The purpose of the work is to find out dielectric characteristics of samples of polyvinyl alcohol and composites based on it in the frequency range below 100 Hz. In this work, films based on polyvinyl alcohol (PVA) with the addition of sodium chloride and fullerenol were fabricated, and the frequency dependences of dielectric permittivity, dielectric loss, and dissipation factor in the range of 0.01 – 100 Hz were measured and analyzed.

This work presents the results of comparison of optical properties at room temperature and electrical characteristics of films of polyvinyl alcohol (PVA) and nanocomposite based on PVA with small additives of fullerenol C60(OH)44 in a wide frequency range (25 Hz - 1 MHz) at temperatures from 294 to 398 K. The addition of 2 wt.% fullerenol leads to a significant absorption of light by such a film in the UV region of the spectrum (IR spectra of both film samples were identical), as well as to a decrease in dielectric permittivity c '. The c " frequency dependences of both films showed peaks in the low-frequency region, which shifted towards higher frequencies when the films were heated. The values of the activation energy of conduction at direct current for PVA and polymer nanocomposite were found to be about 1.5 eV. An explanation of the observed effects is proposed.

In this article we present the results of time-of-flight mass spectrometry of volatile products formed during the electrical breakdown of polyethylene terephthalate and polypropylene polymer films in high vacuum. During the breakdown of films, all the substance emitted from the breakdown channel is a gas of low-molecular products of destruction of macromolecules. The breakdown mass spectra do not contain lines of carbon molecules, the presence of which could indicate carbonation of the channel. To explain the formation of charge carriers, the ionization mechanism of destruction of macromolecules in an electric field is used without the involvement of impact ionization. The final stage of electrical breakdown (the flow of a high-density conduction current) occurs when the critical concentration of traps and electrons ~1024 m-3 is reached. Keywords: electrical breakdown, mass spectrometry, thermodestruction, ionization, macromolecule, trap.

The pulsed electrical strength of PP and PET films has been investigated. It has been established that the breakdown of these films is possible both at the front and at the plateau of the pulse. A jump in the durability of the films has been recorded during the transition from breakdown at the front to breakdown at the plateau of the pulse. It has been shown that the processes preparing the electric breakdown of the films develop faster at the front, and not at the plateau of the pulse. A possible physical mechanism explaining this effect has been discussed.

The paper presents the results of experimental study of the influence of the doping agent (acid) nature on the conductivity, Seebeck coefficient, and thermoelectric power factor of composite material based on multilayer carbon nanotubes coated with polyaniline. Polyaniline was deposited on carbon nanotube surfaces by heterophase synthesis (in-situ polymerization), by oxidative polymerization of aniline in the presence of nanotubes dispersed in the reaction medium. Hydrochloric, camphorsulfonic and dodecylbenzenesulfonic acids were used as doping agents. The effect of temperature on the conductivity, Seebeck coefficient and thermoelectric power factor of the investigated composite materials has been studied in the range from 300 to 410 K. Comparison of the influence of the acid volatility on the changes in these parameters in the heating-cooling cycle allowed us to conclude that the decrease in conductivity and increase in the Seebeck coefficient when heating composites doped with different acids is caused by the acid removal from the samples.

The optical and electrical properties of PVA films and PVA + C6o(OH)44 nanocomposite have been compared. It was found that even a small addition of fullerenol molecules to PVA leads to its coloration, and the nanocomposite films become opaque in the UV region of the spectrum. It is shown that at elevated temperatures, noticeable differences in the conductivity and low-frequency dielectric permittivity of PVA films and PVA+fullerenol composite films are observed. Their possible causes are analyzed.

Electron-hole recombination, which occurs in polymer dielectrics in strong electric fields, and weak partial discharges in these materials are considered as possible additional factors that accelerate the aging process of polymers in an alternating electric field compared to a constant one. The effect of these factors on the rate of formation of defects (ruptures of macromolecules) is estimated. It is shown that in polymer dielectric films at a concentration of micropores of 104-105 cm-3 and intensity of partial discharges of ~ 0.01 pC, the main factor determining the decrease in electrical durability in an alternating electric field should be considered the processes of electron-hole recombination, leading to the breaking of bonds in excited macromolecules, and not erosion of the polymer as a result of partial discharges. Assuming that breakdown occurs when a critical concentration of defects that arise in a polymer dielectric due to electron-hole recombination is reached, a relation is obtained for calculating the field dependence of durability at an alternating voltage. It is shown that the calculation results are consistent with the known experimental data.

The pulsed electrical strength of 2 µm thick polypropylene (PP) and 2.5 µm thick polycarbonate (PC) films was investigated under pulsed conditions. The most probable values of breakdown strengths for the thin films studied were obtained using the Weibull distribution. It is shown that within the temperature range of 293-363 K the breakdown strength of PP is practically independent of temperature and is about 500 MV/m, whereas for PC it decreases linearly from 700 MV/m to 500 MV/m.

In this work, a comparative experimental study of the dielectric properties of films based on the piezoelectric polymer PVDF and its copolymer PVDF-TrFE, as well as fibrous samples made from PVDF-TrFE was carried out. The dielectric properties of biocompatible polymer composite materials based on PVDF - TrFE copolymer fibers modified by coating with various conductive polymers (polypyrrole and polyaniline) were also investigated and analyzed, and the dielectric response of the synthesized composites to environments with different acidity was studied. It was found that the studied composites based on piezoelectric and conductive polymers are characterized by a strong dependence of capacitance values on the acidity of the environment. The results obtained can be considered as the basis for creating working elements of new medical sensors that respond to the acidity of the environment.

The paper presents the results of an experimental study of the electric conductivity and thermoelectric properties of a new coordination polymer (CP) based on phenazine ligands (Phz) and silver (Ag) synthesized by a one-step method. This method produces phenazine by oxidative dimerization of aniline under the action of AgNO3 followed by release of metal nanoparticles and subsequent self-organization of Phz with excess AgNO3 into the CP. The used method of the Phz-Ag synthesis was found to make possible obtaining CP with conductivity of about 1300 S/cm commensurable with the modern record value for CPs. The obtained experimental data led to the conclusion that the studied CP Phz-Ag possesses a metallic type of conductivity. A physical mechanism of forming this property was put forward.

A large-sized fullerene molecule contributes to the significant dipole moment of C 60 O 2 molecular groups. The application of the «grain-interlayer» model for describing the dielectric spectrum of a material consisting of layers with different conductivity types made it possible to estimate a dipole moment of 3.1 D. A polarizability equal to 120 Å 3 was calculated using the Clausius-Mosotti model and 150 Å 3 using the Kirkwood model. By constructing dependences of the polarizability and dipole moment on the depth of the fullerene film crystallite saturation with oxygen, we could evaluate the correctness of the chosen depth values at the resulting dielectric permittivity values.

In this article we present the results of time-of-flight mass spectrometry of volatile products formed during the electrical breakdown of polyethylene terephthalate and polypropylene polymer films in high vacuum. During the breakdown of films, all the substance emitted from the breakdown channel is a gas of low-molecular products of destruction of macromolecules. The breakdown mass spectra do not contain lines of carbon molecules, the presence of which could indicate carbonation of the channel. To explain the formation of charge carriers, the ionization mechanism of destruction of macromolecules in an electric field is used without the involvement of impact ionization. The final stage of electrical breakdown (the flow of a high-density conduction current) occurs when the critical concentration of traps and electrons ≈ 10^24 1/m^3 is reached.

The article deals with the influence of an external electric field on the maximum dielectric loss tangent $(\text{tg}\delta)_{max}$ and relaxation time $\tau$ in Si(p)–C 60 –InGa structures. The results of the description of the dependencies $(\text{tg}\delta)_{max}(\mathrm{U}_{bias})$ and $\tau(\mathrm{U}_{bias})$ using the Wagner-Koops «grain-layer» model and the Debye equations are given. According to the above model, the experimental results of $(\text{tg}\delta)_{max}$ are well approximated at an electric field strength of $F > 2.4\ \text{MV}/\mathrm{m}$ . The maximum relaxation time is $\tau=22$ ms and is observed at $F=2.8\text{MV}/\mathrm{m}$ .

In the paper, the effect of temperature (range 22 - 140 degrees C) on the power factor (PF) of composite material made of multi-walled carbon nanotubes with a 10 run thick polyaniline coating applied to their surface has been studied. The conductivity value of the coating was varied by treating the composite with buffer solutions of different pH values. The nano-tubes were randomly oriented relative to each other in the composite samples under study. It was found that the composite material where polyaniline was in an oxidized conductive form had the highest PF value. In that sample, the PF values were about 0.5 mu W/(m.K-2) at room temperature and about 1 mu W/(m.K-2) at 140 degrees C.

We present the results of an experimental study of the pulse electrical strength of polyethylene terephthalate and polypropylene films when they are subjected to a single electric pulse. It has been found that the breakdown of these films is possible both at the front and at the plateau of the pulse, and the probability of breakdown at the front increases with pulse amplitude. We recorded a jump in the durability of the films at the transition from breakdown at the front to breakdown at the pulse plateau. It is shown that the processes that prepare the film electrical breakdown develop faster at the pulsefront than at the plateau. We discuss a possible physical mechanism to explain this effect. Keywords: polymers, polypropylene, polyethylene terephthalate, pulsed electrical breakdown, electroluminescence.

The dielectric and physical-mechanical properties of organophosphorus polyurethane ionomers based on the ethers and aminoethers of ortho-phosphoric acid have been investigated. The influence of the content of ionogenic groups and polyphosphate structures on the dielectric properties of polyurethanes has been analyzed. It is shown that the values of dielectric permittivity and tangent of dielectric loss in a wide frequency range increase with the content of ionogenic groups in polyurethanes studied. In this case, the increase in conductivity is diffusive in nature and is due to the mobility of protons within the phosphate anion clusters. The compositions of samples with a combination of high dielectric properties and excellent physical-mechanical and adhesion characteristics have been determined. These are samples in which polyphosphate structures are present in addition to phosphate anions.

The dielectric permittivity and loss factor of polyvinyl alcohol films in the frequency range of 100 Hz to 1 MHz at room temperature are studied. The laboratory manufacturing technology of polyvinyl alcohol films with thickness of 50–60 microns has been worked out. It has been shown that the dielectric characteristics of the films remain stable for a long time and do not depend on the thermal history of the samples. High values of dielectric permittivity ( $\varepsilon^{\prime}\sim 10$ ) and small losses ( $\text{tg}\delta\sim 0.09$ ) in the frequency range from 1 kHz to 10 kHz allow recommending polyvinyl alcohol as an OFET gate dielectric for devices operating in this frequency range.

We present the results of an experimental study of the pulse electrical strength of polyethylene terephthalate and polypropylene films when they are subjected to a single electric pulse. It has been found that the breakdown of these films is possible both at the front and at the plateau of the pulse, and the probability of breakdown at the front increases with pulse amplitude. We recorded a jump in the durability of the films at the transition from breakdown at the front to breakdown at the pulse plateau.It is shown that the processes that prepare the film electrical breakdown develop faster at the pulsefront than at the plateau. We discuss a possible physical mechanism to explain this effect.

The article emphasizes that conducting polymers could be a worthy alternative to the common inorganic thermoelectrics. It is possible due to specific modification of polymer morphology or composite preparation. The present work gives an outline of the synthesis of one-dimensional (1D) structured polypyrrole nanotubes and polypyrrole composites based on carbon nanotubes. Measurements of specific conductivity and Seebeck coefficient were performed in temperature range from 300 K to 415 K. Based on the results, power factor temperature dependency was calculated and studied. Evaluation of thermoelectric properties changes by specific morphology and composites preparation will help to determine optimal conditions for power factor maximum to reach.

The effect of temperature on the impulse electrical strength of a polyethylene terephthalate (PET) film with a thickness of $2.5 \mu\mathrm{m}$ was studied. Statistical analysis of the obtained results was carried out. It was found that the probability distribution of the breakdown strength of the film under study corresponds to the Weibull law. It was shown that the value of the most probable breakdown voltage of a PET film in the range from 293 to 363 K does not depend on temperature.