Conductivity Of Polymer Films Research Articles

ДЖОНШЕРОВСКИЙ УНИВЕРСАЛЬНЫЙ ДИНАМИЧЕСКИЙ ОТКЛИК В ТОНКИХ ПЛЕНКАХ ПОЛИДИФЕНИЛЕНФТАЛИДА

It is known that the supramolecular structure of organic materials can have a significant effect on the conductivity of polymer films in both constant and alternating fields. In particular, the presence of associative supramolecular formations can lead to a significant increase in the local dielectric constant. At the same time, the presence of different types of supramolecular ordering can lead to the predominance of certain charge transfer mechanisms in polymer films, and, consequently, to the presence of a dependence of conductivity on the electric field strength. The degree of molecular ordering, both on the surface and in the bulk of a polymer film, can also have a significant effect on polarization. In this regard, studying the influence of the supramolecular structure on the conductivity of polymer films in an alternating electric field is an urgent task.Previously, using various methods, it was established that the supramolecular structure of films with a thickness of more than 300 nm is determined mainly by supramolecular formations of an associative structure. The structure of films with a thickness of 100 to 300 nm is determined by the mixed structure of globular and associative formations. The structure of films less than 100 nm thick is determined by supramolecular formations of a globular. It was also established by the method of thermally stimulated depolarization that three regions are observed on the dependence of the activation energy of capture centers on the thickness of the polymer film, corre- sponding to different supramolecular organizations.In this work, the dependence of the conductivity of poly (diphenylene phthalide) films in an alternating electric field in the low-frequency range from 0.1 to 106 Hz on the supramolecular structure of polymer films was studied. It was found that the type of dependence of the conductivity of polymer films on the frequency of an alternating field depends on the thickness and supramolecular structure of the polymer films, as well as the electric field strength. The applicability of the Jonsher’s model, which describes the conductivity of amorphous materials in an alternating electric field, for thin polymer films is discussed. A correlation between the power-law dependence index and the supramolecular structure of the polymer film and the influence of dipole polarization and injection of charge carriers into the bulk of the polymer film on the conductivity of the polymer film have been revealed.

Electric conductivity of polymer films filled with magnetic nanoparticles

The conductivity of polymer composites with magnetic nanoparticles (MNP) containing magnetite and other MNP (Ni, Cu–Ni) in the layers and planar cells with Al electrodes is studied. For soluble polymers (polyvinylpyrrolidone and polyvinyl alcohol) containing 1–10 wt % of magnetite MNP, a substantial effect of MNP on surface conductivity is detected over a wide range (from 10–10 to 10–3 Ω–1). It is shown that the addition of magnetite MNP not only results in a considerable change in cell conductivity, but also leads to its partially irreversible variation (by an order of magnitude or more) via minor modifications of the experimental conditions (temperature, electric field). For high-resistance samples with low probabilities of conducting chain formation, temperature current peaks are observed upon moderate heating (up to 350 K). These peaks are similar to the maxima observed upon polymer electret thermodischarges when the charges are captured by the deep centers associated with separate MNP or MNP aggregates. The type and position of the maxima are determined by the characteristics of the polymer matrix. For polyvinylpyrrolidone composites, the maxima are observed some time after heating (the echo effect). With composites based on solventborne polymers (polyalkanesterimides, soluble polyimide) and Ni, Cu–Ni MNP, no change in film conductivity measured electrophotographically is observed, due to the formation of a dielectric coating formed by polymer macromolecules adsorbed on the MNP surface. An explanation based on the possible formation of magnetic aggregates of magnetite MNP and conducting chains is proposed. Magnetic aggregation IPM is proposed as one way of controlling cell conductivity.

Measurement of in-plane thermal conductivity in polymer films

Measuring the in-plane thermal conductivity of organic thermoelectric materials is challenging but is critically important. Here, a method to study the in-plane thermal conductivity of free-standing films (via the use of commercial equipment) based on temperature wave analysis is explored in depth. This subject method required a free-standing thin film with a thickness larger than 10 μm and an area larger than 1 cm2, which are not difficult to obtain for most solution-processable organic thermoelectric materials. We evaluated thermal conductivities and anisotropic ratios for various types of samples including insulating polymers, undoped semiconducting polymers, doped conducting polymers, and one-dimensional carbon fiber bulky papers. This approach facilitated a rapid screening of in-plane thermal conductivities for various organic thermoelectric materials.

Investigation of PSt-MWCNT concentration on epoxyacrylate photopolymerization and conductivity of polymer films

Photopolymerization kinetics and conductivity changes of epoxyacrylate composites for various loading modified PSt-MWCNT weight fractions changing from 0.0025 to 0.2wt.% were evaluated by performing photo differential scanning calorimetry (photo-DSC) and four point conductivity measurements. 0.2% PSt-MWCNT additive polymeric films had their electrical conductivity boosted by 6% more than non-additive polymeric films.

Nonlinear response and two stable electroconducting states in transparent plasticized PVC films

The electric conductivity of transparent plasticized poly(vinyl chloride) (PVC) films with thicknesses about 30–50 μm has been studied in electric fields with strengths significantly below the breakdown level. It is established that the PVC films exhibit spontaneous reversible transitions between two stable states—with high and relatively low conductivities, in which the bulk resistivity amounts to ∼103 and 106 Ω m, respectively. Relaxation current-voltage characteristics have been measured in a continuous regime, which allowed the Debye relaxation processes to be taken into consideration and effects related to the nonlinearity and transitions between indicated states to be separated. A regime with deterministic switching between the two conducting states has been observed. A simple qualitative model that describes the anomalous character of conductivity in polymer films is proposed.

Generation of Anisotropic Conductivity in Polymer Films Using Localized Microvoids Formed by Solvent Crazing as Nanoreactors

An approach to generate localized, isolated percolating networks of Ag nanoparticles in the micropores of solvent-crazed PET films is presented. The films show a resistance of 6.32 Ω in the directi...

Modification of Electronic Transport in Polymer and Carbon Films by High and Low Energy Ion Irradiation

ABSTRACTWe have explored the origin of the ion-induced conductivity in polymer films and the distinction between low energy ion-implantation and high-energy ion irradiation. In experiments involving irradiation of polymer and carbon films with ions of energy from 200 keV to 25 MeV we have established that with both low and high energy ions the polymers undergo carbonization. However, the saturation resistivity obtained with low energy implantation is four to six orders of magnitude larger than those obtained by high energy ion irradiation. In experiments on irradiation of carbon films low energy ions caused a two orders of magnitude increase in the resistivity while high energy ion caused a two orders of magnitude decrease. This implies that the structure of the carbonized polymer is different for the low and the high energy ion irradiation. While in the former case there may be no crystalline order in the films; in the latter case, a microcrystalline graphitic structure is obtained (with four orders of magnitude larger conductivity than in the former case). The formation of graphitic crystalline order with increasing high energy ion dose was verified by electron energy loss spectroscopy. This is an interesting example of crystallization induced by electronic excitation alone with no macroscopic thermal effect.

Ion-beam-induced conductivity in polymer films

Polymer films darken upon irradiation with energetic ion beams. At high doses (1016–1017 cm−2) of 2-MeV Ar+ ions, the resistivity of these insulating films decreases dramatically to 3.5×10−3 Ω cm. Furthermore, over a wide range of doses (1014–1015 cm−2) these films exhibit a temperature-dependent resistivity characteristic of carrier transport via hopping between isolated conducting islands. Rutherford backscattering measurements indicate that while a substantial amount of the carbon is retained in the film, other constituent elements are lost. Raman spectra show that the films are highly disordered at large ion doses.

Ionic conduction in polymer films: IV. The effect of pigmentation with iron oxide

AbstractIonic conduction in continuous polymer films is of two types. Inverse conduction occurs when the resistance of the film runs counter to, and direct conduction when the resistance follows, that of the external solution. The effect of pigmentation with iron oxide on the type of conduction has been examined in the case of films prepared from a pentaerythritol alkyd, a phenolformaldehyde tung oil and an epoxypolyamide varnish. It was found that upon progressive pigmentation the percentage samples showing direct conduction rose and then fell, furthermore no change in glass transition temperature was observed. It is suggested that this may be due to the segregation of low molecular weight material around the pigment particles thus screening them from the main bulk of the polymer.

Anomalous conduction in polymer films at high DC fields

Anomalous conduction in polymer films at high DC fields

Ionic conduction in polymer films. III Influence of temperature on water absorption

AbstractThe variation of water absorption with temperature of three varnish films, a pentaerythritol alkyd, an epoxy‐polyamide and a phenol‐formaldehyde tung oil, has been measured. In the case of the first two, minima were observed the temperatures of which corresponded to glass transition temperatures of the polymers. In contrast, films of the phenol‐formaldehyde tung oil varnish showed neither a minimum in the water absorption‐temperature curve nor a glass transition temperature over the range 5–34°C. Further work is necessary to establish whether this relationship has general application.

Ionic conduction in polymer films: II. Inhomogeneous structure of varnish films

AbstractIonic conduction in polymer films is of two types. Inverse conduction, I, occurs when the resistance runs counter to that of the external solution, and Direct conduction, D, when the resistance follows that of the external solution.The distribution of areas having D properties has been established for films of a pentaerythritol alkyd, a phenol‐formaldehyde tung oil and a polyamide‐cured expoxide varnish, and it is shown that D conduction cannot be ascribed to capillaries, unless they are of molecular dimensions. It is concluded that these films have a very heterogeneous structure and that I and D areas are brought about by differences in crosslinking density within the film.

Ionic conduction in polymer films I. Influence of electrolyte on resistance

AbstractIonic conduction in continuous polymer films is of two types. Inverse conduction occurs when the resistance of the film runs counter to, and direct conduction when the resistance follows, that of the external solution. The two types are interconvertible; the controlling factor is the water content of the film, which is governed by the nature of the polymer, the mode of preparation of the film, and the conditions of exposure.

Ionic conduction in polymer films and related systems

AbstractIn polymer films, electrical conduction by ion transport is a significant process which is potentially capable of revealing various aspects of the film's morphology. In this report, further details and consequences of conduction experiments with ion‐doped cellulose 2.5 acetate will be discussed along with some corroborating evidence for a large number of organic liquids. The most important conclusions are: (1) sorbed moisture provides charge carriers by dissociation to H+ and OH−, and (2) the effective dielectric constant ϵ′ is increased by sorbed moisture to a value above that of the pure polymer, or organic liquid, so that barriers to the dissociation of ionic species are greatly reduced. Furthermore, the theory of weak electrolytes may be applied to “strong electrolytes” within solid polymeric and/or liquid organic systems.

Study of the anisotropy of thermal conductivity in polymer films oriented along a single axis

Study of the anisotropy of thermal conductivity in polymer films oriented along a single axis

Conductivity of polymer films at high frequencies

Conductivity of polymer films at high frequencies