POLYM. ENG. SCI., 59:198–205, 2019. © 2018 Society of Plastics Engineers

Spring-like electroactive actuators based on paper/ionogel/metal nanocomposites

We report about a novel class of electroactive nanocomposites designed to perform spring-like actuation at low applied voltages. These systems are based on the impregnation of plain paper with a highly conductive ionogel, interpenetrating nanostructured conducting electrodes are printed on the paper/ionogel substrate by supersonic cluster beam deposition. Due to the structure and mechanical properties of the paper substrates, helix-shaped actuators can be obtained by coiling strips of the nanocomposites, thus enabling the production of electroactive components exhibiting motion up to two millimeters with a polarization of 5 V. Our approach constitutes a promising solution for the development of adaptive soft robotic architectures and smart flexible systems with bio-inspired motility.

Enhanced energy storage in polyvinylidenefluoride (PVDF) + BaZrO3 electroactive nanocomposites

PVDF + BaZrO3 electroactive nanocomposite thin film has been prepared by solution casting method. The structural analysis was carried out by using x-ray diffraction pattern and atomic force microscopy (AFM). Generally, the performance of dielectric capacitors toward higher energy density and higher operating temperatures has been drawing increased interest. In this regard, the present study was focussed on the fabrication and characterization of PVDF + BaZrO3 electroactive nanocomposites in view of enhancing the energy density at elevated temperature. Cole-Cole plot is an agreement with multiple relaxation process in electroactive nanocomposites. Dielectric energy storage performance is assessed for PVDF nanocomposites with different wt% of BaZrO3 at different frequencies and temperature. It has been observed that with increase of temperature, the permittivity increased while the energy density slightly decreased but significantly higher than pure polymer PVDF. A high energy density of 6.88 J/cm3 was obtained for BaZrO3 electroactive nanocomposites at 50 °C and 5.06 J/cm3 at 70 °C. Overall, the testing results indicate that using nanocomposites of PVDF and BaZrO3 as a dielectric component is promising for implementation to preserve high energy density values up to temperatures of 70 °C.The enhancement of dielectric permittivity and the energy density is attributed due to increase of interracial charge density. The effect of BaZrO3 nanoparticles in energy density of PVDF is first time reported.

Fabrication, electrochemical and catalytic properties of the nanocomposites composed of phosphomolybdic acid and viologen-functionalized multi-walled carbon nanotubes

Electroactive nanocomposites composed of phosphomolybdic acid (PMA) and viologen-functionalized carbon nanotubes were synthesized and used as heterogeneous catalysts for the electrocatalytic reduction of bromate. Viologen (V) was first covalently anchored on the surface of multi-walled carbon nanotubes (MWNTs) to produce positively charged MWNT-V polyelectrolyte, which was then combined with PMA through electrostatic interaction to form MWNT-V@PMA nanocomposites. Thermogravimetric analysis revealed that the organic species in the MWNT-V polyelectrolyte was about 30% in weight. Composition, structure, and morphology of the nanocomposites were investigated by using UV-vis, infrared, Raman and X-ray photoelectron spectroscopy as well as field emission transition electron microscope. The thickness of organic substituents, viologen, and PMA in the nanocomposites was approximately 10 nm covered on the surface of MWNTs. Cyclic voltammogram measurements for the casting films of MWNT-V@PMA nanocomposites revealed four couples of redox waves with cathodic potentials at about −0.56, −0.19, 0.02, 0.21 V, and anodic ones at about −0.46, −0.11, 0.12, 0.31 V (vs Ag/AgCl), respectively, among which the first one corresponded to the electron transfer process of viologens and others to that of the PMA adsorbed. Finally, the MWNT-V@PMA modified electrodes were used as heterogeneous catalysts for the electrocatalytic bromate reduction, which revealed an almost linear correction between the current density and the bromate concentrations in the concentration range from 1 to 15 mmol/l.

A new class of ionic electroactive polymers based on green synthesis

In this paper, a novel class of ionic electroactive nanocomposites, named Ionic Polymer-Polymer Metal Composites (IP2MCs) is introduced. IP2MCs are capable of electromechanical transduction and, therefore, they are suitable to be used as nanocomposite artificial muscles. They represent an evolution of a class of totally polymeric ionic electroactive polymers, named Ionic Polymer Composites (IP2Cs), previously proposed by some of the Authors. Compared to the parent technology, IP2MCs exploit both the beneficial effects of electrodes based on polymeric conductors and the use of noble metal (Pt) nanoparticles. The deposition of platinum nanoparticles is obtained through a green chemical reduction process.The fabrication process, and the influence of the novel nanocomposite electrode on the thermal, mechanical, and electromechanical behavior of green IP2MCs are described together with a comparison with the properties of Ionic Polymer Metal Composites (IPMCs) and IP2Cs. Reported results allow concluding that electroactive devices, with performances comparable with those of IPMC actuators, can be obtained. Eventually, the production procedure is more environmental friendly, cheaper and faster than the corresponding technique used for IPMC fabrication.

Multifunctional Electroactive Nanocomposites Based on Piezoelectric Boron Nitride Nanotubes.

Space exploration missions require sensors and devices capable of stable operation in harsh environments such as those that include high thermal fluctuation, atomic oxygen, and high-energy ionizing radiation. However, conventional or state-of-the-art electroactive materials like lead zirconate titanate, poly(vinylidene fluoride), and carbon nanotube (CNT)-doped polyimides have limitations on use in those extreme applications. Theoretical studies have shown that boron nitride nanotubes (BNNTs) have strength-to-weight ratios comparable to those of CNTs, excellent high-temperature stability (to 800 °C in air), large electroactive characteristics, and excellent neutron radiation shielding capability. In this study, we demonstrated the experimental electroactive characteristics of BNNTs in novel multifunctional electroactive nanocomposites. Upon application of an external electric field, the 2 wt % BNNT/polyimide composite was found to exhibit electroactive strain composed of a superposition of linear piezoelectric and nonlinear electrostrictive components. When the BNNTs were aligned by stretching the 2 wt % BNNT/polyimide composite, electroactive characteristics increased by about 460% compared to the nonstretched sample. An all-nanotube actuator consisting of a BNNT buckypaper layer between two single-walled carbon nanotube buckypaper electrode layers was found to have much larger electroactive properties. The additional neutron radiation shielding properties and ultraviolet/visible/near-infrared optical properties of the BNNT composites make them excellent candidates for use in the extreme environments of space missions.

Bending actuation and charge distribution behavior of polyurethane/carbon nanotube electroactive nanocomposites

The electroactive nanocomposite films were fabricated using polyurethane (PU) with modified carbon nanotubes (CNTs) as the filler. The CNTs were modified using microwave‐induced polymerization route and they were found to be highly dispersed in polar solvents such as dimethylformamide. The modified CNTs were characterized using transmission electron microscopy, field emission scanning electron microscopy, thermogravimetric analysis, and X‐ray photoelectron spectroscopy. To evaluate these films we mainly focused on electrical properties such as actuation behavior, resistivity, impedance analysis, and space charge measurements. We found that the PU/CNT films bent toward the cathode when an electric field was applied and they reverted to its original position when the electric field was removed. Upon the incorporation of CNTs as the filler for the polymer, the electrical properties of the films improved significantly. Asymmetric charge accumulation was observed from space charge measurements in some of the films and this explains the bending deformation and the actuation behavior. POLYM. COMPOS., 262–269, 2016. © 2014 Society of Plastics Engineers

Multilayer Films Electrodes Consisted of Cashew Gum and Polyaniline Assembled by the Layer-by-Layer Technique: Electrochemical Characterization and Its Use for Dopamine Determination

We take advantage of polyelectrolyte feature exhibited by natural cashew gum (Anacardium occidentale L.) (CG), found in northeast Brazil, to employ it in the formation of electroactive nanocomposites prepared by layer-by-layer (LbL) technique. We used polyaniline unmodified (PANI) or modified with phosphonic acid (PA), PANI-PA as cationic polyelectrolyte. On the other hand, the CG or polyvinyl sulfonic (PVS) acids were used as anionic polyelectrolytes. The films were prepared with PANI or PANI-PA intercalated with CG or with PVS alternately resulting in four films with different sequences: PANI/CG PANI-PA/CG, PANI/PVS and PANI-PA/PVS, respectively. Analysis by cyclic voltammetry (CV) of the films showed that the presence of gum increases the stability of the films in acidic medium. The performance of the modified electrode of PANI-PA/CG was evaluated in electro analytical determination of dopamine (DA). The tests showed great sensitivity of the film for this analyte that was detected at 10−5 mol L−1.

Polypeptide-guided assembly of conducting polymer nanocomposites

A strategy for fabrication of electroactive nanocomposites with nanoscale organization, based on self-assembly, is reported. Gold nanoparticles are assembled by a polypeptide folding-dependent bridging. The polypeptides are further utilized to recruit and associate with a water soluble conducting polymer. The polymer is homogenously incorporated into the nanocomposite, forming conducting pathways which make the composite material highly conducting.

Natural Gum-Assisted Phthalocyanine Immobilization in Electroactive Nanocomposites: Physicochemical Characterization and Sensing Applications

Natural gums have been traditionally applied in cosmetics and the food industry, mainly as emulsification agents. Due to their biodegradability and excellent mechanical properties, new technological applications have been proposed involving their use with conventional polymers forming blends and composites. In this study, we take advantage of the polyelectrolyte character exhibited by the natural gum ChichA (Sterculia striata), extracted in the Northeastern region of Brazil, to produce electroactive nanocomposites. The nanocomposites were fabricated in the form of ultrathin films by combining a metallic phthalocyanine (nickel tetrasulfonated phthalocyanine, NiTsPc) and the ChichA gum in a tetralayer architecture, in conjunction with conventional polyelectrolytes. The presence of the gum led to an efficient adsorption of the phthalocyanine and enhanced the electrochemical response of the films. Upon combining the electrochemical and UV-vis absorption data, energy diagrams of the ChichA/NiTsPc-based system were obtained. Furthermore, modified electrodes based on gum/phthalocyanine films were able to detect dopamine at concentrations as low as 10-5 M.

Ferrocene Groups Tethered to Clay Surfaces : Effect of Surfactant Chain Length on Electroactivity

A homologous series of ferrocenyl surfactants, where 6, or 11, have been intercalated into thin clay films in an effort to design novel electroactive nanocomposites. Cyclic voltammetry of clay-modified electrodes has been used to investigate the electrochemical properties of the surfactants. The rate of intercalation into the clay and steady-state currents were found to be highly dependent on chain length. Of the three, the compound containing one carbon in the chain is the only molecule to be effectively modeled by an ion-exchange mechanism, implying that the ferrocene resides close to the surface of the clay. The electrochemistry of the two longer chain compounds is markedly different from the one with a single carbon in the chain. The six- and eleven-carbon chain compounds have been shown to generate a larger capacitive current in the clay and represent possible charge-storage devices. © 2002 The Electrochemical Society. All rights reserved.