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This paper presents a hierarchically designed polymer nanocomposite approach in which nanofillers at ultralow volume loading generate large dielectric enhancement in blends of high temperature dielectric polymers with tailored nanostructures. We blend poly(1,4-phenylenen ether sulfone) (PES) with polymers, such as polyetherimide (PEI), that possess more coiled chain conformations to tailor polymer nano-morphologies. Making use of such blends as the matrix, dilute nanocomposites with 0.65 vol. % loading of alumina nanoparticles (20 nm size) generate a marked enhancement in dielectric performance, i.e., raising the dielectric constant K from PES K = 3.9 (and PEI K = 3.2) to the dilute nanocomposites K = 7.6, a much higher enhancement compared with the dilute nanocomposites employing neat polymers as the matrix. The results show that polymer blends with tailored nano-morphologies as the matrix can lead to higher dielectric enhancement in dilute nanocomposites compared with neat polymers as the matrix. [ABSTRACT FROM AUTHOR]

The recent finding of large electrocaloric effect in several ferroelectric polymers creates unique opportunity for developing compact size solid state cooling cycles beyond the traditional mechanical vapor compression cycles. Here, we show that, by employing regeneration process with solid state regenerators, a chip scale Electrocaloric Oscillatory Refrigeration (ECOR) can be realized. A prototype ECOR is fabricated and characterized. More than 6 K temperature span is obtained near room temperature between the hot and cold sides of a 2 cm long device. Finite volume simulation validates the test results and shows the potential high performance of the ECOR. [ABSTRACT FROM AUTHOR]

We report the directly measured electrocaloric effect (ECE) (the adiabatic temperature change ΔT) of relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer and its blend with poly(vinylidene fluoride-chlorotrifluoroethylene). The results show that the directly measured ΔT in the relaxor terpolymer is much larger than that deduced from Maxwell relation and that the relaxor terpolymer possesses a giant ECE at room temperature. The large difference between the directly measured ΔT and that deduced indicates that the Maxwell relation, which is derived for ergodic systems, is not suitable for deducing ECE in the relaxor ferroelectric polymers, which are nonergodic (polar-glass) material systems. [ABSTRACT FROM AUTHOR]

A magnetoelectric (ME) composite through thermal mediation is presented, which is different from the traditional strain/stress mediated ME composites. The ME laminate uses the large magnetocaloric effect, that is, a temperature change induced in the ferromagnetic Gd crystal by a magnetic field, and a large pyroelectric response in the relaxor ferroelectric polymer. Consequently, a simple laminate composite can produce a ME response ∼0.5 V/(cm Oe). The ME coefficient was further enhanced to ∼0.9 V/(cm Oe) by exploiting the magnetic flux concentration effect. The approach opens up an avenue in developing ME materials for broad range of applications. [ABSTRACT FROM AUTHOR]

We investigate the electromechanical response of conductor network composite (CNC) fabricated by the layer-by-layer (LbL) self-assembly method. The process makes it possible for CNCs to be fabricated at submicron thickness with high precision and quality. This CNCs exhibits high strain ∼6.8% under 4 V, whereas the RuO2/Nafion CNCs exhibit strain ∼3.3%. The high strain and submicron thickness of the LbL layers in an ionic polymer metal composite (IPMC) yield large and fast actuation. The response time of a 26 μm thick IPMC with 0.4 μm thick LbL CNCs to step voltage of 4 V is 0.18 s. [ABSTRACT FROM AUTHOR]

The evolution of relaxor ferroelectric behavior of poly(vinylidene fluoride trifluoroethylene chlorofluoroethylene) [P(VDF-TrFE-CFE)] terpolymer nanorods with diameters reduced from 200 to 25 nm was investigated. It was observed that all the nanorods studied exhibited relaxor ferroelectric behavior, as characterized by the dielectric peak shifting toward high temperatures with increasing frequency. The frequency-permittivity peak temperature characteristics fit well with the Vogel–Fulcher (VF) relation. Moreover, the freezing temperature in the VF relation decreased with the reduction of nanorod diameter, indicating that the scaling down of the lateral size of nanorods influenced the relaxor ferroelectric behavior of the terpolymer. [ABSTRACT FROM AUTHOR]

This paper investigates the electrical breakdown of a polar fluoropolymer, poly(vinylidene fluoride-hexafluoropropylene) which exhibits an exceptionally high discharged electrical energy density (>25 J/cm3). It is shown that above room temperature, the breakdown strength decreases with temperature. It is further shown that such a temperature dependence of breakdown strength is consistent with the electromechanical breakdown model by taking into consideration of the plastic deformation of semicrystalline polymers. [ABSTRACT FROM AUTHOR]

This paper investigates dielectric properties of the blends of poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer and poly(vinylidene fluoride-chlorotrifluoroethylene) copolymer. The high field (>50 MV/m) polarization response of the blends with a small amount of copolymer (5 and 10 wt % copolymer) is higher than that of the neat terpolymer due to the interface contribution. At the same time the breakdown field was also greatly improved by mixing a small amount of the copolymer with the terpolymer. Consequently, a higher energy density of about 11.5 J/cm3 is obtained in these blends in contrast to about 9 J/cm3 in the terpolymer. [ABSTRACT FROM AUTHOR]

We report a class of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymers synthesized via reductive dechlorination from P(VDF-CTFE) [termed as the reduced P(VDF-TrFE) copolymer], which exhibit ferroelectric relaxor behavior at high temperature (∼100 °C). It was found that the reduced P(VDF-TrFE) 66/34 mol % copolymer has very high content of head-to-head and tail-to-tail defects, which may act as random defects, leading to the observed ferroelectric relaxor at high temperature. Furthermore, the reduced copolymer also exhibits a high melting point (∼200 °C), which also makes it attractive for high-temperature dielectric applications. [ABSTRACT FROM AUTHOR]

We investigate the energy harvesting with an electrostrictive polymer, possessing high electromechanical response and elastic energy density, which make it possible to generate high electric energy density and attractive for the active energy harvesting scheme. It is shown that combining the active energy harvesting scheme and high electromechanical response of the polymer yields a harvested electric energy density of ∼40 mJ/cm3 with a 10% efficiency. [ABSTRACT FROM AUTHOR]

The authors show that a high transverse piezoelectric response with both high piezoelectric d31 (d31=43.1 pm/V) and electromechanical coupling k31 coefficients (k31=0.187), much higher than those in the piezoelectric poly(vinylidene fluoride) and poly(vinylidene fluoride-trifluoroethylene) copolymers, can be obtained in poly(vinylidene fluoride-hexafluoropropylene) [P(VDF-HFP)] 10 wt % copolymers under quasistatic condition. Furthermore, the copolymers also display a higher d31 coefficient compared to the d33 coefficient, which seems to be unusual compared with most other piezopolymers. The experimental data suggest that the origin of the unusual piezoelectric response in these P(VDF-HFP) copolymers originates from a reversible change between a poled α-like structure and β-like structure. The phase change nature also results in a large frequency dispersion of the piezoelectric response and a smaller d31 (=20.5 pm/V) at 50 kHz. [ABSTRACT FROM AUTHOR]

We introduce a stencil mask method to fabricate metallic patch arrays on the electrostrictive poly(vinylidene fluoride–trifluoroethylene) copolymer films. The resulting frequency selective surfaces exhibit resonance responses in the infrared region. Furthermore, the resonant frequency can be tuned by the strain change in the copolymer films. The results demonstrate that the stencil mask method is useful for depositing metallic patterns on a subset of substrates such as polymers that would be damaged by solvents used in conventional photolithography techniques. [ABSTRACT FROM AUTHOR]

By combining the high-dielectric copper phthalocyanine oligomer (PolyCuPc) and conductive polyanline (PANI) within polyurethane (PU) matrix an all-organic three-component dielectric-percolative composite with high dielectric constant is demonstrated. In this three-component composite system, the high-dielectric-constant PolyCuPc particulates enhance the dielectric constant of the PU matrix and this combined two-component dielectric matrix in turn serves as the high-dielectric-constant host for the PANI to realize percolative phenomenon and further enhance the dielectric response. As a result, an electromechanical strain of 9.3% and elastic energy density of 0.4 J/cm3 under an electric field of 20 V/μm can be induced. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report on the performance of micromachined unimorph actuators [(polymer micromachined actuator PMAT)] based on the electrostrictive poly(vinylidene fluoride–trifluoroethylene) [P(VDF–TrFE)] copolymer. Because of the high electrostrictive strain and high elastic energy density (∼1 J/cm[sup 3]) of the active polymer [the electrostrictive P(VDF–TrFE)], the PMAT exhibits a very high stroke level with high load capability and high displacement voltage ratio. In addition, the experimental data also demonstrate that the PMAT is capable of operating over a broad frequency range (>100 kHz). The PMAT performance was modeled and the agreement between the modeling results and experimental data confirms that the response of the PMAT indeed follows the design parameters. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A correction to the article "Large electric tunability in poly(vinylidene fluoride-trifluoroethylene) based polymers," by S. G. Lu, B. Neese, B. J. Chu, Y. Wang, and Q. M. Zhang is presented.

Provides a corrected reprint of the article 'Ferroelectric and Electromechanical Properties of Poly(Vinylidene-Fluoride-Trifluoroethylene-Chlorotrifluoroethylene) terpolymer,' by Haisheng Xu, Z.-Y. Cheng, Dana Olson, T. Mai, Q.M. Zhang and G. Kavarnos, currently published in 2001 issue of 'Applied Physics Letters' journal.