Crystal structure of polyvinylidene fluoride

Gal'perin, Ye.L.; Strogalin, Yu.V.; Mlenik, M.P.

doi:10.1016/0032-3950(65)90032-8

Cited by 36 publications

(26 citation statements)

References 1 publication

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“…As another possible structure giving the same result in the structure factor calculation, it is considered that each chain has statistical deflection along the chain axis. 3 This statistically deflected chain, however, is less likely to exist than the alternately deflected chain owing to the intrachain steric hindrance.…”

Section: Discussionmentioning

confidence: 99%

Crystal Structures of Three Crystalline Forms of Poly(vinylidene fluoride)

Hasegawa

Takahashi

Chatani

et al. 1972

Polym J

864

506

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ABSTRACT:The crystal structures of three forms of poly(vinylidene fluoride) were studied by X-ray diffraction method. Although the structure of form I has been determined to be a fully extended planar zigzag by Lando, et al. [orthorhombic; a= 8.58 A, b=4.91 A, and c(fiber axis)=2.56 A; space group Cm2m(C;!)], an alternatelydeflected molecular structure was postulated in order to release the steric hindrance between the fluorine atoms along the chain. A satistically disordered packing of such deflected chains satisfies the observed fiber period and improves appreciably the structure factor agreement. Form II is monoclinic [pseudo-orthorhombic; a=4.96 A, b=9.64 A, c(fiber axis)=4.62 A, and /3=90°; space group P21/c(C~h)], and its cell contains two molecular chains. The molecular conformation is essentially the TGTG type (internal rotation angles, 179° and 45°), and the glide plane of the molecular chain coincides with the c glide plane of the lattice. It is suggested that form III is monoclinic [a= 8.66 A, b=4.93

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Section: Discussionmentioning

confidence: 99%

Crystal Structures of Three Crystalline Forms of Poly(vinylidene fluoride)

Hasegawa

Takahashi

Chatani

et al. 1972

Polym J

864

506

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“…phase was detected at the deformation stage where necking was initiated at the centre of their tensile samples. Most of the studies of the e-phase to/?-phase transformation during deformation have been by X-ray diffraction [7][8][9][10][11] and infrared spectroscopy [9,12,13]; only a few studies [12,14,15] of the stress-induced e ~ /? phase transformation have been done by electron microscopy and electron diffraction.…”

Section: Introductionmentioning

confidence: 99%

Deformation and transformation mechanisms of poly(vinylidene fluoride) (PVF2)

Hsü

Geil

1989

J Mater Sci

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The deformation process and the accompanying ~ -~ /~ phase transformation of poly(vinylidene fluoride), drawn at 82 to 90 and 130 ~ has been characterized by electron microscopy and X-ray and electron diffraction. Micronecking occurs at both draw temperatures, fibrils and mosaic blocks being drawn off the edges of the micronecks. The degree of phase transformation, at the same elongation, is dependent on the draw temperature; at 130 ~ C the majority of the sample remains in the c~ phase at the natural draw ratio. The phase transformation at both draw temperatures accompanies the transformation from lamellar (block) structure to fibril.

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“…In summary, what we have learned is that there is a basic constraint equation that determines when a material characterized by a permittivity, has its differential capacitance go negative, and that for a ferroelectric material, [49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65] no matter what the viewpoint, energy or current (or charge), this value can never be negative and that this may occur for either sign of the dc capacitance (see Appendix A). Furthermore, there is another similar constraint equation for obtaining positive differential energy capacitance, and that this, as before, may occur for either sign of the dc capacitance.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of the differential capacitance for ferroelectric materials using either charge-based or energy-based expressions

Krowne

2014

J. Adv. Dielect.

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Differential capacitance is derived based upon energy, charge or current considerations, and determined when it may go negative or positive. These alternative views of differential capacitances are analyzed, and the relationships between them are shown. Because of recent interest in obtaining negative capacitance for reducing the subthreshold voltage swing in field effect type of devices, using ferroelectric materials characterized by permittivity, these concepts are now of paramount interest to the research community. For completeness, differential capacitance is related to the static capacitance, and conditions when the differential capacitance may go negative in relation to the static capacitance are shown.

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Crystal structure of polyvinylidene fluoride

Cited by 36 publications

References 1 publication

Crystal Structures of Three Crystalline Forms of Poly(vinylidene fluoride)

Crystal Structures of Three Crystalline Forms of Poly(vinylidene fluoride)

Deformation and transformation mechanisms of poly(vinylidene fluoride) (PVF2)

Evaluation of the differential capacitance for ferroelectric materials using either charge-based or energy-based expressions

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