Structural control of the dielectric, pyroelectric and ferroelectric properties of poly(vinylidene fluoride-<i>co</i>-trifluoroethylene) thin films

Ng, Calvin Yi Bin; Gan, Wee Chen; Velayutham, Thamil Selvi; Goh, Boon Tong; Hashim, Roslan

doi:10.1039/c9cp01556f

Cited by 16 publications

(24 citation statements)

References 38 publications

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“…Information about the phase behavior in the vicinity of T c can be obtained from DSC measurements and from the T -dependence of the dielectric function, as depicted in Figures and , respectively. Thermal treatment can affect the crystallinity and the exact temperature of the Curie transition. − ,− Specifically, it was shown that annealing at temperatures above T c results in higher crystallinity of the PE phase. Furthermore, the formation of different ferroelectric crystalline phases with different thermodynamic stability (conformational and packing defects) has been reported following annealing at temperatures below the T c . − ,− Here, the P(VDF-TrFE) copolymers were annealed at 413 K (a temperature in the region between the Curie and melting transitions) for 2 h. − ,− …”

Section: Results and Discussionmentioning

confidence: 99%

“…31−33 The transition temperatures between the different crystalline phases are prone to copolymer composition, 22,28 processing (solvent-casting, spin-coating, etc. ), 25,29,34 mechanical drawing or poling, [23][24][25]34 and thermal treatment. 23−25,34−36 For compositions higher than 70 mol %, it was demonstrated (i) a strong thermal hysteresis at T c 37,38 and (ii) an approximately linear increase at T c with pressure, 39,40 suggesting a first-order transition.…”

Section: Introductionmentioning

confidence: 99%

“…The latter (also known as DFE, i.e., the defective ferroelectric phase) is characterized by incorporating gauche defects in trans sequences. ,− Furthermore, a relaxor FE phase, bearing a combination of trans planar and 3/1 helical conformations, was reported in P(VDF-TrFE) copolymers with VDF content below 55%. − It was further suggested that a morphotropic phase boundary, similar to that previously found in perovskites, bridges the competing FE and relaxor phases and enhances the piezoelectric properties. − The transition temperatures between the different crystalline phases are prone to copolymer composition, , processing (solvent-casting, spin-coating, etc. ), ,, mechanical drawing or poling, − , and thermal treatment. − ,− For compositions higher than 70 mol %, it was demonstrated (i) a strong thermal hysteresis at T c , and (ii) an approximately linear increase at T c with pressure, , suggesting a first-order transition. For copolymers with VDF content below 70 mol %, a second-order transition was proposed based on the negligible thermal hysteresis, ,,, whereas a first-order transition was suggested from isochronal P -dependent measurements. , Hence, there is an inconsistency concerning the exact order of the phase transformation at T c for nearly equimolar compositions.…”

Section: Introductionmentioning

confidence: 99%

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P(VDF-TrFE) Copolymer Dynamics as a Function of Temperature and Pressure in the Vicinity of the Curie Transition

2022

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We report on the phase behavior and the respective dynamics in random P(VDF-TrFE) copolymers using standard and temperature-modulated differential scanning calorimetry, X-ray diffraction, and a combination of temperature-and pressuredependent dielectric spectroscopy measurements. Depending on the copolymer composition, the coexistence of three/four weakly ordered phases was identified in the vicinity of the Curie transition (T c ). With respect to the dynamics, we demonstrate that the segmental dynamics associated with the relaxation of constrained amorphous VDF segments at the crystal/amorphous "phase" can be used as a marker of the Curie transition. The corresponding segmental relaxation freezes at about 50 K above the lower liquid-toglass temperature associated with the freezing of amorphous segments away from the interface. Pressure-dependent dielectric measurements provided quantitative insight into (i) the molecular origin of the segmental processes (by employing the pressure sensitivity of relaxation times and the pressure coefficient of the respective T g 's), (ii) the nature of the phase transition at T c , and (iii) information about the stability of phases under the variation of temperature and pressure (through the T−P phase diagram). We show that T c increases linearly with pressure and is accompanied by small volume changes, implying a weakly f irst-order thermodynamic transition. Furthermore, pressure stabilizes the ferroelectric phase over a broader temperature range. This could extend the operating temperature range of ferroelectric devices based on P(VDF-TrFE) copolymers.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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P(VDF-TrFE) Copolymer Dynamics as a Function of Temperature and Pressure in the Vicinity of the Curie Transition

2022

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“…For both fluoropolymers, we observed a typical rice grain-like structure, a well-known feature of P(VDF-TrFE)-based formulation for polymerization pro-cesses at temperatures below the paraelectric temperature, T para (ferroelectric-paraelectric phase transition). For the copolymer composition used in this work (monomers ratio of 70:30), a paraelectric temperature of 130 • C has been previously reported [41]. Annealing of the PVDF-based polymer films at different temperatures is expected to induce drastic changes in surface morphology: from rice-grain (<T para ) to a rod-like structure (~T para ), where surrounding non-crystalline molecules are further incorporated, to lamella-structure for higher temperature (>T para ).…”

Section: Dielectric Characterization Of P(vdf)-based Filmsmentioning

confidence: 93%

High-k Fluoropolymers Dielectrics for Low-Bias Ambipolar Organic Light Emitting Transistors (OLETs)

2021

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Organic light emitting transistors (OLETs) combine, in the same device, the function of an electrical switch with the capability of generating light under appropriate bias conditions. In this work, we demonstrate how engineering the dielectric layer based on high-k polyvinylidene fluoride (PVDF)-based polymers can lead to a drastic reduction of device driving voltages and the improvement of its optoelectronic properties. We first investigated the morphology and the dielectric response of these polymer dielectrics in terms of polymer (P(VDF-TrFE) and P(VDF-TrFE-CFE)) and solvent content (cyclopentanone, methylethylketone). Implementing these high-k PVDF-based dielectrics enabled low-bias ambipolar organic light emitting transistors, with reduced threshold voltages (<20 V) and enhanced light output (compared to conventional polymer reference), along with an overall improvement of the device efficiency. Further, we preliminary transferred these fluorinated high-k dielectric films onto a plastic substrate to enable flexible light emitting transistors. These findings hold potential for broader exploitation of the OLET platform, where the device can now be driven by commercially available electronics, thus enabling flexible low-bias organic electronic devices.

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“…Poly(vinylidene fluoride) (PVDF), as a stimuli-response biomaterial with significant piezoelectricity, pyroelectricity, triboelectricity, and ferroelectricity properties, has shown several potential medical device applications as wearable sensors, personal health monitoring, and electronic skin among others. − The ability to harvest low-level electrical energy in response to energy from the external environment has raised the possibilities to obtain self-powered medical devices. , Wearable medical devices based on energy harvesting from the surroundings can make devices smart, more compact, and IoT-enabled, with very low consumption of power. They can effectively deploy for real-time, personalized, and remote monitoring of several vital parameters of patients, such as oxygen level, glucose concentration, and heart and breath rates.…”

Section: Introductionmentioning

confidence: 99%

Flexible Nanogenerator from Electrospun PVDF–Polycarbazole Nanofiber Membranes for Human Motion Energy-Harvesting Device Applications

Sengupta

Das

Dasgupta

et al. 2021

ACS Biomater. Sci. Eng.

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Poly(vinylidene difluoride) (PVDF) has become the polymer matrix of choice for fabrication of wearable electronics and physiological monitoring devices. Despite possessing a high piezoelectric constant, additives are required to increase the charge transfer from PVDF matrix to connected signal readout units. Many of these additives also stabilize the β-phase of PVDF, which is associated with highest piezoelectric coefficients. However, most of the additives used are often brittle ceramic-phase materials resulting in decreased flexibility of the devices and offsetting the gain in β-phase content. Intrinsically conducting polymers (ICP), on the other hand, are ideal candidates to improve the device-related properties of PVDF, due to their higher flexibility than ceramic fillers as well as ability to form conducting network in PVDF membranes. This work reports the performance and device feasibility of PVDF–polycarbazole (PCZ) electrospun nanofiber membranes. A higher β-phase was observed by FTIR spectroscopy in PVDF/PCZ compared to other PVDF phases. Moreover, a higher open-circuit potential was recorded over PVDF/polyaniline composites, which were studied for comparison. The addition of PCZ reduced the flexibility of pure PVDF nanofibers by 20% only. Besides, the work investigated the bacterial biofouling and cell compatibility of the matrix, as essential properties to examine any putative medical device application. PVDF/PCZ membranes were then used to develop a nanogenerator, which was capable of instantly lighting an entire LED array employing the rectified output power, and charged up a 2.2 μF capacitors using a bridge rectifier through a vertical compressive force applied periodically. Finally, the nanogenerator demonstrated electrical energy harvesting from movements of various parts of the human body, such as toe and heel movement and wrist bending. In conclusion, PCZ can be considered as an attractive, biocompatible, and anti-biofouling conducting polymer for electrical actuation and flexible electronic device applications.

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Structural control of the dielectric, pyroelectric and ferroelectric properties of poly(vinylidene fluoride-co-trifluoroethylene) thin films

Abstract: P(VDF-TrFE) is optimized effectively via thermal treatment and its molecular motions after poling are revealed.

Cited by 16 publications

References 38 publications

P(VDF-TrFE) Copolymer Dynamics as a Function of Temperature and Pressure in the Vicinity of the Curie Transition

P(VDF-TrFE) Copolymer Dynamics as a Function of Temperature and Pressure in the Vicinity of the Curie Transition

High-k Fluoropolymers Dielectrics for Low-Bias Ambipolar Organic Light Emitting Transistors (OLETs)

Flexible Nanogenerator from Electrospun PVDF–Polycarbazole Nanofiber Membranes for Human Motion Energy-Harvesting Device Applications

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