The stability of polyaniline in strongly alkaline or acidic aqueous media (original) (raw)
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Effects of Dopant Ions on the Properties of Polyaniline Conducting Polymer
ORIENTAL JOURNAL OF CHEMISTRY, 2018
This work will show, for the frst time, the effect of nicotinic acid (NA) and 2-methylnicotinic acid (MNA)on the synthesis and properties of conducting polyaniline (PANI). The work investigates the effects of sulphuric acid (H2SO4), nicotinic acid (NA), and 2-methylnicotinic acid (MNA) on the synthesis and properties of polyaniline. The results show that the preparation of polyaniline from a sulphuric acid electrolyte is faster than the preparation from nicotinic acid and 2- methylnicotinic acid electrolytes. Moreover, the electrical conductivity and thermal stability of PANI/H2SO4 were greater than PANI/NA and PANI/MNA. All the polymers prepared in this study were identifed using FT-IR. Scanning electron microscopy (SEM) was used to examine the morphologies of the PANI samples, from which it was determined that PANI/H2SO4 has a fbrous and open structure with a higher porosity morphology compared to PANI/NA and PANI/MNA. The electrical conductivities of the PANI samples were measured as 1.09 S cm-1, 0.65 S cm-1 and 0.089 S cm-1 for PANI/H2SO4, PANI/NA and PANI/MNA, respectively. The thermal stability of PANI was examined using the Thermogravimetric Analysis (TGA) technique. PANI/H2SO4 was found to degrade between 450-500°C, while PANI/NA and PANI/MNA decomposed at temperatures between 300-400°C.
PANI Conductivity: A Dependence of the Chemical Synthesis Temperature
This work evaluated the influence of the synthesis temperature on the polyaniline (PANI) properties obtained by in-situ polymerization onto a poly (terephthalate) (PET) substrate. The residual mass of these syntheses was dried under vacuum, obtaining PANI powders for each temperature investigated. PANI/PET thin films and PANI powders were characterized by atomic force microscopy (AFM), field emission scanning electron microscopy (FEG-SEM), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Vis) and four-point probe techniques. The UV-Vis results showed that the synthesized PANI presents the emeraldine oxidation state. By means of XRD technique, it was possible to verify that the PANI powders present crystalline form. The AFM and FEG-SEM techniques showed that the decrease in PANI/PET and PANI powders electrical conductivity with increasing of the synthesis temperature is related to the polymeric aggregates morphology.
Materials
Polyaniline (PANI) was synthesized chemically with the modified rapid mixing protocol in the presence of sulfuric acid of various concentrations. A two-step synthetic procedure was utilized maintaining low-temperature conditions. Application of the modified rapid mixing protocol allowed obtaining a material with local ordering. A higher concentration of acid allowed obtaining a higher yield of the reaction. Structural characterization performed with Fourier-transform infrared (FTIR) analysis showed the vibration bands characteristic of the formation of the emeraldine salt in both products. Ultraviolet–visible light (UV–Vis) spectroscopy was used for the polaronic band and the p–p* band determination. The absorption result served to estimate the average oxidation level of PANI by comparison of the ratio of the absorbance of the polaronic band to that of the π–π* transition. The absorbance ratio index was higher for PANI synthesized in a more acidic solution, which showed a higher dop...
Thermal stability of polyaniline
Polymer Bulletin, 2000
Among conducting polymers with metallic characteristics, polyaniline (PANI) is claimed to have one of the highest environmental stability. From an industrial point of view it would be useful to be able to thermally process this material into useful products using conventional techniques such as extrusion, stretching, rolling, etc., which generally are carried out at elevated temperatures. Somewhat surprisingly, relatively few studies have addressed the thermal stability of PANI, in particular that of the non-protonated emeraldine base form. Therefore, a study of the thermal properties was performed to examine the thermal stability of this material and to identify the optimum processing and maximum application temperatures.
Thermo-analyses of polyaniline and its derivatives
Thermochimica …, 2010
In this work, is presented the thermal behavior of polyaniline (PANI) and its derivatives poly(oethoxyaniline) (POEA) and poly(o-methoxyaniline) (POMA), which were studied by using differential scanning calorimetry (DSC), modulated DSC (TMDSC), respectively, and thermal gravimetric analysis (TGA). The results from diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and thermal analysis showed the formation of crosslinking isomerization reaction during the heating process. The results showed that the maximum weight loss and the crystallinity degree depend on the type of the aromatic ring substituent group, i.e. hydrogen, ethoxy or methoxy.
Materials Research, 2011
In order to study the influence of different sulfonation routes on its thermal and structural properties sulfonated polyaniline (SPAni) was prepared. FT-IR revealed that the formation of PAni salt or ring sulfonation depends on the route. UV-visible spectra pointed out that the level of the PAni protonation was dependent on the sulfonation route. A new approach was given for TG/DTG and DSC results correlating different energy levels with the distinguished sulfonation routes. The TG/DTG degradation steps and the amount of the released material corroborated the structural differences of the polyanilines. For each DSC first regime of heating, a broad and intense peak (from-30 to 250 °C) with different level of energy was noticed. That peak could be ascribed to the multiple relaxations and breaking of the PAni intra and inter hydrogen bonds after sulfonation.
Effect of Elevated Temperature on the Reactivity and Structure of Polyaniline
Macromolecules, 2002
The structure and oxidation state of emeraldine base polyaniline (PANI) in N-methylpyrrolidinone solutions that have been heated to 120-190°C have been characterized by solid-state NMR, UV/vis, FTIR, and GPC. The spectroscopic studies reveal that the polymer is completely converted to its fully reduced leucoemeraldine form after heating at 175-190°C for only 2 h, and bubbling oxygen gas through the solutions after heating results in partial reoxidation of the polymer. Cross-links, consisting of phenazine structures, have been identified in PANI films cast from heated NMP solutions by 15 N interrupted decoupling solid-state NMR. After heating, the polymer is partially cross-linked with the cross-link density increasing with annealing temperature, and the non-cross-linked regions are the reoxidizable portions of the polymer. A mechanism by which the cross-linking reaction of PANI leads to the polymer reduction is discussed. Scheme 3. Structure of PANI Generated in Heated NMP Solutions 7580 Mathew et al.
Ageing of PANI: chemical, structural and transport consequences
Synthetic Metals, 1999
Chemical, structural and transport consequences of PANI have been studied for two types of samples: hydrochloric acid protonated PANI powders and camphorsulfonic acid protonated PANI films cast from m-cresol solutions. Different characterization techniques have been applied: elemental analysis, FIIR, XPS, XRD, and conductivity measurements. The combination of-these techniques enables us to identify three main degradation processes: dedoping, oxidation/hydrolysis/scission of the chains, and crosslinking. The impact of ageing on transport properties is briefly discussed and a simple model taken into account the kinetics of the conductivity decay is postulated.
Thermal dynamic processing of polyaniline with dodecylbenzene sulfonic acid
Journal of Applied Polymer Science, 1997
To attain an intrinsically conductive and processible polymer, polyaniline (PANI)/dodecylbenzene sulfonic acid (DBSA) blends of several compositions were processed at various elevated temperatures in a Brabender plastograph. The blends' temperatures during processing, as affected by the blends' composition and initial process temperature, were monitored. Accordingly, the process includes the following main stages: heating the blend, exothermic PANI-DBSA doping reaction accompanied by a paste to a solidlike transition, and plasticization of the resulting PANI/DBSA complex by the excess DBSA. Composition analysis of the process products sampled at the various stages showed that the initial blends, prior to their thermal processing, already consisted of partially doped PANI particles, having a core/shell structure; the core consists of PANI base and the shell of PANI(DBSA) 0.32 complex. In addition, at the pasteto-solidlike transition, the doping reaction is completed; further mixing does not affect the complex composition, but results in conductivity reduction. The morphology of the blends sampled at the various processing stages was studied by electron microscopy. From the conductivity and processibility point of view, optimal PANI/DBSA blend composition and processing temperature were identified.
Polyaniline Conducting Electroactive Polymers Thermal and Environmental Stability Studies
E-Journal of Chemistry, 2006
In the current studies, polyaniline (PANi) was prepared both chemical and electrochemically in the presence of different bronsted acids from aqueous solutions. The effect of thermal treatment on electrical conductivity, and thermal stability of the PANi conducting polymers were investigated using 4-point probe and TGA techniques respectively. It was found that polymer prepared by CV method is more thermally stable than those prepared by the other electrochemical techniques. In this paper we have also reviewed some fundamental information about synthesis, general properties, diverse applications, thermal and environmental stability of polyaniline conducting polymers.