Thermal effects on the percolation behavior of polyvinylidene fluoride/nickel composites

Percolation theory predicts the ideal percolation threshold (P_C) for insulator/conductor composites (ICC) to be at 0.16 of the conductor volume fraction in the composite. In this article, we have investigated the percolation behavior in polyvinylidene fluoride/nickel (Ni) composites by varying the Ni concentration. It is observed that the thermal effect/time of heat treatment play a crucial role in changing the value of P_C in a simple random continuum percolative ICC. The effect is attributed to decrease in: (i) intercluster distance, (ii) viscosity of the polymer, and (iii) wetting of the polymer to metal. The heat energy helps the polymer matrix to be melted as a result the metal particles/clusters come closure, that causes an increase in the cluster size of the metal particles. The overall effect is lowering of P_C mainly due to decrease in intercluster distance. A drastic enhancement in the dielectric permittivity with increase of metal content is explained using boundary layer capacitive effect arising due to Maxwell–Wagner–Sillars interfacial polarization of accumulated charges at the metal–polymer interfaces and blocking of charge carriers at the insulating boundary. The substantial enhancement of ac conductivity at the P_C is attributed to leakage of charge carriers across the insulating barrier. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Compatibilized polypropylene nanocomposites containing expanded graphite and graphene nanoplatelets

We present a non-covalent compatibilization approach to prepare polypropylene (PP) composites containing expanded graphite (EG) and graphene nanoplatelets (GNPs) by melt compounding. This method involves PP matrix functionalization with pyridine (Py) moieties, which are capable of engaging in π-π interactions with the surface of the EG and GNPs. The addition of 10 wt% of PP grafted with amino-pyridine (PP-g-Py) to neat PP facilitated the break-up of EG particles, by intercalating between their layers and facilitating their separation into smaller tactoids. GNPs were prepared starting from EG through a thermomechanical exfoliation method. Addition of GNPs to PP resulted in well-dispersed platelets having aspect ratios as high as 40, whereas in the presence of the PP-g-Py compatibilizer the matrix contained sub-micron scale platelets. The electrical percolation thresholds were in the vicinity of 6 and 10 vol% in the compatibilized PP-EG and PP-GNP composites, respectively, and the maximum value of the electrical conductivity achieved was 10⁻¹ S/m for the compatibilized GNP composites. Addition of GNPs resulted in increases in the flexural moduli by as much as 95% compared to the unfilled PP, whereas the impact strength remained unaffected up to 10 wt% GNP content.     

Dielectric Spectroscopy of Conducting Polyaniline Polymer

The dielectric spectroscopy of conducting polyaniline polymers (PANI) in the form of emeraldine base and emeraldine salt was carried out in the temperature range 30 to 80°C and in the frequency range 1 Hz to 1 MHz. The imaginary part of the impedance (Z″) versus frequency exhibits a relaxation peak, the positions of the peaks are shifted toward lower frequencies for concentrations below 0.1 M, whereas the peaks are shifted to higher frequencies for concentrations above 0.1 M. The PANI samples were protonated (doped) externally with various concentrations of aqueous sulfuric acid in the range of 0.05 to 0.2 molar. The thermal behavior of undoped and doped PANI samples has been analyzed, using thermal gravimetric analysis and differential scanning calorimetry techniques, and reveal that transition in the thermal behavior has been observed for concentrations above 0.1 molar. The a.c. conductivity measurements reveal that insulator to metal transition in the conductivity of these samples was observed for acid concentration greater than 0.1 molar. The a.c. conductivity for the protonated samples bellow 0.1 molar follows an Arrhenius behavior ?σ/?T < 0 with two activation energies, while ?σ/?T > 0 for acid concentration greater than 0.1 M.     

Polyaniline nanocomposites with negative permittivity

In this review, the fundamentals of negative permittivity are critically discussed. Current research on polyaniline and its nanocomposites with negative permittivity are presented in detail. The reasons why these unique materials show negative permittivity are analyzed. This knowledge will be useful for future metacomposite design and manufacturing. These polymeric materials with negative permittivity are envisioned to create next‐generation left‐hand media for cloaking, subwavelength imaging, stealth, and invisibility applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2238–2244, 2013     

Polyaniline salt containing dual dopants,pyrelenediimide tetracarboxylic acid,and sulfuric acid: Fluorescence and supercapacitor

Storage of energy is considered as the most germane technologies to address the future sustainability. In this study, aniline was chemically oxidized with a controlled concentration of pyrelenediimide tetracarboxylic acid (PDITCA) by ammonium persulfate to polyaniline salt (PANI‐H₂SO₄‐PDITCA), with nanorods morphologies, having a sensibly decent conductivity of 0.8 S cm^?1, wherein H₂SO₄ was generated from ammonium persulfate during polymerization. PANI‐H₂SO₄‐PDITCA salt showed bathochromic fluorescence shift (595 nm) compared to PDITCA (546 nm). The Brunauer–Emmett–Teller surface area of the PANI‐H₂SO₄‐PDITCA‐25 and PANI‐H₂SO₄‐PDITCA‐50 were 18.3 and 21.4 m² g^?1, respectively. Furthermore, its energy storage efficiency was evaluated by supercapacitor cell configuration. The composite PANI‐H₂SO₄‐PDITCA‐50 showed capacitance 460 F g^?1 at 0.3 A g^?1 and large cycle life 85,000 cycles with less retention of 77% to its original capacitance (200 F g^?1) even at a better discharge rate of 3.3 A g^?1. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45456.     

Polyaniline self‐assembled with DTPA: Facilely tuned morphology and properties

The effects of pH profile and “soft template” during aniline chemical oxidative polymerization (COP) were investigated and evaluated simultaneously with diethylene triamine pentaacetic acid (DTPA) as a structural directing agent. Formation of PANI nanotubes and nanoparticles, smooth microspheres, and urchin‐like microspheres were illustrated by evaluating the pH profile during aniline COP while considering the “soft template” effects of DTPA. PANI nanosheets with two semicurled edges were found in the system producing nanotubes, which provides an evidence for the “curling mechanism” of PANI nanotube formation. With different pH profiles, chemical structures and aggregation structures of the as‐synthesized PANI micro/nanostructures are similar, whereas their conductivity, wettability, Cr (VI) adsorption, and electrochemical behaviors are distinct. The present study indicates that if properly conducted, pH profile adjustment is more effective than “soft template” to control the morphology and to optimize the performance of PANI micro/nanostructures. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42403.     

Impact damage sensing of multiscale composites through epoxy matrix containing carbon nanotubes

Carbon nanotubes are used to provide increased electrical conductivity for polymer matrix materials, thus offering a method to monitor the structure's health. This work investigates the effect of impact damage on the electrical properties of multiscale composite samples, prepared with woven fiberglass reinforcement and epoxy resin modified with as‐received multi‐walled carbon nanotubes (MWCNTs). Moreover, this study addresses potential bias from manufacturing, and investigates the effectiveness of resistance measurements using two‐ and four‐point probe methods. Transmission electron microscopy and static tensile tests results were used to evaluate, respectively, the dispersion of MWCNTs in the epoxy resin and the influence of the incorporation of these nanoparticles on the static tensile properties of the matrix, and interpret results from the resistance measurements on impacted specimens. In this study, the four‐point probe method is shown to be much more repeatable and reliable than the two‐point probe method. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polyaniline nanofibers for In situ MAO‐catalyzed polymerization of ethylene

In this work electro‐conductive polyaniline nanofibers (PAni‐nanofibers) were prepared via interfacial methodology. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations revealed that the synthesized PAni‐nanofibers present high aspect ratio with an average diameter of 80 nm, while they exhibit high conductivity (DC conductivity values: 4.19 ± 0.21 S cm^?1). After specific treatment to remove moisture and remaining trapped HCl from PAni‐nanofibers, it was possible to prepare promising polyethylene (PE)/PAni composites by in situ polymerization of ethylene using bis(cyclopentadienyl) zirconium(IV) dichloride (Cp₂ZrCl₂) and methylaluminoxane (MAO) as catalytic system. More precisely, various contents of PAni‐nanofibers (from 0.2 to 7 wt %) were successfully incorporated in the in situ produced PE/PAni nanocomposites. PAni‐nanofibers were found to affect significantly the crystallization of the polyolefinic matrix while preserving its thermal stability. Preliminary measurements of electric properties showed PAni‐nanofibres are able to bring electro‐conductive properties to the in situ polymerized PE/PAni composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41197.     

Polyaniline/poly(ethylene terephthalate) conducting composite fabric with improved fastness to washing

In this article, we report a novel method for the design and development of a polyaniline (PANI)/poly(ethylene terephthalate) (PET) conducting composite fabric based on in situ polymerization. With the aim of improving fabric–PANI adhesion and good fastness to washing, we took some special steps: the alkali reduction pretreatment of the PET fabric before the polymerization of aniline onto the fabric, the introduction of squeezing the laboratory padder on the fabric to push the reagent into the inner part of the fabric, and short immersion time of the aniline‐absorbed fabric in oxidant solution. Factors affecting the conductivity and fastness to washing, including the alkali reduction percentage, the wet pickup of the reagent‐absorbed fabric, the immersion time in oxidant solution, and the reaction time, are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5775–5780, 2006     

Molecular composites created by the solution blending of polyaniline and sulfonated poly(ether sulfone)

New conducting thermally stable blends of polyaniline (PANi) with sulfonated poly(ether sulfone) as a matrix were prepared by a solution‐blending method. Camphorsulfonic acid (CSA) was used as a protonic agent for PANi. A sulfonyl group was introduced into the poly(ether sulfone) to enhance the coulomb interaction among the blends. The influence of the sulfonated group in poly(ether sulfone) was monitored with electrical property measurements. Ultraviolet–visible spectra of the blend compositions showed a well‐developed polaron band. The compatibility of the blends, that is, hydrogen bonding and dispersion at the molecular level, was ascertained with X‐ray diffraction and Fourier transform infrared (FTIR) spectroscopy; these supported intermolecular interaction. A smooth and uniform morphology was observed in the blends. The electrical conductivity of the blends increased up to 14 S/cm with the protonation of the PANi complex with CSA, and the percolation threshold was found to be 2 wt % PANi. These new blends showed increases in conductivity and compatibility over other PANi–poly(ether sulfone) blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and electrochemical properties of hollow polyaniline microspheres by a sulfonated polystyrene template

Hollow polyaniline microspheres (HMsPANI) for supercapacitors were prepared successfully with sulfonated polystyrene microspheres as the template. The prepared electrode materials of HMsPANI consisted of nanoparticles and, thus, had a hierarchical structure. The electrochemical behaviors of the materials were investigated with cyclic voltammetry and galvanostatic charge–discharge tests. A maximum specific capacitance of 421 F/g was achieved in a 1M H₂SO₄ solution, with the potential ranging from ?0.2 to 0.8 V (vs a saturated calomel electrode), in a three‐electrode glass cell at room temperature for the HMsPANI electrode. This suggested its potential application in electrochemical capacitors. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polyaniline grafted chitosan/GO-CNT/Fe3O4 nanocomposite as a superior electrode material for supercapacitor application

Developing appropriate stable electroactive electrode materials for supercapacitor application is the challenging issue, which attracts enormous attention in recent decades. In this regard, Fe₃O₄ nanoparticles are firstly synthesized on chitosan/graphene oxide-multiwall carbon nanotubes (CS/GM/Fe₃O₄). Then, polyaniline (PANI) is grafted on it via in situ chemical polymerization and named as CS/GM/Fe₃O₄/PANI. The as-prepared nanocomposites are characterized by Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy. The capacitive properties of the electrodes are investigated in a three electrode configuration in 0.5 M Na₂SO₄ electrolyte by various electrochemical techniques. The specific capacitance of CS/GM/Fe₃O₄/PANI electrode is 1513.4 Fg⁻¹ at 4 Ag⁻¹ which is 1.9 times higher than that of CS/GM/Fe₃O₄ (800 Fg⁻¹). Meanwhile, the electrodes exhibit appropriate cycle life along with 99.8% and 93.95% specific capacitance at 100 Ag⁻¹ for chitosan/GO-CNT/Fe₃O₄ and polyaniline grafted chitosan/GO-CNT/Fe₃O₄, respectively.     

Polymerization at the gas/solution interface: Preparation of polymer microstructures with gas bubbles as templates

We report on the chemical polymerization of 2‐methoxyaniline at the interface between an aqueous solution and air. The polymer is formed in the interfacial region, whereas the soluble trimer is yielded in the bulk of the polymerization solution. The preferential polymerization of 2‐methoxyaniline is discussed in terms of monomer and oligomer accumulation at the interface, which influences the reactivity of these species and allows further polymerization. The phenomenon of polymer growth is employed to selectively deposit polymeric material onto glass slides decorated with gas microbubbles. Because of preferential polymerization at the bubble/solution interface, hemispherical features are produced on the surface of glass. When some polymeric material is mechanically removed, microrings or microholes are obtained. The anomalous polymerization of 2‐methoxyaniline is compared to that of 2‐methylaniline. This monomer polymerizes uniformly within the entire volume of the reaction mixture; thus, no preferential polymer formation at the gas/solution interface is observed. As a result, deposition on microbubble‐decorated glass slides produces polymeric films containing a number of microholes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Application of polypyrrole to flexible substrates

Conducting polymers such as polypyrrole may be useful in smart packaging products, provided application methods can be developed that circumvent the insolubility and infusibility of these materials. Experiments were conducted in five research areas relevant to the application of polypyrrole to nonrigid substrates. The studies reveal that application of polypyrrole from the liquid phase, either by deposition from depleted bulk solution or inkjet printing dispersions, is unlikely to give films as regular as those produced by vapor phase polymerization. Using the latter approach, two potential methods of applying patterned polypyrrole films to nonrigid substrates were developed. The first used hypochlorite to pattern a continuous film of polypyrrole, previously applied by vapor phase polymerization. The second used inkjet printing to apply an oxidant solution, whose pH had been raised with a volatile base, to nonrigid substrates. The higher pH reduced corrosion of the print head, increasing the lifetime of printers exposed to oxidative compounds. The base was subsequently evaporated by heating, and the dried oxidant used as a template for vapor phase polymerization of polypyrrole. This method gave smooth, shiny and adherent polypyrrole films on papers and polyester transparency, with high resolution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3938–3947, 2007     

Synthesis and characterization of novel polythiophenes containing poly(ethylene oxide) side chains

Thiophene copolymers and their derivatives with poly(ethylene oxide) side chains were synthesized. The starting monomers were 3‐hexylthiophene and 2‐(3‐thienyl) ethanol with poly(ethylene oxide) grafted to the side chains. New functionalized polythiophenes were prepared by both chemical oxidation with FeCl₃ and electropolymerization. The conjugating polymers were characterized. The structures of the polythiophene derivatives agreed with the design. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1803–1808, 2006     

Development of electromagnetic interference shielding materials from the composite of nanostructured polyaniline‐polyhydroxy iron‐clay and polycarbonate

In the present study, we demonstrate the development of novel electromagnetic interference shielding material from the composite of nanostructured polyaniline‐polyhydroxy iron‐clay and polycarbonate through solution blending process. Onset of percolation threshold has been manifested from the morphological studies in combination with electrical conductivity measurements. Temperature‐dependent electrical conduction mechanism was studied by applying Mott theory and was found to follow 3D variable range hopping (VRH) model. The presence of interaction between the host matrix and the nanofiller was studied by rheological property measurement in combination with Fourier transform infrared spectroscopy. Films were further characterized for electromagnetic interference (EMI) shielding efficiency and thermomechanical properties. Results suggest that these transparent composite films can be used for the fabrication of EMI shielding/electrostatic dissipation material for the encapsulation of electronic devices and as electrostatic material for high technological applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Soluble and conductive polypyrrole copolymers containing silicone tegomers

Soluble and processable conductive copolymers of silicone tegomers and pyrrole were developed. This was easily accomplished by the oxidative polymerization of pyrrole monomer by Ce(IV) salt in the presence of silicone tegomers with hydroxyl chain ends. The resulting copolymers were soluble in dimethylformamide. The products were characterized by Fourier transform infrared, ¹H‐NMR, and four‐point probe conductivity, and their surface properties were investigated with contact‐angle measurements. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2896–2901, 2003     

Thermally stable conducting composites based on a carbon black‐filled polyoxadiazole matrix

New thermally stable conducting materials can be obtained by dispersing conducting carbon black into poly(4,4′‐diphenylether‐1,3,4‐oxadiazole) (POD–DPE) solution in NMP. The blend preparation process resulted in quite good dispersed composite and a relatively low percolation threshold (around 5 wt % of CB). The effect of the compressive stress on the resistivity of composite has been evaluated. The resistivity decreases continuously as the applied pressure is increased. In addition to the electrical conductivity, the presence of carbon black resulted in higher thermally stable materials. The thermal stability, electrical conductivity, and pressure‐sensible characteristics make this conducting material a good candidate for application in manufacture of pressure sensors for high temperature ambient. This material shows a typical semiconductor behavior, characterized by an increase of conductivity with the temperature. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1631–1637, 2004     

Polyaniline/silver/cerium nitrate ternary composite: Synthesis,characterization and enhanced electrochemical properties

Polyaniline/Ag/Ce (NO₃)₃ ternary composites were prepared by in situ polymerization in a poly (2‐arcylamido‐2‐methylpropane sulfonic acid) aqueous solution. Fourier transform infrared spectroscopy and Ultraviolet‐visible spectroscopy analyses indicated that Ce ions had a conjugated interaction with N, O of polyaniline (PANI), and poly (2‐arcylamido‐2‐methylpropane sulfonic acid). By comparison with PANI and PANI binary composite, this ternary composite had a better thermal stability, a high conductivity (3.49 S/cm), a large capacitance, and a high electrochemical activity. Especially, the corrosion potential of this ternary composite can reach ?418 mV and the inhibition efficiency can be increased by 68.08%. This ternary porous composite has promising applications in capacitor, conductive materials, anticorrosion coating, and other related fields. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42785.     

Polyaniline salts as polymer‐based solid acid catalyst for low molecular weight poly(lactic acid)

Polymer‐based solid acid catalyst, polyaniline (PANI) salt, is used for the first time to synthesize polymer. In continuation of our work to synthesize organic chemicals using PANI‐based solid acid catalyst, in this work, polylactic acid is synthesized by the condensation polymerization of lactic acid using PANI salts. PANI salts are characterized by FTIR, FE‐SEM, and TGA analyses. Polymerization of lactic acid in xylene solvent at 140°C for 24 h with the use of very low amount of PANI catalysts gave polylactic acid (PLLA) in the order: PANI‐MSA (46%) > PANI‐TFA (33%) > PANI‐Bi(OTf)₃ (27%) > PANI‐Cu(OTf)₂ (20%) > PANI‐Yb(OTf)₃ (15%). Molecular weights of PLLA synthesized using PANI‐MSA and PANI‐TFA are found to be 4385 and 4830, respectively. This methodology gives highly crystalline polymer with mushroom cap‐like morphology. Advantage of this methodology is the use of easily synthesizable, recyclable, easily handlable, cheaper, and eco‐friendly nature of the catalyst. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41147.