Effect of HCl Concentration and Acetone Washing on the Dielectric and Conduction Properties of Polyaniline Salts

Aims: The aim of the work is to study the effect of acid concentration and acetone washing on electrical properties of Polyaniline (PANI) salts prepared through chemically oxidative polymerization. Background: The frequency dependent conductivity and dielectric permittivity provide important information on the electrical properties of conducting polymers which gives information regarding their utility in electronic applications. Objective: Hence, the present study is based on the comparative the electrical properties study (dielectric and electrical conductivity) of PANI salts prepared in two different media like water and 1M HCl along with study regarding effect acetone washing on the said electrical properties of the polymer samples. Methods: PANI salts are synthesized through chemical oxidative polymerisation of aniline hydrochloride with the oxidant ammonium persulphate in two different media like water and 1M HCl. One part of the PANI salt samples were washed with distilled water after synthesis and another part of the polymer samples were washed with distilled water followed by acetone to study the effect of acetone washing on the electrical properties of polymer samples. Results: Non-acetone washed PANI salt prepared in water medium shows the highest dielectric as well as electrical conductivity due to the increased charge carriers provided both by long chain polymer as well as short chain oligomers. When the acid concentration is increased to 1M there may be loss of protons accompanied by pairing of free radicals to form quinoimine units that leads to the loss of charge carriers consequently decreasing the dielectric constant and electrical conductivity. Conclusion : PANI salt prepared in water shows the highest dielectric as well as conductivity due to the increased charge carriers provided both by long chain polymer as well as short chain oligomers.

Synthesis, Electrical Conductivity, and Dielectric Behaviour of Nano Polyaniline doped with H2SO4; HCl and (HCl + NaNO2) mixture: A comparative study with acetone washing

Acid doped Polyaniline (PANI) due to their increased electrical conductivity, are considered to be the most promising conducting filler materials. Hence, the present study, reports the synthesis of the nano PANI followed by acid doping, electrical conductivity and dielectric properties measurements of H2SO4; HCl and (Conc. HCl + NaNO2mixture) doped PANI. In order to know the effect of acetone washing on the electrical properties of acid doped PANI samples, the electrical properties of the non-acetone washed acid doped PANI samples are compared with that of their acetone washed counterparts. The PANI salt was prepared by conventional route using aniline hydrochloride and ammonium persulphate as an oxidant. PANI salt was subjected to 0.5M NaOH to form PANI base, which was further doped separately with H2SO4; HCl and (Conc. HCl + NaNO2mixture) respectively followed by acetone washing. A comparative electrical conductivity study between the acetone washed and unwashed PANI salt and H2SO4, HCl and Conc. HCl + NaNO2 mixture doped PANI were characterized by dielectric and impedance study.

The Impact of In Situ Polymerization Conditions on the Structures and Properties of PANI/ZnO-Based Multiphase Composite Photocatalysts

We have synthesized polyaniline/ZnO-based (PANI/ZnO) multiphase composite photocatalysts from acid media by a newly proposed two-step in situ polymerization. The first step of synthesis yielded PANI salt required for the PANI/ZnO synergistic effect. In the second step, the aniline oxidation continued, without ZnO dissolution, and it produced PANI base. Thus, both PANI salt and base phases in the composites were detected by FTIR and UV/Vis, while the presence of both ZnO and PANI polymer was confirmed by XRD. Additionally, XRD also showed Zn5(OH)8(NO3)2·2H2O and Zn(SO4)(H2O) phases in PANI/ZnO-based multiphase composites. Furthermore, the impact of the synthesis conditions on the morphology of the composites was investigated by FE-SEM. The images displayed that ZnO particles were encapsulated in PANI sheets that were formed by the aniline oligomers. Photocatalytic evaluation of PANI/ZnO-based catalysts (i.e., degradation of Acid Blue 25 dye) was conducted and the obtained results confirmed that all the studied composites experienced the PANI/ZnO synergistic effect. It was observed that the best photocatalytic properties were held by the PANI/ZnO_2 sample due to its optimal particle size.

The Study of Optical Energy Gap, Refractive Index, and Dielectric Constant of Pure and Doped Polyaniline with HCl and H2SO4 Acids

Polyaniline (PANI) salt in its pure and doped forms find extensive applications in making devices such as polymer light emitting diodes, photovoltaic, sensors, batteries, and super capacitors. PANI salt has been synthesized successfully through chemically oxidative polymerization of aniline in the presence of hydrochloric acid (HCl) and sulfuric acid (H2 SO4 ) using ammonium peroxydisulfate as an oxidizing agent. The absorption spectra of pure PANI salt and its doped state, in HCl and H2 SO4 media, have been studied in the wavelength range from 200 to 1100 nm using ultraviolet and visible near infrared spectrophotometer. Tauc’s formula, Lambert-Beer’s relation, and Fresnel’s formula were employed in the MATLAB program to calculate the optical energy gap, refractive index, and dielectric constant. Results showed that doping with HCl and H2 SO4 acidic mediums caused a reduction in the direct energy gap of the pure PANI from 2.69eV to 2.42 eV and 2.54 eV, respectively. The reduction in optical energy gap is associated with the increase in refractive index. The refractive index (2.92) has a higher value of PANI doped with HCl. Higher refractive index values are for better-structured films.

Cost Effective Chemical Oxidative Synthesis of Soluble and Electroactive Polyaniline Salt and Its Application as Anticorrosive Agent for Steel

The cost effective synthesis of electroactive polyaniline (PANI) while retaining its desirable properties is one of the most debatable and challenging tasks for researchers in the field. Herein, we report a cost effective inverse emulsion polymerization pathway for the synthesis of soluble and processable PANI salt by using diesel as a novel dispersion medium. Different reaction parameters and their effects on the properties and yield of polyaniline were optimized. The polymer exhibited a highly porous morphology and was found to be stable up to 417 °C. The PANI salt showed good solubility in common solvents, such as chloroform, N-Methyl-2-pyrrolidone (NMP), dimethyl sulphoxide (DMSO) and in a 1:3 mixtures by volume of 2-propanol and toluene. The coating of the synthesized PANI salt on stainless steel has shown good corrosion resistant behavior in marine water by reducing the corrosion rate to 67.9% as compared to uncoated stainless steel.

Writing in a Polyaniline Film with Laser Beam and Stability of the Record: A Raman Spectroscopy Study

Lines were drawn on polyaniline (PANI) salt films with laser beam, and then the samples were left to age in air at room temperature. Both the irradiated and intact parts of the sample and their ageing were studied with Raman spectroscopy. It was found that the laser-written record is reasonably stable. The degradation of polyaniline by laser irradiation and ageing was compared to the changes in PANI during heating. In all cases, deprotonation and crosslinking of PANI chains proceed but the relative rates of the processes vary with degradation conditions.

Influence of ethanol on the chain-ordering of carbonised polyaniline

Polyaniline (PANI) was prepared by the oxidation of aniline hydrochloride with ammonium peroxydisulphate in water or in a water-ethanol mixture. In the presence of ethanol, PANI nanotubes and nanorods were observed. Both products were carbonised in a nitrogen atmosphere at 650°C. Initial and carbonised products were characterised by scanning and transmission electron microscopies, thermogravimetric analysis and wide-angle X-ray scattering. Their molecular structure was studied by UV-VIS, infrared, and Raman spectroscopies. Carbonised sample obtained from the PANI salt prepared in the presence of ethanol exhibits Raman spectrum which corresponds to a more ordered carbon-like material than carbonised samples obtained from the PANI base and the PANI salt prepared in pure water. The influence of ethanol present in the reaction mixture on the molecular and supra-molecular structure of PANI and, consequently, on the enhancement of chainordering of carbonised PANI is discussed.

Antibacterial properties of polyaniline-silver films

In 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.

The Microstructure of Polyaniline Coatings Electropolymerized on Pb Substrate in Aniline+Oxalic Acid Electrolyte

The electropolymerizition of polyaniline (PANI) on Pb substrate was performed by potentiostatic or galvanostatic method in aniline＋oxalic acid electrolyte. The PANI coatings were characterized by FTIR, XRD and SEM methods. The results showed that the PANI coatings have a crystalline-amorphous composite structure whose degree of crystallinity is about 30%~50%. They belong to a conducting emeraldine salt form and contain varied amounts of water (hydrated PANI salt). The PANI coating synthesized at low current density is in a more reduced state. There is a fibrillar-like morphology for the PANI coatings electrodeposited on Pb substrate.

Effects of Polymer Particles Suspending in Dielectric Fluid on Surface Roughness of EDM

Suspending powder in dielectric fluid of EDM (electrical discharge machining) has been developed to improve the quality of machined surface recently. The used powders are usually Al, Cu, Cr and so on metal powder because conductive particle can increase the spark gap and improve surface roughness of machined surface. Semi-conductive powder, Si is also utilized for the sake of increasing machining speed. This paper presents a new tryout to suspend polymer particles in the dielectric fluid of EDM. Experimental results show that the EDM process with suspending polymer particles still can be carried out but its surface roughness is not so good in conventional EDM oil. However the conventional EDM oil was taken the replace of silicone oil, suspending polyaniline (PANI-emer) of high molecular weight (Mw~65000) has finer improvement even better than using Si powder. Its surface roughness achieves less than Ra 0.2μm at low concentration and will be decreased gradually with increasing the concentration of PANI-emer (Mw~65000). The surface roughness is Ra 0.14μm when the powders concentration is 10g/l. Even for different type of polyaniline shows different machining characteristics. The surfaces roughness becomes worse when the concentration of low molecular weight PANI-emer (Mw~20000) is higher. An electric-conductive PANI-salt powder has a rapid decrease of surface roughness with increasing its concentration than other materials.