Electrostrictive Behavior Research Articles

Enhanced Electrostrictive Behavior in BNT-Based Ternary Piezoceramics via Antiferroelectric Domain Engineering

Enhanced Electrostrictive Behavior in BNT-Based Ternary Piezoceramics via Antiferroelectric Domain Engineering

Semi-analytical modeling of electro-strictive behavior in dielectric elastomer tube actuators

Dielectric elastomer tube actuators (DETAs) facilitate versatile soft robotic motions when activated by electric fields. However, optimizing their performance necessitates understanding complex deformation behaviors under different electrical loading patterns. While prior analytical models provide valuable insights, many rely on assumptions like infinite-length and uniform conditions, limiting their ability to capture experimentally-observed nonuniform deformations. This paper presents a semi-analytical approach permitting both radial and longitudinal electrostatic effects by modeling a dielectric tube of effectively infinite-length. It also incorporates the crucial compression-torsion behavior for soft actuator designs. We validate the model against finite element simulations, achieving excellent agreement. Our efficient technique successfully predicts intricate deformation phenomena in DETAs under combined electrical, mechanical, and geometric effects. Results show the model effectively captures axial and twisting deformations, overcoming limitations of linear twist angle assumptions. This analytical framework offers a powerful tool for optimizing next-generation soft actuators across diverse cutting-edge engineering and robotic applications.

Impedance Study of Temperature-Stable Relaxor Dielectrics in the System of BCT-BMT Ceramics.

Preparation of a lead-free system (Ba0.8Ca0.2)TiO3-xBi(Mg0.5Ti0.5)O3 (BCT-BMT) with x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 was carried out using a solid-state reaction technique. X-ray (XRD) diffraction analysis confirmed a tetragonal structure for x = 0, which shifted to cubic (pseudocubic) at x ≥ 0.1. From Rietveld refinement, a single phase with a tetragonal symmetry model (P4mm) was observed for x = 0, and however, for sample x = 0.1 and sample x = 0.5, the data are modeled to cubic (Pm3m). Composition x = 0 showed a prominent Curie peak, typical of ordinary ferroelectrics with a Curie temperature (Tc) ∼130 °C, modified to a typical relaxor dielectric at x ≥ 0.1. However, samples at x = 0.2-0.5 displayed a single semicircle attributed to the bulk response of the material, whereas a slightly depressed second arc appeared for x = 0.5 at 600 °C, indicating a slight contribution to the electrical properties, ascribed to the grain boundary of the material. Finally, the dc resistivity increased with the increase of the BMT content and the solid solution increased the activation energy from 0.58 eV at x = 0 to 0.99 eV for x = 0.5. Adding the BMT content eliminated the ferroelectric behavior at compositions x ≥ 0.1 and led to a linear dielectric response and electrostrictive behavior with a maximum strain of 0.12% for x = 0.2.

Electrostrictive and Structural Properties of Poly(Vinylidene Fluoride-Hexafluoropropylene) Composite Nanofibers Filled with Polyaniline (Emeraldine Base).

Previous studies have reported that poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) copolymers can exhibit large electrostrictive strains depending on the filler. This work examines the electrostrictive and structural properties of P(VDF-HFP) nanofibers modified with conductive polymer polyaniline (PANI). The P(VDF-HFP)/PANI composite nanofibers were prepared by an electrospinning method with different PANI concentrations (0, 0.5, 1, 1.5, 3 and 5 wt.%). The average diameter, water contact angle and element were analyzed by SEM, WCA and EDX, respectively. The crystalline, phase structure and mechanical properties were investigated by XRD, FTIR and DMA, respectively. The dielectric properties and electrostrictive behavior were also studied. The results demonstrated that the composite nanofibers exhibited uniform fibers without any bead formation, and the WCA decreased with increasing amount of PANI. However, a high dielectric constant and electromechanical response were obtained. The electrostrictive coefficient, crystalline, phase structure, dielectric properties and interfacial charge distributions increased in relation to the PANI content. Moreover, this study indicates that P(VDF-HFP)/PANI composite nanofibers may represent a promising route for obtaining electrostrictive composite nanofibers for actuation applications, microelectromechanical systems and sensors based on electrostrictive phenomena.

Phase and Structure Behavior vs. Electromechanical Performance of Electrostrictive P(VDF-HFP)/ZnO Composite Nanofibers

In this work, we improved the electromechanical properties, electrostrictive behavior and energy-harvesting performance of poly(vinylidenefluoridene-hexafluoropropylene) P(VDF-HFP)/zinc oxide (ZnO) composite nanofibers. The main factor in increasing their electromechanical performance and harvesting power based on electrostrictive behavior is an improved coefficient with a modified crystallinity phase and tuning the polarizability of material. These blends were fabricated by using a simple electrospinning method with varied ZnO contents (0, 5, 10, 15 and 20 wt%). The effects of the ZnO nanoparticle size and content on the phase transformation, dielectric permittivity, strain response and vibration energy harvesting were investigated. The characteristics of these structures were evaluated utilizing SEM, EDX, XRD, FT-IR and DMA. The electrical properties of the fabrication samples were examined by LCR meter as a function of the concentration of the ZnO and frequency. The strain response from the electric field was observed by the photonic displacement apparatus and lock-in amplifier along the thickness direction at a low frequency of 1 Hz. Moreover, the energy conversion behavior was determined by an energy-harvesting setup measuring the current induced in the composite nanofibers. The results showed that the ZnO nanoparticles’ component effectively achieves a strain response and the energy-harvesting capabilities of these P(VDF-HFP)/ZnO composites nanofibers. The electrostriction coefficient tended to increase with a higher ZnO content and an increasing dielectric constant. The generated current increased with the ZnO content when the external electric field was applied at a vibration of 20 Hz. Consequently, the ZnO nanoparticles dispersed into electrostrictive P(VDF-HFP) nanofibers, which offer a large power density and excellent efficiency of energy harvesting.

Growth of single crystals of 0.75(Na0.5Bi0.5)TiO3-0.25(Sr0.7Ca0.3)TiO3 and characterisation of their electrical properties

Single crystals of 0.75(Na0.5Bi0.5)TiO3-0.25(Sr0.7Ca0.3)TiO3 (NBT-25SCT) were grown by top-seeded solid state crystal growth. X-ray diffraction of a polycrystalline ceramic sample and Raman scattering of a single crystal reveal that rhombohedral symmetry is predominant in the structure. The relative permittivity curves of (001), (110) and (111)-oriented single crystals show them to possess relaxor ferroelectric behaviour. The polarization vs. electric field and bipolar strain vs. electric field behaviour of the crystals differ greatly depending on crystallographic orientation. NBT-25SCT single crystals with (111) and (110) orientation show typical ferroelectric/piezoelectric behaviour whereas the (001) orientation initially shows electrostrictive behaviour followed by ferroelectric/piezoelectric behaviour at higher electric fields. Parametric impedance modelling over a wide temperature range is performed by considering mixed ionic and electronic conduction as well as universal dielectric response behaviour. The fitted parameters can represent the features of the raw data, allowing identification of the transition points and associated processes.

Observation of enhanced electrostrictive strain in (1-2x)Na0.5Bi0.5TiO3-xBaTiO3-xBiAlO3 lead-free ceramics

Herein, the author reports the observation of composition dependent piezoelectric and electrostrictive behaviour in lead free (1-2x)Na0.5Bi0.5TiO3-xBaTiO3-xBiAlO3: NBT-BT-BAO [x = 0.01, 0.03, 0.05, 0.07, 0.09] ceramics synthesized through standard solid state reaction route. X-ray diffraction analysis of the samples confirms existence of structural phase transition from monoclinic to pseudocubic with increase of BT and BAO concentration supported by Raman spectroscopic analysis. A flipping from piezoelectric (x≤ 0.03) to near-electrostrictive (x≥ 0.05) characteristics has been realized from strain vs electric field measurements. Especially, (1-2x)Na0.5Bi0.5TiO3-xBaTiO3-xBiAlO3: x = 0.05 showed an enhanced strain of 0.33 %, Smax/Emax of 425 pm/V and an electrostrictive co-efficient (Q33) of 0.034 m4C−2 could be attributed to the presence of MPB by the co-existence of monoclinic and pseudocubic phases. Further, minimal temperature dependence of the electrostrictive strain is inferred from temperature dependent polarization and strain measurements.

Improvement in energy conversion of electrostrictive composite materials by new approach via piezoelectric effect: Modeling and experiments

This study proposes a new model that couples the piezoelectric and electrostrictive behavior to minimize the polarization power of composite polymer. The development of this model is capable to predict the energy harvesting abilities of an electrostrictive composite. To improve the dielectric permittivity of electrostrictive polymer, the particles of PZT have been incorporated in order to increase the conversion efficiency of the composite. Dielectric characterization tests showed an increase in dielectric permittivity by a factor of 4.5 compared to pure polymer. Experimental measurements of harvested power validate the analytical model and demonstrate a good correlation between the two data. An equivalent of an electrical scheme has been developed, which allows modeling the two behaviors. The harvested power density under low frequency at 2% of strain can reach 0.30 μW/cm3 for 33% of PZT without the polarization field, including the conversion efficiency becomes higher. The energy harvester property of this material composite has excellent potential for several self‐powered applications such as wireless sensor networks and the internet of things.

Effect of beta-based sterilization on P(VDF-TrFE-CFE) terpolymer for medical applications

Electroactive polymers (EAP) are one of the latest generations of flexible actuators, enabling new approaches to propulsion and maneuverability. Among them, poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene/chlorotrifluoroethylene), abbreviated terpolymer, with its multifunctional sensing and actuating abilities as well as its impressive electrostrictive behavior, especially when being doped with an plasticizer, has been demonstrated to be a good candidate for the development of low-cost flexible guidewire tip for endovascular surgery. To minimize the possibility of bacterial, fungal, or viral disease transmission, all medical instruments (especially components made from polymers) must be sterilized before introduction into the patient. Gamma/beta (γ/β) irradiation is considered to be one of the most efficient techniques for targeted reduction of microbials and viruses under low temperature, often without drastic alterations in device properties. However, radiation may cause some physical and chemical changes in polymers. A compromise is required to ensure sufficient radiation for microbial deactivation but minimal radiation to retain the material’s properties. The main idea of this study aims at assessing the electromechanical performances and thermal/dielectric properties of β-irradiated terpolymer-based sterilization treatment. Ionizing β-rays did not cause any significant risk to the neat/plasticized terpolymers, confirming the reliability of such electrostrictive materials for medical device development.

Tuning rigidity and negative electrostriction of multi-walled carbon nanotube filled poly(lactic acid)

Multi-walled carbon nanotubes (MWCNTs) were utilized as an effective filler and dibutyl phthalate (DBP) as a plasticizer in the electro-responsive poly (lactic acid) matrix. Under on and off electric field, the MWCNT/PLA/DBP composites showed electromechanical recoverability with typical fast response times less than 1 min. The 0.1%v/v MWCNT-1200/PLA/DBP possessed the highest positive storage modulus sensitivity value of 1.95 at the electric field strength of 1.5 kV/mm. The storage modulus response with a value close to zero was observed at a MWCNT content between 0.8 and 0.9 %v/v. At high MWCNT concentrations, the storage modulus response became negative definite at high electric field strengths. This negative electrostriction behavior was in contrast to the positive definite electrostrictive responses of other materials. In the bending experiments, the 0.1%v/v MWCNT-2100/PLA/DBP produced relatively higher bending responses and dielectrophoresis forces at electric field strengths below 300 V/mm. At higher electric field strengths and higher MWCNTs contents, the dipole moment interaction was screened resulting in the decreases in the electrostriction, bending response and dielectrophoresis force. Thus, it has been demonstrated here that the MWCNTs induced the negative electrostriction in the plasticized PLA, possibly through the physical screening and free volume.

Polyvinylidene Fluoride/Hydrogenated Nitrile Rubber-Based Flexible Electroactive Polymer Blend and Its Nanocomposites with Improved Actuated Strain: Characterization and Analysis of Electrostrictive Behavior

A polyvinylidene fluoride (PVDF)/hydrogenated nitrile rubber (HNBR)-based flexible electroactive polymer blend was developed by generating a suitable morphology that showed a judicious combination of strength and flexibility. The blend, containing 30:70 wt/wt ratio of PVDF/HNBR, was thermoplastic elastomeric in nature and exhibited visible planar actuation in the presence of an electric field. To the best of our knowledge, the electromechanical actuation of the thermoplastic elastomeric blend has been reported for the first time. The maximum planar strain was 5%, and the actuation was triggered by the strong induced polarization in both PVDF and HNBR phases that gave rise to a high dielectric constant and low dielectric losses. The interphase between PVDF and HNBR was also very strong, which made the thermoplastic elastomer (TPE) susceptible to withstand high electric field. The TPE also exhibited a bending actuation of 0.6 mm at a low electric field of 20 kV/mm, promising enough to be used in microdevices. Addition of barium titanate (BT) nanoparticles increased the dielectric constant as they were homogeneously distributed in both the phases. The maximum planar actuation (∼10%) was observed at 10 wt % BT loading, whereas 5 wt % loading exhibited the maximum dielectric strength (∼120 kV/mm). At 5 wt % loading, the bending actuation was 0.9 mm at 20 kV/mm, which was 50% higher than that of unfilled TPE. Both the TPE and its nanocomposite also showed good history dependency in a cyclic electric field. In summary, the study provides an attractive and unexplored alternative of developing electromechanically active TPEs and their nanocomposites.

Thermodynamic Behavior of Systems Containing Amino Acids in Aqueous-Lactose Solutions

The hydration of proteins plays a vital role in biological systems, which inspires us to study the molecular interactions in solutions containing amino acids + water + lactose at different temperatures. Therefore, in view of the biological implications of the hydration behavior of amino acids, in the present document we report the key thermodynamic properties: standard molar volumes, $$V_{2,\phi }^{0}$$, and standard molar compressions, $$\kappa_{S,2,\phi }^{0}$$ of glycine, l-serine, l-proline, l-arginine and l-asparagine in 0.10, 0.30 and 0.50 mol·kg−1 aqueous solutions of lactose from density and ultrasonic velocity data at different temperatures, which helps us to understand the effect of lactose on the hydration of the amino acids. We have also reported refractive indices and molar refractions of the studied systems. The results reveal that lactose has a significant effect on the hydration and electrostriction behavior of the amino acids in general and has a dehydration effect in particular on the amino acids. The results have implications in the role of proteins in biological systems.

High Electromechanical Deformation Based on Structural Beta-Phase Content and Electrostrictive Properties of Electrospun Poly(vinylidene fluoride- hexafluoropropylene) Nanofibers.

The poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) polymer based on electrostrictive polymers is essential in smart materials applications such as actuators, transducers, microelectromechanical systems, storage memory devices, energy harvesting, and biomedical sensors. The key factors for increasing the capability of electrostrictive materials are stronger dielectric properties and an increased electroactive β-phase and crystallinity of the material. In this work, the dielectric properties and microstructural β-phase in the P(VDF-HFP) polymer were improved by electrospinning conditions and thermal compression. The P(VDF-HFP) fibers from the single-step electrospinning process had a self-induced orientation and electrical poling which increased both the electroactive β-crystal phase and the spontaneous dipolar orientation simultaneously. Moreover, the P(VDF-HFP) fibers from the combined electrospinning and thermal compression achieved significantly enhanced dielectric properties and microstructural β-phase. Thermal compression clearly induced interfacial polarization by the accumulation of interfacial surface charges among two β-phase regions in the P(VDF-HFP) fibers. The grain boundaries of nanofibers frequently have high interfacial polarization, as they can trap charges migrating in an applied field. This work showed that the combination of electrospinning and thermal compression for electrostrictive P(VDF-HFP) polymers can potentially offer improved electrostriction behavior based on the dielectric permittivity and interfacial surface charge distributions for application in actuator devices, textile sensors, and nanogenerators.

Electrical properties, strain stability and electrostrictive behavior in 0.5BaZr0.2Ti0.8O3-(0.5-x)Ba0.7Ca0.3TiO3-xBa0.7Sr0.3TiO3 lead-free ceramics

To obtain outstanding electrical properties of Barium titanate based ceramics to meet the requirements of the practical applications, a new system of BaZr0.2Ti0.8O3-(0.5-x)Ba0.7Ca0.3TiO3-xBa0.7Sr0.3TiO3 (BZT-BCT-xBST, 0 ≤ x ≤ 0.5) lead-free material was designed. A systematic study about piezoelectric, ferroelectric, and strain properties was carried out in the ceramics. The BZT-BCT-xBST ceramics with x = 0.3 exhibit an enhanced electrical property (e.g., d33∼540 pC/N, kp∼0.42, εr ∼4560, tan δ ∼0.023, and straiñ0.132% @30 kV/cm) as well as a good electrostrictive behavior (Q33 ∼0.0366 m4 C−2, Straiñ0.08%), and Q33 value is compared to PZT-baesd materials. In addition, the influence of external fields (temperature, electric field) on strain stability reveals that the strain under high driving electric fields has comparatively good temperature stability. We firmly believe that such a work can be beneficial to the practical process of BT-based ceramics.

Mesophase Structure‐Enabled Electrostrictive Property in Nylon‐12‐Based Poly(ether‐block‐amide) Copolymers

AbstractTo search for alternative electrostrictive polymers and to understand the underlying mechanism, the structure‐ferroelectric/electrostrictive property relationship for nylon‐12‐based poly(ether‐b‐amide) multiblock copolymers (PEBAX) is investigated. Two PEBAX samples are studied, namely, P6333 and P7033 with 37 and 25 mol.% of soft poly(tetramethylene oxide) (PTMO) blocks, respectively. In both samples, poorly hydrogen‐bonded mesophase facilitates electric field‐induced ferroelectric switching. Meanwhile, the longitudinal electrostrictive strain (S1)–electric field (E) loops are obtained at 2 Hz. Different from conventional poly(vinylidene fluoride‐co‐trifluoroethylene) [P(VDF‐TrFE)]‐based terpolymers, uniaxially stretched nylon‐12‐based PEBAX samples exhibit negative S1, that is, shrinking rather than elongation in the longitudinal direction. This is attributed to the unique conformation transformation of nylon‐12 crystals during ferroelectric switching. Namely, at a zero electric field, crystalline nylon‐12 chains adopt a more or less antiparallel arrangement of amide groups. Upon high‐field poling, ferroelectric domains are enforced with more twisted chains adopting a parallel arrangement of amide groups. Meanwhile, extensional S1 is observed for P6333 at electric fields above 150 MV m−1. This is attributed to the elongation of the amorphous phases (i.e., amorphous nylon‐12 and PTMO). Therefore, competition between shrinking S1 from mesomorphic nylon‐12 crystals (i.e., nanoactuation) and elongational S1 from amorphous phases determines the ultimate electrostriction behavior in stretched PEBAX films.

BaTiO3 nanowires-induced phase transition and thermally stable strain in (Bi0.5Na0.5)TiO3 piezoelectric ceramics

Environment-friendly lead-free piezoceramics with high strain response and extremely excellent stability in a wide operating temperature range are critically important in practical actuator applications. Here, we develop a new strategy to tune the electrostrictive strain behavior in Bi 0.5 Na 0.5 TiO 3 (BNT)-based ceramics via using high aspect ratio BaTiO 3 nanowires (BT NWs) as a modifier. The addition of BT NWs generates a crossover from a typical ferroelectric (BT conventional spherical particles) to a complete ergodic relaxor (ER) phase at ambient temperature, accompanied by a large electrostrictive strain of ∼0.17% with d 33 *( S max / E max ) = 284 pm/V. Such a high electrostrictive strain is extremely thermally stable with only <7% fluctuation from 27 °C to 120 °C. In addition, the BT NWs-modified ceramics also exhibit acceptable fatigue endurance (<30% up to 10 5 cycles) and frequency dependence (<20% at 10Hz–100Hz). These achieved exceptional performances can be ascribed to the BT NWs-driven complete ER phase at room temperature. The findings of this study can inspire enhanced interest in nanowires as a viable modifier to BNT-based materials due to promising potential for practical actuator applications in a wide temperature range.

A microstructure-based approach to modeling electrostriction that accounts for variability in spatial locations of domains

The discovery of polyvinylidene fluoride (PVDF) based family of relaxor ferroelectric (RFE) polymers has attracted attention due to their high electrostrictive strain and relatively low hysteresis loss. These RFE polymers exhibit complex microstructures containing both crystalline domains and amorphous domains; the interactions of the crystalline domains drive the electrostrictive behavior of these EAPs, while the amorphous domains dictate the mechanical behavior of the materials. Furthermore, the crystalline domains are spatially and orientationally distributed across the amorphous medium, further complicating the morphology of RFE polymers. Although a number of studies have focused on experimental and computational investigation of the interaction among different crystalline phases of this family of RFE, electrostriction models that represent the variabilities in the microstructure of biphasic RFE polymers are lacking. The proposed model aims to link the semicrystalline microstructure to the observed electromechanical coupling. An energy density function is constructed for a representative volume element (RVE) of the EAP, including a term for each phase, crystalline and amorphous. The interaction of the crystalline domains is based on the Coulomb interaction energy between a pair of dipoles. The responses of the amorphous domains are predicted by a modified hyperelastic stress–stretch eight-chain model. The total free energy is then analyzed under constitutive laws for an isothermal electromechanical deformation to determine the stresses generated in the RVE. The strain versus electric field, i.e. the electrostriction, relationship is calculated from a self-equilibrium condition of the Cauchy stress. The microstructure of the material is taken into account by applying the dipolar energy to a semicrystalline network model, in which a dipole that represents a crystalline domain is surrounded by an amorphous medium. The semicrystalline RVE experiences interactions with neighboring crystallites, which drives the electrostriction of the material. Two basic cases of the semicrystalline network model are explored to study the effects of spatial variation of crystalline domain locations relative to each other. Furthermore, higher fidelity descriptions of spatial location are introduced through the addition of a probability density function (PDF) of dipoles around a central dipole. Comparing the model to experimental results from the literature allows best-fit determination of the model parameters describing the PDF, e.g. aspects of microstructure, itself. These results, which agree well with experimental data, imply that the model has an ability to infer key information about the microstructure of the material by fitting the distribution of dipoles with a single adjustable parameter. The model is unique in that its descriptions of the crystalline domains is amenable to direct measurement by spectroscopic scattering techniques. Consequently, adjustable parameters in the model are linked to physical characteristics that are quantifiable, such as magnitudes of dipole moments and spatial distribution parameters.The model may also be used to elucidate aspects of network morphology using best fit of these physically meaningful adjustable parameters to experimental data, possibly providing a link between processing-structure-property relationships for future researchers.

Partial molar volumes and compressibilities of α-amino acids from aqueous to aqueous-disodium tartrate solutions at T = (303.15, 308.15 and 313.15) K

Present work reports the densities (ρ) and ultrasonic velocities (u) of four α-amino acids (viz. glycine, l-proline, l-arginine and l-asparagine) in aqueous disodium tartrate (Na2Tar) (0.50, 1.00 and 1.50 mol·kg−1) solutions at T = (303.15, 308.15 and 313.15) K. Apparent molar volumes (V2, ϕ) and apparent molar isentropic compressibilities (κS, 2, ϕ) of amino acids have been calculated from density and ultrasonic velocity data respectively. Standard molar volumes (V2, ϕo) and standard molar compressibilities (κS, 2, ϕ0) were determined from the graphical fittings using standard relations and corresponding standard transfer volumes (ΔtV2, ϕo) and standard transfer compressions (ΔtκS, 2, ϕ0) were calculated. Different thermodynamic parameters have been used to explore solute-solute, solute-solvent interactions and effect of disodium tartrate salt on the hydration and electrostriction behavior of amino acids. A significant effect of added salt on the volumetric and acoustic behavior of studied amino acids through ion-ion, ion hydrophilic-hydrophilic and hydrogen bonding interactions has been observed.

Epoxidised natural rubber–polyaniline dodecylbenzenesulfonate (ENR-PAni.DBSA) blends with adjustable electrostrictive properties

Sulphur-vulcanised epoxidised natural rubber–polyaniline dodecylbenzenesulfonate (ENR-PAni.DBSA) blends with useful electrical conductivities (up to 10−1 S/cm) and adjustable electrostrictive behaviour were successfully produced via a thermomechanical mixing method. A reasonably high level of compatibility between ENR and PAni.DBSA was observed from both Fourier transform infrared spectroscopy and transmission electron microscopy studies. As found from both electrostrictive strain ( Sz) tests, ENR-PAni.DBSA blends with 10.0–30.0 wt% of PAni.DBSA content possessed the best electrostrictive response ( Sz up to 12.25%) with applied electric field strengths up to 50 V/µm. Apart from this, blends with very low and very high PAni.DBSA contents (i.e. ≤5.0 wt% and ≥40.0 wt%) had much poorer electrostrictive responses under the same level of applied electrical field, which is due to their lower dielectric properties and higher level of phase separation between ENR and PAni.DBSA.

Electrostrictive behavior of confined water subjected to GPa pressure

Water inside a nanocapillary exhibits unconventional structural and dynamical behavior due to its ordered structure. The confining walls, density, and lateral pressures control profoundly the microscopic structure of trapped water. Here we study the electrostriction of confined water subjected to pressures of the order of GPa for two different setups: (i) a graphene nanochannel containing a constant number of water molecules independent of the height of the channel, (ii) an open nanochannel where water molecules can be exchanged with those in a reservoir. For the former case, a square-rhombic structure of confined water is formed when the height of the channel is $d=6.5$ \AA{} having a density of $\ensuremath{\rho}=1.42\phantom{\rule{4pt}{0ex}}{\mathrm{g}\phantom{\rule{0.16em}{0ex}}\mathrm{cm}}^{\ensuremath{-}3}$. By increasing the height of the channel, a transition from a flat to a buckled state occurs, whereas the density rapidly decreases and reaches the bulk density for $d\ensuremath{\cong}8.5$ \AA{}. When a perpendicular electric field is applied, the water structure and the lateral pressure change. For strong electric fields $(\ensuremath{\sim}1$ V/\AA{}), the square-rhombic structure is destroyed. For an open setup, a solid phase of confined water consisting of an imperfect square-rhombic structure is formed. By applying a perpendicular field, the density and phase of confined water change. However, the density and pressure inside the channel decrease as compared to the first setup. Our study is closely related to recent experiments on confined water, and it reveals the sensitivity of the microscopic structure of confined water to the size of the channel, the external electric field, and the experimental setup.