Localized molecular excitons in polyaniline

Conwell, E. M.; Paton, A.

doi:10.1016/0009-2614(86)80521-8

Cited by 104 publications

(35 citation statements)

References 5 publications

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“…It is well known that the UVvis spectrum of undoped samples presents two characteristic peaks: one at about 325 nm corresponding to the -* transition, 15 and other in 625 nm attributed to an excitonic transition between the levels of the benzenoid and the quinoid rings. 16 The spectrum of the doped PAN also shows the -* transition peak, but instead the excitonic transition it presents a wide polaronic band, which starts at approximately 500 nm, has a maximum at about 860 nm and extends across the infrared region. 15 The PPES spectra of PAN films, however, showed similar features irrespective of any doping effect.…”

Section: Samples and Photopyroelectric Spectroscopymentioning

confidence: 98%

Photopyroelectric spectroscopy of polyaniline films

Albuquerque

Melo

Faria

2000

J. Polym. Sci. B Polym. Phys.

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Section: Samples and Photopyroelectric Spectroscopymentioning

confidence: 98%

Photopyroelectric spectroscopy of polyaniline films

Albuquerque

Melo

Faria

2000

J. Polym. Sci. B Polym. Phys.

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“…This assignment is based on earlier reports on the doping of PANI with acids. 39,40 PANI in the less doped emeraldine base form exhibited a peak at around 620 nm, corresponding to a localized molecular excitonic transition with the electron on a quinoid moiety and a hole on the neighboring moiety. Upon acid induced doping of the emeraldine base to result in an emeraldine salt, the excitonic transition shifted to 580 nm.…”

Section: Uv-visible Spectroscopymentioning

confidence: 98%

“…Upon acid induced doping of the emeraldine base to result in an emeraldine salt, the excitonic transition shifted to 580 nm. 39,40 With more MWNTs in the composite, we envision an increase in the probable carboxyl groups generated in the MWNTs during oxidative polymerization with ammonium peroxydisulfate, which might result in more induced doping to PDPA. For a comparison, the electronic spectra of doped PDPA are presented in the inset of Figure 7.…”

Section: Uv-visible Spectroscopymentioning

confidence: 99%

Characterization and preparation of new multiwall carbon nanotube/conducting polymer composites by in situ polymerization

Showkat

Lee

Gopalan

et al. 2006

J of Applied Polymer Sci

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ABSTRACT:Composites based on poly(diphenyl amine) (PDPA) and multiwall carbon nanotubes (MWNTs) were prepared by chemical oxidative polymerization through two different approaches: in situ polymerization and intimate mixing. In in situ polymerization, DPA was polymerized in the presence of dispersed MWNTs in sulfuric acid medium for different molar composition ratios of MWNT and DPA. Intimate mixing of synthesized PDPA with MWNT was also used for the preparation of PDPA/MWNT composites. Transmission electron microscopy revealed that the diameter of the tubular structure for the composite was 10 -20 nm higher than the diameter of pure MWNT. Scanning electron microscopy provided evidence for the differences in the morphology between the MWNTs and the composites. Raman and Fourier transform IR (FTIR) spectroscopy, thermogravimetric analysis, X-ray diffraction, and UV-visible spectroscopy were used to characterize the composites and reveal the differences in the molecular level interactions between the components in the composites. The Raman and FTIR spectral results revealed doping-type molecular interactions and coordinate covalent-type interactions between MWNT and PDPA in the composite prepared by in situ polymerization and intimate mixing, respectively. The backbone structure of PDPA in the composite decomposed at a higher temperature (Ͼ340°C) than the pristine PDPA (ϳ300°C). This behavior also favored the molecular level interactions between MWNT and PDPA in the composite.

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“…Typical EB spectrum consists of two absorption bands: the first at 320 nm (ϳ 3.8 eV) originates from the -* transition in the benzenoïd rings, and the second at 640 nm (ϳ 1.9 eV) is associated with the intrachain excitonic transition from the highest occupied energy levels (HOMO) (centered on the benzenoïd rings) to the lowest unoccupied energy level (LUMO) (centered on the quinoïd rings). 30,31 This last transition is the most affected by aging. The maximum of the absorption due to excitonic transition (640 nm) presents an hypsochromic displacement with aging time, which is linked to a decrease in the conjugation length.…”

Section: Scheme 1 Crosslinking Mechanism In Ebmentioning

confidence: 99%

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

Kieffel

Travers

Ermolieff

et al. 2002

J of Applied Polymer Sci

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ABSTRACT:Aging experiments, with a special emphasis on the atmosphere effect, have been carried out on undoped polyaniline, in its half-oxidized state, namely emeraldine base (EB). The polymer has been aged under vacuum and in air atmosphere. The chemical degradation has been analyzed by several complementary techniques such as viscosity measurements, FTIR, XPS, and UV-Vis-nIR spectroscopy. We show that emeraldine base exhibits two different degradation mechanisms. The first one is intrinsic to the polymer and occurs independently on aging conditions (vacuum or air). It consists of crosslinking via tertiary amine groups created from imine nitrogen via double-bond breaking. The second mechanism is extrinsic and occurs concomitantly with the first one upon aging in air. It consists of oxygen incorporation in a form of carbonyl groups and chain scission. Both degradation pathways result in a decrease of the electrical conductivity of the polymer due to the lowering of the average conjugation length.

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Localized molecular excitons in polyaniline

Cited by 104 publications

References 5 publications

Photopyroelectric spectroscopy of polyaniline films

Photopyroelectric spectroscopy of polyaniline films

Characterization and preparation of new multiwall carbon nanotube/conducting polymer composites by in situ polymerization

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

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