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

Abstract

Substituted 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

The structural factors affecting the sensory properties of polyaniline derivatives

“…26 Despite the numerous advantages of PANI as a sensitive material in resistive sensors, a large number of studies are being carried out to improve its sensitivity, selectivity, and response time by structure derivations, copolymerization, varying the dopant, and introducing various components into the conductive polymer. [27][28][29] The structural exibility of PANI allows it to adjust and control its physical and chemical characteristics. For example, the introduction of a substituent into a polymer promotes an increase in solubility, which facilitates the formation of thin lms for sensors and can induce additional interaction with analytes.…”

Polymerization of new aniline derivatives: synthesis, characterization and application as sensors

“…The formation of a more aligned structure of the PANI derivative favors the charge transfer along the polymer chain. 43 It is also assumed that saturation of the polymer with moisture is accompanied by the formation of a complex due to the transfer of an unshared electron pair from the nitrogen atom in the polymer to water molecules. 43 The results of measuring the current–voltage characteristics confirm the assumption that the mobility of charge carriers along individual polymer chains and across adjacent chains is high due to the geometrically ordered, closely packed structure of the polymer chains.…”

“…43 It is also assumed that saturation of the polymer with moisture is accompanied by the formation of a complex due to the transfer of an unshared electron pair from the nitrogen atom in the polymer to water molecules. 43 The results of measuring the current-voltage characteristics conrm the assumption that the mobility of charge carriers along individual polymer chains and across adjacent chains is high due to the geometrically ordered, closely packed structure of the polymer chains. 44 On the other hand, the polymer chains within the microaggregated P-MB polymer lm were much less ordered and less densely packed, which resulted in a greater number of structural defects that apparently improve the sensitivity to ammonia vapor (Fig.…”

P1.8.3 Ink-Jet Printed Conducting Polyaniline based Flexible Humidity Sensor

“…Thus, the partial charge transfer process of conducting species with that of water molecules results in the decrease in the sheet resistivity. The detailed mechanism of the humidity sensing by polyaniline is explained in our earlier publication [13]. The almost linear variation with respect to % RH can be used in an amplifier circuit for converting the measured values into measurable % RH values.…”