Preparation of polyaniline/phosphorylated poly(vinyl alcohol) nanoparticles and their aqueous redispersion stability

A novel approach for the preparation of the colloidal conducting polyaniline (PANI) nanoparticles was developed. The polyaniline/partially phosphorylated poly(vinyl alcohol)(PANI/P‐PVA) nanoparticles were prepared by the chemical oxidative dispersion polymerization of aniline monomer in 1.0 M HCl aqueous media with the partially phosphorylated poly(vinyl alcohol) (P‐PVA) as the stabilizer and codopant. The PANI/P‐PVA nanoparticles were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), electrical conductivity measurement, and redispersion stability testing. All the results were compared with the properties of the conventional polyaniline in the emeraldine salt form (PANI ES). It was found that the P‐PVA/aniline feeding ratio obviously affected the morphology, redispersion stability and electrical conductivity of the PANI/P‐PVA nanoparticles. When the P‐PVA/aniline feeding ratio ranged from 50 to 60 wt %, the PANI/P‐PVA nanoparticles showed spherical shape with good uniformity, significant redispersion stability in aqueous media, and good electrical conductivity up to 7 S/cm. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Molecular composites obtained by polyaniline synthesis in the presence of p‐octasulfonated calixarene macrocycle

Polyaniline (PANI) molecular composites were synthesized by chemical oxidative polymerization of the aniline and aniline dimer, N‐phenyl‐1,4‐phenylendiamine, in the presence of a macrocycle, calix[8]arene p‐octasulfonic acid (C8S), using ammonium peroxidisulfate as oxidant. The macrocycle has acted both as acid dopant and surfactant to obtain processable PANI‐ES. The PANI/calix[8]arene p‐octasulfonic acid composite was also obtained by a simple doping of PANI emeraldine base form with calix[8]arene sulfonic acid. The structure of materials was confirmed by Fourier transform infrared, UV–vis and nuclear magnetic resonance spectroscopy. All synthesized composite materials are amorphous and soluble in chloroform, dimethylsulfoxide, NMP, showing excellent solution‐processing properties combined with electrical conductivity. Cyclic voltammetry evidenced a good electroactivity for the composite films. Dielectric properties (dielectric constant and dielectric losses) were determined and are comparable with those of other PANI/ionic acid polymer composites. Preliminary studies have evidenced a high dielectric constant (10⁴ at 100 Hz) and electrical conductivity of 6 × 10^?3 S/cm for PANI composites. From sulfur elemental analysis of the PANI/calixarene, it results that the content in macrocycle is ～30% (weight). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Comparison between different conditions of the chemical polymerization of polyaniline on top of PET films

Composites produced during the in situ chemical polymerization of aniline on top of a poly(ethylene terephthalate) (PET) film, in different conditions, were studied by open‐circuit potential (Voc), ultraviolet‐visible, and infrared spectroscopy, electrical conductivity measurements, scanning electron microscopy, and atomic force microscopy. The polymerization monitoring by Voc showed a maximum associated with the intermediate pernigraniline oxidation state and a final formation of polyaniline (PANI) in the doped emeraldine salt (ES) form. Furthermore, high electrical conductivity values were obtained for the PANI–ES coating prepared under selected conditions. A globular formation was observed for the doped PANI–ES coating with globules of sizes of the same order and same shape of the PET, demonstrating the influence of the substrate on the coating morphology. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1220–1229, 2001     

Fabrication and properties of solution‐cast polyaniline/carboxymethylchitin blend films

Blend films consisting of polyaniline in emeraldine base form (PANI EB) dispersed in partially cross‐linked carboxymethylchitin (CM‐chitin) were prepared by solution casting, and characterized for their physical, thermal, and electrical properties. Homogeneous and mechanically robust blend films were obtained having PANI EB contents up to 50 wt % in the CM‐chitin matrix. FTIR spectra confirm intimate mixing of the two blend components. The thermal stability of the blend films increased with increase of PANI EB content, suggesting the formation of an intermolecular interaction, such as hydrogen bonding, between PANI EB and CM‐chitin chains. The addition of PANI EB into the pure CM‐chitin film resulted in a decrease in electrical conductivity of the films owing to disruption of ionic conduction of the CM‐chitin structure. After doping the blend films by immersion in HCl solution, the electrical conductivity of the HCl‐doped films increased with increase of the PANI EB content to a maximum value of the order of 10^?3 S/cm at 50 wt % PANI EB content. The electrical conductivity of the blend films was also dependent on the HCl concentration as well as on the type of acid dopant. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and properties of polyaniline electrospun fiber web

The objective of this study is to fabricate the highly electrical conducting polymer fibers applicable to many conducting materials. Therefore, we tried to prepare polyaniline (PANI) thin fiber web by an electrospinning process by the following steps. First, PANI emeraldine base (EB) was prepared by oxidative polymerization. Second, the PANI EB was doped with 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPSA), and subsequently that was dissolved in trifluoroacetic acid (TFA). Third, the PANI‐AMPSA solution was electrospun by an electrospinning process. Consequently, the PANI doped with AMPSA was successfully electrospun into thin fiber form, and the electrical conductivity was superior. Also, the electrical conductivity of the PANI‐AMPSA electrospun was increased by a simple redoping process with AMPSA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of hollow polyaniline microtubes and microbelts with nanostructured walls in sodium dodecyl sulfate micellar solutions

Doped polyaniline in its emeraldine salt form (PANI‐ES) were successfully prepared by in situ chemical oxidative polymerization using various concentrations of sodium dodecyl sulfate (SDS) micellar solutions. Structural analysis using field‐emission scanning electron microscopy and high‐resolution transmission electron microscopy showed that the morphologies of fabricated PANI‐ES contain hollow tube‐like and belt‐like structures with thickness in the range of 100–200 nm, diameters in the range of 1–5 μm, and lengths up to several tens and hundreds of micrometers. The changes of morphology from particle‐like into microtube‐like or microbelt‐like structure with nanostructured walls are strongly dependent on the concentration of SDS. The conductivities of fabricated PANI‐ES with 0.1 M SDS content at room temperature are 80% higher than those of PANI‐ES without SDS, perhaps because SDS may serve as a dopant or the formation of one‐dimensional structure to improve the conductivity of PANI‐ES. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Dependence of the electrical conductivity and elastomeric properties on sample preparation of blends of polyaniline and natural rubber

Blend films (free‐standing) containing 20% in volume of polyaniline (PANI) in 80% of natural rubber (NR) were fabricated by casting in three different ways: (1) adding PANI‐EB (emeraldine base) dissolved in N‐methyl‐2‐pyrrolidone (NMP) to the latex (NRL), (2) adding PANI‐EB dissolved in m‐cresol to NR dissolved in xylol (NRD), (3) overlaying the surface of a pure NR cast film with a PANI layer grown by in situ polymerization (NRO). All the films were immersed into HCl solution to achieve the primary doping (protonation) of PANI before the characterization. The main goal here was to investigate the elastomeric and electrical conductivity properties for each blend, which may be applied as pressure and deformation sensors in the future. The characterization was carried out by optical microscopy, dc conductivity, vibrational spectroscopy (infrared absorption and Raman scattering), thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and tensile stress–strain curves. The results suggest that the NRL blend is the most suitable in terms of mechanical and electrical properties required for applications in pressure and deformation sensors: a gain of conductivity without losing the elastomeric property of the rubber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1498–1503, 2005     

Facile in-situ preparation of polyaniline/graphene nanocomposites using methanesulfonic acid

Polyaniline (PANI)/graphene composites were prepared by the in-situ polymerization of aniline in a 1 M aqueous solution of methanesulfonic acid (MSA) containing graphene, which was prepared separately from graphite powders by simple sonication in MSA. Graphite powders spontaneously exfoliated to form graphene (GPM), which was then quenched with excess water, filtered, and dried to produce powders. The dried graphene powders produced were re-dispersed well in a 1 M MSA aqueous solution, in which the in-situ polymerization of aniline was performed. The resulting PANI/GPM composite had a conducting emeraldine salt (ES) form, and showed good electrical and thermal properties, compared to pure PANI prepared using a 1 M HCl solution. The PANI/GPM composite could be dissolved in a MSA solution and spin-coated in a conducting ES form of PANI. In contrast, the ES form produced from a HCl solution was insoluble in organic solvents and needed to be reduced to convert it to the emeraldine base form to produce a PANI solution. Therefore, the in-situ preparation of PANI/graphene composites using MSA provides a facile means of improving the thermal and electrical properties of PANI and its processability.     

Potassium iodate–initiated polymerization of aniline

Potassium iodate–initiated polymerization of aniline was carried out in an acidified aqueous medium in the presence and in the absence of sodium thiosulfate salt. The nature of the polyaniline (PANI) produced depended on the aniline/potassium iodate (A/PI) mole ratio. Green emeraldine salt (ES) and blue pernigraniline salt (PS) were produced at A/PI mole ratios greater than 2 and less than 2, respectively. The sodium thiosulfate salt played a significant role in the purification and properties of PANI. The optimum aniline‐to‐oxidant mole ratio was found to be 2 : 1. Spectral, thermal, and electrical characteristics and viscosity of the materials were studied and compared with the results. A reaction scheme has been proposed to elucidate the role of iodine(V). Sodium thiosulfate makes it easier for iodine to be separated from a system and increases the conductivity of the products. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1626–1631, 2007     

Photo‐induced protonation and conductivity of polyaniline/poly(ethylene glycol) and polyaniline/[poly(ethylene glycol)‐grafted polyaniline] composites

Composites of polyaniline in its emeraldine base form (PANI‐EB) and photo‐acid generators (PAG) show an increase in conductivity upon photo‐irradiation due to the protonation of PANI‐EB. Such materials may be utilized to fabricate conducting patterns by photo‐irradiation. However, the conductivity obtained by direct irradiation of PANI‐EB/PAG composites was normally quite low (<10^?3 S/cm) due to aggregation of highly loaded PAG. In this work, poly(ethylene glycol) (PEG), which is a proton transfer polymer, was added to PANI‐EB/PAG. Results showed that addition of low M_w (550) PEG significantly enhance the photo‐induced conductivity. Conductivities as high as 10^?1–10⁰ S/cm were observed after photo‐irradiation. This conductivity is comparable to that of PANI‐salt synthesized by oxidizing aniline in the presence of an acid. High M_w (8000) PEG is much less effective than PEG 550, which is attributed to its lower compatibility with PANI. PEG‐grafted PANI (N‐PEG‐PANI) was also studied as an additive. Composites of PANI‐EB and N‐PEG‐PANI showed conductivity as high as 10² S/cm after treatment with HCl vapor. The photo‐induced conductivity of the N‐PEG‐PANI/PANI‐EB/PAG composite reached 10^?2–10^?1 S/cm. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Self‐doping of polyaniline prepared with the FeCl3/H2O2 system and the origin of the Raman band of emeraldine salt at around 1375 cm−1

Stepwise addition of H₂O₂ in small portions into the polymerization mixture reduces the number of defects in polyaniline (PANI) prepared with the Fe³⁺/H₂O₂ system, although it does not eliminate them completely. PANIs slightly self‐doped with phenolic groups are thus obtained, which show conductivity from 2.65 to 0.38 S cm^?1 as the total H₂O₂/aniline mole ratio is increased from 0.125 to 1.25. The conductivity shows a good correlation with the A_B/A₉₀₀ UV?visible absorbance ratio of the PANI emeraldine salt form (PANI ES), much better than with the A_B/A_Q ratio of the corresponding emeraldine base form. This corresponds well with the assignment of the band at 900 nm to polaronic transitions. Partial self‐doping of PANIs with weakly acidic phenolic groups allowed evidence to be obtained for the assignment of Raman bands at 1370 cm^?1 and 734 cm^?1 (for λ_exc = 780 nm) to vibrational modes of highly localized polarons. The presence of the band at 880 cm^?1 in the IR spectra of these PANI ES samples that are totally free of sulfate ions proves that this band is associated with a vibrational mode of PANI ES and need not be assigned to a mode of HSO₄^? ions, as has been suggested by some authors. © 2015 Society of Chemical Industry     

DGEBA‐grafted polyaniline: Synthesis,characterization and thermal properties

The utilization of conducting emeraldine salt (PANI‐ES) and intrinsic leucoemeraldine polyaniline (PANI‐LEB) in the synthesis of DGEBA‐grafted PANI via anionic copolymerization is described. The structures of copolymers obtained were characterized by FTIR, ¹³C and ¹H NMR. The extent of grafting was verified by THF Soxhlet (solvent extraction). The thermal properties of these new copolymers were described and their conductivities were reported. Results obtained indicated that the graft copolymer exhibited higher electrical and thermal conductivities than that of the blend counterpart. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

MnO2/Cr2O3/PANI nanocomposites prepared by in situ oxidation polymerization method: Optical and electrical behaviors

Metal oxide–polyaniline (PANI) nanocomposite with spherical morphologies were prepared in a one-pot oxidation–reduction method via various salts as reactive oxidants. Aniline monomers polymerize as a shell on the surface of one-pot prepared metal oxides, when the aqueous solutions of aniline, a free-radical oxidant, and/or a metallic salt were exposed together. The particle size and morphology of as-prepared narrowly dispersed PANI nanocomposites were revealed by field emission scanning electron microscope images. Fourier transform infrared spectra of nanocomposites indicate that the PANI exists in the emeraldine form. The ultraviolet–visible analysis not only shows PANI is in the emeraldine form, but also indicates modified optical properties of PANI in the composite form. The hypsochromic shift of the n–π* and polaron transitions of PANI reveals the incorporation of PANI by metal oxides. The direct current (dc) electrical conductivity (σ) of as-prepared nanocomposites was measured by a four-probe method in the room temperature. Compared to PANI nanoparticles, the electrical conductivity of the composites increased with the presence of metal oxides in the nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47219.     

Electroconductive polyblend fibers of polyamide‐6/polypropylene/polyaniline: Electrical,morphological, and mechanical characteristics

Melt spun drawn fibers were prepared using a ternary blend of PP/PA6/PANI‐complex (polypropylene/polyamide‐6/polyaniline‐complex). Their electrical and mechanical properties were compared to those of binary blend fibers of PP/PANI‐complex. The results of the morphological studies on 55:25:20 PP/PA6/PANI‐complex ternary fibers were found to be in accordance with the predicted morphology for the observed conductivity vs. fiber draw ratio. The scanning electron microscopy (SEM) micrographs of the ternary blend illustrated at least a three‐phase morphology of a matrix/core‐shell dispersed phase style, with widely varying sizes of droplets. This resulted in a dispersed morphology that, in some parts of the blend, approached a bicontinuous/dispersed phase morphology due to coalescence of the small droplets. The matrix was PP and the core‐shell dispersed phase was PA6 and PANI‐complex, in which a part of the PANI‐complex had encapsulated the PA6 phase and the remaining was solved/dispersed in the PA6 core, as later confirmed by X‐ray mapping. When the ternary blend fibers were compared to the binary fibers, the formers were able to combine better conductivity (of an order of 10^?3 S cm^?1) with a greater tensile strength only at a draw ratio of 5. This indicated that the draw ratio is more critical for the ternary blend fibers, because both conductivity and tensile strength depended on the formation of fibrils from the core‐shell dispersed phase of the PA6/PANI‐complex. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Preparation and self‐assembly of polyaniline nanorods and their application as electroactive actuators

To improve the performance of ion‐exchange polymer–metal composite (IPMC) actuators, an electrical pathway material for enhancing the surface adhesion between the membrane and the metal electrodes of the IPMC was studied. As an efficient electrical pathway material, polyaniline nanorods (PANI‐NRs) doped with p‐toluene sulfonic acid (TSA) were synthesized with a template‐free method. The factors affecting polyaniline morphology were studied with various dopant concentrations and oxidant feeding rates. Highly conductive PANI‐NRs were formed when they were synthesized with ammonium persulfate at a 5.0 mL/min oxidant feeding rate and doped with 0.125M TSA. The conductivity of the PANI‐NRs was 1.15 × 10^?1 S/cm, and their diameters and lengths were 120–180 nm and 0.6–2 μm, respectively. To apply the membrane as an actuator, perfluorosulfonated ionomer (Nafion)/PANI‐NR blends were prepared by solution blending and casting. The actuating ability of the three‐layered membrane consisting of Nafion/PANI‐NR blends was then examined and compared with that of Nafion only. The actuating ability of the IPMC was improved when Nafion/PANI‐NRs were used as electrical pathways. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermal and morphological studies of chemically prepared emeraldine‐base‐form polyaniline powder

In this study, emeraldine base (EB)‐form polyaniline (PANI) powder was chemically prepared in 1M HNO₃ aqueous solution. The thermal characteristics and chemical structures of this powder were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and X‐ray diffraction (XRD). A polarizing optical microscope was also used to examine the crystalline morphology of this sample. The results indicated that the EB‐form PANI powder had a discernible moisture content. Moreover, in the first run of DSC thermal analysis, the exothermic peak at 170–340°C was due to the crosslinking reaction occurring among the EB‐form PANI molecular chains. FTIR and XRD examinations further confirmed the chemical crosslinking reaction during thermal treatment. TGA results illustrated that there were two major stages for weight loss of the EB‐form PANI powder sample. The first weight loss, at the lower temperature, resulted from the evaporation of moisture. The second weight loss, at the higher temperature, was due to the chemical structure degradation of the sample. The degradation temperature of the EB‐form PANI powder was around 420–450°C. The degradation temperature of emeraldine salt (ES)‐form PANI powder was lower (around 360–410°C) than that of the EB form (around 420–450°C). From the TGA results, I roughly estimated that 2.74 aniline repeat units, on average, were doped with 1 HNO₃ molecule in the ES‐form PANI. I found a single crystalline morphology of EB‐form PANI, mostly like a conifer leaf. More complex, multilayered dendritic structures were also found. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2142–2148, 2003     

Reverse micelle facilitated synthesis of nanostructured polyaniline as the counter electrode materials in dye-sensitized solar cells

ABSTRACT

We report a reverse-micelle emulsion polymerization of nanostructured PANI using a nonionic surfactant Polyglyceryl-2-Dipolyhydroxystearate (PGPH) at various concentrations from 2% to 6% (v/v). SEM images show that the obtained morphologies are irregular agglomerates at low PGPH concentration and relatively regular granules at high PGPH concentration. FTIR and Raman spectra show that the synthesized PANI is in the form of Emeraldine salt (PANI ES) with electrical conductivity around 10^?3 S cm^?1. Photovoltaic current-voltage (J-V) measurements show the highest power conversion efficiency is achieved at 1.71% at 6% (v/v) of PGPH.     

Properties of (Low‐density polyethylene)/(natural rubber)/(water hyacinth fiber) composites: The effect of polyaniline

The effects of polyaniline (PANI)‐modified water hyacinth fiber on the properties of (low‐density polyethylene)/(natural rubber)/(water hyacinth fiber) (LDPE/NR/WHF) composites were studied. The composites were prepared by using a Brabender Plasticorder at 160^oC and a rotor speed of 50 rpm for 6 minutes. LDPE/NR/WHF_PANI composites exhibited higher tensile strength, Young's modulus, elongation at break, melting temperature, and electrical conductivity but lower molar sorption, capacitance, percentage crystallinity, and interparticle spacing than LDPE/NR/WHF composites. Scanning electron microscopy morphology showed a better interfacial adhesion of PANI‐modified water hyacinth fiber (WHF_PANI) and the LDPE/NR phases than when unmodified WHF was used. J. VINYL ADDIT. TECHNOL., 20:122–130, 2014. © 2014 Society of Plastics Engineers     

Doping effect of organic sulphonic acids on the solid‐state synthesized polyaniline

Polyaniline (PANI) salts doped with organic sulfonic acids (methanesulfonicacid, p‐toluenesulphonic acid, and dodecylbenzenesulphonic acid) were first synthesized by using solid‐state polymerization method. The polymers were characterized by Fourier transform infrared (FTIR) spectra, ultraviolet‐visible spectrometry, X‐ray diffraction, cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, and conductivity measurements. It was found that PANI doped with p‐toluenesulphonic acid is formed in conductive emeraldine oxidation state, and displayed higher doping level and cyrstallinity. On the contrary, PANI doped with dodecylbenzenesulphonic acid was lower at doping level and highly amorphous. In accordance with these results, the conductivity and electrochemical acitivity was also found to be higher in p‐toluenesulphonic acid‐doped PANI, and these properties were opposite in the case of dodecylbenzenesulphonic acid. The results also revealed that the morphology of dodecylbenzenesulphonic acid‐doped PANI was remarkably different from other PANI salts. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Study on soluble polyaniline by positron annihilation technique

The solubility, electrical conductivity, and other properties of polyaniline (PANI) are highly dependent on its oxidation state. In this work, polyaniline (PANI1) prepared by peroxodisulphate induced polymerization of aniline in acidic aqueous medium in presence of benzenediazonium chloride salt was found to exist in lower oxidation state than emeraldine form of PANI and was highly soluble in common organic solvents. This polymer was subjected to positron annihilation spectroscopic study to investigate the correlation between the oxidation state of the polymer and defect sites generated by different degrees of protonation that in turn affect its electrical conductivity. The positron annihilation lifetime data were resolved to yield a three‐component fit for PANI1 subjected to different levels of protonation. The variation of positron annihilation parameters (τ_1,I₂) and Doppler broadening parameters (R, S) as a function of protonation level of the polymer indicate the dopant sites increase initially on protonation and reach a saturation value after a certain level of acidification. The lower value of electrical conductivity and the intensity of intermediate lifetime component (I₂) for PANI1 compared to PANI in emeraldine oxidation state indicate the presence of lesser number of quinoid–imine moieties that could undergo protonation and thus yield highly enriched trapping centers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011