Polyaniline Blends Research Articles

Dendrites and pillars in spin cast blends of polyaniline or its oligomeric analogue

In the present work morphological structures were examined which are formed spontaneously during the spin-casting of polymer blends. Mixtures of polyaniline (PANI) (doped with camphorsulfonic acid, CSA) or its oligomeric counterpart (N,N′-diphenyl-p-phenylenediimine, DPI) and a conventional polymer (polystyrene, PS or poly(methyl methacrylate), PMMA) were studied. The samples were manufactured in controlled humidity conditions (relative humidity, RH = 10%, 60% or 95%). In case of PANI(CSA)/PS (or PMMA) blends, hierarchic structures arise. They are built of large (>10 μm) PS-rich (or PMMA-rich) dendrites and sub-micron PANI-rich pillars in the pores of PS (PMMA) host. In analogous PS/DPI films, DPI dendrites embedded in the PS film are observed. This microstructure formation route, based on solution blend processing, is an alternative to chemical synthesis of fibres and columns. Film structures were determined with microscopic (optical, Atomic Force Microscopy) and spectroscopic techniques (dynamic Secondary Ion Mass Spectroscopy and X-ray Photoelectron Spectroscopy). Structure formation models are presented. Diffusion-Limited Aggregation is postulated for solution droplets agglomerating as PS-rich fractals (with low attachment probability P) and for crystallizing DPI dendrites (with higher P value and hence larger and less compact fractals, as observed).

Effect of pressure on the structure and electrical conductivity of cardanol–furfural–polyaniline blends

AbstractPressure‐sensitive polymers that simultaneously present reasonable electrical conducting properties, useful thermosetting behavior, and softness are hard to develop. To combine these properties into a single material, a cardanol‐based phenolic resin was prepared and blended in situ with polyaniline (PAni). The final polymer blend was composed of a soft solid material that could not be dissolved in ordinary solvents. Samples were characterized through X‐ray scattering, Fourier transform infrared (FTIR) spectroscopy, and electrical conductivity and pressure sensitivity measurements. FTIR results indicate that the insertion of PAni into the blends did not change the chemical nature of the resin. According to wide‐angle X‐ray scattering results, PAni was dispersed homogeneously in the final polymer samples; this improved the sensitivity of the electrical conductivity to pressure variations, as confirmed through electromechanical tests. Pressure sensitivity and electromechanical analyses indicated that the produced blends could be used as pressure‐sensing materials. Among the tested materials, the blends containing 5 wt % PAni·H2SO4 presented the largest compression sensitivity values. Finally, it was shown for the first time through XRD analyses under pressure that PAni chains were considerably disturbed by compressive stresses. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Structural, Electrical, Mechanical, and Thermal Properties of Electrospun Poly(lactic acid)/Polyaniline Blend Fibers

AbstractConducting electrospun fiber mats based on PLA and PAni blends were obtained with average diameter values between 87 and 1 006 nm with PAni quantities from 0 to 5.6 wt.‐%. Structural characteristics of fiber mats were compared to cast films with the same amount of PAni and studied by SEM, SAXS, and AFM. Thermal properties of fiber mats and cast films were compared by DSC analyses. Mechanical properties of fiber mats were also evaluated. It was found that electrospinning process governs the crystal structure of the fibers and strongly affects fiber properties. New properties of PLA/PAni blends are reported due to the size fiber reduction.magnified image

Chitin–polyaniline blend as humidity sensor

A new processable and humidity sensitive chitin–polyaniline blend has been developed. Polyaniline is blended with chitin by solution blending method. The free standing films of blends are stable under ambient condition. The characterization of the blends is done by UV–vis absorption spectrum, FTIR, conductivity studies, thermogravimetric analysis and SEM. Conductivity of the self-doped blends increases from less than ≈10−7S/cm to 2.15×10−5S/cm, depending on the percentage of polyaniline in the blend. When these blends are doped with HCl conductivity rises to ≈9.68×10−2S/cm. Spectroscopic analysis shows interaction between chitin and polyaniline and the electronic states are similar to those of the emeraldine and protonically doped forms of polyaniline. These blend films are used for the construction of resistive based humidity sensor. A linear response of resistance with humidity is observed. It shows a small hysteresis and its response is stable even after 75 cycles of humidity exposure. Effect of electron beam irradiation on the humidity response has also been studied. Sensitivity is improved upon irradiation and doping. Further effect of thickness and electrode separation on humidity response is also studied. Response time for the humidity sensor is less than 30s. The constructed humidity sensor shows good results in the 10–100% humidity and in the temperature range of 20–60°C.

Enhanced EMI shielding efficiency using carbon, graphite, and polyaniline blends

AbstractConducting polymers have found significant applications in the past decade in industrial, scientific, and medical (ISM) fields. The characteristic features of conducting polymers like reversible proton doping, variable conductivity, facile synthesis, and low cost make them potential candidates in various microelectronic applications. Conventional microwave absorbing materials such as carbon and graphite in the powder form were blended with polyaniline as base at different proportions and microwave properties such as transmission, reflection, and shielding efficiency (SE) were evaluated from S parameter measurements using HP 8714ET network analyzer. The newly developed polyaniline blend exhibits high‐electromagnetic interference shielding efficiency when compared with previously developed materials and is a promising candidate for shielding applications. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 393–397, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24939

DC conductivity study of polyaniline and poly(acrylonitrile-butadiene-styrene) blends

In this study, conducting blends of poly(acrylonitrile-butadiene-styrene) and polyaniline doped with dodecylbenzene sulfonic acid were prepared by solution blending. In order to understand the electrical conduction mechanism of the samples, DC electrical conductivity measurements of the blends were carried out in the temperature range of 80–320 K. The experimental results fit well with Mott's model of three-dimensional variable range hopping conduction. The values of Mott's temperature, density of states at the Fermi energy, average hopping distance and barrier height for the composites were calculated and presented.

Conducting polystyrene/polyaniline blend through template-assisted emulsion polymerization

Electrically conducting polystyrene (PS)/polyaniline blends have been prepared through a one-step “anilinium-surfactant template”-assisted emulsion polymerization at room temperature. The self-assembled cylindrical An+PDPSA− micelle formed inside the PS matrix can act as a structure directing template cum dopant. Morphological observation under scanning electron microscopic studies revealed that during the progress of polymerization, the initially formed nanostructured conducting polyaniline was changed into cubic/hexagonal/lamellar particles and finally transformed into a percolated structure inside the PS matrix. Blend was further characterized by UV-Vis spectroscopy, FTIR spectroscopy, X-ray diffraction, electrical conductivity, thermal stability, dielectric property, rheological property, and electromagnetic shielding efficiency. The key finding of this work is that the conductive blend prepared through micelle-guided polymerization exhibited superior electrical conductivity (9.6 S/m) with low percolation threshold concentration (5 wt%), excellent thermal stability, electromagnetic interference (EMI) SE of 1–10 dB which makes it a promising candidate for EMI shielding and antistatic discharge matrix for the encapsulation of microelectronic devices.

Long-Term Stability of Humidity Sensor Using Polyaniline Blend Films Upon DC Operation

Resistive-type humidity sensors using polyaniline blend films were fabricated, and their long-term stability upon application of dc voltage was investigated. The use of blended films of electron-conducting polyaniline (PANI) and polystyrene was effective in depressing the sensor drift caused by polarization and/or electrolysis, which is a serious problem for polyelectrolyte sensors. However, another kind of drift caused by morphological change in the blend film was observed. To prevent this morphological change, cross-linked polystyrene with divinylbenzene (c-PSt) was used as a matrix polymer. The sensor using blended films of PANI and c-PSt exhibited excellent initial sensing characteristics and improved long-term stability.

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.

Synthesis and properties of polyaniline–cellulose acetate blends: The use of sugarcane bagasse waste and the effect of the substitution degree

Membranes of blends of polyaniline (PANi) and cellulose acetate (CA) produced from sugarcane bagasse with different degrees of substitution were produced and characterized using various techniques. Results showed that incorporation of PANi into the CA matrices leads to significant alterations of the blend morphologies, with phase separation, and that these differences are less significant for PANi/cellulose triacetate blends. The blends also showed a significant increase in electrical conductivity, with that of PANi/cellulose diacetate demonstrating an almost 200-fold increase.

Effect of composition on the dielectric relaxation of zeolite-conducting polyaniline blends

The complex permittivity of conducting polyaniline and zeolite-polyaniline blends was measured in the frequency range of 10−2–2×106 Hz from room temperature to liquid nitrogen temperature. A loss peak is detected for 25, 35, and 50 wt % zeolite blends. Its position in the frequency domain, activation energy, and intensity is a function of composition. The experimental results are interpreted through the competing multiple role of zeolite: as being less conducting than polyaniline, it impedes the electric charge flow by dividing large conducting polyaniline regions into smaller pieces, subsequently provides short-range pathways, and, moreover, enriches the blend in interfaces separating zeolite from polyaniline.

Development of conducting polyaniline/poly(lactic acid) nanofibers by electrospinning

AbstractUltrafine fibers consisting of blends of polyaniline doped with p‐toluene sulfonic acid and poly(L‐lactic acid) were prepared by electrospinning. The presence of polyaniline resulted in fibers with diameters as thin as 100–200 nm and a significant reduction of bead formation. These fibers were visually homogeneous, and this indicated good interactions between the components of the polyaniline/poly(L‐lactic acid) blend. The high interaction between the components and the rapid evaporation of the solvent during electrospinning resulted in nanofibers with a lower degree of crystallinity in comparison with cast films. The electrical conductivity of the electrospun fiber mats was lower than that of blend films produced by casting, probably because of the lower degree of crystallinity of the polyaniline dispersion and the high porosity of the nonwoven mat. This novel system opens up new and interesting opportunities for applications in biomedical devices, biodegradable materials, and sensors, among other things. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Hopping conduction on PAni/PSS blends

Conducting blends of polyaniline (PAni) and sulfonated polystyrene (PSS) were obtained by in situ polymerization. We prepared PAni/PSS blends with molar ratio of 1:2 and PSS sulfonated at the degrees of 13, 21 and 30 mol%. The blends were investigated by d.c. conductivity and scanning electron microscopy (SEM). Increasing sulfonation degree increases the conductivity and the miscibility of the blends was observed by SEM. The electrical conductivity of blends was evaluated from 100 to 300 K. We show that three-dimensional variable range hopping is observed. From the hopping parameter we obtained the mean hopping distance, the density of active centers and the energy associated with it. The hopping distance was compared to the mean distance of sulfonic groups of the PSS, indicating that interchain 3D variable range hopping is dominant at low temperatures.

Development of electromagnetic shielding materials from the conductive blends of polyaniline and polyaniline-clay nanocomposite-EVA: Preparation and properties

Electromagnetic interference shielding composite materials were developed from the conductive blends of nanostructured polyaniline (PANI) and polyaniline-clay nanocomposite (PANICN) with ethylene vinyl acetate (EVA) as host matrix. Electrically conducting nanostructured PANI and PANICNs were prepared using amphiphilic dopants, 3-pentadecyl phenol 4-sulphonic acid (3-PDPSA) derived from cashew nut shell liquid, a low cost renewable resource based product and dodecyl benzene sulfonic acid (DBSA). Effects of type and quantity of conductive fillers on the electrical conductivity, mechanical properties, thermal stability, morphology and electromagnetic shielding efficiency were investigated. The presence of exfoliated nanoclay and interaction between the conductive filler–host matrix in conductive films containing PANICNs manifested from the measurement on rheological property. Films with conductive filler (∼15% loading) showed a shielding effectiveness of ∼40–80 dB at 8 GHz which makes these conducting composites potential candidate for the encapsulation as EMI shielding materials for electronic devices.

Application of polyaniline/nylon composites coating for corrosion protection of steel

In this research, we investigated the corrosion inhibition properties of polished steel plates (low carbon) coated with a polyaniline (emeraldine base form) blend with nylon 66 (termed PANi/Ny) via cast method with formic acid as the solvent. Polyaniline (PANi) was prepared chemically from aqueous solution using aniline (0.2 M) as a monomer and ammonium persulfate (0.2 M) as an oxidant. The polymer powder produced was changed into emeraldine base (EB) form after treatment with dilute ammonia solution (0.5 M) in order to do further processing. The corrosion experiments were performed in the open circuit, exposing samples to different aggressive and corrosive conditions (e.g., NaCl, HCl). To produce a good comparison, the corrosion study was performed on both polymer-coated and bare-steel samples. Corrosion monitoring was performed by simple immersion tests and determination of the concentration of iron ions and metal weight loss in test solutions. It was found that PANi/Ny coatings can provide an anodic protection against corrosive environments in which the metals are exposed. The corrosion rate for the polymer coated steel was significantly lower than the bare steel (~10–15 times).

Electronic conduction mechanism in chitin–polyaniline blend

The electrical conductivity of chitin–polyaniline blend doped with HCl has been studied in the temperature range 323–373 K for various blend compositions. Conductivity of blends increases from less than ≈10 −7 S/cm to 2.15 × 10 −5 S/cm, depending on the percentage of polyaniline in the blend due to self-doping of LiCl. When these blends are doped with HCl conductivity raises to ≈9.68 × 10 −2 S/cm. Current–voltage data is analyzed using various models available. The results suggest Schottky–Richardson and one-dimensional variable range hopping mechanisms for undoped blend and one-dimensional variable range hopping mechanism in the case of doped blend.

New in situ Blends of Polyaniline and Cardanol Bio‐Resins

AbstractCardanol, a well known natural resource, was used to produce a polymer resin in the presence of formaldehyde, catalyzed by H2SO4. Before reticulation, PAni · H2SO4 was blended with the resin. The blended material was cast into poly(propylene) cups and kept inside a desiccator under vacuum until complete water evaporation. The final in situ polymer blend was solid and could not be dissolved in ordinary solvents, indicating that a reticulated material had been obtained. Samples prepared similarly were then characterized, showing that the produced blends can be used as pressure sensing materials.magnified image

Synthesis and Characterization of Porous Polyaniline Conductive Polymers

Polyaniline conductive polymers exhibit great potential for linear actuator applications. Many recent studies report methods to develop polyaniline-based materials with increased mechanical properties, electrical conductivity, and faster response time during actuation. In this study, porous blends of poly(methylmethacrylate) and polyaniline are processed using a two phase batch foaming setup. The effect of materials, processing, and system parameters on the physical properties of the resulting cellular structure are investigated. Hence, the effect of density and cell morphology on the electrical conductivity is elucidated.

An EPR investigation of conductive polyaniline–poly(methyl methacrylate‐co‐acrylic acid) blends

AbstractA conductive blend of polyaniline (PANI) with sodium form poly(methyl methacrylate‐co‐acrylic acid) copolymer (PMMAA) was prepared by in situ dispersion polymerization. The PANI‐PMMAA blends were characterized with UV–vis, FTIR, and electron paramagnetic resonance (EPR) spectra. The effects of PANI and temperature on the electronic properties of the PANI‐PMMAA blends were studied with EPR technique. The PANI and temperature affect the intermolecular interaction between PANI and PMMAA and then determines the EPR parameters (A/B ratio, g factor, T2, ΔHpp, Ns, and lineshape). POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

New polyaniline(PAni)-polyelectrolyte (PDDMAC) composites: Synthesis and applications

Conducting and electroactive polymer blends of polyaniline (PAni) with polyelectrolyte, poly(diallydimethylammoniumchloride) (PDDMAC) have been synthesized by an in situ polymerization method and the resulting composites have been characterized by FT-IR, UV–Vis, XRD, AFM and electrochemical techniques. The blends are conducting and electroactive with even lower loadings of PAni and can be cast as films. The conductivity of the cast films containing 0.04–1.5 wt% PAni ranged from 4.5 × 10 −6 to 42 × 10 −6 S/cm. Some of the composites are tested for their corrosion inhibition property for pure iron in 1 M HCl solutions and were found to be active inhibitors.