Thermal analysis of polyaniline Part I. Thermal degradation of HCl-doped emeraldine base

doi:10.1016/0379-6779(91)91770-B

Synthetic Metals

Volume 40, Issue 2, 1 April 1991, Pages 137-153

https://doi.org/10.1016/0379-6779(91)91770-B Get rights and content

Abstract

Hydrochloric acid-doped emeraldine base has been subjected to programmed thermal degradation under high vacuum conditions. The temperature profiles of the degradation processes have been mapped using thermogravimetry (TG) in conjunction with thermal volatilization analysis (TVA). Product distributions have been ascertained using the fractionating capability of the TVA system in conjunction with ancillary techniques of analysis such as infrared (IR) and proton nuclear magnetic resonance (NMR) spectroscopy and gas chromatography-mass spectrometry (GC-MS). At low temperatures (c. 200 °C) HCl gas is evolved. At higher temperatures the polymer is subject to complex and overlapping processes involving chain scissions, ring fusions and fragmentations, and heterocycle production. These observations are rationalized through the construction of a family of plausible reaction mechanisms which are consistent with our measured product distributions.

References (18)

J. Tang et al.
Synth. Met.
(1988)
A.G. MacDiarmid et al.
Synth. Met.
(1987)
J.-C. Chiang et al.
Synth. Met.
(1986)
I.C. McNeill
Eur. Polym. J.
(1967)
I.C. McNeill
Eur. Polym. J.
(1970)
I.C. McNeill et al.
Polym. Deg. Stab.
(1985)
A.G. Green et al.
J. Chem. Soc.
(1910)
A.G. Green et al.
J. Chem. Soc.
(1912)
T. Hjertberg et al.
J. Polym. Sci. Part C, Polym. Lett. Ed.
(1985)

There are more references available in the full text version of this article.

Cited by (98)

Probing molecular ordering in the HCl-doped polyaniline with bulk and nanofiber morphology by their thermal behavior
2015, Polymer Degradation and Stability
Citation Excerpt :
The TGA profiles for PANI-ES bulk and fibers are very similar, and present three major events of mass loss in the temperature ranges of 25–100, 120–200 and 300–700 °C. The event at lower temperature is assigned to water and adsorbed hydrogen chloride loss [28–32], the event at intermediate range (120–200 °C) is assigned to the loss of strongly bonded HCl dopant [28,30,32–34], and the mass loss at higher temperature range is assigned to an irreversible and complex polymeric decomposition [18,28–30,32,35]. These results are in agreement with those reported in the literature [18,28–30,33,34,36].
Conducting polymers are an amazing class of materials, which provide new approaches in material design. The study of the thermal stability of polyaniline (PANI) is of great importance since heating is the initial step in several polymer processing methods. Concerning the studies of PANI's thermally induced structural changes, it has been observed that structural changes lead to the formation of phenazine-like structures or induce the thermal dedoping depending on the morphology and doping level, however, it was not completely clear the reason why some polymers presented the dedoping and others the cross-linking reaction after heating. In this paper, the influence of the morphology (bulk or nanofibers) on the thermal behavior of doped PANI (PANI-ES) have been investigated using the mass spectrometry-coupled thermogravimetric analysis, Raman spectroscopy and scanning electron microscopy. Our data have shown that nanofibers of PANI-ES are resistant to the thermal induced dedoping process and the major structural change have been the formation of high amount of phenazine-like segments, while for bulk PANI-ES, the dedoping process has been favored. The amount of phenazine-like segments induced by heat was dependent not only the presence of the polaronic segments but also on the molecular ordering.
Effect of thermal treatment on conductometric response of hydrogen gas sensors integrated with HCl-doped polyaniline nanofibers
2014, Materials Chemistry and Physics
In this work, we investigated the effect of thermal treatments on the transduction of HCl-doped polyaniline (PANI) nanofibers integrated in conductometric devices upon exposure to 1% H₂ (carried by N₂). After drying in N₂ at ∼25 °C for 12 h, our devices showed a ∼10% decrease in electrical resistance upon exposure to 1% H₂. However, devices subject to 12-h drying in N₂ at ∼25 °C followed by further thermal treatments in N₂ at 100 °C, 164 °C or 200 °C for 30 min showed different transduction behaviors. The devices subject to thermal treatments at 100 °C and 164 °C showed a ∼7% decrease and <0.5% variation in electrical resistance, respectively. More interestingly, the device subject to the thermal treatment at 200 °C showed a transduction behavior with obvious opposite polarity, i.e. a ∼5% increase in electrical resistance upon exposure to 1% H₂. Further analysis indicated that the observed results were related to the thermal treatments which caused HCl-doped PANI nanofibers to undergo (i) water desorption, (ii) crosslinking and/or (iii) partial carbonization.
Transparent electrodes based on conducting polymers for display applications
2013, Displays
The materials science and engineering related to the fabrication of conducting polymer thin films and the progress in the development of devices integrated with organic transparent electrodes based on conducting polymers for display applications are reviewed. Transparent electrodes are essential components for many display modules. With the evolution of display technologies, conducting polymers are recently emerging as important alternative materials for the fabrication of transparent electrodes. Conducting polymers offer some advantages, such as light weight, low cost, mechanical flexibility and excellent compatibility with plastic substrates for the development of next-generation display technologies and, in particular, are expected to play an important role in the development of flexible display technologies.
X-ray irradiation: A non-conventional route for the synthesis of conducting polymers
2011, Synthetic Metals
Citation Excerpt :
However, a very significant weight loss begins to occur above 365 °C which is attributed to thermal decomposition of the molecular main chains. This thermal behavior seems to be in agreement with the results found for polyaniline synthesized by conventional techniques [21,22]. As to the yield (%) and electrical conductivity σ (S cm−1) measurements for PANI obtained by X-ray irradiation to a total dose of 5 kGy, we obtained the values of 5.1 and 0.7 × 10−3, respectively.
A non-conventional methodology for polyaniline (PANI) synthesis using X-ray irradiation is presented in this article, and shows the oxidants normally used in the (chemical or electrochemical) conventional synthesis of PANI are not necessary. The method uses only high energy photons to interact with nitrate ions (NO₃⁻) and aniline monomer in an aqueous solution. The polymerization mechanism has also been investigated using radical scavenger (DMSO), and the results suggest that the hydroxyl radical (OH) generated in situ during exposure to X-ray could be the main agent responsible for oxidation and subsequent polymerization of the aniline monomer. Characterization of the morphology of the polymer by scanning electron microscopy (SEM) reveals that the PANI obtained by X-ray presents a predominantly fibrillar morphology with an average fiber diameter of 90 nm. Additionally, thermogravimetric analysis (TGA), elemental analysis, gel permeation chromatography (GPC), conductivity measurements, and spectroscopic characterization in the UV–vis and IR regions, showed that the polymer obtained is the polyemeraldine salt (the conducting form of the polymer).
Structure and Properties of Conducting Polymer Composites
2023, Structure and Properties of Conducting Polymer Composites
Chitosan/Hydroxyethyl Cellulose Gel Immobilized Polyaniline/CuO/ZnO Adsorptive-Photocatalytic Hybrid Nanocomposite for Congo Red Removal
2022, Journal of Polymers and the Environment

View all citing articles on Scopus

View full text

Original research paperThermal analysis of polyaniline Part I. Thermal degradation of HCl-doped emeraldine base

Abstract

Synth. Met.

Synth. Met.

Synth. Met.

Eur. Polym. J.

Eur. Polym. J.

Polym. Deg. Stab.

J. Chem. Soc.

J. Chem. Soc.

J. Polym. Sci. Part C, Polym. Lett. Ed.

Original research paper
Thermal analysis of polyaniline Part I. Thermal degradation of HCl-doped emeraldine base