Annealing Effects of Dilute Polyaniline/NMP Solution

Abstract

The annealing effects of a dilute polyaniline solution on chemical and physical properties were investigated. Emeraldine base (EB) of polyaniline prepared by the conventional procedure was dissolved in 1-methyl-2-pyrrolidinone (NMP). After heating at 60−140 °C for 2 h, the color of PANi solution changed from deep blue to various colors depending on the annealing temperature. This solution was filtered and cooled at −5 °C to preserve an undoped structure. Changes of physical and chemical properties were investigated using ultraviolet−visible (UV−vis), Fourier transform infrared (FT-IR) spectroscopy, electron spectroscopy for chemical analysis (ESCA), and dynamic light scattering (DLS). By contrast to the previously reported reductive reaction, we concluded that the annealing of dilute EB/NMP solution resulted in cross-linking. This was indicated by the decrease of the mutual diffusion coefficient at infinite dilution (D 0) and the increase in the apparent hydrodynamic radius (R h) of EB with the annealing temperature evidenced by the DLS and the increase of the cyclic-N portion from ESCA results. The annealing also produces a polyelectrolyte chain, supported by FT−IR and DLS measurements.

Vacuum‐Processed Polyaniline–C60 Organic Field Effect Transistors

“…The characteristic peaks at $330 and $628 nm correspond to those reported in the literature. [5,15,18,19,32,35] In the UV-Vis spectrum of the sublimated material, displayed in Figure 5b, the exciton-type absorption of the quinoid ring peak centered at $628 nm is not present, confirming the chemical reduction of the deposited material. Both investigation techniques therefore indicate that the vacuum deposited material is not identical with the precursor polyaniline in the emeraldine base oxidation state, but is actually a material with the oxidation state intermediate between the half oxidized emeraldine base and fully reduced leucoemeraldine base.…”

Thermal aging of undoped polyaniline: Effect of chemical degradation on electrical properties

“…To a first approximation the spectrum can be fitted with four lines corresponding to four types of nonequivalent carbon atoms: the aromatic or quinone carbons bonded to hydrogen (C-H) at the bonding energy of 285 Ϯ 0.1 eV, aromatic carbons bonded to amine nitrogen (C-N) at 285.8 Ϯ 0.1 eV, quinone carbons bonded to imine nitrogen (C¢N) at 286.5 Ϯ 0.1 eV, and carbons of carbonyl groups (C¢O) at 288.1 Ϯ 0.1 eV. 22 The following composition of the surface can be established on the basis of Cls spectrum of pristine EB: C-H: 66%, C-N: 23%, C¢N: 8% and C¢O: 3%, which is slightly different than the theoretically predicted one, i.e., C-H: 66.66%, C-N: 25%, C¢N: 8.33%. These results confirm that carbonyl groups are present even in nonaged polymer, at least on its surface.…”

“…One must note, however, that the discrimination between a quinone type carbon atom bonded to nitrogen and an aromatic carbon atom bonded to nitrogen may be, in some cases, difficult due to small difference in the values of the energy of binding (EB) and large halfwidth of the peak. 22 For these reasons we carried out Nls XPS measurement, which give much clearer results. The Nls spectra were fitted using three contri- butions: imine nitrogen (-N¢C) at 398.8 Ϯ 0.1 eV, secondary amine nitrogen at 399.9 Ϯ 0.1 eV, and tertiary amine nitrogen at 400.8 Ϯ 0.1 eV.…”

“…The Nls spectra were fitted using three contri- butions: imine nitrogen (-N¢C) at 398.8 Ϯ 0.1 eV, secondary amine nitrogen at 399.9 Ϯ 0.1 eV, and tertiary amine nitrogen at 400.8 Ϯ 0.1 eV. [22][23][24][25][26] Alternatively the presence of this peak of low intensity can be attributed to incomplete dedoping of polyaniline, which shows the presence of Cl even in samples treated with NH 3aq for extended time and then carefully washed. In such a case this peak must originate from charged nitrogen species (-NH ϩ -) as postulated in refs, 10, 12, and 22.…”

Synthesis and characterization of new biocompatible copolymer: chitosan-graft-polyaniline

“…Conducting polymers find applications in fields like: sensors, electro catalysts, microelectronics, electromagnetic shielding, rechargeable batteries and controlling systems. [1][2][3][4].…”