Preparation Of Polyaniline Research Articles

SERS, FT-IR and photoluminescence studies on single-walled carbon nanotubes/conducting polymers composites

Surface-enhanced Raman scattering (SERS), Fourier transform infrared (FT-IR) and photoluminescence (PL) spectroscopies were used to investigate composites based on single-walled carbon nanotubes (SWNTs) and different conducting polymers like polyaniline (PANI), poly-paraphenylene vinylene (PPV) and poly 3-hexylthiophene (3-PHT). In the case of SWNTs/PANI, different composites are obtained by adding dispersed SWNTs powder to the polymer solutions and by chemical polymerization of aniline in presence of SWNTs. The difference originates in the irreversible chemical transformation of SWNTs in the polymerization medium. The synthesis medium used for the preparation of PANI transforms SWNTs in fragments of shorter length like closed-shell fullerenes. This explains the similarity of SERS and FT-IR spectra of the composites PANI/SWNTs and PANI/C 60, chemically synthesized. Electrochemical polymerization of aniline in an HCl solution on a SWNT film leads to a covalent functionalization of SWNTs with PANI. In this case, Raman scattering data suggest an additional nanotubes roping with PANI as a binding agent. A post treatment with the NH 4OH solution of polymer-functionalized SWNTs involves an internal redox reaction between PANI and carbon nanotubes. As a result, the polymer chain undergoes a transition from the semi-oxidized state into a reduced one. In the case of PPV and 3-PHT, the effect of the concentration of SWNTs on the photoluminescence properties will be described and compared, as probes of interaction.

Polyaniline microtubes synthesized via supercritical CO 2 and aqueous interfacial polymerization

We report a new route to prepare polyaniline (PANI) microtubes via supercritical (SC) CO 2/aqueous interfacial polymerization. The synthesis is based on the well-known chemical oxidative polymerization of aniline in an acidic environment, with ammonium peroxydisufate (APS) as the oxidant, and sodium dodecyl sulfate (SDS) surfactant was used as the template. The main feature of this route is that the monomer (aniline) which is dissolved in SC CO 2 phase, slowly polymerized at the interface of SC CO 2 and aqueous solution to form the PANI microtubes. The morphologies, phase structure, composition and some properties of PANI microtubes were characterized by TEM, SEM, XRD, IR, XPS UV–vis and SYSTEM DM digital multimeter, respectively.

Preparation of polyaniline–TiO 2 composite film with in situ polymerization approach and its gas-sensitivity at room temperature

Polyaniline composite was prepared with chemical oxide method by adding a small amount of TiO 2 sol–gel. This film on the interdigital electrodes of carbon paste was formed via spin-coating or immersion method with in situ polymerization approach. And its gas-sensitivity to trimethylamine was examined at room temperature. The results indicated that, the heat stability of polyaniline film was improved obviously by adding 10 wt% TiO 2. Meanwhile, this film still showed excellent gas-sensitivity to trimethylamine of 5.14 × 10 −7 mol mL −1, its value of gas-sensitivity was up to three to five orders of magnitude within 3 min, and had good selectivity to analogy gases. The film also exhibited good reproducibility and stability, and easily recovered with high-purity N 2 at room temperature.

Preparation of organo-soluble polyanilines in ionic liquid

A method for preparation of organo-soluble polyaniline (PANI) is described. Oxidative coupling polymerization of anilium chloride with ammonium persulfate in a new ionic liquid, 2-hydroxyethyl ammonium formate (HAF), gives organo-soluble polyaniline with appreciable molecular weights ( M w = 86,400). Interestingly polyaniline (PANI) prepared by this method is highly soluble in many organic solvents such as acetone, tetrahydrofurane, dioxane, dimethyformamide and N-methyl, 2-pyrrolidinone. Thin films of PANI prepared at 0 °C (by solvent casting) show reasonable conductivities (up to 37.0 S cm −1) when doped with p-toluene sulfonic acid.

High-Performance Polyaniline Prepared via Polymerization in a Self-Stabilized Dispersion

We report a new synthetic method for the preparation of high-performance polyaniline, implementing a new concept of self-stabilized dispersion polymerization. In contrast with conventional homogeneous or dispersion polymerization methods that use an aqueous medium containing aniline, acid, and oxidant, our new polymerization is performed in a heterogeneous biphasic system of organic and aqueous medium without any stabilizers. Here, the monomers and growing polymer chains act as stabilizers, resulting in excellent dispersion of the organic phase inside the aqueous reaction medium. Polymerization based on this concept has produced high-quality samples with few structural defects; the doped polyanilines exhibit conductivities (σDC ∼ 600–800 S cm–1) almost three times that of the samples prepared using conventional methods. Moreover, the new polyaniline system shows a honeycomb-like morphology with great porosity, leading to a system with excellent processibility.

Permeation of sodium dodecyl sulfate through polyaniline-modified cellulose acetate membranes

The preparation of polyaniline (PANi)–cellulose acetate (CA) blends by casting films from a suspension, is reported. Two membranes were prepared from different solvents, one with a homogeneous and the other a heterogeneous dispersion of PANi in CA matrices. The membranes were characterized by X-ray diffraction, SEM, DSC, and FTIR, and the results were compared with those obtained for pure CA and PANi films. The transport properties of water and sodium dodecyl sulfate (SDS) in membranes of the PANi–CA blends and of CA were analysed. The transport of SDS and water depends on both the bulk/polymer density and the PANi content. In the homogeneous blend, the interaction between SDS and the polymer plays an important role in the transport mechanism. An irreversible interaction is observed, which can be monitored by UV–vis spectroscopy. The spectra of homogeneous, highly transparent PANi–CA blends show a pronounced sensitivity to SDS concentration, with detection limits [SDS]≥0.1 mM for films with a PANi concentration of 0.05% w/v.

Electrochemistry of Conductive Polymers 36. pH Dependence of Polyaniline Conductivities Studied by Current-Sensing Atomic Force Microscopy

We demonstrate from our current-sensing atomic force microscopic studies that both electrical and topographical properties of electrochemically prepared polyaniline (PAn) films are affected by their preparation conditions. The electrical properties of the fully doped PAn films prepared in 0.30 M nitric acid with its pH and ionic strength adjusted to 0.50 can be described as a conductor with an average conductivity of 49 (+/-13) S/cm with primarily a compact structure resulting from a relatively small growth rate. The doped PAn films prepared at pH 5.0, for example, have compact structures with large grains and lightly doped semiconducting properties with an average conductivity of about 1.54 (+/-0.09) x 10(-4) S/cm. From these data, we conclude that the degree of protonation of the monomers and the main reactions taking place during an early stage of the polymerization reaction are important factors determining the chemical structures as well as their conductivities and morphologies of the PAn films.

Electrochemical Synthesis and Characterization of Homo- and Copolymer of Aniline and o-Anisidine in Various Organic Salts

An attempt has been made to prepare polyaniline (PA), poly (o-anisidine) (POA), and their copolymer poly (aniline-co-o-anisidine) (PA-co-POA) thin films dopped by several organic salts with varying size of cation, using an aqueous solution of H2SO4 as the electrolyte. The effect of using a dopant in presence of an electrolyte is studied less in the field of conducting polymers. Various organic salts, viz., potassium acetate, sodium acetate, and magnesium acetate were used as dopants at room temperature. The films were electropolymerized in solution containing 0.1 M monomer(s), 1 M H2SO4 as electrolyte, and 1 M organic salt by applying the sequential linear potential scan rate 50 mV/s between − 0.2 and 1.0 V vs. Ag/AgCl electrode. The electrosynthesized films were characterized by cyclic voltammetry, UV–Visible spectroscopy, and conductivity measurements. The UV–Visible spectra were obtained ex situ in DMSO and peaks were observed to appear at about 810–826 nm with a shoulder at 416–426 nm for the emeraldine salt (ES) phase of PA, POA, and PA-co-POA without any doping salt. In the presence of salts, a shift for these absorptions was observed to lower wavelength (786–810 nm); however, a shift of shoulder to higher wavelength (424–435 nm) occurred. In the overall study, an increase in conductivity was observed for all aforesaid dopants; among these, potassium acetate was found to be the best.

Preparation of polyaniline coated poly(methyl methacrylate) microsphere by graft polymerization and its electrorheology

Monodisperse acrylic microspheres (diameter 9.2 μm) (An-PGMA) with aniline moieties on the surface were initially prepared by a seeded emulsion method, and then composite particles (PA-PGMA) possessing polyaniline (PANI) shell were prepared via an in situ polymerization of aniline using An-PGMA particles as a core material inducing grafting polymerization of aniline. The PANI layer was found to be formed on the An-PGMA surface from the microscopic image, 13C FT-NMR and TGA of the PA-PGMA particles. Suspension of the PA-PGMA particle dispersed in silicone oil showed typical electrorheological (ER) characteristics under external electric fields.

A sonochemical method for the synthesis of polyaniline and Au–polyaniline composites using H 2O 2 for enhancing rate and yield

We report on a simple and novel sonochemical method for the preparation of polyaniline (PANI), as well as its composite, with Au nanoparticles. This technique utilizes ultrasound radiation as an energy source to facilitate the reaction by reducing the reaction time, as well as significantly increasing the yield. The tremendous increase in the reaction rates is explained on the basis of the intensive bubble collapse conditions, which rapidly generate the oxidative radicals necessary for polymerization.

Preparation of polyaniline coating on a stainless-steel wire using electroplating and its application to the determination of six aromatic amines using headspace solid-phase microextraction

A novel polyaniline (PANI) coating was prepared on a stainless-steel wire for solid-phase microextraction by electroplating method. For better mechanical strength, the stainless-steel wire was used instead of the fused silica fiber. The electroplating method had advantages of ease of preparation and simple equipments. The PANI fiber was evaluated by analyzing six aromatic amines (aniline, N,N-dimethylaniline, m-methylaniline, 2,4-dimethylaniline, 2-chloroaniline, 3,4-dichloroaniline) in water. After the analytical procedure was optimized, the linearity was from 4.8 to 2.75 × 104 μg L−1 and the detection limits was from 0.019 to 1.06 μg L−1. Relative standard deviations were found to be 2.02–6.00%. Good recoveries were obtained when wastewater samples were analyzed.

Preparation of polyaniline coating on a stainless-steel wire using electroplating and its application to the determination of six aromatic amines using headspace solid-phase microextraction

A novel polyaniline (PANI) coating was prepared on a stainless-steel wire for solid-phase microextraction by electroplating method. For better mechanical strength, the stainless-steel wire was used instead of the fused silica fiber. The electroplating method had advantages of ease of preparation and simple equipments. The PANI fiber was evaluated by analyzing six aromatic amines (aniline, N, N-dimethylaniline, m-methylaniline, 2,4-dimethylaniline, 2-chloroaniline, 3,4-dichloroaniline) in water. After the analytical procedure was optimized, the linearity was from 4.8 to 2.75 × 10 4 μg L −1 and the detection limits was from 0.019 to 1.06 μg L −1. Relative standard deviations were found to be 2.02–6.00%. Good recoveries were obtained when wastewater samples were analyzed.

Electrochemistry of Conductive Polymers. 32. Nanoscopic Examination of Conductivities of Polyaniline Films

The conductivities of electrochemically prepared polyaniline (PAn) films have been determined using an atomic force microscopic tip with a conducting probe after the films were doped/dedoped at various potentials. The results indicate that the PAn films are rather inhomogeneous, even though the film is doped or dedoped until no further anodic or cathodic currents flow. This inhomogeneity was shown to be present even in the PAn nanostructures. The conductivities of the film ranged as widely as by three orders of magnitude on the same surface of 2 × 2 μm2 depending on the location, at which the measurements were made. The range of highest conductivities was obtained when the film was doped at +0.30 V vs Ag|AgCl (in saturated KCl) while the one dedoped at −0.30 V and the one oxidized at +0.80 V were practically insulating. It was also discovered that the film prepared in the perchloric acid medium displayed very poor electrical characteristics compared to those prepared in the nitric acid medium. It is concluded from this study that the electrical properties are determined by the morphology of the film, which in turn is determined by the preparation conditions.

Effects of conductive polyaniline (PANI) preparation and platinum electrodeposition on electroactivity of methanol oxidation

A modified galvanostatic method, termed the ‘pulse galvanostatic method’ (PGM) was used to synthesize nanofibular polyaniline (PANI). In contrast to granular PANI prepared by the conventional galvanostatic method (GM), nanofibular PANI has better conductivity and higher specific surface area. The nanofibular PANI electrode modified by Pt microparticles, at the same Pt loading, exhibits a considerably higher electrocatalytic activity on the methanol oxidation than that of the granular PANI electrode modified by Pt microparticles. Furthermore, the PGM method can be used as a good method for Pt microparticle electrodeposition. The composite electrode composed of PANI and Pt microparticles has the best electrocatalytic activity in the experimental range. The effects of Pt loading and methanol concentration, on the electrocatalytic activity for methanol oxidation have also been researched.

Polyaniline and Carbon Nanotubes Based Composites Containing Whole Units and Fragments of Nanotubes

Using surface-enhanced Raman scattering (SERS) and Fourier transform infrared (FTIR) spectroscopy, we show that composites based on polyaniline (PANI) and single-walled carbon nanotubes (SWNTs) are different when they are prepared by two different methods: (1) by adding dispersed SWNTs to the polymer solutions and (2) by chemical polymerization of aniline in the presence of SWNTs. The difference originates from the irreversible chemical transformation of SWNTs in the polymerization medium. The synthesis medium used for the preparation of PANI transforms SWNTs into fragments of shorter length like closed-shell fullerenes. This explains the similarity of SERS and FTIR spectra of the composites PANI/SWNTs and PANI/C60 chemically prepared. All compounds exhibit an absorption band at 1144 cm-1 in their FTIR spectra, increasing with the carbon nanoparticules content, as a signature of a charge transfer between the constituents. Besides, the FTIR spectrum of the compounds obtained by adding SWNTs to the polymer...

SYNTHESIS AND CHARACTERIZATION OF POLYANILINE AND POLY-ORTHO-METHOXYANILINE. BEHAVIOUR AGAINST CARBON STEEL CORROSION

In the present study the preparation of polyaniline (PANI) and poly-ortho-methoxyaniline (POMA) by chemical method, with different synthesis conditions, has been described. The obtained polymers were characterized by lnfrared and UV-Vis absorption techniques. The morphology of the resulting polymeric films was examined by scanning electron microscopy (SEM). The dissolution inhibitive action on carbon steel was determined measuring the amount of iron(II) in the solution by the o-phenanthroline method. The results indicate that modified carbon steel presents a decrease in their dissolution within the corrosive medium. Also, this method confirmed that PANI-coated samples exhibited satisfactory protection against dissolution and are much more effective than POMA coated ones

Studies on electrochemical, optical and electrical conductivity characteristics of copolymer of polyaniline-co-poly( o-toluidine) using various organic salts

An attempt has been made to prepare polyaniline (PA), poly( o-toluidine) (POT) and their copolymer polyaniline-co-poly( o-toluidine) (PA–POT) thin films doped by several organic salts with varying size of cation, using aqueous solution of H 2SO 4 as electrolyte. Effect of dopant in the presence of electrolyte is rarely studied in the field of conducting polymers. Various organic salts as dopants, viz. potassium acetate, sodium acetate and magnesium acetate were used at room temperature. The films were electropolymerized in solution containing 0.1 M monomer(s), 1 M H 2SO 4 as electrolyte and 1 M organic salt by applying sequential linear potential scan rate 50 mV/s between −0.2 and 1.0 V versus Ag/AgCl electrode. The electro-synthesized films were characterized by cyclic voltammetry, UV–Visible spectroscopy and conductivity measurements. The UV–Visible spectra were obtained ex situ in dimethyl sulfoxide (DMSO) and peaks are observed to appear at about 800–810 nm with a shoulder at 410–420 nm are for emeraldine salt (ES) phase of PA, POT, PA–POT without any doping salt. In the presence of salts, a shift for these absorptions was observed to lower wavelength (758–786 nm), however, a shift of shoulder to higher wavelength (413–425 nm). In overall study, an increase in conductivity was observed for all aforesaid dopants and among these, potassium acetate was found to be the best.

Studies on Influence of Inorganic Dopants in Presence of Electrolyte on the Conductivity of Polyaniline, Poly(o-Anisidine), and Their Copolymer Thin Films

An attempt was made to prepare polyaniline (PA), poly(o-anisidine) (POA), and copolymer polyaniline–poly(o-anisidine) (PA–POA) thin films dopped by several inorganic saltas (sulfates and chlorides) with varying sizes of cations using an aqueous solution of H2SO4 as an electrolyte. Various inorganic salts as dopants, viz., K2SO4, Na2SO4, Li2SO4, MgSO4, KCl, NaCl, LiCl, and MgCl2, were used at room temperature. The films were electropolymerized in solution containing 0.1-M monomer(s), 1-M H2SO4 as electrolyte, and 1-M inorganic salt by applying sequential linear potential scan rate 50 mV/s between −0.2 to 1.0 V vs Ag/AgCl electrode. The electrosynthesized films were characterized by cyclic voltammetry, UV–visible spectroscopy, and conductivity measurements, using a four-probe technique. It was observed that the UV–visible peaks usually appearing at about 810 to 826 nm with a shoulder at 416 to 426 nm, showed a shift in presence of doping salt for the emeraldine salt (ES) phase of PA, POA, PA–POA. In the overall study, a significant increase in conductivity is observed for all dopants mentioned above, and among them K2SO4, is found to be the best in sulfate category and KCl in chloride category.

Effect of inorganic dopants (in presence of electrolyte) on the conductivity of polyaniline, poly(o-toluidine) and their copolymer thin films

An attempt has been made to prepare polyaniline (PA), poly(o-toluidine) (POT) and copolymer (PA-POT) thin films doped by several inorganic salts (sulphates and chlorides) with varying size of cation using aqueous solution of H 2SO 4 as electrolyte. Effect of dopant in presence of electrolyte is rarely studied in the field of conducting polymers. Various inorganic salts as dopants, viz. K 2SO 4, Na 2SO 4, Li 2SO 4, MgSO 4, KCl, NaCl, LiCl and MgCl 2 are used at room temperature. The films were electropolymerized in solution containing 0.1 M monomer, 1 M H 2SO 4 as electrolyte and 1 M inorganic salt by applying sequential linear potential scan rate 50 mV/s between −0.2 and 1.0 V versus Ag/AgCl electrode. The electrosynthesized films were characterized by cyclic voltammetry, UV–visible spectroscopy and conductivity measurements using four-probe technique. It was observed that the UV–visible peaks are appearing at about 800–810 nm with a shoulder at 410–420 nm for emeraldine salt (ES) phase of PA, POT and PA-POT without any doping salt. In the presence of salts, a shift for these absorption spectra is observed to lower wavelength in 760–800 nm, however, a shift of shoulder is to higher wavelength in 435–445 nm. In the overall study, an increase in conductivity is observed for all above-mentioned dopants, and among these, K 2SO 4 is found to be the best in sulphate category and KCl in chloride category.

Improved Electrorheological Effect in Polyaniline Nanocomposite Suspensions

We prepared polyaniline (PANI)/clay composites that are composed of both PANI–clay nanocomposite particles and pure PANI particles. The PANI–clay nanocomposite particles were made during the polymerization process, wherein PANI particles are attached on the surface of exfoliated clay particles modified by an aminosilane group. The PANI/clay composites were used as electrorheological fluids (ERFs) by dispersing them in silicon oil. The PANI–clay nanocomposite particles, which can form columnar structure under an electric field, strongly enhance the mechanical rigidity of the suspensions. The maximum yield stress of the PANI/clay composite suspensions (15 wt% in silicon oil) was 1.6 kPa at 3 kV/mm, while that of pure PANI was 300 Pa at the same electric field. A mechanism to explain the yield behaviors of the PANI-based nanocomposite suspensions is proposed.