Electrochromic properties of sulfonic acid ring-substituted polyaniline in aqueous and non-aqueous media

It is a simple way to prepare the sulfonic acid ring-substituted polyaniline (SPAn) electrode via the directly chemical reaction of polyaniline (PAn) film polymerized on the indium-tin oxide (ITO) conducting glass with the concentrated sulfuric acid. The in situ visible spectra show that the color of the SPAn film in 0.3 M Na₂SO₄ solution with pH 7.0 still changes with the applied potential. The pH range for the change in the color of the SPAn film is larger than that of polyaniline film. In 0.25 M LiClO₄ propylene carbonate (PC) solution, the color of the SPAn film changes from blue via green to transparent yellow as the applied potential decreases from 0.80 to −0.20 V (Ag/AgCl with saturated KCl solution), and this change is reversible. Based on the result from the cyclic voltammogram, SPAn in the non-aqueous solution has a good electrochemical activity and a fast charge transfer characteristic. The XPS spectrum of SPAn indicates that polyaniline in the concentrated sulfuric acid can be sulfonated.     

Durability properties of concrete with blended cements

The study of chloride‐induced corrosion started more than three decades ago, after extensive cases of damage were observed on reinforced concrete structures in coastal regions and on infrastructural objects exposed to salt action. Nowadays, the basis for sustainable concrete industry lies in these three aspects: reducing CO₂ emissions by using by‐products of other industries (slag, fly ash, silica fume) for cement production, conservation of natural resources by replacing part of the aggregate with recycled construction waste, as well as use of recycled water in concrete production, and finally, construction of durable concrete structures. Durability design procedures for reinforced concrete structures in aggressive environments are still to a large extent empirical, especially in the case of using blended cements. The type of cement has a considerable effect on the properties of concrete, especially concrete resistance to the penetration of chloride ions. The paper presents results of testing durability and deformational properties of concrete produced with quaternary‐blended cement. A clearer insight into these properties is a necessary starting point for the performance‐based design of concrete prepared with blended cements, leading to more durable and corrosion‐free concrete structures in aggressive environments.     

Sorption properties of fullerene-modified polystyrene

Polystyrene is modified with fullerene, and composite films are obtained. The kinetics of sorption of heavy metal ions from aqueous electrolyte solutions on the initial and modified polystyrene films is studied. The efficiency of sorption of copper ions of the modified polymer is found to be four times higher than on the unmodified samples. The selectivity of sorption on the composite can be presented with the following order: Cu(II) ≥ Cd(II) > Ni(II) > Zn(II). The interaction between polystyrene and fullerene is studied by IR spectroscopy.     

Synthesis and anticorrosion properties of polydiphenylamine blended vinyl coatings

Inherently conducting polymers such as polyaniline and polypyrrole containing organic coatings have been found to offer corrosion protection of steel in acid and neutral media. In this study, the use of polydiphenylamine in vinyl coating for corrosion protection of steel in 3% NaCl solution is reported. The polydiphenylamine was prepared by chemical oxidative method of diphenylamine by ammonium persulfate in hydrochloric acid medium. The synthesized polydiphenylamine (PDPA) was blended with vinyl resin at 0–5% concentrations and the corrosion protection performance of the coating on steel was evaluated by EIS for a period of 80 days. It has been found that the coating containing 3% PDPA is able to protect steel more effectively.     

Spectroscopic investigation of oxidation of p-toluene sulfonic acid doped polypyrrole

Oxidative degradation of electrochemically synthesized p-toluene sulfonic acid doped polypyrrole, PTS-PPY was studied by the application of evolved gas analysis using IR spectroscopy and direct insertion probe pyrolysis mass spectrometry techniques. It has been observed that PPY films prepared in aqueous media contained high concentration of oxygenated species even if the synthesis potential was kept low. The extent of overoxidation associated to ketone formation increased by increasing the applied potential and thermal ageing. The decrease in conductivity is attributed to the replacement of dopant, as a result of nucleophlic attack on the polycationic chain, by hydroxide and/or O₂. Pyrolysis analyses also indicated that chemically prepared samples were oxygenated in air more readily and yielded mainly CO groups. Presence of hydroxide groups for these samples may be associated with the adsorption of H₂O in air or H₂O present during synthesis as an impurity. The direct insertion probe pyrolysis mass spectrometry technique was shown to be a very powerful technique for not only determining the thermal decomposition products but a investigating the interaction of dopant and oxygenated species with the polymer matrix.     

Dielectric properties of polymer composites with TlInSe2 semiconductor filler

The dielectric properties of polymer composites on the basis of polyethylene and polypropylene with TlInS₂ semiconductor filler are investigated. It is shown that the changes in these properties that were observed are caused by polarization processes occurring on the polymer-filler interface.     

Dielectric properties of sintered aluminum nitride

In the present work, the effects of sintering additives on dielectric loss tangent (tan δ) of AlN ceramics were explored. Different amounts of Y₂O₃ and Mg₃N₂ were respectively added as sintering additives to AlN powders, and pressureless-sintering was performed at 1900 °C for 2 h in a nitrogen flow atmosphere. The resulted AlN ceramics became denser due to the addition of Mg₃N₂, and nearly fully dense sample was obtained with a relative density of 0.998. tan δ decreased with increasing Mg₃N₂ amount and it was found to depend on the density of the AlN ceramic. The best tan δ value of 3.9 × 10⁻⁴ was obtained by adding 1 mol% of Y₂O₃ and Mg₃N₂ together.     

Dielectric properties of polymer-based microheterogeneous insulator

The study of the dielectric behavior of polymer-based insulating materials used in high voltage equipment is presented in this work. The materials tested are microheterogeneous in nature with mineral particles (calcium fluoride) dispersed in a semicrystalline polymeric matrix (polytetrafluoroethylene). The dielectric properties are analyzed in a wide frequency (or time) range by a combination of two techniques: the short time response is assessed by measuring the complex permittivity in the frequency domain (20 Hz–1 MHz), and the long term response is studied by measuring the polarization current in the time domain (1–600 s) thus covering more than eight decades in frequency or time. The modelling used to describe microheterogeneous dielectrics is shown to fit the experimental data. However, exposure to moisture is shown to induce strong relaxational effects. These effects vanish in a reversible way by drying treatment (i.e. removal of water molecules). These additional relaxations are discussed in term of conductivity effects occurring at the interface matrix-filler particles. When mechanical and dielectric spectroscopy studies are compared, it is to be underlined: (i) that the presence of water molecules has no significant effects on internal friction spectra; and (ii) solid state transformations in the non polar polymeric matrix induce strong mechanical and non significant dielectric relaxations. This is an example of complementary relaxation spectroscopy techniques when the coupling between the atomic motions and the excitation is not the same.     

Dielectric properties and conductivity of zinc ferrite and zinc ferrite doped with yttrium

The electrical properties of spinel ferrites are determined by the different factors, of which synthesis method, chemical composition and grain size have the most important role. In this paper we investigate dielectric behavior and conductivity of the nanosized ZnFe₂O₄ and Y_0.15Zn_0.85Fe₂O₄ powders obtained by the coprecipitation method. The frequency dependence of the dielectric permittivity, the loss factor, and the conductivity of the samples are determined in the frequency range from 1 Hz to 100 kHz, at temperatures from 300 to 350 K. The dielectric behavior of ferrites is explained by the interface polarization, arising from the heterogeneous nature of its structure. Increasing trend of electrical conductivity (σ) and decreasing trend of the dielectric permittivity () with increasing frequency are explained by the Koops model. The maximum values of tan δ are noticed in the frequency range from 1 to 10 kHz.     

Highly crystalline and soluble dodecylbenzene sulfonic acid doped poly(o-toluidine)

Dodecylbenzene sulfonic acid (DBSA) doped poly(o-toluidine) (POT) was synthesized by oxidative polymerization technique. The optical, structural, morphological, thermal and electrical properties of the POT-DBSA have been investigated. It was found that conducting emeraldine salt of POT-DBSA is stable in chloroform. X-ray diffraction showed that the POT-DBSA is a highly crystalline polymer due to formation of H-bonding across chains. The scanning electron micrograph reveals a flaky like feature with few globular structures and the size of the grain was about 3 μm. The highest conductivity of POT-DBSA was found to be 1.88 × 10^?3 S/cm at 1:1 molar ratio of oxidant to o-toludine and at 0.18 M of DBSA. Schottky diode based on POT-DBSA was fabricated using Al as Schottky contact and Cu as an Ohmic contact. The junction parameters including ideality factor and barrier height of the diode was 3.0 and 0.989 eV, respectively.     

Dielectric properties of thiophene based conducting polymers

Dielectric properties of some conducting polymers were investigated and their electrical properties are compared with each other. Temperature dependencies of their electrical properties are investigated throughout the work. Electrical behaviors of the synthesized systems constitute a good infrastructure for both understanding the intrinsic mechanisms and optimizing new synthesizes. It is found that, it can be possible to attain desired electrical properties by small synthesis modulations in thiophene based polymer materials.     

Synthesis of polyaniline/camphor sulfonic acid in formic acid medium and their blends with polyamide-6 by in situ polymerization

Blends of polyaniline doped with camphor sulfonic acid (PAni.CSA) and polyamide 6 (PA6) were prepared for the first time by the in situ polymerization of aniline in the presence of a solution of PA6 in formic acid. The conductivity values of the blends prepared by both solution cast and in situ polymerization are in the range useful for electrostatic charge dissipation materials. The conductivity of the blend containing 10% of PAni.CSA was higher, when the in situ polymerization process was used, indicating the formation of conducting pathways in a higher extension. Most of the blends prepared by the in situ polymerization presented only one irreversible peak in the cyclic voltammetry, which is attributed to the presence of defects along the PAni.CSA chains. These defects may be caused by the presence of formic acid as the solvent, as observed by Fourier transformer infrared spectroscopy of the pure polyaniline prepared in the presence of formic acid.     

Effects of content of polyaniline doped with dodecylbenzene sulfonic acid on transparent PANI-SiO2 hybrid conducting films

Transparent PANI-SiO₂ conducting films were prepared by hybrid of dodecylbenzene sulfonic acid-doped polyaniline (DBSA-PANI) and 3-glycidoxypropyltrimethoxysilane (GPTMS) through sol–gel route. The influence of content of DBSA-PANI on the structural, electrical and optical properties of the films was investigated. Sheet resistance of the hybrid films was 5.1 kΩ/□ and visible light transmittance was 75%, when the content of DBSA-PANI was 30 wt.%. Thermogravimetric analysis (TG) showed that the obtained films were thermally stable under 120 °C and optical bandgap of the hybrid films was determined from Tauc plots.     

The molecular weight of sulfonic acid ring-substituted polyaniline by laser light scattering

The weight average molecular weight ( ) of the sodium salt of as-synthesized sulfonic acid ring-substituted polyaniline (SPAN) was determined by light scattering measurements. The water solution of SPAN was first reduced with hydrazine to render the solution almost colorless. The of the reduced SPAN sodium salt was found to be 11 000. It is concluded that the lower limit of the number of ring-nitrogen units per polymer chain is 39 in the as-synthesized SPAN.     

Electroactive polymer hydrogels composed of polyacrylic acid and poly(vinyl sulfonic acid) copolymer for application of biomaterial

The volume change of hydrogels has potential for application of biomaterials that quickly can reduce by an applied electric field. This volume change of the hydrogel was similar to natural muscle, can be utilized as biosensors and as artificial muscle when employing an electrical stimulus.     

三层涂层柔性复合材料介电性能和力学性能

研究了铁氧体含量、碳化硅含量、石墨含量对三层涂层复合材料介电常数的影响,在上述实验基础上制备了介电性能最佳的涂层复合材料,并测试了该复合材料的剪切、拉伸、弯曲性能。结果表明:铁氧体含量为60%,碳化硅含量为36%,石墨含量为24%时,铁氧体/碳化硅/石墨三层涂层复合材料的介电性能良好;该复合材料具备良好的剪切、拉伸、弯曲性能。     

Dielectric properties of concrete and their influence on radar testing

Sub-surface radar is becoming increasingly popular as an inspection method. Interpretation can be enhanced if uncertainties about the dielectric properties of the concretes under investigation are removed. The need for reliable data to identify possible variations of the dielectric properties of different concrete mixes and their condition on site has led to a systematic laboratory based experimental programme under the auspices of a major European Commission (Brite-Euram III Framework 4) funded project. Some key results from this recently completed work are presented in this paper with practical implications related to field surveys of structural concrete.     

An investigation of the structural and thermodynamic properties of polystyrene fullerene-containing films

Polystyrene films doped with small additives of fullerenes (w = 0–1 × 10^?3) are obtained. The nonmonotonic dependence of the glass transition point on composition with a minimum at w = 1 × 10^?4 is revealed by the DSC method. It is concluded that there is a plasticizing action of small amounts of filler at w < 1 × 10^?4 and domination of the effect of intermolecular interactions of fullerene with polystyrene at w > 1 × 10^?4. It is established by small-angle X-ray scattering that composites containing fullerenes in the amount w > 1 × 10^?4 are characterized by the greatest mobility of the segments in the modified polymer chains.     

Preparation and properties of conducting composites of polypyrrole and porous cross-linked polystyrene with and without supercritical carbon dioxide

Composites of polypyrrole (PPy) and porous cross-linked polystyrene (PCPS) were prepared using a two-step batch method proposed by Ruckenstein and Park. However, the solvent employed by Ruckenstein and Park (methanol) in the polymerization step of their method was replaced with supercritical CO₂. For comparison purposes, PPy/PCPS composites were also prepared using no solvent in the polymerization step. Conductivities as high as 10⁻² S cm⁻¹ were obtained, with or without the use of supercritical CO₂. Uniformity of conductivity was determined via surface and bulk conductivity measurements, as well as by a new volume conductivity measurement that provides a measure of spatial (three-dimensional) distribution of the conducting component in the composite.The conductivity of composites prepared with or without the use of supercritical CO₂ conformed to the same percolation behavior with respect to the amount of PPy formed. The percolation threshold in all cases was as low as 4 wt.%. The mechanical strength of the composites was found to be about the same as that of the host PCPS, as was the thermal stability. Therefore, the conductive component did not appear to adversely affect these properties of the host. Finally, the temperature behavior of the conductivity could be correlated with Mott's variable-range hopping (VRH) model for three-dimensional electronic transport.     

Dielectric properties of polycrystalline Cu-Zn ferrites at microwave frequencies

The real dielectric constant ?′ and complex dielectric constant ?″ of Cu_1−xZn_xFe₂O₄ have been measured at room temperature in the high frequency range 1 MHz to 1.8 GHz. At low frequencies the dielectric loss is found to be constant up to 1.4 GHz and there is a sudden rise at 1.5 GHz. A qualitative explanation is given for the composition, frequency dependence of the dielectric constant and dielectric loss of Cu_1−xZn_x Fe₂O₄. These are correlated with the W-H plot which gives the information about change in the average crystal size and strain of the samples. The micro-morphological features of the samples were obtained by Scanning Electron Microscopy (SEM). The micrograph shows that the increase of the Zn content in Cu ferrite increases the grain size.