Download or read book Confined Ferroelectric Properties in Poly vinylidene Fluoride PVDF based Random Copolymers and Graft Copolymers for Electric Energy Storage Applications written by Fangxiao Guan and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Novel Ferroelectric Behavior in Poly vinylidene Fluoride co trifluoroethylene based Random Copolymers written by Lianyun Yang and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: High dielectric constant and low loss polymer dielectrics are desired for applications such as energy storage, electrocaloric cooling, and electrostrictive actuation. Several types of polarizations can be utilized to enhance dielectric constant of polymer dielectrics. Polymers with permanent dipoles can be good candidates to achieve high dielectric constant and low loss properties because of their dipolar polarization. There are several situations of dipolar polarization for polar polymers with permanent dipoles, which depend on different dipole/domain structures. Our work focuses on the novel ferroelectric behavior of ferroelectric polymers. The mechanism for novel ferroelectric behavior can be explained by the crystal pinning effect from crystal isomorphism. The physical pinning effect in P(VDF-TrFE-CFE) is weak and double hysteresis loop (DHL) is thus observed. The chemical pinning effect in e-beam P(VDF-TrFE) or P(VDF-TrFE-CTFE) is strong and only single hysteresis loop (SHL) is observed. Besides P(VDF-TrFE-CTFE), DHLs can also be achieved in P(VDF-TrFE-TrFE)-g-PS graft copolymer by the nanoconfined effect. Crystal orientation and temperature effects on the DHL behavior of the graft copolymer were studied. Clear dielectric, rather than ferroelectric, behavior is observed from the non-oriented graft polymer sample. But stable DHLs are observed for the oriented films up to 75 C. Above 100 C, huge broadening of the D-E loops shows up due to the electrical conduction and ion migrational losses. The electrical conduction loss plays an important role on the insulation property of dielectric polymers, especially at high temperatures and under high electric fields. As an example, a commercial biaxially oriented PVDF (BOPVDF) film was selected to study the electrical conduction under different electric poling conditions. The dipoles from either amorphous or crystalline phase do not have much influence on the electronic conduction. The electronic conductivity for the BOPVDF film is low below 25 C. Above 25 C, the electronic conductivity first increases, then decreases upon increasing the poling fields. These changes can be attributed to the effect from polarized ions. Above 75 C, electronic conductivity substantially increase due to injected space charges. Meanwhile, PVDF starts to undergo electrochemical reactions, emitting HF gas which can corrode metal electrodes.
Download or read book Polymer Nanocomposites for Dielectrics written by Katie Zhong and published by CRC Press. This book was released on 2017-01-12 with total page 311 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymers have been used as dielectric materials owing to their light weight, great flexibility, and processability as well as high insulation properties. To enhance their performance for various desired dielectric applications, fabrication of polymeric nanocomposites is believed to be one of the most effective approaches. By controlling the nanomaterial dispersion and interfacial structures with the polymer matrices in nanocomposites, dielectric properties can be tailored for specific applications. This book reviews representative polymer nanocomposite systems, focusing on the roles of nanodispersion, interfacial structures, and properties of polymer matrix materials in the dielectric properties and energy storage performance. The book reviews various dielectric relaxation models applicable to the analysis of polymer nanocomposites. It compiles the recent progress in new dielectric polymer nanocomposites based on biomaterials and hybrid nanomaterial systems for advanced dielectric applications.
Download or read book High Energy capacitance Density Poly vinylidene Fluoride Based Polymers for Energy Storage Capacitor Applications written by Xin Zhou and published by . This book was released on 2009 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: The increased energy levels and continued demands for miniaturization of many devices such as hybrid electric vehicles, pulsed power systems, and switched-mode power supplies call for advanced polymer film capacitors with a high energy density (HED) [1], which cannot be met in current low dielectric constant (3.2) polymers(energy density ~ 2 J/cm^3) [2]. Poly(vinylidene fluoride) (PVDF) features a high dielectric constant (12) [3], and has the potential to reach a high energy density. This dissertation introduces general considerations leading to and the results of ultra-high energy density ( 25 J/cm^3) in PVDF-based copolymers P(VDF-HFP)(HFP: hexafluoropropylene) 95.5/4.5 mol% and P(VDF-CTFE) (CTFE: chlorotrifuoroethylene) 91/9 mol% [4], [5], which represents an order of magnitude improvement of the energy density over currently used polymers. In addition, this dissertation is devoted to developing a fundamental understanding of several newly observed phenomena in these HED polymers, which are not present in the currently low dielectric constant polymers. In polymer film capacitors, high fields have been used to realize high energy density. Therefore, the emphasis is paid to understand the response behaviors of these HED polymer dielectrics at high fields, particularly the losses and the breakdown mechanism. Based on these investigations and fundamental understandings, different approaches are introduced to further improve performance of these HED polymers. This dissertation demonstrates that in these HED fluoropolymer films the losses increase rapidly with applied electric fields. Immediately beyond the weak field, the losses can be caused by the ferroelectric domain wall type motions, similar to those in magnetic materials as described by Rayleigh's law [6]. On the other hand, a complex notation has been extensively used to describe the dielectric behavior [7]. In this dissertation, we extend this complex notation to the non-linear region to include the losses [8]. As the field increases further (> 100 MV/m), the loss due to the ferroelectric switching dominates. At very high fields (> 250 MV/m), it is the conduction loss that dominates. Even for state-of-the-art capacitor films that are widely regarded as "linear" dielectrics, the conduction loss can become higher at high fields due to a non-linear increase in the conduction [9]. In PVDF-based polymers, it is well known that polymer modifications and processing conditions can significantly influence the ferroelectric loss [10]. Therefore, two approaches were investigated to reduce the ferroelectric switching loss: (1) the irradiation method [11] to destabilize the polar conformation and correspondingly reduce the ferroelectric loss and (2) the biaxial stretching method. The film processing study revealed that the orientation of polymer chains parallel to the film surface improves the breakdown strength and reduces the conduction loss in PVDF-based polymers, while a random orientation of polymer chains along the film surface is desired to reduce the ferroelectric loss. In order to reduce the conduction loss, we take the general approach to employ a blocking layer which possesses a higher resistivity compared to the original film [12]. However, for these HED polymers, the blocking layer should also meet the requirements: (1) a dielectric constant closer to the original film (~ 13) to maintain a high energy density and (2) a low temperature fabrication because of the low melting temperature (~ 160 oC) of PVDF-based polymers. Hence, insulating polymers of low dielectric constants (3.2) cannot meet the first requirement and will significantly reduce the energy density. On the other hand, ceramics can meet the first requirement. However, their high temperature fabrication process ( 300 oC) [13] is not compatible with PVDF-based polymers. In this study, we demonstrated that very high resistivity with a dielectric constant of ~ 7 can be obtained with Si3N4 deposited at 100 oC and that the conduction loss of the resulting bilayered films can be much less than a single layer of PVDF-based copolymers. In the study of the electrical breakdown in these HED capacitor films, it was observed that although the temperature dependence of the breakdown strength in the P(VDF-HFP) 95.5/4.5 mol% films is consistent with the electromechanical (EM) breakdown [14], the widely accepted EM breakdown model of Stark-Garton significantly overestimates the breakdown strength. We show that this discrepancy lies in the fact that the Stark-Garton model fails to capture the mechanical properties of the polymers that experience a plastic deformation. Furthermore, we introduce a more general power law relation to characterize the elastic-plastic deformation of polymers. This newly developed model agrees well with the experimental data [15], and should be applicable to any polymer dielectrics in their electromechanical breakdown because of the universal validity of this model to describe the mechanical behavior of polymer dielectrics.
Download or read book Experimental Investigation on Ferroelectric and Flexoelectric Properties of Poly vinylidenefluoride hexafluoropropylene PVDF HFP Copolymer Films written by Ho Joon Lee and published by . This book was released on 2010 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: The electric polarization induced by the non-uniform deformation, i.e. the direct flexoelectric effect, in poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) has been investigated. The ferroelectric properties of PVDF-HFP copolymer films were measured. The primary goal of the research in this thesis is to understand the properties of both ferroelectricity and flexoelectricity of PVDF-HFP copolymer films under different circumstances. It is well known that PVDF homo polymer mainly has three phase structures, α phase (TGTG'), β phase (TTTT), and γ phase (TTTGTTTG'), depending on the chain conformations as the trans (T) or the gauche (G) linkages. Only β phase and γ phase possess piezoelectric responses. The direct flexoelectric effect can exist in any phase. This is because the inhomogeneous deformation can break the inversion symmetry and induce electric polarization even in non-piezoelectric crystalline materials.^However, in PVDF-HFP copolymer, the molecular chain conformations of PVDF are modified by HFP monomers. Although the mixture of two polymers can be regarded as a random amorphous structure, their molecular chain conformations may splay to different directions if a non-uniform deformation is applied to them. Therefore both ferroelectric and flexoelectric properties of PVDF-HFP copolymers might be significantly different from that of PVDF homo polymers. In our experimental studies, the unaligned PVDF-HFP copolymer films were initially synthesized by using the solution polymerization process and then characterized via X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The flexoelectric coefficients of those polymer films were then measured. Both the enhanced direct flexoelectric effect and the ferroelectric-like behavior were observed in the polymer films.^However, the flexoelectric coefficient of PVDF-HFP copolymers we measured is almost 50% smaller than that of the unaligned PVDF homo films. The experimental results also demonstrate that the ferroelectric-like behavior in PVDF-HFP copolymers under different conditions might be induced by their spatially distributed space electric charges. The measured flexoelectric coefficient (μ13) and the piezoelectric coefficient (d13) can also give us valuable information about the property degradation, or aging phenomena, in polymer films and the related polymer devices.
Download or read book PVDF Based Ferroelectric Polymers written by and published by de Gruyter. This book was released on 2017-05-23 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book begins by introducing signals and systems, and then discusses Time-Domain analysis and Frequency-Domain analysis for Continuous-Time systems. It also covers Z-transform, state-space analysis and system synthesis. The author provides abundant examples and exercises to facilitate learning, preparing students for subsequent courses on circuit analysis and communication theory.
Download or read book Ferroelectric Polymers written by E. Fukada and published by CRC Press. This book was released on 1989 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains four papers commencing with an introduction to early studies in piezoelectricity, pyroelectricity and ferroelectricity in polymers. Other topics discussed include - ferroelectric properties of fluoride copolymers; structural phase transition in ferroelectric fluorine polymers; and pressure effect on phase transition in ferroelectric polymers .
Download or read book Effects of Configurational Changes on Molecular Dynamics in Polyvinylidene Fluoride and Poly vinylidene Fluoride trifluoroethylene Ferroelectric Polymers written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Here, we present a comparative study of proton dynamics in unpoled non-ferroelectric polymer polyvinylidene fluoride (PVDF) and in its trifluoroethylene containing ferroelectric copolymer (with 70/30 molar proportion), using quasi-elastic neutron scattering. The neutron data reveal the existence of two distinct types of molecular motions in the temperature range investigated. Moreover, the slower motion, which is characterized in details here, is ascribed to protons jump diffusion along the polymeric carbon chains, while the faster motion could be attributed to localized rotational motion of methylene groups. At temperatures below the Curie point (T-c similar to 385 K) of the composite polymer, the slower diffusive mode experiences longer relaxation times in the ferroelectric blend than in the bare PVDF, although the net corresponding diffusion coefficient remains comparatively the same in both polymers with characteristic activation energy of E-A approximate to 27-33 kJ/mol. This arises because of a temperature dependent jump length r(0), which we observe to be effectively longer in the copolymer, possibly due to the formation of ordered ferroelectric domains below Tc. Above Tc, there is no appreciable difference in r(0) between the two systems. Our observation directly relates the known dependence of Tc on molar ratio to changes in r(0), providing fundamental insight into the ferroelectric properties of PVDF-based copolymers.
Download or read book New Properties and Applications of Polyvinylidene Based Ferroelectric Polymer written by J.L. Wang and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: There are different kinds of novel properties and applications of polyvinylidene difluoride (PVDF)-based ferroelectric polymer films. Several issues associated with the structure, properties, and applications of PVDF-based ferroelectric polymer films are discussed. The main achievements of the research include high electric tunability of relaxor ferroelectric Langmuir-Blodgett (LB) terpolymer films, the creep process of the domain switching in poly(vinylidene fluoride-trifluoroethylene) ferroelectric thin films, transition from relaxor to ferroelectric-like phase in poly(vinylidene fluoride-trifluoroethylene -chlorofluoroethylene) terpolymer ultrathin films, abnormal polarization switching of relaxor terpolymer films at low temperatures, huge electrocaloric effect in LB ferroelectric polymer thin films, self-polarization in ultrathin LB polymer films, enhanced dielectric and ferroelectric properties in artificial polymer multilayers, and transition of polarization switching from extrinsic to intrinsic in ultrathin PVDF homopolymer films.
Download or read book Ferroelectric Polymers written by Hari Singh Nalwa and published by CRC Press. This book was released on 1995-06-20 with total page 913 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work covers the chemistry and physics of polymeric materials and their uses in the fields of electronics, photonics, and biomedical engineering. It discusses the relationship between polymeric supermolecular structures and ferroelectric, piezoelectric and pyroelectric properties.
Download or read book Understanding Ferroelectricity in Nylon Homopolymers Copolymers and Terpolymers written by Zhongbo Zhang and published by . This book was released on 2018 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the past half century, there has been tremendous growth in exploring the chemistry, physics and material science of poly(vinylidene fluoride) (PVDF)-based ferroelectric polymers. With high breakdown strength, easy processing, and outstanding insulating features, these all-organic electrically active materials are attractive for many advanced electrical (e.g., pyroelectric and piezoelectric) applications. Concurrently, the research about ferroelectricity in polymers also began for energy storage applications through controlling crystalline structure and tuning the corresponding ferroelectric properties, e.g., novel relaxor ferroelectricity with slim double- or single- hysteresis-loop (DHL and SHL) behavior in PVDF copolymers and terpolymers. On the other hand, research activities also focused on searching for other classes of ferroelectric polymers, such as ferroelectric polyamides, cyanopolymers, polyureas, and polyuerathane. However, not much progress has been achieved as considerable as what has been achieved for PVDF-based polymers. In this thesis, we focus on the novel ferroelectric behaviors in polyamide-based polymers, trying to deeply understand the origin of ferroelectricity in aliphatic and aromatic nylons, and generalize the relaxor ferroelectric behavior into this hydrogen-bonding system. It has been commonly considered that only odd-numbered nylons, which prefer polar crystalline structure, are able to show ferroelectric hysteresis loops. In contrast, even-numbered nylons, such as nylon-12 and nylon-6 should not exhibit any ferroelectricity due to their nonpolar crystalline structure. However, in our study, ferroelectric properties are also reported for mesomorphic even-numbered nylons. The structure of the mesophases in quenched samples was considered to contain multiple twists in the chain conformation and dangling/weak hydrogen bonds, which enabled dipolar switching, forming electric-field-induced ferroelectric domains. This study shows that different from ferroelectric PVDF-based polymers, the polar crystalline structure is not the prerequisite for ferroelectricity in nylons. Instead, mesophases with enlarged interchain spacing and disordered hydrogen bonds are the key to ferroelectricity. With the understanding of ferroelectricity in n-nylons, further weakened hydrogen bonding and more twisted chain conformation (e.g., the all-trans conformation of nylon-12 under poling) are expected to facilitate dipolar relaxation and prevent the large ferroelectric domain from growing up. The simplest way to weaken hydrogen bonds is to raise the temperature. Upon increasing temperature to 100 °C, the D-E loops became increasingly narrower, finally leading to slim DHLs for nylon-6 and nylon-12. The observed DHL behavior was attributed to the electric-field-induced reversible transitions between the paraelectric (less twisted chains) and ferroelectric (more twisted chains) states in the mesomorphic crystal of even-numbered nylons. Furthermore, the SHL relaxor ferroelectric property was successfully achieved in a polyamide terpolymer, PA(11-co-12-co-NM11) based on 11-aminoundecanoic acid (AUA), 12-aminododecanoic acid (ADA), and N-methyl-11-aminoundecanoic acid (NM11), utilizing the principle of nanosized ferroelectric domains (or nanodomains). The hydrogen-bonding interaction was intentionally weakened by chemically introducing defects in the crystalline phase of nylon terpolymers. More importantly, the N-CH3 groups were expected to participate in the isomorphic crystals, blocking the formation of hydrogen bonds and inducing chain twisted in the mesophase. Finally, the ferroelectric switching behavior in the amorphous phase of a nearly 100% amorphous nylon, Selar, was investigated. Similarly, ferroelectricity in the glassy phase was also highly dependent upon hydrogen-bonding interaction. When the hydrogen-bonding was weak such as in the quenched film, significant ferroelectric switching took place. Otherwise, the quenched and annealed films did not exhibit any ferroelectric switching. High-voltage broadband dielectric spectroscopy was used to study chain segmental motion in Selar. The result indicated that it was the cooperative short-range segmental motions in the main-chain dipolar glass polymer that primarily contributed to the observed ferroelectricity.
Download or read book Ferroelectric Materials for Energy Applications written by Haitao Huang and published by John Wiley & Sons. This book was released on 2019-01-04 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides a comprehensive overview of the emerging applications of ferroelectric materials in energy harvesting and storage Conventional ferroelectric materials are normally used in sensors and actuators, memory devices, and field effect transistors, etc. Recent progress in this area showed that ferroelectric materials can harvest energy from multiple sources including mechanical energy, thermal fluctuations, and light. This book gives a complete summary of the novel energy-related applications of ferroelectric materials?and reviews both the recent advances as well as the future perspectives in this field. Beginning with the fundamentals of ferroelectric materials, Ferroelectric Materials for Energy Applications offers in-depth chapter coverage of: piezoelectric energy generation; ferroelectric photovoltaics; organic-inorganic hybrid perovskites for solar energy conversion; ferroelectric ceramics and thin films in electric energy storage; ferroelectric polymer composites in electric energy storage; pyroelectric energy harvesting; ferroelectrics in electrocaloric cooling; ferroelectric in photocatalysis; and first-principles calculations on ferroelectrics for energy applications. -Covers a highly application-oriented subject with great potential for energy conversion and storage applications. -Focused toward a large, interdisciplinary group consisting of material scientists, solid state physicists, engineering scientists, and industrial researchers -Edited by the "father of integrated ferroelectrics" Ferroelectric Materials for Energy Applications is an excellent book for researchers working on ferroelectric materials and energy materials, as well as engineers looking to broaden their view of the field.
Download or read book Understanding the Effects of Defect Modification on the Structure and Properties of Fluorinated Polymers and Implications for Capacitive Energy Storage Technologies written by Matthew Gadinski and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As the world begins to turn to alternative energy technologies and our electronic devices have become more both mobile and integral to everyday life, increasing interest has been focused on energy storage technologies. Capacitors are one of these energy storage technologies that utilize the polarization of an insulating material sandwiched by two electrodes as a means to store electric charge. Polymers are a preferred dielectric material for capacitors because of both their performance and practicality. However, polymer dielectrics are limited in energy density by low dielectric constant, and high loss at elevated temperature. This work aims to address these issues in order to enable polymer dielectrics for future applications and demands. As most polymer tend to have low dielectric constants (~2-3), but impressive breakdown strengths, only a moderate improvement in dielectric constant has the potential to vastly improve the energy density of polymer capacitors. As such tremendous interest has been placed on poly(vinylidene fluoride) (PVDF) which has a dielectric of 10+ due to the highly polar C-F bonds of its backbone. To improve PVDF's performance defect monomers have been introduced to tailor the polymorphic crystalline phase to tune its properties. Additionally, this defect modification has implications for piezoelectric, electrocaloric, and thermoelectric applications of PVDFIn Chapter 2 a copolymer of VDF and bromotrifluoroethylene (BTFE) was produced. The effect of BTFE on the structure and dielectric properties of the resulting copolymer had not been previously evaluated, and its synthesis allowed for the comparison to previously reported VDF based copolymers including P(VDF-CTFE) and P(VDF-HFP). Through 19F NMR it was determined due to reactivity ratio differences of BTFE in comparison to previously explored copolymers, BTFE during synthesis is much more likely to link with itself. This results in long runs of BTFE-BTFE defects along with isolated single defects. These long runs are found to have dramatic effects on the distribution of chain conformations determined from FTIR, the melting temperature and total crystallinity determined by DSC, and the crystallite size, lattice spacing, and crystalline phase as determined by XRD. These results indicate that P(VDF-BTFE) has a mix of both included (single) and excluded defects (runs of defects) that rapidly inhibit crystallinity and alter phase. The dielectric analysis also confirmed this by a broadening of the Tg peak in the temperature dependent dielectric spectroscopy with increasing BTFE content in the monomer feed indicative of expansion of the interlamellar region due to defect exclusion.Chapter 3 explores P(VDF-BTFE) copolymers for capacitive energy storage. Due to the rapid decrease in crystallinity only low concentration copolymers (>2 mol %) BTFE were used. This was ultimately a result of stretching being required for high energy density to be exhibited. The 0.5 mol% BTFE copolymer samples was found to possess a discharge energy density of 20.8 J/cm3 at 750 MV/m along with the highest breakdown strength of any reported PVDF based copolymer. It was found that for this small amount of defect monomer the [gamma] phase of PVDF was stabilized and mixed with [beta] phase and along with small crystallite size accounted for the high breakdown strength and energy density. Additionally, by utilizing only a small amount of defect monomer the decrease in crystallinity and melting temperature observed in previously examined PVDF copolymers was avoided.Chapter 4 examines a terpolymer of VDF, trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE). The terpolymers of VDF have gained extensive interest as the use of the two defect monomer increases the dielectric constant to 40+ along with altering the polarization behavior from a normal ferroelectric to a relaxor ferroelectric characterized by a slim hysteresis loop. The current understanding of this behavior suggests that only the size of the third bulky monomer (CTFE in this case) determines whether a single hysteresis (SHL) or double hysteresis loop (DHL) will develop. This chapter shows that for a single composition of the terpolymer normal ferroelectric, SHL, and DHL behavior can be tuned through processing of the film. This was rationalized as films give long times to crystallize developed large ferroelectric domains within a paraelectric matrix resulting in the DHL behavior due to reversible switching of these domains. While if these films were stretched below the Tc SHL behavior was observed as this had the effect of dispersing these domains within the crystal. Chapter 5 changes focus to high temperature performance of polymer capacitors. The primary strategy to enable high temperature polymer capacitors has been the utilization of high Tg polymers because of their thermal stability. While these polymers have demonstrated stable dielectric properties at low field and high breakdown strengths at elevated temperatures, the high field loss limits their use at even mildly elevated temperature well below Tg. Additionally, these polymers are expensive, brittle, and difficult to process, essentially defeating some of the primary reasons for utilizing a polymer in the first place. This chapter examines a commercially available, extrudable, high temperature fluoropolymer, known as polychlorotrifluoroethylene (PCTFE). The same defect monomer discussed with PVDF above. While this polymer showed comparable performance to BOPP at room temperature, it showed equally susceptible to high field loss at elevated temperature. However, the chlorine of the monomers allow for crosslinking of this polymer by commercially used peroxide/co-agent chemistry. Crosslinking lead to a substantial improvement of the crosslinked film over the pristine polymer, and superior energy density to the commercial high Tg polymers up to 150 °C. The reason for the improvement was found to be the formation of chemical defects produced during the crosslinking that were excluded from the crystalline phase. Through TSDC it was found that these defects concentrated in the interlamellar region led to a substantial enhancement of the charge trapping properties of this relaxation.
Download or read book The Applications of Ferroelectric Polymers written by T. T. Wang and published by . This book was released on 1988 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Understanding the Composition structure property Relationships and Enhancing the Electromechanical Responses in Ferroelectric Polymers written by Zhubing Han and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Poly(vinylidene fluoride) (PVDF)-based ferroelectric polymers enable a wide range of advanced applications with new functionalities and structure designs due to their high electroactivity, intrinsic flexibility and biocompatibility. One unique feature of these polymers is that their dielectric, ferroelectric and electromechanical properties can be modulated by varying their chemical composition and the processing conditions. Despite the progress over the last decades, a more comprehensive understanding on the composition--structure--property relationships in PVDF-based ferroelectric polymers is still needed to achieve rational design of new materials with enhanced performance. The scope of this dissertation aims to understand the influence of monomer defects on the structures and ferroelectric properties of PVDF-based terpolymers, and to enhance their electromechanical performance enabled by the rational design of new polymer structures and compositions. After a general background introduction, the dissertation starts with two chapters discussing the effect of two different comonomers as chain defects on the structures and ferroelectric properties of the corresponding terpolymers. Chapter 2 reveals that the incorporation of bulky 2-chloro-1,1-difluoroethylene (CDFE) can gradually convert the ferroelectric P(VDF-TrFE) (TrFE: trifluoroethylene) into a relaxor ferroelectric terpolymer as confirmed by the dielectric and structural characterizations. The CDFE comonomer serves as an effective chain defect to destabilize the ferroelectric domain by introducing the gauche conformation. The P(VDF-TrFE-CDFE) with 3.8 mol% CDFE exhibits typically relaxor ferroelectric behaviors such as strong frequency-dependence of dielectric properties, broad and diffuse ferroelectric phase transition, and weak remanent polarization. Chapter 3 systematically investigates the effect of another comonomer defect, vinyl fluoride (VF), which has a smaller size than VDF. It is found that VF plays an opposite role compared with the bulky chlorinated comonomers. Increasing molar content of VF leads to an increase in the Curie temperature and the coercive field of the terpolymers. Structural characterizations and simulations evidences confirm that the all-trans conformation remain energetically more favored than the gauche conformation regardless of the VF content. The results stress the vital role of comonomer structure and size in modulating the structures and properties of the ferroelectric polymers. The next two chapters focus on improving the electromechanical performance of the PVDF-based polymers. In Chapter 4, a series P(VDF-TrFE-CTFE) (CTFE: chlorotrifluoroethylene) with systematic composition variations have been synthesized. Structural characterizations show that the terpolymers with 1.7 to 5.0 mol% CTFE exhibit a mixture and competition of the normal ferroelectric and relaxor ferroelectric phases as a result of the incorporation of CTFE. Specifically, a maximum longitudinal piezoelectric coefficient (d33) of -55.4 pm/V has been observed in P(VDF-TrFE-CTFE) 64.5/33.1/2.4 mol%, corresponding to an 85% improvement compared with the commercial benchmark P(VDF-TrFE) 65/35 mol%. This strategy can potentially be expanded to other polymer systems to improve the piezoelectric response. Chapter 5 aims to enhance the low-electric-field electrostrictive strain in relaxor ferroelectric polymers. The small electrostrain of current relaxor ferroelectric P(VDF-TrFE-CFE) (CFE: 1-chloro-1-fluoroethylene) and P(VDF-TrFE-CTFE) terpolymers at low electric field impedes their usefulness in actuating devices. In situ structural characterizations under the electric field reveal that the electrostrictive strain originates from the field-induced phase transition in P(VDF-TrFE-CFE) and the lattice compression in P(VDF-TrFE-CTFE). Inspired by the distinct functions of CFE and CTFE, a series of P(VDF-TrFE-CFE-CTFE) tetrapolymers have been synthesized, which exhibit significant enhancement of electrostrictive strain at both low and high electric fields due to the synergistic effect of CFE and CTFE. These results provide new insight into the origin of electrostriction in the relaxor ferroelectric polymers, and the tetrapolymers in this study can potentially be used to prototype soft actuators. It is anticipated that the materials, methodologies and results developed in this dissertation will not only provide new insights and understandings on the structure-property relationship in ferroelectric polymers, but also stimulate future work to further enhance the performance in these materials in order to meet the material requirement for practical applications.
Download or read book Ferroelectric Properties and Polarization Switching Kinetic of Poly vinylidene Fluoride trifluoroethylene Copolymer written by Duo Mao and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ferroelectric Polymers for Organic Electronic Applications written by Nicoletta Spampinato and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic electronics represent a realistic alternative to conventional silicon-based technologies through the design, synthesis and implementation of functional organic materials into light and flexible devices. Organic materials, such as small molecules or organic polymers, are advantageous for their low-cost, flexibility and easy processing. Thanks to the economical and timesaving advantages, organic electronics have emerged as an innovative field with application in energy, environment, health, information and communication technologies.Organic electronics originates from the discovery of polymers with semiconducting functionalities. However, one should not neglect another class of outstanding polymers, the ferroelectric polymers. The electroactive nature of ferroelectric polymers, which are also pyroelectric and piezoelectric, combined with the intrinsic advantages of polymers have designated them as constituent elements of a widespread range of organic electronic devices. The most well-known family of ferroelectric polymers is that of poly(vinylidene fluoride), P(VDF), and its copolymers with trifluoroethylene, P(VDF-co-TrFE). Energy harvesting, data storage and sensing, main applications of organic electronics, can potentially all be realised using these exceptional functional materials.Since ferroelectricity is a structure-dependent property an insight into the interrelations between structure and final ferroelectric properties is indispensable in order to improve existing applications of ferroelectric polymers in organic electronics and to promote the introduction of P(VDF-co-TrFE) in new application fields. P(VDF-co-TrFE) as semi-crystalline polymer possess crystalline properties which are sensitive to thermal treatment. Since only the crystalline regions contribute to ferroelectric switching and not the amorphous ones, the degree of crystallinity is a key factor to modulate the ferroelectric properties. Moreover, crystallites orientation as well as the presence of defects within the crystallites are crucial parameters playing an important role in defining the final performance of the devices in which P(VDF-co-TrFE) is incorporated.Herein stands the aim of this thesis: reach an exhaustive understanding of processing-structure-function relationships that will serve as tool to modulate ferroelectric devices performances.Going one step further, the potential applications of P(VDF-co-TrFE) in organic electronics are explored by investigating it in: (1) medical piezoelectric catheter sensors for measuring cardiac function and eventually for detecting cardiac disease and (2) electronic devices in which P(VDF-co-TrFE) is blended with the semiconducting polymer poly(3-hexylthiophene), P3HT. The latter has already been applied in non-volatile ferroelectric memory diodes and the potential use in organic photovoltaics is explored.
