Confined crystallization of PVDF and a PVDF‐TFE copolymer in nanolayered films

Mackey, Matt; Flandin, Lionel; Hiltner, A.; Baer, E.

doi:10.1002/polb.22375

Cited by 65 publications

(57 citation statements)

References 24 publications

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“…The discrepancy with the measured value of 46.0 implies that eq is not adequate. Further structural information such as crystal morphology and aspect ratio would be useful to test more advanced models using tortuosity factors and clarify this point …”

Section: Resultsmentioning

confidence: 99%

High diffusion barrier and piezoelectric nanocomposites based on polyvinylidene fluoride‐trifluoroethylene copolymer and hydrophobized clay

Vacche

Oliveira

Sereda

et al. 2017

J Polym Sci B Polym Phys

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Nanocomposites based on polyvinylidene fluoride–trifluoroethylene copolymer and up to 4 vol % of hydrophobized clay nanoparticles are investigated. The structure, piezoelectric properties, and oxygen permeability of solvent cast films are analyzed before and after annealing above the Curie temperature of the polymer. Exfoliation of the clay takes place at concentrations up to 1 vol %, beyond which it rapidly drops and is absent at a concentration of 4 vol %. The presence of clay does not change the crystallinity of the polymer, but leads to a threefold decrease of the oxygen permeability at a concentration of 0.5 vol %. Annealing at 130 °C increases the crystallinity, the proportion of β phase up to 94%, and the piezoelectric coefficient by 20–40% at clay fractions below 1 vol %. Annealing also leads to a remarkable 3‐ to 10‐fold decrease of O2 permeability and to intriguing changes of the activation energy for O2 transport, which decreases from 56 kJ/mol for the as‐cast polymer to below 10 kJ/mol for the polymer and exfoliated composite. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1828–1836

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Section: Resultsmentioning

confidence: 99%

High diffusion barrier and piezoelectric nanocomposites based on polyvinylidene fluoride‐trifluoroethylene copolymer and hydrophobized clay

Vacche

Oliveira

Sereda

et al. 2017

J Polym Sci B Polym Phys

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“…F (β) is the relative proportion of β‐phase, ρ is the density of the copolymer (1.78 g cm −3 ), ρ c is the density of the crystalline phase, calculated from the proportion F (β) (Fig. ) and the density of the α‐phase crystals (1.99 g cm −3 ) and β‐phase crystals (1.90 g cm −3 ) …”

Section: Discussionmentioning

confidence: 99%

“…, as reviewed by Takahashi et al). The classic Nielsen (eq ) and Cussler (eq ) “nanocomposite” models have been used to analyze the permeation properties of polyethylene terephthalate and PVDF, respectively:

\frac{P}{P_{0}} = \frac{1 - X_{v}}{1 + a X_{v} / 2}

\frac{P}{P_{0}} = \frac{1 - X_{v}}{1 + {(a X_{v} / 2)}^{2}}

where a is the aspect ratio of the crystallites. These two models are shown in Figure , for the two extreme cases of aspect ratio a = 1 and a = infinite.…”

Section: Discussionmentioning

confidence: 99%

Process influences on the structure, piezoelectric, and gas‐barrier properties of PVDF‐TrFE copolymer

Oliveira

Leterrier

Månson

et al. 2014

J Polym Sci B Polym Phys

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The influence of annealing between the Curie transition and the melting point of solvent cast polyvinylidene fluoride trifluoroethylene copolymer films on the crystalline structure, mechanical and electrical properties, and oxygen permeability is investigated. Annealing leads to remarkable changes in the structure and properties of the copolymer, within the first four hours of treatment, and with kinetics depending on the temperature. The crystallinity increases by 19% (relative), resulting in a 10 K increase in the Curie transition, a 4 K increase of the melting temperature and a 2 K decrease in the glass transition temperature. A crystalline phase transition from the paraelectric a-phase to the ferroelectric b-phase is also evidenced using in-situ X-ray diffraction. The elastic modulus is found to increase by more than threefold at room temperature and the loss peak at the glass transition is considerably reduced. The piezoelectric coefficient is found to increase by 40% and the dielectric properties are significantly changed. The most remarkable influence is the tenfold reduction of the oxygen permeability, with a drastic reduction of the activation energy for oxygen transport. The improvement in oxygen barrier properties of the annealed copolymer is attributed to the restricted mobility of oxygen molecules in the semicrystalline polymer with nanometer sized crystallites. 1 Among the different PVDF polymorphisms (a, b, c, d, and E) the polar alltrans, ferroelectric b-phase (orthorhombic conformation) is responsible for the greatest piezo activity in these materials.

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“…Thickness effects in WAXD have also been observed in confined crystallization studies. 25 In the 7 lm control and 2 L PC/P(VDF-HFP) film, the meridional (020) WAXD reflection indicate an on-edge crystal orientation with the crystallographic b-axis perpendicular to the layers (Figs. 10(a) and 10(b)).…”

Section: Effect Of Layer Thickness On the Low Frequency Dielectricmentioning

confidence: 99%

Layer confinement effect on charge migration in polycarbonate/poly(vinylidene fluorid-co-hexafluoropropylene) multilayered films

Mackey

Schuele

Zhu

et al. 2012

Journal of Applied Physics

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Structural and dielectric properties of ferroelectric poly(vinylidene fluoride-trifluoroethylene) thin films with different bottom electrodes Forced assembly microlayer coextrusion was used to produce polycarbonate/poly(vinylidene fluoride-co-hexafluoropropylene) [PC/P(VDF-HFP)] layered films for dielectric capacitor applications. Low field dielectric spectroscopy was systematically carried out on the layered films and controls. A low frequency relaxation was found that shifted to higher frequency and decreased in intensity as the P(VDF-HFP) layer thickness was reduced. The interfacial Maxwell-Wagner polarization, being layer thickness independent, could not account for this reduced low frequency relaxation behavior as the layer thickness decreased. Charge diffusion models by Sawada and Coelho, however, satisfactorily predicted the observed layer thickness effect, indicating that the migration of impurity ions in the P(VDF-HFP) layer caused the low frequency relaxation. A new, convenient fitting procedure was developed for the Sawada model yielding an ion concentration and diffusion coefficient of 2 Â 10 21 ions/m 3 and 2 Â 10 À13 m 2 /s, respectively, for films with layer thicknesses of 430 to 50 nm. Thicker layers of 7000 nm had significantly different diffusion parameters, which were attributed to differing crystal orientations in the P(VDF-HFP) layers. These findings show that low ion concentrations, whether from catalyst residue and processing or intentionally added, significantly affect the dielectric properties and can play a vital role in many applications (i.e., LCD displays, solar cells, light-emitting electrochemical cells, capacitors).

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Confined crystallization of PVDF and a PVDF‐TFE copolymer in nanolayered films

Cited by 65 publications

References 24 publications

High diffusion barrier and piezoelectric nanocomposites based on polyvinylidene fluoride‐trifluoroethylene copolymer and hydrophobized clay

High diffusion barrier and piezoelectric nanocomposites based on polyvinylidene fluoride‐trifluoroethylene copolymer and hydrophobized clay

Process influences on the structure, piezoelectric, and gas‐barrier properties of PVDF‐TrFE copolymer

Layer confinement effect on charge migration in polycarbonate/poly(vinylidene fluorid-co-hexafluoropropylene) multilayered films

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