The structure and properties of block poly(vinylidene fluoride) and systems based on it

Kochervinskiĭ, V. V.

doi:10.1070/rc1996v065n10abeh000328

Cited by 104 publications

(119 citation statements)

References 285 publications

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“…22 It is known that for the latter the conformation of plain zigzag is typical, with dipolar moment perpendicular to the macromolecular axis, while the chains in a-phase have TGTG À conformation, which have nonzero component of the dipole moment m jj directed along the chain axis. 8 The axes are oriented practically perfectly along the drawing axis in textured PVDF films with a-phase macromolecular crystals. In these films, if the external electric field is applied along and then across the drawing axis, the contribution of m jj to the mechanism of a c -relaxation can be revealed.…”

Section: Introductionmentioning

confidence: 99%

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Dielectric relaxation in vinylidene fluoride–hexafluoropropylene copolymers

Kochervinskiĭ

Malyshkina

Markin

et al. 2007

J of Applied Polymer Sci

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The molecular mobility in copolymers of vinylidene fluoride-hexafluoropropylene VDF/HFP of 93/7 and 86/14 ratios has been investigated by means of broadband dielectric relaxation spectroscopy (10 À1 -10 7 Hz), differential scanning calorimetry DSC (À100 to 1508C), and of wide angle X-ray diffraction WAXS. Four relaxation processes and one ferroelectric-paraelectric phase transition have been detected. The process of the local mobility b-(at temperatures below glass transition point) is not affected by chemical composition of the copolymer and the formed structure. Parameters of segmental mobility in the region of glass transition (a a -relaxation) depend on the ratio of comonomer with lower kinetic flexibility. a c -relaxation is clearly observed only in VDF/HFP 93/7 copolymer, which is characterized by a higher crystallinity and a higher perfection of crystals of a-(a p -) phase. Diffuse order-disorder relaxor type ferroelectric transition connected with the destruction of the domains in low-perfect ferroelectric phase in the amorphous regions has been detected for both copolymers. An intensive relaxation process (a-process) was observed for both copolymers in high-temperature region. DSC data shows that it falls on the broad temperature region of aphase crystals melting. It is considered to be connected with the space charge relaxation.

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Section: Introductionmentioning

confidence: 99%

“…As the basic component of a copolymer is PVDF with strongly pronounced polymorphism, 4,8 it is worth to discuss relaxation processes in this polymer. They were studied both experimentally and by computer modeling.…”

Section: Introductionmentioning

confidence: 99%

Dielectric relaxation in vinylidene fluoride–hexafluoropropylene copolymers

Kochervinskiĭ

Malyshkina

Markin

et al. 2007

J of Applied Polymer Sci

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“…1, the lamellae are embedded in amorphous interlayers. Previous x-ray and infrared-spectroscopy studies have demonstrated that, in addition to the T conformation, chains occurring in a mixed conformation, TG (gauche) or TG − , are also present in P (VDF-TrFE) [32]. They should be located in the amorphous interlayers.…”

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confidence: 99%

Two-Step Polarization Switching in Ferroelectric Polymers

Jonas

et al. 2015

Phys. Rev. Lett.

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The correlation between hierarchical structures and polarization switching in ferroelectric poly (vinylidene fluoride-ran-trifluoroethylene) has been probed by combining transmission electron microscopy studies with piezoresponse force microscopy observations. Differences are demonstrated between homogeneous and anisotropic thin films with well-defined lamellar orientation, with the later exhibiting quadrangular domain shape and double hysteresis. We propose that the polarization switching within lamella is dominated by domain wall flow motion, while the amorphous components between lamellae impede full polarization switching. The coupling between lamellae is controlled by a creep process. These results and interpretations explain well the seemingly contradicting polarization reversal dynamics reported and offer opportunities to change domain reversal speed by making ferroelectric polymer nanostructures.

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“…Weak absorption bands at 552 cm -1 from CF 2 bending and 813 cm -1 from CH 2 rocking vibrations are generally assigned to the c-polymorph phase. [10,24] The 1113 cm -1 relatively intense peak in films deposited by continuous CVP process is assigned to the c-phase. [27] In pulsed deposited CPV films, the 1113 cm -1 peak is absent and other c-phase [28]…”

Section: Molecular Structure Of Filmsmentioning

confidence: 99%

“…[10][11][12] Most studies done on freestanding, ∼1-5 lm thick films formed by melt-extrusion [13] and solution-casting, [14] establish the effects of thermal, mechanical (stretching), and polar treatments on changes in crystallinity and orientation which are essential to realize their unique piezo-and ferroelectric properties. [10][11][12]15] For emerging microelectronics applications, growth techniques to form ferroelectric PVDF thin films in the nanometer thickness range are more relevant, but are not possible by these techniques. Furthermore, the ability of the deposition technique for integration of PVDF films in Si-device structures with sub-micrometer surface features is also an important consideration.…”

Section: Introductionmentioning

confidence: 99%

Ferroelectric Poly(vinylidene fluoride) Thin Films Grown by Low‐Pressure Chemical Vapor Polymerization

Rastogi

Desu

2006

Chemical Vapor Deposition

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Ferroelectric poly(vinylidene fluoride) polymer (VDF 2 ) n thin-film formation by a low-pressure chemical vapor polymerization (CVP) process is described. The process involves polymerization of an isotropic vinylidene fluoride monomer condensate layer by cleavage of C double bonds using :CF 2 initiators derived from hot-filament, thermochemical decomposition of the hexafluoropropylene oxide C 3 F 6 O. Two different growth modes on the film surface and in the bulk are identified by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) studies. Surface impingement of :CF 2 induces lateral growth of molecular chains in trans conformation. Due to the initiation of polymerization at random surface sites, amorphous b-phase growth is also observed. Bulk growth of polymer film involves chain formation dominated by gauche conformations having a predominance of the a-phase. Ferroelectric investigations of (VDF 2 ) n films show spontaneous polarization and hysteresis effects, which improves on crystallization. Typical polarization values of 3.5 and 1.5 lC cm -2 in the planar and normal directions, respectively, are observed after crystallization. Structural defects in the molecular chains give rise to space charge conduction which affects polarization switching properties. The low-pressure CVP technique is compatible with sub-micrometer semiconductor device fabrication and also provides a novel method for incorporating additional functional units into the molecular chains to control the film properties.

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The structure and properties of block poly(vinylidene fluoride) and systems based on it

Cited by 104 publications

References 285 publications

Dielectric relaxation in vinylidene fluoride–hexafluoropropylene copolymers

Dielectric relaxation in vinylidene fluoride–hexafluoropropylene copolymers

Two-Step Polarization Switching in Ferroelectric Polymers

Ferroelectric Poly(vinylidene fluoride) Thin Films Grown by Low‐Pressure Chemical Vapor Polymerization

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