This paper considers the uniaxial orientation effect on the structure and piezoelectric properties of vinylidene fluoride-tetrafluoroethylene copolymer ferroelectric films. The films were exposed to uniaxial orientation stretching in a temperature range from 20 °C to 60 °C; then, they were contact polarized under normal conditions. The temperature dependence of the electric strength was determined. The longitudinal piezoelectric coefficient d₃₃ values were measured by the quasi-static Berlincourt method. The piezoresponse force microscopy (PFM) method was used to investigate the film domain structure before and after polarization, and the local piezoelectric coefficient values were also calculated. Phase composition was studied using differential scanning calorimetry and infrared spectroscopy with the Fourier transform. It was found that uniaxial orientation stretching contributed to an increase in the piezoelectric coefficient d₃₃ from 5 pC/N to 16–20 pC/N. The results obtained indicate the importance of the amorphous phase contribution to the formation of the piezoelectric properties in polymeric materials.

Copolymers based on vinylidene fluoride are potential materials for ferroelectric memory elements. The trend in studies showing that a decrease in the degree of crystallinity can lead to an unexpected increase in the electric breakdown field is noted. An analysis of the literature data reveals that in fluorine-containing ferroelectric polymers, when using a bipolar triangular field, the hysteresis loop has an unclosed shape, with each subsequent loop being accompanied by a decrease in the dielectric response. In this work, the effect of the structure of self-polarized films of copolymers of vinylidene fluoride with tetrafluoroethylene and hexafluoropropylene on breakdown processes was studied. The structure of the polymer films was monitored using infrared spectroscopy (IR) and X-ray diffraction. Kelvin probe force microscopy (KPFM) was applied to characterize the local electrical properties of the polymers. For the films of the first copolymer, which crystallize in the polar β-phase, asymmetry in the dielectric response was observed at fields greater than the coercive field. For the films of the copolymers of vinylidene fluoride with hexafluoropropylene, which crystallize predominantly in the nonpolar α-phase, polarization switching processes have also been observed, but at lower electric fields. The noted phenomena will help to identify the influence of the structure of ferroelectric polymers on their electrical properties.

Glow-discharge plasma (GDP) poling is revisited as an electrode-free method for activating piezoelectricity in poly(vinylidene fluoride) (PVDF) films. Although this method was proposed several decades ago, its effect on the properties of PVDF films has remained poorly understood. In this work, we demonstrate that GDP enables efficient poling of oriented PVDF films without pre-deposited electrodes and investigate the relationship between plasma treatment time, structural evolution, and piezoelectric response. Commercially available 25 μm-thick oriented PVDF films (PolyK) were treated in a DC glow discharge for 15 s to 15 min and characterized using FTIR, DSC, piezoresponse force microscopy, UV–Vis–NIR spectrophotometry, quasi-static d₃₃ measurements and water contact-angle measurements. GDP poling produced a side-averaged piezoelectric coefficient d₃₃ of up to ~25 pC/N within 1–5 min, with local maxima at approximately 1, 2.5, and 5 min. This behavior was accompanied by pronounced changes in the domain structure, including an increase in the ferroelectric domain size from 86 to 552 nm, while the crystallinity and electroactive phase fraction changed only moderately. Plasma treatment also increased the wettability of the plasma-facing surface, reducing the water contact angle from about 85° to 42° within 3 min. At longer treatment times (>5 min), however, the piezoelectric response decreased and the optical transparency deteriorated because of increased haze and turbidity, most likely associated with plasma-induced chemical modification of the surface layers. These results indicate that GDP poling has an effective processing window of 1–5 min. The proposed approach provides a vacuum-compatible and electrode-free route for preparing PVDF films with increased surface wettability for flexible piezoelectric sensors, wearable electronics, and integrated polymer-based devices, because it is compatible with electrode deposition on an already activated polymer surface within a single vacuum cycle.

The paper considers the uniaxial orientation effect on structure and piezoelectric properties of the vinylidene fluoride-tetrafluoroethylene copolymer ferroelectric films. The films were exposed to uniaxial orientation stretching in the temperature range from 20°C to 60°C; then, they were contact polarized under the normal conditions. Temperature dependence of the electric strength was determined. The longitudinal piezoelectric coefficient d33 values were measured by the quasi-static Berlincourt method. The piezoresponse force microscopy (PFM) method was used to investigate the film domain structure before and after polarization, and the local piezoelectric coefficient values were also calculated. Phase composition was studied using the differential scanning calorimetry and the infrared spectroscopy with the Fourier transform. It was found that uniaxial orientation stretching contributed to an increase in the piezoelectric coefficient d33 from 5 pC/N to 16…20 pC/N. The results obtained indicate importance of the amorphous phase contribution to formation of the piezoelectric properties in polymeric materials.

Polarization of a polyvinylidene fluoride (PVDF) film containing 6 mol % tetrafluoroethylene in glow discharge plasma was examined. The polarization efficiency of the PVDF film produced in Russia was compared to that of a foreign counterpart. This parameter was evaluated using the measurements of the longitudinal piezoelectric coefficients d ₃₃ via the quasi-static Berlincourt method. The structural changes were studied by Fourier transform infrared spectroscopy. The changes in morphology and optical properties were investigated by polarization microscopy. The results show that, based on the calculated values of the piezoelectric coefficients, the Russian PVDF film polarized in glow discharge plasma is comparable to the foreign counterpart.

The problem of interaction of microelectromechanical systems and structures with electron and ion beams applied for the tasks of cryovacuum and space electronics and control of space telescopes is posed in the introduction, and the need for modeling the above effects in ground experiments is demonstrated. A technique for modeling the effect of charged particle beams on the polymer ferroelectric and piezoelectric structures, such as the interacting polymer fibers / «fuzzy neuromorphic connectomes» is proposed and implemented based on time-resolved electron microscopy tools with real-time data analysis, up to stroboscopic electron microscopy. In particular, a 2D Fourier transform and subsequent calculation of integral spatial characteristics (ISCs), analysis of the interframe correlations, complex wavelets are used. The experiments demonstrate piezoelectric fiber dynamics of microelectromechanical systems, detected by the change in 2D Fourier spectra of the fiber structures over time under the electron beam. The dynamics of fiber structures and networks with their topology changing under the electron beam is also shown. Time-lapse recording data prove that in some cases such structures can operate as drive (control) electromechanical elements, elastic elements (springs), contactors or locking (blocking) elements. The mechanical fracture of microfibers is also demonstrated. The possibility of coupling several fibers of different thickness and electrophysical properties to achieve complex control over microelectromechanical structures and systems based on them is also shown. The discussion points out the prospects of studying the above structures and systems both within the framework of polymer microelectromechanics or mechatronics, and for creating neuromimetic network structures for sensorics and adaptive motorics, actuated by the charged particle beams (electrons, ions, etc.) and inducing the fiber MEMS dynamics of the «artificial muscle» type, operating based on the principles of teinochemistry and chemomechanics of polymers with field-controlled adaptive «fuzzy» connection formation.