PVDF-TrFE Copolymer Research Articles

Detection of high sensitive acoustic region for sensible applications of electrospinning based PVDF-TrFE nanofiber sensor

Cardinal amount of assessment has been vested on using Polyvinylidene Fluoride-co-Trifluoroethylene (PVDF-TrFE) electrospinning based nanofibers for subtle applications as acoustic sensor. In the current course of experiment, utilizing electron, proton and ionic conductive properties of the PVDF-TrFE co-polymers in conjunction with aluminum (Al) and copper (Cu) as electrodes, demonstrates strong acoustic to electric conversion ability within the audible frequency range of 30 Hz to 15 KHz and fortuitously, sensitive acoustic region has been commended for intricate medical applications. Furthermore, enhanced sensitivity was observed due to advance charge polarization by using Polydimethylsiloxane (PDMS) wrapped on the fabricated device. The standard β-Phasic Perovskite polymer sensor with a sensing congregation can relay convergent sound directly to the nanofiber layer and the resultant sensitivity shows as high as 11 VPa−1 at 40 Hz to 60 Hz incident frequency of normal conversation, which can be efficacious for developing high-performance acoustic based biomedical sensors.

Additive manufacturing of single- and double-layer piezoelectric PVDF-TrFE copolymer sensors

Abstract The sensitivity of piezoelectric PVDF sensors is directly related to the concertation and orientation of the polar phases. Previous efforts in obtaining oriented polar phases during 3D printing proved to be challenging. In this paper the superiority of the co-polymer PVDF-TrFE when compared to PVDF for 3D printing is demonstrated. In contrast to PVDF, PVDF-TrFE forms nearly pure β-phase in solidification from melt. The emergence of more β-phase than the non-polar α-phase is demonstrated with XRD results. 3D printed double-layer samples were produced consisting of one electroactive layer of PVDF-TrFE, and a non-electroactive substrate and protective layer of PVDF. The 3D printed samples were poled with corona discharge to produce output signals up to 130V DC peak-to-peak from a simple impact test (flicking) on a 20×30 mm sample. We also observed high sensitivity to 2mm dynamic displacement loads that produced ~19V. The results presented here are considerably higher than any reported results from other additive manufacturing methods.

Actuation efficiency of polyvinylidene fluoride-based co- and ter-polymers

Poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) ter-polymers reach strain up to 4% with the application of an electric field. This is several times larger than PVDF-TrFE co-polymers. However this large strain comes with reduced stiffness, which is detrimental to ter-polymers integration in heterogeneous structures. Here we compare the actuation capabilities of cantilevers with P(VDF-TrFE-CTFE) and P(VDF-TrFE) as active layer. Our ter-polymers exhibit CTFE composition ranging from 0 to 9.7%. We compared the electrical and mechanical displacements as well as the electromechanical coupling of these devices. We found that ter-polymer devices with CTFE ratio below 8% are ferroelectric whereas they become relaxor beyond 8% of CTFE. The maximum deflections of all cantilevers at high electric field are comparable, though slightly larger for the ter-polymer with 5% CTFE. The main finding of this paper concerns the effective electromechanical coupling of ter-polymers that is at best only half of the co-polymer one.

Ferroelectric to paraelectric phase transition mechanism in poled PVDF-TrFE copolymer films

Direct experimental insights into the structural and dynamical mechanisms for ferroelectric \ensuremath{\beta} to paraelectric \ensuremath{\alpha} phase transition in a poled PVDF-TrFE copolymer is obtained from in situ x-ray diffraction and quasielastic neutron scattering measurements at high temperatures. It is observed that the \ensuremath{\beta}-to-\ensuremath{\alpha} phase transition proceeds through two energetically distinct processes, which are identified here as the nucleation and growth of an intermediate \ensuremath{\gamma} phase with random skew linkages followed by a \ensuremath{\gamma}-to-\ensuremath{\alpha} transition. The two energetically distinct microscopic processes can explain the stages of evolution for \ensuremath{\beta}-to-\ensuremath{\alpha} phase transition observed from heat flow measurements.

Enhanced Piezoelectricity of Nanoimprinted Sub-20 nm Poly(vinylidene fluoride–trifluoroethylene) Copolymer Nanograss

In this paper, sub-20 nm ferroelectric PVDF–TrFE copolymer nanograss structures with aspect ratios up to 8.9 were developed. This study demonstrated sub-20 nm PVDF–TrFE nanograss structures that are nanoimprinted using a silicon nanograss mold in a single step. Vertically oriented PVDF–TrFE nanopillars were poled using the developed flip-stacking poling method. According to the PFM measurements, the piezoelectricity of flat thin films fabricated in this work reaches 14.0 pm/V. The maximum output voltage of the single PVDF–TrFE nanopillar was 526 mV, and the maximum piezoelectricity of the single PVDF–TrFE nanopillar was 210.4 pm/V. The piezoelectricity of the developed PVDF–TrFE nanograss structures was 5.19 times larger than that of the PVDF–TrFE flat thin films. The developed technique is simple, economical, and easy to fabricate. The developed ferroelectric PVDF–TrFE copolymer nanograss structures, which showed enhanced piezoelectricity compared to the PVDF–TrFE flat thin films, have potential applicat...

Contributions of distinctive dynamic processes to dielectric response of a relaxorlike reduced poly(vinylidene fluoride-trifluoroethylene) copolymer

Dynamic processes in relaxorlike reduced polyvinylidene fluoride-trifluoroethylenePVDF-TrFE copolymer have been studied by measurements of the temperature and frequency-dependent linear and thirdorder nonlinear dielectric response. Dielectric analysis of relaxor polymers has, namely, been incomplete until now, i.e., data interpretation was complicated by the fact that two similar types of dynamics, relaxorlike behavior in the crystalline part of the system and glass-to-rubber transition in the amorphous matrix, take place in the same temperature range and thus superimpose in the detected response. On the other hand, here, in the PVDF-TrFE system, synthesized via reductive dechlorination from the polyvinylidene fluoridechlorotrifluoroethylene, relaxor peaks take place at much higher temperatures, thus both dynamics can be investigated separately. Analysis of the experimental data reveals that the relaxorlike dielectric dynamics in the reduced PVDF-TrFE copolymer, which is now not influenced by processes in the amorphous matrix, indeed is almost identical to that observed in classical relaxor systems and, furthermore, reminiscent of the dynamic behavior observed in various spin glasses. Also, a clear indication was obtained that all polar dynamic processes terminate down to 100 K and that below this temperature only nonpolar contributions govern the dielectric response of the reduced PVDF-TrFE copolymer.

Effect of Thickness on Electrical Properties of PVDF-TrFE (51/49) Copolymer

In this study, polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) in the composition from 51/49, was deposited on platinum for a metal-ferroelectric-metal structure. From XRD patterns, the 70 nm- and 140 nm-thick PVDF-TrFE films showed the intensity peak of near connected to a ferroelectric phase. Moreover, the thicker film indicated the higher intensity than thinner one. The difference of the remanent polarization (2Pr) at 0 V is decreased gradually from 10.19 to as the thickness decrease from 140 to 70 nm. However, when the thickness decreased to 50 nm, the 2Pr rapidly drop to so the minimum critical thickness might be at least 70 nm for device. Both different thickness films, 70 and 140 nm, indicated that the characteristic of current density-voltage was measured for below 15 V and the thicker film maintained relatively lower current density than thinner one. From these results, we can expect that the electrical properties for the devices particularly ferroelectric thin film transistor using PVDF-TrFE copolymer were able to be on the trade-off relationship between the remanent polarization with the bias voltage and the leakage current.

1T Memory Cell Based on PVDF-TrFE Field Effect Transistor

ABSTRACTInterest in PVDF-TrFE copolymers as ferroelectric material for Memory application is driven by the prospect of having low cost, low operating voltage and fully organic device. Some previous studies reported FET designs using copolymers [refs 1,2] but none of these structures were fully integrated on silicon wafers and using a MOSFET fabrication process. We present for the first time the integration of a PVDF-TrFE (70%-30%) layer into a standard n-MOS transistor through a quasi-standard semiconductor technology. This allows us to achieve a Non Volatile Memory cell and at the same time to compact capacitor-transistor ferroelectric cell into a one-transistor memory cell.

Evaluation of piezoelectric poly(vinylidene fluoride) polymers for use in space environments. I. Temperature limitations

AbstractSmart materials, such as thin‐film piezoelectric polymers, are interesting for potential applications on Gossamer spacecraft. This investigation aims to predict the performance and long‐term stability of the piezoelectric properties of poly(vinylidene fluoride) (PVDF) and its copolymers under conditions simulating the low‐Earth‐orbit environment. To examine the effects of temperature on the piezoelectric properties of PVDF, poly(vinylidenefluoride‐co‐trifluoroethylene), and poly(vinylidenefluoride‐co‐hexafluoropropylene), the d33 piezoelectric coefficients were measured up to 160 °C, and the electric displacement/electric field (D–E) hysteresis loops were measured from −80 to +110 °C. The room‐temperature d33 coefficient of PVDF homopolymer films, annealed at 50, 80, and 125 °C, dropped rapidly within a few days of thermal exposure and then remained unchanged. In contrast, the TrFE copolymer exhibited greater thermal stability than the homopolymer, with d33 remaining almost unchanged up to 125 °C. The HFP copolymer exhibited poor retention of d33 at temperatures above 80 °C. In situ D–E loop measurements from −80 to +110 °C showed that the remanent polarization of the TrFE copolymer was more stable than that of the PVDF homopolymer. D–E hysteresis loop and d33 results were also compared with the deflection of the PVDF homopolymer and TrFE copolymer bimorphs tested over a wide temperature range. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1310‐1320, 2005

Influence of poling and annealing on the nonlinear dielectric permittivity of PVDF-TRFE copolymers

The linear and second order permittivities of as-prepared and annealed, poled and unpoled PVDF-TRFE 56/44 mol% copolymer film are investigated as a function of temperature. In contrast to annealed PVDF-TRFE, the linear permittivity of unannealed PVDF-TRFE and its temperature dependence is not influenced by poling. This effect can be explained by the existence of domain walls in the crystalline regions of annealed samples, while the smaller crystallites in unannealed samples are always in a single domain state. Thus the poling degree dependence of the linear permittivity of annealed samples may therefore be an effect of domain wall motion. The second order permittivity is a measure of the remanent polarization. Samples poled before the first annealing exhibit a small persistent polarization that remains stable in the paraelectric phase, in contrast to samples which remain unpoled before annealing. This non-switchable polarization is unchanged after several heating cycles and even after poling in the opposite direction. An explanation for this fixed polarization are non-switchable dipoles which form an intermediate phase between the crystalline and the amorphous phase.

Micromechanical properties of electron irradiated PVDF-TrFE copolymers

Micromechanical spectroscopy is a sensitive probe of phase transitions occurring in semicrystalline polymers. We used this approach to investigate the effect of irradiation on phase transitions in ferroelectric PVDF-TrFE copolymers. It appears that the glass-rubber transition and the Curie transition are both affected by bombardment with fast electrons, but in a different way. The observed changes in the elastic modulus, mechanical losses and thermal expansion results are consistent with a decrease in the degree of crystallinity.

Pyroelectric detection of PVDF-TrFE copolymer film by irradiation of CO2 laser.

The pyroelectric current of ferro-electric polymer strongly depends on a poling field. The currentof poly·vinylidene-trifluoroethylene (P·VDF-TrFE) copolymer induced by CW-CO2 laserirradiation steeply increases at the field higher than 0 .4 MV/cm. This magnitude of poling fieldcorresponds to an internal field induced by the poling process . The induced current of P·VDF-TrFE film copolymer depends on the VDF concentration, and it almost constant over therange of 54-66 mol%. The film poled by a high electric field (≥1MV/cm) could be used as a veryconvenient pyro-electric detective material.