Polyaniline/thermoplastic polyurethane blends: Preparation and evaluation of electrical conductivity

Conducting polymer blends whose undiluted components have different properties are promising materials for specific applications and have attracted interest in recent years. The aim of this study was to obtain and evaluate the electrical conductivity of polyaniline doped with dodecylbenzenesulfonic acid (PAni.DBSA)/polyurethane thermoplastic (TPU) blends. The PAni.DBSA was synthesized from DBSA-aniline (DBSAn) salt through an emulsion polymerization in tetrahydrofurane (THF) or in the presence of polyurethane thermoplastic solution, resulting in pure PAni.DBSA or PAni.DBSA/TPU blends. Blends of PAni.DBSA/TPU were also prepared through casting, at room temperature, after dissolving both components in THF as a common solvent. The insulator-conductor transition was very sharp and the percolation threshold was lower than 2.7 wt% of PAni.DBSA. The electrical conductivity of PAni.DBSA/TPU blends, prepared by both methods, reached maximum values at a PAni.DBSA concentration of 40 wt%, close to the value observed for the undiluted conducting polymer. However, for a PAni.DBSA content lower than 30 wt%, the electrical conductivity was dependent on the blend preparation method. Blends were characterized by infrared spectroscopy, thermogravimetric analysis (TG) and optical microscopy. The electrical conducting characteristics of the PAni.DBSA/TPU blends prepared using different procedures indicate a high potential for their successful application in electrical processes.     

Effects of mixed conductivity of nanocomposite membranes MF-4SC/PANI

Changes in the conducting and hydrophilic properties of composites MF-4SC/polyaniline (PAni) under conditions of prolonged synthesis have been studied. A maximum of PAni content of about 0.20 by weight, which can be incorporated into the matrix of MF-4SC under these conditions of synthesis, is determined. Percolation behavior of electrical conductivity of the composites after drying was observed. The conductivity of PAni salt inside MF-4SC was estimated within the frames of the percolation model. Using the fibrous cluster model of the membrane and the conductivity data on individual PAni, theoretical assessment of the electrical conductivity of nanocomposite MF-4SC/PAni has been performed. Reasons for a significant reduction in the conductivity of PAni during its integration into the structure of the initial matrix were discussed. A scale of membrane conductivity, reflecting changes in the electrical conductivity of composites at various stages of synthesis, was drawn.     

Electrical conductivity of poly(vinylidene fluoride)/polyaniline blends under oscillatory and steady shear conditions

Blends of poly(vinylidene fluoride) (PVDF) and polyaniline (PAni) were prepared through melt blending in a batch mixer. The morphology, rheological behavior and electrical conductivity were investigated through transmission electron microscopy (TEM) and combined electro-rheological measurements. Through TEM analysis, it was possible to observe that all blends showed typical phase separation with the presence of conductive polymer aggregates. Deformations imposed during a strain sweep caused, not only disturbance of the linear viscoelastic behavior, but also changes in electrical conductivity. The oscillatory shear altered the morphology, breaking the PAni domains into smaller ones. This effect increases the distance between them and, consequently, resulted in a decrease of the electrical conductivity. The measurements under quiescent conditions and steady shear proved that the disturbance in morphology for PVDF/PAni system is non-recoverable. Through combined electrical and rheological measurements, it was possible to achieve good correlation between the electrical and flow behavior of PVDF/PAni blends.     

Characterization,morphology, thermal and mechanical properties of conductive polyaniline‐functionalized EPDM elastomers obtained by casting

Conductive elastomeric blends based on ethylene–propylene–5‐ethylidene–2‐norbornene terpolymer (EPDM) and polyaniline doped with 4‐dodecylbenzenesulfonic acid [PAni(DBSA)] were cast from organic solvents. Functionalization of the elastomer was promoted by grafting with maleic anhydride. Vulcanization conditions were optimized with an oscillating disk rheometer. The conductivity, morphology, thermal stability, compatibility, and mechanical behavior of the obtained mixtures were analyzed by in situ direct current conductivity measurements, atomic force microscopy, transmission electron microscopy, wide‐angle X‐ray scattering, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical thermal analysis, stress–strain and hysteresis tests. The vulcanization process was affected by temperature, the PAni content, and maleic anhydride. A reinforcement effect was promoted by the vulcanizing agent. The formation of links between the high‐molar‐mass phases and oligomers of PAni(DBSA) in the elastomeric matrix enhanced the thermal stability and ultimate properties of the blends. By the appropriate control of the polymer blends' composition, it was possible to produce elastomeric materials with conductivities in the range of 10^?5–10^?4 S · cm^?1 and excellent mechanical properties. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1767–1782, 2004     

DC conductivity and spectroscopic characterization of binary dopant (ZrO2/AgI)‐doped polyaniline

Binary dopant mixture of (ZrO₂/AgI) (v/v) is prepared in different ratios to enhance the conductivity of the synthesized PANI. DC conductivity of (ZrO₂/AgI) (v/v) doped PANI samples is measured in the temperature range (300‐400K). The calculated values of pre‐exponential factor (σ₀) indicates that conduction is taking place through hopping process due to localized states present near the Fermi level. Structural changes due to interaction of dopant species with PANI are studied through FT‐IR and Photoluminescence characterization. Photoluminescence (PL) spectra of the doped samples occurred in the form of peaks and the intensities of these peaks vary according to the concentration of dopant mixture. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2682–2687, 2007     

Structural and electrical properties of crystals of substituted polyaniline

The simultaneous polymerization and crystallization of aniline has been reported earlier. In this article, the X‐ray crystal structure analysis, SEM morphological analysis and electrical properties of such crystals of oligo‐polyanilines are being reported. The structural analysis shows a pseudo‐orthorhombic lattice. The SEM images reveal flaky and triangular growth habit with granular overgrowths on the surface. The bulk conductivities achieved vary from 10^?5 S/cm to 10^?7 S/cm as the oxidant concentration is reduced from 5 to 0.1%. The temperature dependence showed a transition point upto which there is a decrease in current and above which the current increases. The ESR studies reveal polarons involved in charge conduction and their concentration is proportional to the oxidant concentration. The X‐ray patterns, conductivities, and ESR results have been correlated with the degree of polymerization results obtained from GPC studies. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1127–1137, 2007     

Thermoelectric power and conductivity of different types of polypyrrole

We have measured the thermoelectric power and conductivity as a function of temperature of a wide range of polypyrrole samples, including a film of soluble polypyrrole synthesized chemically, and wrinkled films synthesized using indium–tin oxide electrodes; other samples investigated include high‐conductivity polypyrrole films synthesized at different temperatures and current densities, films grown on nonconducting substrates, and polypyrrole gas sensors. The thermoelectric powers are remarkably similar and metal‐like for the medium and high conductivity samples but show nonzero extrapolations to zero temperature for wrinkled samples. The temperature dependence of conductivity tends to be greater for samples of lower conductivity. In contrast to polyaniline and polyacetylene, a crossover to metallic sign for the temperature dependence of conductivity at higher temperatures is not observed in any of our samples; the fluctuation‐induced tunnelling and variable‐range hopping expressions account for nearly all our conductivity data except for low‐temperature anomalies. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 953–960, 1999     

Electrical conductivity and polarization processes in nanocomposites based on isotactic polypropylene and modified synthetic clay

The direct‐current and alternating‐current electrical behavior of nanocomposites, formed by isotactic polypropylene partially modified with maleic anhydride and filled with different amounts of modified synthetic clay, has been studied; moreover, the conduction mechanisms and the relaxation processes that take place in the materials have been investigated. The nanocomposites containing small clay contents exhibit direct‐current insulating properties comparable to or even higher than those observed in the polymeric matrix. However, as the synthetic clay content increases, the ionic contribution to conductivity becomes considerable. The nanocomposites also show a slightly higher permittivity and loss factor than the host material because of the appearance of a thermally activated relaxation process in the frequency range of 10^?2 to 10² Hz at the investigated temperatures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 705–713, 2007     

Thermal lensing in poly(vinyl alcohol)/polyaniline blends

Nonlinear optical properties of poly(vinyl alcohol) (PVA)/polyaniline (PAni) blends were measured with the single‐beam Z‐scan technique with Fourier analysis. The results obtained with continuous wave (cw) excitation indicated that the self‐phase modulation had a thermal origin. Besides the Z‐scan technique, we also employed the time‐resolved mode‐mismatched thermal lens (TL) technique to obtain the temperature coefficient of the optical path length, ds/dT, and the thermal diffusivity coefficient, D, for the specific concentrations used in our blends. ds/dT varied between ?0.8 and ?1.0 × 10^?4 K^?1, whereas the thermal diffusivity varied between 1.0 and 1.3 × 10^?3 cm²/s. The TL technique was further used to study the aging of the blends as they were heated to 90 °C. Unlike the electrical conductivity of PAni films, which presented a strong dependence on the doping level, the thermooptic properties presented only a slight variation with doping. This feature indicated that the PVA/glutaraldehyde network made the main contribution to the thermooptic properties (D and ds/dT) in the PAni blends. Similarly, dimethyl sulfoxide as a solvent determined the thermooptic properties of PAni solutions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1949–1956, 2002     

Secondary doping in poly(3,4‐ethylenedioxythiophene):Poly(4‐styrenesulfonate) thin films

The electrical and structural properties of poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) thin films deposited from aqueous dispersion using different concentrations of selected secondary dopants are studied in detail. An improvement of the electrical conductivity by three orders of magnitude is achieved for dimethyl sulfoxide, sorbitol, ethylene glycol, and N,N‐dimethylformamide, and the secondary dopant concentration dependence of the conductivity exhibits almost identical behavior for all investigated secondary dopants. Detailed analysis of the surface morphology and Raman spectra reveals no presence of the secondary dopant in fabricated films, and thus the dopants are truly causing the secondary doping effect. Although the ratio of benzenoid and quinoid vibrations in Raman spectra is unaffected by doping, the phase transition in PEDOT:PSS films owing to doping is confirmed. Further analysis of temperature‐dependent conductivity reveals 1D variable range hopping (VRH) charge transport for undoped PEDOT:PSS, whereas highly conductive doped PEDOT:PSS films exhibit 3D VRH charge transport. We demonstrate that the charge ‐ hopping dimensionality change should be a fundamental reason for the conductivity enhancement. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1139–1146     

Why does the electrical conductivity in PEDOT:PSS decrease with PSS content? A study combining thermoelectric measurements with impedance spectroscopy

We have investigated the electrical transport properties of poly(3,4‐ethylenedioxythiophen)/poly(4‐styrene‐sulfonate) (PEDOT:PSS) with PEDOT‐to‐PSS ratios from 1:1 to 1:30. By combining impedance spectroscopy with thermoelectric measurements, we are able to independently determine the variation of electrical conductivity and charge carrier density with PSS content. We find the charge carrier density to be independent of the PSS content. Using a generalized effective media theory, we show that the electrical conductivity in PEDOT:PSS can be understood as percolation between sites of highly conducting PEDOT:PSS complexes with a conductivity of 2.3 (Ωcm)^?1 in a matrix of excess PSS with a low conductivity of 10^?3 (Ω cm)^?1. In addition to the transport properties, the thermoelectric power factors and Seebeck coefficients have been determined. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Polymer electrolyte membranes based on p‐toluenesulfonic acid doped poly(1‐vinyl‐1,2,4‐triazole): Synthesis,thermal and proton conductivity properties

Throughout this work, the synthesis, thermal as well as proton conducting properties of acid doped heterocyclic polymer were studied under anhydrous conditions. In this context, poly(1‐vinyl‐1,2,4‐triazole), PVTri was produced by free radical polymerization of 1‐vinyl‐1,2,4‐triazole with a high yield. The structure of the homopolymer was proved by FTIR and solid state ¹³C CP‐MAS NMR spectroscopy. The polymer was doped with p‐toluenesulfonic acid at various molar ratios, x = 0.5, 1, 1.5, 2, with respect to polymer repeating unit. The proton transfer from p‐toluenesulfonic acid to the triazole rings was proved with FTIR spectroscopy. Thermogravimetry analysis showed that the samples are thermally stable up to ～250 °C. Differential scanning calorimetry results illustrated that the materials are homogeneous and the dopant strongly affects the glass transition temperature of the host polymer. Cyclic voltammetry results showed that the electrochemical stability domain extends over 3 V. The proton conductivity of these materials increased with dopant concentration and the temperature. Charge transport relaxation times were derived via complex electrical modulus formalism (M*). The temperature dependence of conductivity relaxation times showed that the proton conductivity occurs via structure diffusion. In the anhydrous state, the proton conductivity of PVTri1PTSA and PVTri2PTSA was measured as 8 × 10^?4 S/cm at 150 °C and 0.012 S/cm at 110 °C, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1016–1021, 2010     

Predicting the proton conductivity of perfluorosulfonic acid membrane via combining statistical thermodynamics and molecular dynamics simulation

The electrochemical properties of a perfluorosulfonic acid (PFSA) membrane are estimated using a combination of molecular dynamics simulation and statistical thermodynamic model. We obtain all parameters in an ionic conductivity model from an atomistic simulation and remove all adjusted model parameters. From a microscopic point of view, the hydrated PFSA membrane shows micro‐phase segregation which separated into hydrophilic and hydrophobic phases. Our present work originates with this phenomenon and we treat this phase segregation as if it is a continuous phase for each of which the proton (H⁺) is transported inside the PFSA membrane/solvent (water and alcohols) mixture. The chemical potential for a given system is estimated using a molecular simulation technique to predict the van der Waals interaction energy between the polymer and solvent. In addition, the self diffusion coefficients are calculated from the molecular dynamics simulation. We study various polymer/solvent compositions to understand the concentration dependence of self diffusion coefficient. Our self diffusion coefficients and also the predicted final ionic conductivity agree well with previously reported experimental data. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1455–1463, 2011     

Facile one‐pot synthesis and characterization of novel nanostructured organic dispersible polyaniline

Novel polyaniline (PANI) with nanotube, nanosheet, and nanofiber shapes was facilely synthesized by a self‐templating one‐pot process. Anilinium‐dodecylsulfate (DS) complex, obtained by mixing equivalent amounts of aniline and sodium dodecylsulfate (SDS), played a template‐like role in forming PANI nanostructures. It was found that the morphology and electrical conductivity of the PANI nanostructures changed with the amount of SDS and the reaction temperature. Nanotube‐shaped PANI synthesized at the temperature of anilinium‐DS complex formation in presence of SDS (concentration <0.12 M) showed high conductivity (12.9 S/cm). At higher temperature, the morphology changed to shape of a rose flower and electrical conductivity decreased to 3.95 S/cm. This suggested that both temperature and SDS concentration were key parameters for controlling the formation of the anilinium‐DS complex that acted as a template. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1024–1029, 2009     

An overview on the recent developments in polyaniline‐based supercapacitors

With the ever‐increasing depletion of nonrenewable fossil fuel reserve, greater attention has been directed towards renewable energy storage devices. One of the most important of such devices is the supercapacitor, which exhibits high specific capacitance. Polyaniline (PAni) is a versatile conducting polymer, which has demonstrated excellent electrochemical properties along with good stability and ease of synthesis. Therefore, PAni has been extensively used in the fabrication of supercapacitors. In the last few decades, researchers have studied the effect of morphology, developed during the synthesis of PAni, on its electrochemical properties. It is known that the electrical conductivity and the electrochemical properties of PAni get influenced by the level and type of dopant used, the method of synthesis adopted, and the surface area and porosity possessed. However, it has been realized that supercapacitors based on PAni suffer from short cycle life. This led to development of PAni composites with carbon‐based materials and transition metal oxides. In this review, focus has been laid on the achieved performance levels of the recently developed PAni‐based supercapacitors. In addition, an attempt has been made to study the fundamental aspects of the conductivity and the electrochemical properties of PAni and their effect on the supercapacitor performance. Moreover, several new interesting applications of PAni‐based supercapacitors have also been included in this review.     

Chemical modification of metallocene‐based polyolefinic elastomers by acrylic acid and its influence on physico‐mechanical properties: Effect of reaction parameters,crystallinity and pendant chain length

In this investigation, solution grafting of acrylic acid (AA) in presence of benzoyl peroxide (BPO) was carried out onto metallocene‐based “poly(ethylene‐octene) elastomers” (POE) as well as “poly(ethylene‐butene) elastomers” (PBE), to impart polarity on the non‐polar rubbery matrix and also to study the effects of crystallinity and pendant chain length on the “grafting percentage” and “percent gel yield” at optimized conditions for all the POE and PBE systems. Reaction parameters were optimized on the basis of the relative proportions of graft and gel formations obtained through %weight gain, Fourier Transform infrared spectroscopy and elemental analysis. The effect of grafting at its maximum level on various physico‐mechanical properties was also thoroughly investigated by using X‐ray diffraction (XRD), differential scanning calorimetry (DSC), mechanical, dynamic mechanical (DMTA), and thermogravimetric analysis (TGA) and the properties were correlated with the structure of the modified polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5529–5540, 2007     

Charge transfer in and conductivity of molecularly doped thiophene‐based copolymers

The electrical conductivity of organic semiconductors can be enhanced by orders of magnitude via doping with strong molecular electron acceptors or donors. Ground‐state integer charge transfer and charge‐transfer complex formation between organic semiconductors and molecular dopants have been suggested as the microscopic mechanisms causing these profound changes in electrical materials properties. Here, we study charge‐transfer interactions between the common molecular p‐dopant 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane and a systematic series of thiophene‐based copolymers by a combination of spectroscopic techniques and electrical measurements. Subtle variations in chemical structure are seen to significantly impact the nature of the charge‐transfer species and the efficiency of the doping process, underlining the need for a more detailed understanding of the microscopic doping mechanism in organic semiconductors to reliably guide targeted chemical design. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 58–63     

Poly(vinylidene fluoride)/polyaniline/carbon nanotubes nanocomposites: Influence of preparation method and oscillatory shear on morphology and electrical conductivity

Nanocomposites of poly(vinylidene fluoride) (PVDF)/polyaniline (PAni)/carbon nanotubes (CNT) were prepared through melt blending using three different methods. The PVDF, CNT and PAni were added into the internal mixer at the same time in method I. In method II, PAni was polymerized in the presence of different amounts of CNT, and then added to PVDF. In method III, PAni was obtained with half the CNT content, and then added to PVDF with the other half of CNT. The morphology, rheological behavior and electrical conductivity of these systems were investigated through transmission electron microscopy (TEM) and combined electro-rheological measurements. As expected, the preparation method strongly influenced the final morphology of the nanocomposites, as shown by TEM analysis. The deformation and destruction of PAni-PAni and CNT-CNT bonds during the oscillatory shear experiments strongly affected the electrical conductivity, probably in two different ways: it breaks the PAni into smaller domains and also disrupts the CNT percolated network. Concluding, a good correlation between the electrical, flow behavior and preparation method could be achieved for PVDF/PAni/CNT nanocomposites, mainly by means of the combined electro-rheological measurements.     

Synthesis of core‐shell silver–polyaniline nanocomposites by gamma radiolysis method

Core‐shell silver (Ag)–polyaniline (PAni) nanocomposites have been synthesized by the in‐situ gamma radiation‐induced chemical polymerization method. Aqueous solution of aniline, a free‐radical oxidant, and/or silver metal salt were irradiated by γ‐rays. Reduction of the silver salt in aqueous aniline leads to the formation of silver nanoparticles which in turn catalyze oxidation of aniline to polyaniline. The resultant Ag‐PAni nanocomposites were characterized by using different spectroscopy analyses like X‐ray photoelectron, UV–visible, and infrared spectroscopy. The optical absorption bands revealed that the bands at about 400 nm are due to the presence of nanosilver and the blue‐shifted peak at ～ 555 nm is due to the presence of metallic silver within the PAni matrix. X‐ray diffraction pattern clearly indicates the broad amorphous polymer and the sharp metal peaks. Scanning electron microscopy and transmission electron microscopy of the nanocomposite showed a uniform size distribution with spherical and granular morphology. Thermogravimetric analysis revealed that the composites have a higher degradation temperature than polyaniline alone. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5741–5747, 2007     

Influence of multiwall carbon nanotubes on morphology and electrical conductivity of PP/ABS blends

Polypropylene (PP) and acrylonitrile‐butadiene‐styrene (ABS) blends with multiwall carbon nanotubes (MWNT) were prepared by melt mixing. PP/ABS blends without MWNT revealed coarse co continuous structures on varying the ABS content from 40 to 70 wt %. Bulk electrical conductivity of the blends showed lower percolation threshold (0.4–0.5 wt %) in the 45/55 co continuous blends whereas the percolation threshold was between 2 and 3 wt % in matrix‐particle dispersed morphology of 80/20 blends. Interestingly, droplet size was observed to decrease with addition of MWNT above percolation threshold in 80/20 blends. Further, the bulk electrical conductivity was found to be dependent on the melt flow index of PP. The non‐polar or weakly polar nature of blends constituents resulted in the temperature independent dielectric constant, dielectric loss, and DC electrical conductivity. Rheological analysis revealed the formation of 3D network‐like structure in 80/20 PP/ABS blends at 3 wt % MWNT. An attempt was made to understand the relationship between rheology, morphology, and electrical conductivity of these blends. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2286–2295, 2008