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The article presents a study that synthesizes substituted polyaniline, poly(N-ethyl aniline) (PNEA), added with camphor sulphonic acid (CSA) and p-toluene sulphonic acid (p-TSA), by a single-step chemical polymerization method that utilizes ammonium phersulphate as an oxidizing agent. The authors reported that the single-step polymerization process to directly synthesize the conducting emeraldine salt phase of the polymers using CSA and p-toluene sulphonic acid as dopants. The change in resistance with respect to the relative humidity is also discussed.

Abstract: 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. [Copyright &y& Elsevier]

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). [ABSTRACT FROM AUTHOR]

Abstract: 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). [Copyright &y& Elsevier]

Substituted polyaniline, poly(o-toluidine), was synthesized by oxidative chemical polymerization method. Acetic, formic and oxalic acids were used as dopants during the polymerization process. Synthesized polymers were subjected to the spectroscopic and thermal analysis. Spectroscopic and thermal properties of the polymers are found to be affected by the type of the dopant ion used for doping purpose. Formation of different oxidation states of the polymer were confirmed by the spectroscopic (UV-Vis and FT-IR) analysis. Three step decomposition pattern similar to that of polyaniline are observed in the thermogram. The percentage yield as well as conductivity is found to be higher in formic acid doped polymer than that doped with acetic and oxalic acid. Increase in conductivity with increasing temperature was observed in all the polymers. [Copyright &y& Elsevier]

Discusses the synthesis of a conducting polymer, polyaniline, by chemical polymerization using different inorganic acids as protonic acid media. Granular type of morphology; Folded lamellar structure derived from the fibers; Link between conductivity and increase in temperature.

Abstract: The results of synthesis of Ag-Polyaniline nanocomposite along with an investigation of optical fiber based humidity sensor using evanescent wave absorption spectroscopy are discussed. The sensor was fabricated using Ag-Polyaniline nanocomposite deposited on an optical fiber clad and tested in the range of 5–95% relative humidity (RH). Optimization of clad length (2–8mm) was done and then particle size (15–30nm) variation of silver nanoparticles in Polyaniline composite was studied for better performance of sensor. The effect of particle size on sensing humidity was investigated. The reduction of particle size, leads to a dramatic improvement in sensitivity and speed of response. The optimized clad length of 6mm exhibits the better results for 15nm particle size of Ag nanoparticles dispersed in Polyaniline. The sensor response is fully reversible having almost 1% of standard deviation. Response time of the sensor is 30s with a slow recovery of 90s. [Copyright &y& Elsevier]

Abstract: Spin coated films of Co-Polyaniline nanocomposite are evaluated for their transmission properties using He–Ne laser for humidity sensing. The thickness (17–29μm) of the films is varied by multiple deposition of Co-Polyaniline nanocomposite on a glass substrate. The samples exhibit typically two to three regions in their sensitivity curve when tested in the relative humidity (RH) range of 20–95%. The sensitivity ranges from 0.1mV/%RH to 12.26mV/%RH for lower to higher thickness. The sensors show quick response of 8s (20–95%RH), and a recovery time of 1min (95–20%RH) with good repeatability, reproducibility and low hysteresis effect. The sensitivity of the sensor increases with humidity and thickness. Material characterization is done by X-ray diffraction (XRD), scanning electron micrograph (SEM) and Fourier transform infra-red spectroscopy (FTIR). [Copyright &y& Elsevier]