Trifluoroethylene Research Articles

Effect of film thickness on laser induced surface structures formation on optically transparent polymer films

Laser-induced periodic surface structures can be prepared on polymer thin films, despite the absence of light absorption at the wavelength of the irradiating laser, by using a bilayer approach. Nanostructuring of a poly(3-hexylthiophene-2,5-diyl) (P3HT) layer, by laser irradiation at 532 nm, covered by a thin layer of a non-absorbing polymer, in this case, the ferroelectric copolymer poly(vinylidene fluoride - trifluoro ethylene),P(VDF-TrFE), allows the development of a grating-like structure on the surface. The range of thicknesses of the upper layer, which leads to the formation of LIPSS, has been determined. It is verified that for a thickness larger than 40 nm, no periodic structures are formed, neither in the upper layer nor in the bottom P3HT one. This can be explained considering a mechanical restriction which prevents P3HT rearrangement. The upper nanostructured surface layer exhibits ferroelectric properties as proven by piezoresponse force microscopy measurements.

Tunable properties of poly(vinylidene fluoride)-derived polymers for advancing battery performance and enabling diverse applications

This study uses molecular dynamics (MD) simulations to examine the thermal, structural, mechanical, and dynamic characteristics of poly(vinylidene fluoride) (PVDF) and its copolymers. We constructed and simulated three copolymers by replacing 0 to 50 mol% of PVDF monomers with trifluoroethylene (TrFE), hexafluoropropylene (HFP), and chlorotrifluoroethylene (CTFE) in order to investigate their properties. Additionally, we conducted a simulation of a polyelectrolyte model using the copolymers we constructed, along with LiFSI salt and FEC solvent, in order to evaluate the ionic conductivity. The calculated properties, such as melting temperature, thermal conductivity, Young’s modulus, and ionic conductivity, were found to be dependent on the molar fraction of substituted monomers. We observed specific peaks in the ionic conductivity calculated at room temperature, with maximum values of 3.32 × 10−5 S/cm for P(VDF-3 mol% HFP) and 2.56 × 10−5 S/cm for P(VDF-10 mol% TrFE). The molecular dynamics simulation results were consistent with experimental findings and provided insights into the adjustable atomistic details of fluorinated polymers derived from PVDF.

Microstructure and mechanical properties of BT/PVTC composite ferroelectric thin films.

Ferroelectric ceramic polymer composites have become the preferred electrocaloric materials due to their light weight and high polarization strength. But the mechanical properties were desired to be improved. In this study, the polyvinylidene fluoride trifluoro ethylene chloride (PVTC) and barium titanate (BT) composites were prepared, and the microstructure and mechanical properties were investigated by molecular dynamics simulations and experiments. It was found that with the increase of BT ceramic content in the composites, the yield stress is significantly reduced, which can be reduced by 16.07%. By comparing with the experimental data, the agglomeration and stress mechanism of the composites were proposed. The microstructure of the composite was analyzed using radial distribution function, self-diffusion coefficient, and glass transition temperature. The agglomeration mechanism of the composite was revealed from the microscopic point of view, and the rationality of the agglomeration behavior was verified by experiments. The calculations were performed by Material Studio 2019 software and the COMPASS force field was adopted.

Ferroelectric and relaxor ferroelectric activities of the P(VDF‐TrFE) and its blends synthesized by (SiMe3)3SiH hydrogenation process

AbstractA group of ferroelectric polyvinylidene‐trifluoroethylene (P(VDF‐TrFE)) with 6, 9, 20, and 50 mol% trifluoroethylene (TrFE) is synthesized by an hydrogenation process using a new catalyst (SiMe3)3SiH from polyvinylidene‐chlorotrifluoroethylene. We find the crystalline region of hydrogenated P(VDF‐TrFE) 80/20 mol% is β crystal phase predominant, which is responsible to the favorable ferroelectric property. Moreover, polyvinylidene fluoride (PVDF) blending is used to fabricate the ferroelectric and relaxor ferroelectric properties of P(VDF‐TrFE) 80/20 mol%. Interestingly, with the increasing of PVDF content, PVDF/P(VDF‐TrFE) has three successional conversion stages of ferroelectricity, antiferroelectricity, and relaxor ferroelectricity, respectively, indicating that the β crystal domains in hydrogenated P(VDF‐TrFE) films gradually reduces with the introduction of PVDF. Otherwise, after an unidirectional stretching process, the ferroelectricity of relaxor PVDF/P(VDF‐TrFE) blend film is reformed. As such, the maximum polarization (Pm) and remnant polarization (Pr) of stretched PVDF/P(VDF‐TrFE) with 90 wt% PVDF reached to 13.8 and 7.5 μC/cm2 under 200 MV/m, respectively. Thus, the three methods proposed in this work including fabricating configuration by changing TrFE content, physical blending by introduction of PVDF, and simple stretching can modify the ferroelectric performances of this hydrogenated P(VDF‐TrFE), which also provides a reference of application of this polymer on ferroelectric areas.

Design and characterization of molecular, crystal and interfacial structures of PVDF-based dielectric nanocomposites for electric energy storage.

PVDF-based polymers with polar covalent bonds are next-generation dielectric materials for electric energy storage applications. Several types of PVDF-based polymers, such as homopolymers, copolymers, terpolymers and tetrapolymers, were synthesized by radical addition reactions, controlled radical polymerizations, chemical modifications or reduction with the monomers of vinylidene fluoride (VDF), tetrafluoroethylene (TFE), trifluoroethylene (TrFE), hexafluoropropylene (HFP) and chlorotrifluoroethylene (CTFE). Owing to rich molecular structures and complicated crystal structures, PVDF-based dielectric polymers can show versatile dielectric polarization properties, including normal ferroelectrics, relaxor ferroelectrics, anti-ferroelectrics and linear dielectrics, which are beneficial for designing polymer films with high capacity and high charge-discharge efficiency for capacitor applications. Furthermore, to satisfy the requirements of practical high-capacity capacitors, the polymer nanocomposite method is another promising strategy to achieve high-capacitance dielectric materials by the addition of high-dielectric ceramic nanoparticles, moderate-dielectric nanoparticles (MgO, and Al2O3), high-insulation nanosheets (BN), etc. It is concluded with the current problems and future perspectives of interfacial engineering, such as core-shell strategies and hierarchical interfaces in polymer-based composite dielectrics for high-energy-density capacitor applications. In addition, an in-depth understanding of the roles of interfaces on the dielectric properties of nanocomposites can be achieved by indirect analysis techniques (theoretical simulation) and direct analysis techniques (scanning probe microscopy). Our systematic discussions on molecular, crystal and interfacial structures provide guidance for designing fluoropolymer-based nanocomposites for high-performance capacitor applications.

Integration of Screen Printed Piezoelectric Sensors for Force Impact Sensing in Smart Multifunctional Glass Applications

Screen printed piezoelectric polyvinylidene fluoride–trifluoro ethylene (PVDF–TrFE)‐based sensors laminated between glass panes in the temperature range 80–110 °C are presented. No degradation of the piezoelectric signals is observed for the sensors laminated at 110 °C, despite approaching the Curie temperature of the piezoelectric material. The piezoelectric sensors, here monitoring force impact in smart glass applications, are characterized by using a calibrated impact hammer system and standardized impact situations. Stand‐alone piezoelectric sensors and piezoelectric sensors integrated on poly(methyl methacrylate) are also evaluated. The piezoelectric constants obtained from the measurements of the nonintegrated piezoelectric sensors are in good agreement with the literature. The piezoelectric sensor response is measured by using either physical electrical contacts between the piezoelectric sensors and the readout electronics, or wirelessly via both noncontact capacitive coupling and Bluetooth low‐energy radio link. The developed sensor concept is finally demonstrated in smart window prototypes, in which integrated piezoelectric sensors are used to detect break‐in attempts. Additionally, each prototype includes an electrochromic film to control the light transmittance of the window, a screen printed electrochromic display for status indications and wireless communication with an external server, and a holistic approach of hybrid printed electronic systems targeting smart multifunctional glass applications.

Effect of the TrFE Content on the Crystallization and SSA Thermal Fractionation of P(VDF-co-TrFE) Copolymers.

In this contribution, we study the effect of trifluoro ethylene (TrFE) comonomer content (samples with 80/20, 75/25, and 70/30 VDF/TrFE molar ratios were used) on the crystallization in P(VDF-co-TrFE) in comparison with a PVDF (Poly(vinylidene fluoride)) homopolymer. Employing Polarized Light Optical Microscopy (PLOM), the growth rates of spherulites or axialites were determined. Differential Scanning Calorimetry (DSC) was used to determine overall crystallization rates, self-nucleation, and Successive Self-nucleation and Annealing (SSA) thermal fractionation. The ferroelectric character of the samples was explored by polarization measurements. The results indicate that TrFE inclusion can limit the overall crystallization of the copolymer samples, especially for the ones with 20 and 25% TrFE. Self-nucleation measurements in PVDF indicate that the homopolymer can be self-nucleated, exhibiting the classic three Domains. However, the increased nucleation capacity in the copolymers provokes the absence of the self-nucleation Domain II. The PVDF displays a monomodal distribution of thermal fractions after SSA, but the P(VDF-co-TrFE) copolymers do not experience thermal fractionation, apparently due to TrFE incorporation in the PVDF crystals. Finally, the maximum and remnant polarization increases with increasing TrFE content up to a maximum of 25% TrFE content, after which it starts to decrease due to the lower dipole moment of the TrFE defect inclusion within the PVDF crystals.

Effects of solvents on synthesis of piezoelectric polyvinylidene fluoride trifluoroethylene thin films

• Polyvinylidene fluoride thin films were developed with multiple dissolving solvents. • High dipole moment solvents increased piezoelectric properties. • Propylene carbonate used to synthesize polyvinylidene fluoride. Polyvinylidene Fluoride (PVDF) and its co-polymer formulations, such as tri-fluoroethylene (TrFE) have been extensively researched as a thin flexible piezoelectric material for a wide range of applications, and new methods of synthesizing the material are continuously being investigated. Researchers have used various solvents to synthesize the PVDF film, yet the effects of these solvents on the piezoelectric properties have not been systematically investigated. The selection of an optimized solvent for polymer dissolution can affect film properties, which could lead to enhanced device performance for piezoelectric-based microsystems. Herein, several solvents were screened for the dissolution of PVDF-TrFE polymer to investigate the effect of solvents and to determine key properties of the solvents that influence the piezoelectric response, so further enhancements can be made in the future. This study investigated 14 different solvents with varying physicochemical properties. The thin films were characterized via X-ray diffraction and quasi-static piezometer measurements. This paper reports that the piezoelectric coefficient of the thin film was highly dependent on the solvent's dipole moment. Our observation revealed that the solvent with the highest dipole moment that was able to completely dissolve the PVDF-TrFE powder produced the film with the highest piezoelectric coefficient. The spin coated film decreased thickness with increasing spin speed, and the piezoelectric coefficient was not affected by the thickness of the film in the range of 1–5 μm.

Regioselective formation of fluorinated metallacycles from fluoroalkenes and an electron-rich Ni(0) difluorocarbene

The reactivity of an electron-rich Ni-difluorocarbene complex, Ni=CF2(dppe)[P(OMe)3] (1), with a variety of fluorinated alkenes was investigated (dppe = 1,2-bis(diphenylphosphino)ethane). Reactions of 1 with perfluoro(methyl vinyl ether) and chlorotrifluoroethylene (CTFE) give regiospecific formation of metallacyclobutanes, in which the carbene C attacks the most electron-rich carbon of the fluoroalkene. Further reaction of the CTFE-derived metallacycle in the presence of tetrahydrofuran affords a single isomer of NiCl(σ-CF2CF=CFH) (dppe), 8, proposed to be formed by Ni-mediated Cα-Cl activation followed by hydride abstraction and loss of HF. Although 1 also undergoes a cyclization reaction with trifluoroethylene (TrFE), instability of the presumed nickelacyclobutane affords the C3 fluoroalkene, F2C=CH(CF3), and subsequent formation of isomeric metallacyclopentanes from two additional TrFEs. Alternatively, reaction of 1 with hexafluoropropene forms an unexpected Ni–CF3 σ-perfluoroallyl complex.

RAFT polymerisation of trifluoroethylene: the importance of understanding reverse additions

This article is the first report of the RAFT polymerisation of trifluoroethylene (TrFE).

Pulsed Gate Switching of MoS2 Field‐Effect Transistor Based on Flexible Polyimide Substrate for Ultrasonic Detectors

AbstractMolybdenum disulfide (MoS2) semiconductors have closely been studied for potential applications in detectors, optoelectronics, and flexible electronics due to its high electrical and robust mechanical performance. Herein, the first experimental study of the high‐speed ultrasound wave detection by the combinational structure of flexible MoS2 field‐effect transistor (FET) and piezoelectric device based on polyvinylidene fluoride trifluoro ethylene P(VDF‐TrFE) is reported. The proposed flexible MoS2 based FET device exhibits maximum mobility of 18.12 cm2 Vs−1, high on/off current ratio of ≈105, high robustness over mechanical tests, and excellent gate‐pulsed switching behavior at different frequencies (10, 100, and 500 kHz), thus, utilized as supporting electronics to detect ultrasound wave at high‐speed. The ultrasound waves are applied to the self‐assembled piezoelectric device under different power scales (0 ≈ 1.5 W cm−2) and the transfer curve of the proposed FET is analyzed. The results show a clear detection of ultrasound waves with high stability and excellent linearity in terms of threshold voltage (Vth) shift and drain current (Ids) under different power levels. Also, the pulsed gate‐switching behavior is analyzed and the ultrasound detection with high stability is observed at high‐speed switching, thus, enabling the development of applications in high‐speed electronic devices and biomedical imaging tools.

Re-evaluation of the Energy Density Properties of VDF Ferroelectric Thin-Film Capacitors.

Large dielectric constants and small remanent polarization of the relaxor-ferroelectric (RFE) polymers are favored for energy-harvesting applications. Here, the energy harvesting of RFE thin films of vinylidene fluoride (VDF)-based terpolymers were re-evaluated. VDF-based terpolymers with trifluoroethylene (TrFE) and chlorofluoroethylene (CFE), CFE terpolymer, and those with TrFE and chlorotrifluoroethylene were used. Thermally annealed CFE terpolymer exhibited an energy density of 8.3 J cm–3 and an energy efficiency of 82% at a field of 280 MV m–1. The high-energy efficiency was related to the narrow bipolar hysteresis of displacement (D)–electric field (E) of the CFE terpolymer film. This narrow D–E hysteresis was a sum of the unipolar hysteresis directed toward the positive electric field region and that toward the negative electric field region, which suggested antiferroelectric-like behavior.

Polymer-Based Membranes for Oily Wastewater Remediation.

The compounds found in industrial wastewater typically show high toxicity, and in this way, they have become a primary environmental concern. Several techniques have been applied in industrial effluent remediation. In spite of the efforts, these techniques are yet to be ineffective to treat oily wastewater before it can be discharged safely to the environment. Membrane technology is an attractive approach to treat oily wastewater. This is dedicated to the immobilisation of TiO2 nanoparticles on poly(vinylidene fluoride–trifluoro ethylene) (PVDF-TrFE) porous matrix by solvent casting. Membranes with interconnected pores with an average diameter of 60 µm and a contact angle of 97°, decorated with TiO2 nanoparticles, are obtained. The degradation of oily wastewater demonstrated the high photocatalytic efficiency of the nanocomposite membranes: Under sunlight irradiation for seven hours, colourless water was obtained.

Polymer Amplification to Improve Performance and Stability toward Semitransparent Perovskite Solar Cells Fabrication

The performance of methylammonium lead triiodide (CH3NH3PbI3)‐based solar cells depends on the crystallization and controlled microstructure. Despite their high performance, long‐term stability is a paramount factor toward large area fabrication and potential industrialization. Herein, poly(vinylidene fluoride–trifluoro ethylene) (P(VDF‐TrFE)) is used as an additive into a low concentration–based perovskite precursor solution to control the crystallinity and microstructure. Perovskite layers of lower thicknesses are derived from low precursor concentration, however, they often suffer from severe voids and roughness. Introducing judicious quantities of P(VDF‐TrFE) improves the surface coverage and smoothness, as well as reduce the grain boundaries in the perovskite. An array of characterization techniques are used to probe the structural, microstructural, and spectroscopic properties. Impedance spectra suggest that the P(VDF‐TrFE) can improve the carrier lifetime and reduce the charge transfer resistance, which in turn allows improvment of photovoltaic performance. For an optimized concentration of P(VDF‐TrFE), the fabricated semitransparent solar cells yield a power conversion efficiency in excess of 10%, which supersedes pristine devices, along with improved stability. The device architecture and the fabrication technique provide an effective route to fabricate cost effective and visible‐light‐semitransparent perovskite solar cells.

Influence of Steric Hindrance on Ferro‐ and Piezoelectric Performance of Poly(vinylidene fluoride)‐Based Ferroelectric Polymers

AbstractPoly(vinylidene fluoride) (PVDF) and copolymers possess excellent ferro‐ and piezoelectric properties, and highly expected to be utilized as sensors in the areas covering the smart wearer, hydrophone, speaker, and medical ultrasonic devices. Besides PVDF in β crystalline phase, the copolymers with trifluoroethylene (TrFE) and tetrafluoroethylene (TFE) are widely investigated both in academia and industry. To illustrate how the steric hindrance between VDF and TrFE/TFE affects the condensed‐state structure and electric properties of the polymers, the electric properties and their dependences on molecular configuration and crystal structures of PVDF, P(VDF‐TrFE), and P(VDF‐TFE) are comparatively investigated. The introduction of same molar contents (20 mol%) of TrFE and TFE monomers into PVDF chain leads to the similar conformation transformation from α (γ ) phase to β phase and similar crystallinity in resultant P(VDF‐TFE) and P(VDF‐TrFE) thanks to the depressed energy of trans conformation and the increased energy barrier between anti‐gauche and trans conformation. That leads to the more preferred β‐phase and ferroelectric domains generated in P(VDF‐TrFE) and P(VDF‐TFE). Both the size of ferroelectric phase, the polarity of the polymer chain, the organization and orientation of the grains along the field are responsible for the excellent piezoelectric field resulted by the varied composition as well.

3D printing of poly(vinylidene fluoride-trifluoroethylene): a poling-free technique to manufacture flexible and transparent piezoelectric generators

Abstract

Hydrogenation of poly(vinylidene fluoride-chlorotrifluoroethylene) via a light initiated radical chain transfer reaction toward silane

To address the challenge of metal contamination, a light initiated radical chain transfer reaction for the controlled hydrogenation of poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-CTFE)) using Tris(trimethylsilyl)silane ((Me3Si)3SiH) is presented. Assisted by light, (Me3Si)3SiH is decomposed into (Me3Si)3Si and H radicals. Cl atoms in CTFE are removed by the (Me3Si)3Si radical and the formed macromolecular radicals would abstract H radicals from (Me3Si)3SiH to generated TrFE units. The generated (Me3Si)3Si would repeatedly remove Cl atoms on P(VDF-CTFE) until all the (Me3Si)3SiH is consumed. By employing this method, high temporal control of the CTFE conversion is achieved. The (Me3Si)3SiH reducing system has been demonstrated to be an environmentally friendly, controllable, metal-free and mild process to synthesize a trifluoroethylene (TrFE) containing fluoropolymer, which has glorious prospects for the synthesis of ferrorelectric fluoropolymers.

Coalescence and split of high-entropy polymer lamellar cocrystals

The solvent evaporation has been identified able to induce the cocrystallization of dissolved polyvinylidene fluoride (PVDF) homopolymer and poly(vinylidene fluoride trifluoroethylene) (PVDF-TrFE) copolymer solutes in this research. Upon the random incorporation of either trifluoroethylene (TrFE) or vinylidene fluoride (VDF) motif during this selected route of cocrystallization, several ferroelectric crystalline phases grow concurrently. For the development of each crystalline form, there is an appropriate composition range of TrFE motif, instead of a specific composition. When the inclusion of TrFE is beyond a threshold level, the non-polar HT-form crystals were found to solely develop upon slow heating above Curie temperature, and therefore inherits various compositions of TrFE motif. During the stay above Curie temperature, stick-like HT-form lamellar cocrystals preferably associate together and coalesce into coarser crystalline lamellae. This coalescence behavior is deduced to be driven by the secondary crystallization above Curie temperature, presumably enabled by the acceptable level of lattice-packing entropy of HT-form cocrystals. During the subsequent cooling below Curie temperature, the coalesced HT-form lamellar cocrystals reversely split into thinner lamellar cocrystals with various types of ferroelectric lattice packing comprising narrower ranges of TrFE composition. The Curie transition of cocrystals is thus accompanied with the alteration of the stacking dispersion of crystalline lamellae within materials, which associates with the variation of motif composition and therefore the lattice-packing entropy.

Re-evaluation of the origin of relaxor ferroelectricity in vinylidene fluoride terpolymers: An approach using switching current measurements

Relaxor-ferroelectric vinylidene fluoride (VDF)-based terpolymers have attracted increased attention for industrial applications because of their large dielectric constants, low voltage operation for nonvolatile memory, and energy storage capabilities. However, the origin of the relaxor ferroelectricity of VDF-based terpolymers is still under investigation. Here, we investigate the ferroelectric behaviour of thin films of terpolymers of VDF, trifluoroethylene (TrFE), and chlorofluoroethylene (CFE) (P(VDF-TrFE-CFE)) and terpolymers of VDF, TrFE, and chlorotrifluoroethylene (CTFE) (P(VDF-TrFE-CTFE)) using switching current – electric field (I-E) loop measurements. I-E loop measurements have substantial advantages because they directly provide information regarding the independent switching behaviour of dipoles. We show that the I-E loops of P(VDF-TrFE-CFE) are the summation of three pairs of Gaussian peak functions. Moreover, we provide definite proof of the presence of double hysteresis loop-like antiferroelectric behaviour and relaxor-ferroelectricity in the nanodomains of the dipoles when applying positive or negative sinusoidal electric fields to the sample films.

Synthesis and characterization of poly(trifluoroethylene-co-hexafluoropropylene) and the optical properties of its thin films

Copolymers of trifluoroethylene (TrFE) and hexafluoropropylene (HFP) were synthesized and characterized by various instrumental techniques. The maximum incorporation of HFP was 19.6 mol%. It was found that the reactivity ratios of TrFE and HFP were r TrFE =4.12 and r HFP ≈0, respectively, by applying Mayo-Lewis method. It was also found that the incorporation of HFP in copolymer chain influenced thermal properties. As increasing HFP content in copolymers, the melting temperature and crystallinity of copolymers were decreased and the glass transition temperature of copolymers gradually shifted to low temperature. Reduced crystallinity of copolymers was helpful to prepare coating layers having much even surface. Compared with coating layer prepared from TrFE homopolymer, the surface roughness was decreased and light transmittance through the coating layer increased when the copolymers of TrFE and HFP were used. This tendency was more appreciable as increasing HFP content in the copolymers.