Conducting Emeraldine Salt Phase Research Articles

Morphology Tuning of Conducting Polyaniline via Static, Liquid-Liquid Interfacial Polymerization Process and its Application for Optical pH Sensing

Abstract Nanorods/nanofibers of conducting polymer, polyaniline (PANI) were synthesized via static, liquid-liquid interfacial polymerization process using ammonium persulphate as an oxidizing agent. The monomer, aniline was dissolved in chloroform comprising the organic phase, while the oxidizing agent, ammonium per sulphate was dissolved in doubly distilled water to form an aqueous phase. Para toluene sulphonic acid (p-TSA) was used as dopant during the polymerization process to dope the polyaniline. The presence of conducting emeraldine salt phase of the polymer was confirmed by UV-Vis. and FT-IR spectroscopic characterization. This was further supported by XRD analysis. The morphological studies are carried out using FE-SEM analysis and revealed the presence of uniform sized nanorods/nanofibers having diameter of ∼90 nm and length up to few microns. This rapid and novel interfacial polymerization process shows the potential of large scale synthesis of uniform sized nanorods/nanofibers of polyaniline. The synthesized nanostructured polyaniline was successfully utilized for the optical pH sensing application in aqueous state.

Development of polyaniline–multiwalled carbon nanotube (PANI–MWCNT) nanocomposite for optical pH sensor

A highly transparent and water soluble nanocomposite of a conducting polymer, polyaniline (PANI) plus multiwalled carbon nanotubes (MWCNTs), was prepared by in situ chemical polymerisation method using sulphonic acid as a dopant. Initially, MWCNTs were functionalised by acid treatment and then dispersed in the monomer, aniline and the resultant MWCNTs coated aniline was polymerised using ammonium per sulphate as an oxidising agent to form PANI–MWCNT nanocomposite. The synthesised nanocomposite was characterised by using spectroscopic (ultraviolet–visible and Fourier transform infrared spectroscopy), field emission scanning electron microscopy and thermal analyses. The ultraviolet–visible spectrum of the salt phase (dark green) of the PANI–MWCNT nanocomposite shows a free carrier tail with increasing absorption at higher wavelength, which confirms the presence of conducting emeraldine salt phase of the PANI; whereas, the base form (deep blue) of the nanocomposite shows a sharp peak at 600 nm representing insulating pernigraniline phase of the polymer. The synthesised nanocomposite was then demonstrated for optical pH sensing.

Synthesis and spectroscopic characterisation of silver–polyaniline nanocomposite

Nanocomposite of silver–polyaniline (Ag–PANI) has been synthesised by the in situ chemical polymerisation method using ammonium persulphate as an oxidising agent in the presence of sulphonic acid dopant. The synthesised Ag–PANI nanocomposite was subjected to the physicochemical characterisation using ultraviolet–visible and Fourier transform infrared spectroscopy. The ultraviolet–visible spectra of the synthesised nanocomposites show the presence of the characteristic absorption peak at ∼340 nm, which corresponds to the π−π* transition, and the shoulder at ∼420 nm corresponds to the polaronic peak of PANI. The surface plasmon resonance of the silver nanoparticles embedded in the polymer matrix, which is appearing at that wavelength, would have been overlapped by the polaronic peak of the PANI. The increasing absorption at higher wavelength confirms the formation of conducting emeraldine salt phase of the PANI, which is further supported by the Fourier transform infrared spectroscopy. The X-ray diffraction and energy dispersive spectroscopy study exposed the existence of silver nanoparticles in the elemental state. The morphology of the nanocomposites was characterised by SEM. Thermogravimetric analysis indicates an enhancement of the thermal stability of the nanocomposite compared with that of pure polymer. The Ag–PANI nanocomposite can be considered as a potential candidate for the applications in sensors, catalysis and electronic devices.

Studies of conducting polyaniline (PANI) wrapped-multiwalled carbon nanotubes (MWCNTs) nanocomposite and its application for optical pH sensing

Highly transparent and water soluble nanocomposite of conducting polyaniline wrapped-multiwalled carbon nanotubes (PANI-MWCNTs) was synthesized by in situ chemical polymerization method using sulphonic acid as a dopant. MWCNTs were functionalized prior to their use and then polymerized using ammonium per sulphate as an oxidizing agent. The nanocomposite was subjected for physico-chemical characterization using spectroscopic (UV–vis and FT-IR), FE-SEM and HR-TEM analysis. The UV–vis spectrum of the salt phase (dark green) of the PANI-MWCNTs nanocomposite shows a free carrier tail with increasing absorption at higher wavelength, which confirms the presence of conducting emeraldine salt phase of the polyaniline and is further supported by FT-IR analysis. However, the base form (deep blue) of the nanocomposite shows a sharp peak at 600nm representing an insulating emeraldine base phase of the polymer. The FE-SEM images show the uniform wrapping/coating of the polyaniline over the functionalized MWCNTs and this is further supported by HR-TEM analysis. The synthesized nanocomposite was then successfully used for the determination of pH of the solution (pH 1–12) and found to be a potential candidate for optical pH sensing.

Ink-jet printed conducting polyaniline based flexible humidity sensor

Ink-jet printed, intrinsically conducting polymer (ICP), polyaniline have been used for humidity sensing at room temperature. Polyaniline based, aqueous ink-jet printable ink has been synthesized by single step, chemical oxidative polymerization technique. Sulphonic acids were used as a dopant during the in situ polymerization process. This is a single step polymerization process for the direct synthesis of conducting emeraldine salt phase of the polymer as an ink formulation. The synthesized polyaniline ink was further characterized by spectroscopic (UV–visible and FT-IR) analysis which confirmed the presence of conducting emeraldine salt phase of the polymer. The viscosity of the ink was measured by using Brook-field viscometer. The successive trials were performed for the printing of IDT pattern on the flexible, untreated polymer substrate using HP ink-jet-printer. The printed sensor was subjected for the humidity sensing measurements. The change in the resistance with change in the %RH was observed. It is suggested that the increase in conductivity at high humidity may be related to a vapour-induced change in the transfer of charge carriers between the polymer chains. The synthesized polyaniline based ink can also be considered as a good candidate for variety of ink-jet printed low cost electronics devices.

Processing and formulation of inkjet printable conducting polyaniline based ink for low cost, flexible humidity sensors using untreated polymeric substrate

Conducting polymer, polyaniline based aqueous inkjet printable ink has been synthesized by a single-step chemical polymerization technique. Sulfonic acids were used as a dopant during the in situ polymerization process. This is a single-step polymerization process for the direct synthesis of conducting emeraldine salt phase of the polymer as an ink formulation. Ammonium persulfate was used as an oxidizing agent to initiate the polymerization. The synthesized polyaniline ink formulation was characterized by UV–vis and FT-IR spectroscopic analysis. The presence of a very sharp peak at 800 nm represents the presence of the conducting emeraldine salt phase of the polymer. This is further supported by FT-IR spectroscopic characterization. The viscosity of the ink was measured by using a Brookfield viscometer. Successive trials were performed for the printing of interdigitated patterns on the flexible untreated polymer substrate using an HP inkjet printer. The printed sensor was subjected to humidity sensing measurements. The change in the resistance with change in the % relative humidity (RH) was observed. The synthesized polyaniline based ink can be considered as a good candidate for a variety of inkjet printed low cost electronics devices.

Microwave-assisted hydrothermal synthesis and characterization of tremella-like polyaniline–vanadium oxide nanocomposite nanosheets

The organic–inorganic hybrid nanocomposite of polyaniline–V2O5 was synthesized by microwave-assisted hydrothermal method. The nanocomposite was separated by filtration and washed with deionized water. Structural study of nanocomposite was performed using XRD. The microstructural study of nanocomposite performed using field emission scanning electron microscopy (FESEM) shows self-assembled plates with curly petal or tremella-like morphology. The nanocomposite was subjected for spectroscopic (UV–vis and FT-IR) analysis. The UV–vis spectra revealed the presence of conducting emeraldine salt phase of the polymer which was further supported by FT-IR analysis.

AC conductivity and dielectric behavior of polyaniline/sodium metavenadate (PANI/NaVO3) composites

The conducting polyaniline/sodium metavenadate (PANI/NaVO 3 ) composites were synthesized by single step in situ polymerization technique by placing finely grinded powder of NaVO 3 during the polymerization of aniline. The formation of mixed phases of the polymer together with the conducting emeraldine salt phase was confirmed by spectroscopic techniques like FTIR. SEM images indicated a systematic morphological variation of particles aggregated in the composite matrix as compared to the pristine PANI. AC conductivity and dielectric behavior of these composites were investigated in the frequency range 50 Hz to 5 MHz. It is found that AC conductivity obeyed the power law index and the variation of conductivity with wt% of NaVO 3 could be related to conductivity relaxation phenomenon. These composites have shown high dielectric constant, which is related to polarization. It is seen that both dielectric constant and dielectric loss decrease with increase in frequency. Variations in measured parameters of AC response with increasing frequency of these composites are found to follow systematic trends that are similar to those observed with temperature and doping.

Synthesis and Characterization of Polyaniline -Crooked Gold Nanocomposite with Reduced Conductivity

Conducting Polyaniline (Pani)-crooked Gold nanocomposites were synthesized by in situ chemo-oxidative polymerization of aniline with previously made crooked gold nanoparticles by using ammonium per oxidisulphate as oxidizing agent and p-toluene sulphonic acid (p-TSA) as dopant. The formation of nano gold was established by UV-visible spectroscopy with a SPR peak at 512 nm and crooked morphology was confirmed by TEM. Spectroscopic analysis confirmed the formation of the conducting emeraldine salt phase of the polymer. Due to clustering of composite nanoparticles, the polymer composite formed one-dimensional rod-like morphologies. Thermogravimetric analysis revealed a typical three-step decomposition pattern pertaining to polyaniline emeraldine salt. The conductivity of the nanocomposite was found to be lower (2.47 S/cm) than the virgin p-TSA doped polyaniline (5.55 S/cm).

Sulphonic acids doped poly(N‐ethyl aniline): A material for humidity sensing application

AbstractSubstituted polyaniline, poly(N‐ethyl aniline) (PNEA), doped with camphor sulphonic acid (CSA) and p‐toluene sulphonic acid (p‐TSA), was synthesized by single‐step chemical polymerization method using ammonium persulphate as an oxidizing agent. This is a single‐step polymerization process to synthesize directly the conducting emeraldine salt phase of the polymer using CSA and p‐toluene sulphonic acid as dopants. The synthesized polymers were characterized by UV–vis and FTIR spectroscopy, scanning electron microscopy, TGA/SDTA, DSC, and conductivity measurements. This single‐step chemical synthesis method offers a polymer having very good physicochemical properties with good electrical conductivity. High temperature conductivity measurements show “thermal activated behavior.” The change in resistance with respect to % relative humidity (% RH) is observed, when pressed pellets of the polymer were exposed to the broad range of humidity (ranging between 20 and 100% RH). POLYM. ENG. SCI., 47:1621–1629, 2007. © 2007 Society of Plastics Engineers

Humidity sensing and electrical properties of polyaniline/cobalt oxide composites

AbstractPolyaniline/cobalt oxide composites were synthesized by an in situ chemical polymerization method with ammonium persulfate as an oxidizing agent. This was a single‐step polymerization process for the direct synthesis of the emeraldine salt phase of the polymer. The polymers were characterized with X‐ray diffraction, scanning electron microscopy, and Fourier transform infrared spectral analysis. The formation of mixed phases of the polymer together with the conducting emeraldine salt phase was confirmed by spectroscopic techniques. High‐temperature conductivity measurements showed thermally activated behavior. A change in the resistance was observed with respect to the relative humidity when the pellets were exposed to a wide humidity range of 10–95%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 653–658, 2007

Spectroscopic and electrical properties of polyaniline/CeO2 composites and their application as humidity sensor

AbstractPolyaniline/CeO2 composites were synthesized by in situ chemical polymerization method using ammonium persulphate as an oxidizing agent. This is the single step polymerization process for the direct synthesis of emeraldine salt phase of polymer. The polymers were characterized by using FTIR spectral analysis, SEM, and XRD studies. Formation of conducting emeraldine salt phase is confirmed by spectroscopic techniques. High temperature conductivity measurements show “thermal activated behavior.” The change in resistance with respect to percentage relative humidity (% RH) is observed, when the pressed pellets of the polymer were exposed to the broad range of humidity (humidity ranging between 10 and 95% RH). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5533–5537, 2006

Synthesis and Characterization of Poly(o-anisidine) Doped with Polymeric Acids

ABSTRACT Conducting poly(o-anisidine) doped with polymeric acids [viz, poly(styrene sulphonic acid) (PSSA), poly(vinyl sulphonic acid) (PVSA) and poly(acrylic acid) (PAA)] was synthesized by in-situ chemical polymerization method using ammonium persulphate as an oxidizing agent. This is a single-step polymerization process for the direct synthesis of emeraldine salt phase of the polymer. The polymers were characterized by using UV-Vis., FT-IR spectroscopy, thermal analysis, and conductivity measurements. Formation of mixed phases of polymer together with conducting emeraldine salt phase are confirmed by spectroscopic techniques. Thermal analysis shows that PAA doped poly(o-anisidine) undergoes three stage decomposition pattern similar to unsubstituted polyaniline. While, in PSSA and PVSA, doped sample splitting up of the second weight loss stage is observed leading to a four-step decomposition pattern. Room temperature conductivity measurements show less conductivity in poly(o-anisidine) than in polyaniline, due to the cumulative steric as well as electronic effects of the bulky methoxy substituent present at ortho position on the benzene ring. Increase in conductivity with increase in temperature is observed by high temperature conductivity measurements, showing “thermally activated behavior.”

Single Step Polymerization of Conducting Poly(O-Toluidine) Doped with Camphor Sulfphonic Acid: Synthesis and Characterization

Single step chemical polymerization of o-toluidine was carried out by using ammonium persulphate as an oxidizing agent. This is a direct process to synthesize the conducting emeraldine salt phase of the polymer using camphor sulphonic acid as a dopant. The polymer was characterized by UV-Vis. and FT-IR spectroscopy, scanning electron microscopy, TGA/DSC, elemental analysis and conductivity measurements. This method offers a polymer having very good physico-chemical properties with good electrical conductivity.

Synthesis and characterization of poly(aniline-co-o-anisidine-co-o-toluidine) thin films in organic sulphonic acids

The effect of organic sulphonic acids on electrochemical, optical and conductivity properties of poly(aniline-co-o-anisidine-co-o-toluidine) terpolymer thin films have been investigated. Homo- and terpolymer thin films were synthesized electrochemically under cyclic voltammetric conditions in aqueous solutions of sulphuric acid, p-toluene sulphonic acid, sulphamic acid and sulphosalicylic acid at room temperature. The films were electro-polymerized in solution containing 0.1 M monomers and the respective electrolyte (1 M sulphuric acid or organic sulphonic acid) by applying a sequential linear potential scan rate of 50 mV/s between −0.2 and 1.0 V versus Ag/AgCl electrode. The electrosynthesized films were characterized by cyclic voltammetry, UV-Vis spectroscopy and conductivity measurement. It is observed that the UV-Vis peaks for sulphuric acid, p-toluene sulphonic acid, sulphamic acid and sulphosalicylic acid are appearing in the region of conducting emeraldine salt phase. In an overall study, the polymers prepared using these three organic sulphonic acids have higher conductivity than sulphuric acid; however, the higher conductivity is observed for p-toluene sulphonic acid as electrolyte in comparison with sulphamic acid and sulphosalicylic acid. Differential scanning calorimetry also proved the formation of terpolymer. A possible reaction mechanism for the homo- and co-polymer has been suggested.

Investigation of Spectroscopic and Thermal Properties of Poly(o‐toluidine) Doped with Polymeric Acids

Single step polymerization of poly(o‐toluidine) was carried out by using ammonium persulphate as an oxidizing agent. Formation of the conducting emeraldine salt phase of the polymer was confirmed by the UV‐visible and FT‐IR spectroscopic analysis. The elemental composition of the polymer was evaluated by using a CHNS analyzer. Thermal stability of these polymers was investigated by the thermogravimetric analysis. Among the three polymeric acids used for doping purposes, poly(acrylic acid) doped material was found to show less thermal stability compared to poly(styrene sulphonic acid) and poly(vinyl sulphonic acid) doped poly(o‐toluidine).

Synthesis and characterization of poly(N‐methyl aniline) doped with sulphonic acids: Their application as humidity sensors

AbstractSingle step chemical polymerization of N‐methyl aniline was carried out by using ammonium persulphate as an oxidizing agent. The conducting emeraldine salt phase of the polymers using camphor sulfonic acid and p‐toluene sulfonic acid as dopants was made by a direct process. The polymers were characterized by UV‐vis and FTIR spectroscopy, scanning electron microscopy, TGA, and conductivity measurements. The synthesized polymers were found to have very good physicochemical properties and good electrical conductivity. Conductivity measurements have shown “thermal activated behavior.” The change in resistance with respect to % relative humidity (RH) was observed, when pressed pellets of the polymer were exposed to the broad range of humidity (ranging between 20 and 100% RH). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 812–820, 2006

Synthesis and humidity sensing properties of conducting poly(N-methyl aniline) doped with different acids

Poly(N-methyl aniline) (PNMA), doped with different acids (viz. HCl, HClO4, H3PO4, H3BO3 and acetic acid) was synthesized by a chemical polymerization method using ammonium persulphate as an oxidizing agent. This is a single step polymerization process to synthesize directly the conducting emeraldine salt phase of the polymer. The synthesized polymers were characterized by UV–vis, TGA/SDTA and conductivity measurements. These polymers were then successfully utilized as humidity sensors. The change in resistance with respect to % relative humidity (% RH) was observed, when pressed pellets of the polymers were exposed to a broad range of humidity (20–100% RH). Among the different acids used for the doping purpose of the polymer, the H3PO4-doped polymer showed the best sensing response and was found to be the best candidate for a humidity sensor.

Spectroscopic, thermal and electrical properties of sulphonic acids doped poly( o-anisidine) and their application as humidity sensor

Poly( o-anisidine), P( o-anis) doped with camphor sulphonic acid (CSA) and p-toluene sulphonic acid ( p-TSA) was synthesized by in situ chemical polymerization method using ammonium persulphate as an oxidizing agent. This is a single step polymerization process for the direct synthesis of emeraldine salt phase of the polymer. The polymers were characterized by using UV–vis and FT-IR spectroscopy, TGA and conductivity measurements. Formation of mixed phases of polymer together with conducting emeraldine salt phase are confirmed by spectroscopic techniques. Thermal analysis shows that poly( o-anisidine) has three stage decomposition pattern similar to unsubstituted polyaniline. The lower conductivity in poly( o-anisidine) compared to polyaniline is due to the cumulative steric as well as electronic effects of the bulky methoxy substituent present on the benzene ring. High temperature conductivity measurements show ‘thermal activated behaviour’. The change in resistance with respect to % relative humidity (RH) is observed, when pressed pellets of the polymer were exposed to the broad range of humidity (ranging between 20–100% RH).

Comparative studies of solid-state synthesized polyaniline doped with inorganic acids

Polyaniline (PANI) salts doped with inorganic acids (HCl, H 2SO 4 and H 3PO 4) were directly synthesized by using solid-state polymerization method. The FTIR spectra, UV–vis absorption spectra and X-ray diffraction patterns were used to characterize the molecular structures of the PANI salts. Voltammetric study was done to investigate the electrochemical behaviors of all these PANI salts. The PANI salts were affected by varying the protonation media (HCl, H 2SO 4 and H 3PO 4). The FTIR and UV–vis absorption spectra revealed that all PANI salts contained the conducting emeraldine salt phase at different oxidation state. The crystallinity of PANI doped with HCl was better than those doped with H 2SO 4 and H 3PO 4. The conductivity of the PANI doped with HCl is the highest among the inorganic acid doped PANI.