The nature of very high electrostriction strains in modified fluorine-containing polymer ferroelectrics is considered. The main modification method is the irradiation of vinylidene fluoride (VDF) copolymers with trifluoroethylene (TrFE) by electrons with energies of several MeV. Such treatment leads to the transition of the ferroelectric phase to the relaxor state and paraelectric phase. These structural changes are caused by the formation of new functional groups in PVDF chains at radiolysis. The effect of the structure on the electrostriction strains is considered. It is shown that the increase in the electrostriction strain after irradiation is related to the increase in the amorphous phase fraction. This increased strain (all other factors being equal) in uniaxial films, in comparison with isotropic ones, indicates that the field of the anisotropic amorphous phase (mesomorphic state) regions plays an important role in the reaction. An analysis of the experimental data shows that the structural changes in the field (leading to electrostriction strains) are controlled to a great extent by the features of cooperative (segmental) mobility of amorphous phase chains.

Highly polar fluorine-containing ferroelectric polymers based on vinylidene fluoride refer to the class of electroactive polymers suitable for various engineering applications. Under usual crystallization conditions, polycrystalline texture is formed, while after high-voltage polarization, it is transformed into a non-centrosymmetric structure, which gives rise to high piezoelectric and pyroelectric responses. Such materials can be used for pyroelectric energy conversion. Owing to high impact strength, ferroelectric polymers can serve as materials for alternative energy sources that convert dynamic impact energy into electricity. The non-linearity of electric response (owing to ferroelectricity) and high breakdown fields offer opportunity of using them in capacitive charge storage devices. The intense dynamics of the amorphous phase provides a rapid discharge of the stored energy into an external circuit. In view of the considerable fraction of the amorphous phase ( 50%) in fluorine-containing ferroelectric polymers and high dielectric permittivity of the amorphous phase, it is possible to change the system entropy by applying an electric field. In the case of pulsed field, this provides a temperature drop; therefore, these materials (especially as composites) are promising for the design of solid-state refrigerators. The high thermoplasticity of these polymers is useful for the design of sensors e.g., microphones) with a patterned active membrane surface and enhanced characteristics. Biocompatibility and low acoustic impedance (close to the impedance of biological tissues) accounts for the possibility of using these polymers as biosensors. When domains are present in a ferroelectric film, strong local electric fields appear, which can affect the activity of living cells. Using the direct and reverse piezoelectric effect, it is possible to stimulate and control the functions of various tissues, including the nervous tissue. The bibliography includes 463 references.

The surface topography and characteristics of a local piezoelectric-response signal in isotropic films of a ferroelectric vinylidene fluoride-tetrafluoroethylene copolymer with a composition of 94: 6...

New functional groups containing Al-C bonds and Al₂O₃ molecules are formed in the surface layer of the polymer during depositing of aluminum on polyethylene films. This effect is absent when Au is deposited on the films. For capacitors with Al and Au electrodes, processes of high-voltage contact polarization and conductivity are studied at various configurations of the external electric field. If Al-C organometallic bonds and Al₂O₃ or, for example, Al-O-C bonds are formed in the surface layer during application of high electric fields, a number of dielectric “anomalies” are observed. They manifest themselves as the fact that an increase in the amount of cycles of a bipolar saw-tooth voltage is accompanied by a marked increase in the residual surface charge density. At such a configuration of the external field, a decrease in its frequency (for region, where dE/dt > 0) leads to a marked reduction in high-voltage dielectric permittivity to negative values. This phenomenon is explained by the fact that, along with the external field, an internal field appears owing to formation of the space charge near metal/polymer boundaries.

This paper is devoted to the study of the structure and thermomechanical properties of PVDF-based ferroelectric polymer film. Transparent electrically conductive ITO coatings are applied to both sides of such a film. In this case, such material acquires additional functional properties due to piezoelectric and pyroelectric effects, forming, in fact, a full-fledged flexible transparent device, which, for example, will emit a sound when an acoustic signal is applied, and under various external influences can generate an electrical signal. The use of such structures is associated with the influence of various external influences on them: thermomechanical loads associated with mechanical deformations and temperature effects during operation, or when applying conductive layers to the film. The article presents structure investigation and its change during high-temperature annealing using IR spectroscopy and comparative results of testing a PVDF film before and after deposition of ITO layers for uniaxial stretching, its dynamic mechanical analysis, DSC, as well as measurements of the transparency and piezoelectric properties of such structure. It is shown that the temperature-time mode of deposition of ITO layers has little effect on the thermal and mechanical properties of PVDF films, taking into account their work in the elastic region, slightly reducing the piezoelectric properties. At the same time, the possibility of chemical interactions at the polymer–ITO interface is shown.