Poly(methyl methacrylate) (PMMA) was introduced into ferroelectric Poly(vinylidene fluoride-co-trifluoroethylene) P(VDF-co-TrFE) via a simple solution blending process and a series of P(VDF-co-TrFE)/PMMA blends with varied PMMA content was obtained in an effort to investigate the confinement effect of PMMA on the crystalline, dielectric, and electric energy storage properties of P(VDF-co-TrFE). PMMA addition could reduce the crystallinity dramatically as well as the crystal size due to its dilution effect and impediment effect on the crystallization of P(VDF-co-TrFE). PMMA introduction is also responsible for the phase transition of P(VDF-co-TrFE) from α phase into γ phase. As expected, both the dielectric constant and loss of the blends are reduced as PMMA addition increases for the dilute, decoupling, and confinement effect of PMMA on the relaxation behavior of crystal phases of P(VDF-co-TrFE) under external electric field. As a result, both the maximum and remnant polarization of the blends are significantly depressed. The irreversible polarization of P(VDF-co-TrFE) is effectively restricted by the addition of PMMA due to its impeding effect on the crystallization of P(VDF-co-TrFE) and restricting effect on the switch of the polar crystal domains. Therefore, the energy loss induced by the ferroelectric relaxation of P(VDF-co-TrFE) is significantly reduced to less than 25% at an electric field of 450 MV/m while the energy storage density is well maintained at about 10 J/cm⁻³ in the blend with 30 wt % PMMA. The results may help to understand how the ferroelectric relaxation affects the energy loss of ferroelectrics fundamentally and design more desirable materials for high energy storage capacitors. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40114.

Poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene) (P(VDF-co-TrFE-co-CTFE)) with internal double bond has been reported with high dielectric constant and energy density at room temperature, which is expected to serve as a promising dielectric film in high pulse discharge capacitors. An environmentally friendly one-pot route, including the controllable hydrogenation via Cu(0) mediated single electron transfer radical chain transfer reaction (SET-CTR) and dehydrochlorination catalyzed with N-containing reagent, is successfully developed to synthesize P(VDF-co-TrFE-co-CTFE) containing unsaturation. The resultant polymer was carefully characterized with ¹H NMR, ¹⁹F NMR, and FTIR. The composition of the resultant copolymer is strongly influenced by reaction conditions, including the reaction temperature, catalyst concentration, the types of ligands and solvents. The kinetics data of the chain transfer and elimination reaction demonstrate their well-controlled feature of the strategy. By shifting the equilibrium between the CTR and elimination reactions dominated by N-compounds serving as ligands in SET-CTR and catalyst in the dehydrochlorination of P(VDF-co-CTFE), P(VDF-co-TrFE-co-CTFE) with tunable TrFE and double-bond content could be synthesized in this one-pot route. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3429–3440

Trifluoroethylene addition and thermal treatment induced crystal phase transition in a series of poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-co-TrFE)] containing varied TrFE molar ratio (6, 9, 12, and 20 mol %) prepared from the hydrogenation of poly(vinylidene fluoride-co-chlorotrifluoroethylene have been investigated by means of Fourier transform infrared spectral (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analyses. The comprehensive applications of the three techniques could distinguish α, β and γ phase of P(VDF-co-TrFE) very well. The multipeak fitting technique of DSC is successfully applied to calculate the percentage of different phases in the samples, which allows us to investigate the phase transition process of P(VDF-co-TrFE) precisely. It is found that the crystal phase of P(VDF-co-TrFE) films is turned from α + γ phase (6 mol % TrFE) to α + γ + β phase (9 and 12 mol % TrFE) to β phase (20 mol % TrFE) at high temperature, and from α + γ phase (6 mol % TrFE) to γ + β phase (9 mol % TrFE) to β phase (>12 mol % TrFE) at low fabricated temperature. Both the fabrication conditions and TrFE addition are responsible for the crystal phase transition of the hydrogenised P(VDF-co-TrFE). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

A series of 2,6-bis(imino)pyridines, as common ligands for late transition metal catalyst in ethylene coordination polymerization, were successfully employed in single-electron transfer-living radical polymerization (SET-LRP) of methyl methacrylate (MMA) by using poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-co-CTFE)) as macroinitiator with low concentration of copper catalyst under relative mild-reaction conditions. Well-controlled polymerization features were observed under varied reaction conditions including reaction temperature, catalyst concentration, as well as monomer amount in feed. The typical side reactions including the chain-transfer reaction and dehydrochlorination reaction happened on P(VDF-co-CTFE) in atom-transfer radical polymerization process were avoided in current system. The relationship between the catalytic activity and the chemical structure of 2,6-bis(imino)pyridine ligands was investigated by comparing both the electrochemical properties of Cu(II)/2,6-bis(imino)pyridine and the kinetic results of SET-LRP of MMA catalyzed with different ligands. The substitute groups onto N-binding sites with proper steric bulk and electron donating are desirable for both high-propagation reaction rate and CCl bonds activation capability on P(VDF-co-CTFE). The catalytic activity of Cu(0)/2,6-bis(imino)pyridines is comparable with Cu(0)/2,2′-bipyridine under the consistent reaction conditions. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4378–4388

Three series of poly (vinylidene fluoride-chlorotrifluoroethylene)/barium titanate (BT) nanocomposites with varied compositions were fabricated via solution cast process followed by thermally treated in different ways. Quenching the composite samples at lower temperature could effectively enhance their dielectric constant, breakdown strength as well as the energy density. The highest energy density (13.6 J/cm³) is observed in the sample quenched from 200°C to −94°C with 5 vol% BT, which is much higher than nanocomposites reported in the current literature. The addition of ceramic particles leads to the improvement of dielectric permittivity and energy density measured under the same electric field. However, the dielectric breakdown strength and the energy density measured at breakdown strength of the resultant composites are reduced as a function of BT content. The fixed maximum electric displacement and reduction of saturation electric field suggest that the addition of ceramic particles with high dielectric constant may help increase the energy density of composites under low electric field but not for high electric field. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers.

Thermal processing at various temperatures has been used to fabricate poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-co-TrFE)] films with varied crystalline properties in an attempt to improve their piezoelectric properties. Although the dielectric constant of the films annealed at higher temperature is smaller than that of cooled and quenched ones, it has been shown that the annealed films possess larger crystallinity and stacked lamellar crystal grain size. The ferroelectric domains deriving from crystal region in all the samples are effectively improved by hot polarization. As a result, the remnant polarizations (P_r) and coercive electric field (E_c) of the corresponding films are improved at a low frequency due to the response of dipoles in crystal phase, and the largest piezoelectric constant in the longitudinal thickness mode (d₃₃=−25 pC/N) is obtained in an annealed copolymer film. The results illustrate improving the crystal structure of P(VDF-co-TrFE) is an effective way to realize high electromechanical properties, which provides broadly applied scenery for this kind of copolymer in piezoelectric components. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

Preparation of functional fluoromaterials through chemical modification of traditional fluoropolymers has been recognized as an economic and convenient strategy to expand the application areas of fluoropolymers. Poly(vinylidene fluoride-co-chlorotrifluoroethylene)-grafted-polyacrylonitrile (P(VDF-co-CTFE)-g-PAN) has been successfully synthesized via single electron transfer–living radical polymerization (SET–LRP) process initiated with macroinitiator P(VDF-co-CTFE) in the presence of trace amount of Cu(0)/tris(2(dimethylamino)ethyl)amine (Me₆-TREN) in dimethyl sulfoxide (DMSO) at ambient temperature. The typical side reactions happened on P(VDF-co-CTFE) induced by the nitrogen-containing solvents and high reaction temperature in atom transfer radical polymerization process could be avoided in SET–LRP process by using the mild reaction conditions. Well-controlled polymerization features were observed under varied reaction conditions including the different reaction temperature, catalyst concentration, as well as monomer amount in feed. An induction period of 0.5–1.0 h in the polymerization procedure was observed at low temperature, which may be attributed to the Cu₂O from the surface of the Cu(0) powder. When Cu(0) catalyst is activated, the introduction period is eliminated. The polymerization rates were decelerated by adding excessive Me₆-TREN for the formation of more stable CuCl₂/(Me₆-TREN)₂. The structure of P(VDF-co-CTFE)-g-PAN was demonstrated by FTIR, NMR, DSC, and TGA. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Poly(vinylidene fluoride) (PVDF) films with various crystal phases (α, β, and γ phases) and varied crystallinities were fabricated via different processes. The influence of the crystalline properties, such as the crystallinity and crystal phases, on the breakdown strength and dielectric and energy storage properties of the films were studied. Under low electric field, the dielectric constant was governed by the crystallinities of the films, and the dielectric loss was more related to the polarity of their crystal phases. Under high electric field, the high polarity of the crystal phases favored high-maximum, remnant, and irreversible polarization of the films. The lower crystallinity of the films with the same crystal phases led to a higher maximum and remnant polarization but a lower irreversible polarization. Under direct-current electric field, the discharged energy efficiency was mainly dominated by the polar nature of crystal phases. Under an electric field below 300 MV/m, the discharged energy density and energy loss of the three kinds of films were rather close, regardless of the phase transition. When the electric field was over 300 MV/m, the overall discharged energy density was dominated by the practical breakdown strength. γ-PVDF with a proper crystallinity and crystal grain size is expected to realize an energy density over 10 J/cm³ under an electric field over 400 MV/m. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Poly(methyl methacrylate) (PMMA) was introduced into poly(vinylidene fluoride) (PVDF) via a solution blending process, and a series of PVDF/PMMA blends were obtained in an effort to reduce the energy loss of pure PVDF. The effects of the composition and thermal treatment on the properties of the polymer blends were carefully studied. The results show that the introduction of PMMA led to a lower crystallinity and a smaller crystal size of PVDF for its dilution effect. As a result, the dielectric constant and energy storage density of the polymer blends were slightly reduced. Meanwhile, the phase transition of the PVDF crystals from the α phase to the β phase happened during the quenching of the blend melt to ice–water; this was also observed in the untreated or annealed blends with PMMA contents over 50 wt %. Compared with the α-PVDF, the PVDF crystals in the β phase possessed a lower melting temperature, a higher dielectric constant, and a lower dielectric loss. The addition of PMMA reduced the energy loss of PVDF significantly, whereas the energy storage density decreased slightly. The optimized blend film with about 40 wt % PMMA and PVDF in the β phase showed a relative high energy storage density and the lowest energy loss. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010