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.

Emeraldine Base Form of Polyaniline Nanofibers as New, Economical, Green, and Efficient Catalyst for Synthesis of Z-Aldoximes

A facile, clean, economical, efficient, and green process was developed for the preparation of Z-aldoximes at room temperature under solvent-free condition using emeraldine base form of polyaniline as novel catalyst. In this methodology, PANI base absorbed the by-product of HCl (polluting chemical) from hydroxylamine hydrochloride and converted to polyaniline-hydrochloride salt (PANI-HCl salt). This PANI-HCl salt could be easily recovered and used in new attempts without any purification in many areas such as catalyst, electrical and electronics applications meant for conducting polymers. As far as our knowledge is concerned, emeraldine base as catalyst in organic synthesis for the first time.

Synthesis and Electrorheological Properties of SiO2/Polyaniline Nanocomposites Prepared by In Situ Polymerization

SiO2/polyaniline (PANI) nanocomposites were obtained by chemical oxidative polymerization using ammonium peroxydisulfate as oxidizing agent. The FE-SEM and TEM images showed that nanocomposites presented the core-shell structure with raspberry morphology. The electrorheological (ER) effect of those materials was enhanced by using the ammonium hydroxide to deprotonate the corresponding PANI base. It was found that the yield stress of those ER fluids and its near linear dependence on the electric field were different from the conventional ER fluids.

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.

Chemical polymerization of aniline in phenylphosphinic acid

The chemical polymerization of aniline was performed in phenylphosphinic acid (APP) medium using ammonium peroxidisulfate as the oxidizing agent, at 0 ?C and 25 ?C. The yield of polyaniline (PANI) was about 60?69 %. The polymerization process required an induction time 8?10 times greater than in other acids (hydrochloric, sulfuric). The average density of the obtained polymer was 1.395 g cm-3 for PANI-salt and 1.203 g cm-3 for PANI-base. The acid capacity of PANI depends on the synthesis parameters and the maximum value was 15.02 meq/g polymer. The inherent viscosity of PANI was 0.662 dl/g at aniline/oxidant molar ratios >2 and 0 ?C. The oxidation state was a function of the synthesis parameters and lay between 0.553?0.625, as determined from UV-VIS and titration with TiCl3 data. The PANI samples were characterized by measurements of their density, inherent viscosity conductivity, acid capacity, FTIR and UV-VIS spectrum, and thermogravimetric data.

Polyaniline. Preparation of a conducting polymer(IUPAC Technical Report)

Eight persons from five institutions in different countries carried out polymerizations of aniline following the same preparation protocol. In a "standard" procedure, aniline hydrochloride was oxidized with ammonium peroxydisulfate in aqueous medium at ambient temperature. The yield of polyaniline was higher than 90 % in all cases. The electrical conductivity of polyaniline hydrochloride thus prepared was 4.4 ± 1.7 S cm-1 (average of 59 samples), measured at room temperature. A product with defined electrical properties could be obtained in various laboratories by following the same synthetic procedure. The influence of reduced reaction temperature and increased acidity of the polymerization medium on polyaniline conductivity were also addressed. The conductivity changes occurring during the storage of polyaniline were monitored. The density of polyaniline hydrochloride was 1.329 g cm-3. The average conductivity of corresponding polyaniline bases was 1.4 x10­8 S cm-1, the density being 1.245 g cm-1. Additional changes in the conductivity take place during storage. Aging is more pronounced in powders than in compressed samples. As far as aging effects are concerned, their assessment is relative. The observed reduction in the conductivity by ~10 % after more than one-year storage is large but, compared with the low conductivity of corresponding polyaniline (PANI) base, such a change is negligible. For most applications, an acceptable level of conductivity may be maintained throughout the expected lifetime.

Solvent, LICL, and Temperature Effects on the Morphological Structure and Electronic Properties of Polyaniline

ABSTRACTExtensive gel permeation chromatography coupled with surface structure measurements clearly indicate that polyaniline (pani) base has a tendency to aggregate as a result of interchain hydrogen-bonding. The aggregation is present in the solid state powder; the extent of aggregation is found to be significantly dependent on the synthetic conditions. Pani base powders having a high degree of aggregation have significantly reduced solubility. The degree of aggregation of pani base in solution is found to be dependent on the solvent, concentration, and temperature. As the solvent becomes a better solvent for the base material, the less aggregated is the structure. Solvents which can strongly interact with the polymer disrupt the aggregation. In addition, salts such as LiCl which complex the polymer via a “pseudo-doping” process, also disrupt the internal pani hydrogen-bonding and deaggregate the polymer. As the polymer is deaggregated to different levels by a solvent or by LiCl, the individual chains can better be solvated and thus a conformational change also occurs. The chains adapt a more expanded coil type of conformation. The degree of expansion depends on the solvation power of the solvent. As the level of deaggregation and subsequent chain expansion increases, a significant red shift is observed in the λmaximum of the exciton absorbance and the surface structure of the polymer becomes smoother. It is found that the LiCl induced morphological changes results in increased conductivity upon doping pani base with a protonic acid.