Polyaniline Salt Research Articles

In-situ prepared polyaniline–silver composites: Single- and two-step strategies

Conducting polymer–metal composites, such as polyaniline–silver, can efficiently be prepared by two ways: (1) by the oxidation of aniline with silver ions or (2) by the reduction of silver ions with polyaniline. Both approaches yield the composites with limited conductivity. In order to increase the content of silver, and thus increase the conductivity, two strategies are proposed: (1) an increase of oxidant-to-aniline mole ratio in the oxidation of aniline with silver nitrate above stoichiometric value in a single step, and thus reduce excess silver ions to silver metal with produced polyaniline, or (2) in two steps, by preparing polyaniline–silver composite at first and then using polyaniline for the reduction of silver ions. The second approach yields the composites of higher conductivity of the order 100Scm−1. The role of aniline oligomers and interfacial barriers is discussed on the basis of UV–vis and FTIR spectra, and on morphology assessment. The changes in conductivity of composites after deprotonation and reprotonation of polyaniline part are also reported. Surprisingly, the conversion of conducting polyaniline salt to a non-conducting polyaniline base may be associated with an increase of composite conductivity.

Synthesis and Characterization of Processable Polyaniline Salts

Polyaniline (PANI) is one of the most promising candidates for possible technological applications. PANI has potential applications in batteries, anion exchanger, tissue engineering, inhibition of steel corrosion, fuel cell, sensors and so on. However, its insolubility in common organic solvents limits its range of applications. In the present study an attempt has been made to synthesize soluble polyaniline salt via inverse polymerization pathway using benzoyl peroxide as oxidant and dodecylbenzenesulfonic acid (DBSA) as dopant as well as a surfactant. A mixture of chloroform and 2-butanol was used as dispersion medium for the first time. The influence of synthesis parameters such as concentration of aniline, benzoyl peroxide and DBSA on the yield and other properties of the resulting PANI salt was studied. The synthesized PANI salt was found to be completely soluble in DMSO, DMF, chloroform and in a mixture of toluene and 2-propanol. The synthesized polymer salt was also characterized with cyclic voltam-metry, SEM, XRD, UV-Vis spectroscopy and viscosity measurements. TGA was used to analyze the thermal properties of synthesized polymer. The extent of doping of the PANI salt was determined from UV-Vis spectra and TGA analysis. The activation energy for the degradation of the polymer was calculated with the help of TGA.

Nano fibre polyaniline containing long chain and small molecule dopants and carbon composites for supercapacitor

Long chain protonic acid (dodecylhydrogen sulfate-DHS) along with small molecule acid (sulfuric acid-H2SO4) was introduced as dopants in polyaniline salt (PANI–H2SO4–DHS), hereafter referred as PANI, via aqueous/emulsion polymerization pathway of aniline. Polyaniline salt–acetylene black composites (PANI–AB) were prepared in one-step via aqueous/emulsion polymerization pathway using various amounts of acetylene black (AB). Formation of PANI and PANI–AB was confirmed from infrared and X-ray diffraction patterns. The highest conductivity obtained for PANI–AB composite was 6.2Scm−1, which is slightly higher than that of PANI (1.3Scm−1). PANI prepared by aqueous polymerization pathway showed nano fibres with diameter of 10–30nm. Use of 5wt% of AB with respect to the amount of aniline used in the polymerization reaction of aniline, PANI–AB showed spheres covered nano fibres with high porosity. By increasing the amount of AB to 10wt%, nano fibres are getting closure, which reduced the porosity. Further increase in the amount of AB to 15wt%, nano fibres disappear. PANI and PANI–AB were used as electrode materials in symmetric supercapacitor cell. Specific capacitance, Energy and power densities of PANI–AB composite were found to be 157.6Fg−1., 15.7Whkg−1 and 600Wkg−1 respectively.

Antibacterial properties of polyaniline-silver films

AbstractIn situ polymerised thin polyaniline (PANI) films produced on polystyrene dishes were tested for their antibacterial activity with respect to Escherichia coli and Staphylococcus aureus, representing both gram-positive and gram-negative bacteria. PANI films were subsequently used for the reduction of silver ions to metallic Ag. PANI salt and base in original forms and after the deposition of Ag were studied. PANI salt showed a significant antibacterial effect against both bacteria strains while the efficacy of neat PANI base was only marginal. After the Ag deposition, the PANI base exhibited different levels of antibacterial effect depending on the type of the bacterial strain; the growth of gram-positive Staphylococcus aureus was inhibited depending on the Ag concentration on the film, while Escherichia coli remained uninfluenced. Efficacy of the PANI salt with deposited Ag against both bacteria strains was comparable with that of PANI alone and was not affected by the Ag concentration. The results show that Ag deposition can be a suitable method for the preparation of PANI base films with improved antibacterial properties.

Electrical transport properties of poly(aniline-co-p-phenylenediamine) and its composites with incorporated silver particles

AbstractStatistical copolymers of aniline and p-phenylenediamine, poly(aniline-co-p-phenylenediamine)s, were synthesised by oxidative polymerisation using various oxidants, ammonium peroxydisulphate or silver nitrate. Depending on the choice of oxidant, copolymers or composites with silver particles were obtained. Different molar concentrations of p-phenylenediamine in the reaction mixture provided materials of different conductivities. The influence of both the copolymer composition and the presence of discrete silver particles on the electric and dielectric properties of the system was studied. The results showed a decrease in the conductivity of copolymers and their composites with the silver content compared with the content of standard polyaniline salt. The reduction in conductivity was described in terms of the decreased density of hopping centres due to defects in the copolymer structure. The dielectric relaxations observed were described in terms of their activation energies and were linked to the corresponding conduction mechanism.

Use of iodine doped polyaniline salt in the stereoselective synthesis of 2-methyl-4-substituted-1,2,3,4-tetrahydroquinoline derivatives

Abstract Polyaniline–iodine salt is proved as a simple, efficient, versatile, recyclable and eco-friendly polymer based solid acid catalyst in the reaction between aromatic amines and N-vinyl pyrrolidone/N-vinyl caprolactam under solvent free condition. Polyaniline salts such as polyaniline-sulfate, polyaniline-hydrochloride and polyaniline-perchlorate are also catalyzing this reaction smoothly.

The Effect of a Small Amount of Water on the Structure and Electrochemical Properties of Solid-State Synthesized Polyaniline

A series of polyaniline (PANI) salts were synthesized with the presence of a small amount of water varying from 0 to 1 mL at the beginning of solid-state polymerization. The structure and morphology of the samples were characterized by fourier transform infrared (FTIR) spectra, ultraviolet-visible (UV-Vis) absorption spectra, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The electrochemical performances of the products were investigated by galvanostatic charge-discharge, cyclic voltammetry, cycling stability and electrochemical impedance spectroscopy (EIS). The results showed that the amounts of water can affect the oxidation degree, conjugate level and crystallinity of PANI salts. All PANI salts showed spherical morphology with the diameter of about 60 nm as shown by TEM. The electrochemical tests showed the highest specific capacitance value 593.3 F.g−1 in 1 M H2SO4 for PANI prepared with the addition of 0.5 mL of water at the beginning of solid-state polymerization.

Electrocatalysis of oxygen reduction reaction on polyaniline-derived nitrogen-doped carbon nanoparticle surfaces in alkaline media

Nitrogen-doped carbon nanomaterials were synthesized by the carbonization of three different nanostructured polyaniline (PANI) salt precursors: PANI 3,5-dinitrosalicylate nanorods, PANI 5-sulfosalicylate nanorods/nanotubes, and PANI hydrogen sulfate nanorods/nanotubes/nanosheets. A comparative study of the electrocatalytic activity of these materials for oxygen reduction reaction (ORR) in alkaline solution was performed by using rotating disk electrode voltammetry. The electrochemical data were correlated to the structural and textural data obtained by Raman spectroscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, elemental analysis and nitrogen sorption analysis. A fine interplay of textural characteristics, overall content of surface nitrogen and content of specific surface nitrogen functional groups were found to be responsible for a considerable variations in electrocatalytic properties toward ORR, involving variations in apparent number of electrons exchanged per O2 molecule (from 2 to nearly 4) and variations in onset potential. The catalyst loading was found to influence remarkably the ORR kinetics. The excellent electrocatalytic activity was found for carbonized PANI 5-sulfosalicylate. Namely, it exhibited the most positive onset potential amounting to −0.05 V vs. SCE at a catalyst loading of 500 μgcm−2. The interrelation between the electrocatalytic activity and the electrical double layer charging/discharging characteristics of the investigated N-doped nanocarbon materials was revealed.

PANI-HBF4: A Reusable Polymer-Based Solid Acid Catalyst for Three-Component, One-Pot Synthesis of 3-Substituted Amino Methyl Indoles Under Solvent-Free Conditions

A simple, fast, efficient, high-yielding, and green process is developed for one-pot, three-component synthesis of 3-substituted amino methyl indoles under solvent-free conditions using polyaniline salt as polymer-based reusable solid acid catalyst at room temperature. The advantages of polyaniline salt catalyst are ease of synthesis and handling, low cost, versatality, and recyclability.

The carbonization of thin polyaniline films

Polyaniline films on silicon and ceramic supports were prepared in situ during the oxidative polymerization of aniline. The films were heated up to 500°C in an inert nitrogen atmosphere. The changes in molecular structure during the carbonization have been studied by infrared spectroscopy and Raman scattering using 514, 633 and 785nm laser excitation lines. The transformation from polyaniline salt to the base form has been detected above 100°C. The conversion to nitrogen-containing carbon-like material followed above 200°C. The molecular structure of the films produced during heating to 500°C contains crosslinked phenazine-like and oxidized quinonoid units. The aniline oligomers deposited on the support in the early stages of aniline oxidation are stable during heating as it has been observed by resonance Raman scattering using 785nm laser excitation line. The water contact angles changed after carbonization, and the films became more hydrophilic as carbonization progressed.

Enhanced thermal stability of multi-walled carbon nanotubes after coating with polyaniline salt

Multi-walled carbon nanotubes (MWCNT) were coated by polyaniline (PANI) in situ during the oxidation of aniline with ammonium peroxydisulfate in a mixture of ethanol (50 vol.%)–water. PANI alone and PANI-coated MWCNT were carbonized under nitrogen atmosphere at 650 °C and the structural changes were studied by infrared spectroscopy and Raman scattering using 633 and 785 nm excitation lines. MWCNT coated with carbonized PANI salt exhibit a Raman spectrum close to that of the pristine MWCNT before heating. In contrast, the spectra of MWCNT and MWCNT coated with PANI base correspond after exposure to 650 °C to a more disordered carbon-like material according to their Raman spectrum. This means that the coating with PANI salt has a protective effect on the structure of MWCNT when exposed to elevated temperature. During heating, the overlayer of PANI salt thermally deprotonates to PANI base at first, and subsequently converts to a carbonized PANI coating. The integrity of the coating is not damaged. When the PANI coating was chemically deprotonated to PANI base before heating, the accompanying volume contraction reduced the contact between MWCNT and PANI base coating and introduced defects, such as cracks. The protective effect of PANI coating was then lost. The possible interactions between PANI and MWCNT are discussed on the basis of Raman spectra.

A kinetic study for the removal of anionic sulphonated dye from aqueous solution using nano-polyaniline and Baker’s yeast

In this study, a method for the removal of anionic sulphonated Acid Red 14 (AR) dye from aqueous solution using the chemical interaction of dye molecules with nano-polyaniline is reported. Nano-polyaniline (PANI) was synthesized by chemical oxidation in presence of different surfactants. The experimental observations from UV/Vis spectroscopy, rule out the possibility of secondary doping of polyaniline salt by AR14 molecules. A possible mechanism for the chemical interaction between the polymer and dye molecules is proposed. In order to get a better comparison, adsorption experiments were also carried out using Baker’s yeast (BY) individually and in mixture with nano-PANI. Kinetic parameters for the adsorption of AR dye on the selected adsorbents are also reported. It was found that application of BY with PANI for the removal of anionic sulphonated dyes such as AR dye from aqueous solution is very promising.

Thermally Stable Forms of Pure Polyaniline Catalyzed by an Acid-Exchanged Montmorillonite Clay Called Maghnite- as an Effective Catalyst

Polyaniline salt form (PANI-ES) was synthesized by oxidative polymerization of aniline using potassium persulfate as an oxidant and an acid-exchanged montmorillonite clay called Maghnite-H+as an effective catalyst. The clay, which was used as a catalyst, was supplied by a local company known as ENOF Maghnia (Western Algeria). The chemical stability of PANI has been investigated by thermogravimetry and differential scanning calorimetry, that a good thermal stability of PANI could be improved by combining PANI with montmorillonite. TGA results illustrated that there were two major stages for weight loss of the ES-form PANI powder sample. The different forms of PANI were characterized by infrared spectroscopy, thermal analysis, and H-NMR spectroscopy and conductivity measurements.

Polyaniline–silver composites prepared by the oxidation of aniline with mixed oxidants, silver nitrate and ammonium peroxydisulfate: The control of silver content

Aniline was oxidized with mixtures of two oxidants, ammonium peroxydisulfate and silver nitrate, to give polyaniline–silver composites with variable content of silver in the composites. The presence of peroxydisulfate has a marked accelerating effect on the oxidation of aniline with silver nitrate. Oxidations in 1 M methanesulfonic acid produced composites in high yield. The molecular structure of the polyaniline was confirmed by UV–visible and FTIR spectra, and the polymeric character was established by gel-permeation chromatography. The content of silver varied between 0 and 70 wt.%. The silver nanoparticles were smaller than 100 nm. The conductivity of the composites was of the order of units S cm −1. Only at high silver nitrate contents in the reaction mixture, the conductivity of products exceeded 100 S cm −1. The conductivity of the composites sometimes increased after deprotonation of the polyaniline salt to a non-conducting base. Such conductivity behaviour is discussed in terms of the percolation model.

Synthesis of Processable Polyaniline and its Anticorrosion Performance on 316LN Stainless Steel

The soluble polyaniline (PANI) salts were synthesized by chemical-oxidative polymerization of aniline using sodium dodecylbenzene sulfonic acid, camphor sulphonic acid and hydrochloric acid as dopants and ammonium per sulphate (APS) as an oxidant. The synthesized PANI were characterized by X-ray diffraction, scanning electron microscope, Fourier transform-infrared spectroscopy and thermogravimetric analysis. It is found that the yield of PANI, electrical conductivity, solubility and thermal stability varies with the dopants and the stoichiometrics of monomer/dopant ratios. The PANI doped sample follows the solubility order as: PANI–SDBS > PANI–CSA > PANI–HCl. Thermal stability of PANI–CSA is grater than PANI–SDBS and PANI–HCl. XRD pattern shows the higher crystallinity for HCl and CSA doped PANI while SDBS doped PANI shows the poor crystallinity. SEM study revealed the partially crystalline and agglomerated morphology of the polymer. According to the results, the corrosion rate or corrosion current of PANI–SDBS salts coated samples varies with molar ratios of SDBS to aniline and the optimum molar ratio of PANI–SDBS coating to achieve the best anticorrosive performance on 316LN SS is 2.5 mol mol−1.

Solid-state oxidation of aniline hydrochloride with various oxidants

Aniline hydrochloride was oxidized in the solid state with three different oxidants: ammonium peroxydisulfate, iron(III) chloride, and silver nitrate. Polyaniline salt was obtained after a few hours when ammonium peroxydisulfate was used as an oxidant. The polymerization of aniline hydrochloride with silver nitrate leads to polyaniline only after several days; in the case of iron(III) chloride, aniline oligomers were obtained. The conductivity of the polyaniline was 0.21 S cm −1 when ammonium peroxydisulfate was applied; it is comparable with the conductivity of a ‘standard’ polyaniline. The oxidation with silver nitrate yields a composite material, polyaniline salt and silver particles, with conductivity 1.5 × 10 −3 S cm −1. Photoacoustic spectroscopy was employed to study the kinetics of the oxidation reaction. Infrared and UV–vis spectra were efficient tools to characterize the final products, and to compare their molecular structure with that of the polyaniline prepared under ‘standard’ conditions in aqueous medium.

Preparation of processible polyaniline-formate salt via emulsifier free inverted emulsion polymerization and its antistatic applications

For the first time, processible polyaniline salt was prepared by inverted emulsion polymerization pathway without using any emulsifier. Aniline oxidation with benzoyl peroxide, in the presence of formic acid, yields novel polyaniline-formate salt containing free formic acid (PANI salt), the latter being trapped due to agglomeration and the presence of cohesive forces between the acid molecules and polyaniline chains. The synthetic procedure, outlined above, constituted the basis for the preparation of PANI salt containing free formic acid. PANI salt was studied by complementary characterization methods: conductivity, FT-IR, XRD, XPS & TGA. PANI salt containing free formic acid turned out to be especially well suited for the fabrication of blends with poly(vinyl alcohol), showing a very low percolation threshold. This lowering of the percolation threshold was attributed to the plasticizing effect of polyvinyl alcohol molecules present in the polymer matrix.

Effect of emulsion polymerisation conditions on electrical performance of polyaniline

PurposeThe aim of the paper is to develop a method of synthesising polyaniline (PANI) with excellent electrical conductivity.Design/methodology/approachThe preparation of PANI was carried out by vibration of emulsifier (SDBS), oxidant (APS) and hydrochloric acid (HCl) solution concentration. The changes of temperature and time of reaction had also been observed and researched.FindingsChanging of reaction conditions was found to have a great influence on polyaniline's conductivity. The optimum condition for preparing polyaniline salt is as follows: the molar ratio of n(An)/n(SDBS)/n(APS) is 10/10/9, the concentration of HCl is 0.9 M, stirred constantly at 0°C for a period of 3 h. By using this emulsion polymerisation pathway the maximum of conductivity of polyaniline is 4.35 s/cm.Practical implicationsThe method can be widely applicable to coatings, preparation of exfoliated clay composites and solution blending with other commodity polymers.Originality/valueThe method could be adapted for use on an industrial scale.

Synthesis of Nano Fiber Form of Polyaniline Salt Containing Dual Dopant by Interfacial Polymerization Pathway for Supercapacitor

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Benzoyl Peroxide Oxidation Route to Nano Form Polyaniline Salt Containing Dual Dopants for Pseudocapacitor

Benzoyl peroxide is used as an oxidant for the oxidation of aniline to polyaniline salt via interfacial polymerization pathway (IP) for the first time in presence of sodium lauryl sulfate as emulsifier and 5-sulfophthalic acid as protonic acid. Polyaniline salt is also synthesized by interfacial polymerization using higher amount of reactants and emulsion polymerization pathways. Polyaniline salts are characterized by FT-IR, XRD and SEM. This polymerization process gives polyaniline salt containing dual dopants (5-sulfophthalic acid and dodecyl hydrogen sulfate) i.e. small and long chain molecules on polyaniline. Polyaniline salt prepared by emulsion polymerization pathway (EP) shows nanowires with a higher yield (0.98 g) compared to that of the interfacial polymerization (IP) pathway (0.73 g), which also shows nanowires morphology. However, very less yield (0.2 g) is obtained by the interfacial polymerization pathway using higher concentration of reactants (IP-H), which shows nanotubes. Polyaniline salt is mixed with Multi-walled carbon nanotube (MWCNTs) material, made electrode with stainless steel mesh and this electrode is used for the study of symmetric supercapacitor cell. Electrochemical performance is found by cyclic voltammetry, charge-discharge and electrochemical impedance spectroscopy. The results clearly indicate that the polyaniline salt containing dual dopants is a very good material for supercapacitor.